Deepwater Program: Studies of Gulf of Mexico Lower Continental Slope 

Communities Related to Chemosynthetic and Hard Substrate Habitats

By Steve W. Ross, Amanda W.J. Demopoulos, Christina A. Kellogg, Cheryl L. Morrison, 

Martha S. Nizinski, Cheryl L. Ames, Tara L. Casazza, Daniel Gualtieri, Kaitlin Kovacs, Jennifer 

P. McClain, Andrea M. Quattrini, Adela Y. Roa-Varón, and Andew D. Thaler

Open-File Report 2012–1032

U.S. Department of the Interior 

U.S. Geological Survey 
ii

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia 2012 

For product and ordering information:

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Suggested citation:

Ross, S.W., Demopoulos, A.W.J., Kellogg, C.A., Morrison, C.L., Nizinski, M.S., Ames, C.L., Casazza, T.L., 

Gualtieri, D., Kovacs, K., McClain, J.P., Quattrini, A.M., Roa-Varón, A.Y., and Thaler, A.D., 2012, 

Deepwater Program: Studies of Gulf of Mexico lower continental slope communities related to 

chemosynthetic and hard substrate habitats: U.S. Geological Survey Open-File Report 2012-1032, 301 p.

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endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

By Steve W. Ross, Amanda W.J. Demopoulos, Christina A. Kellogg, Cheryl L. Morrison, Martha S. 

Nizinski, Cheryl L. Ames, Tara L. Casazza, Daniel Gualtieri, Kaitlin Kovacs, Jennifer P. McClain, Andrea 

M. Quattrini, Adela Y. Roa-Varón, and Andew D. Thaler .......................................................................................... i

1. INTRODUCTION AND PROJECT OVERVIEW .......................................................................................................... 1

2. ENUMERATION OF MICROBES IN CHEMOSYNTHETIC COMMUNITY SEDIMENTS ........................................... 5

2.1 Introduction ............................................................................................................................................................ 5

2.2 Methods ................................................................................................................................................................. 7

2.2.1 Sampling sites ................................................................................................................................................ 7

2.2.2 Sediment Characteristics ................................................................................................................................ 9

2.2.3 Enumeration of microbes .............................................................................................................................. 10

2.3 Results ................................................................................................................................................................ 10

2.3.1 Sediment characteristics ............................................................................................................................... 10

2.3.2 Microbial enumeration .................................................................................................................................. 11

2.4 Discussion ........................................................................................................................................................... 11

2.5 Acknowledgments ............................................................................................................................................... 17

3. FOOD-WEB STRUCTURE OF SEEP SEDIMENT MACROBENTHOS FROM THE GULF OF MEXICO ................ 18

3.1 Introduction .......................................................................................................................................................... 18

3.2 Materials and Methods ........................................................................................................................................ 21

3.2.1 Collection Methods ....................................................................................................................................... 21

3.2.2 Lab Processing ............................................................................................................................................. 24

3.3.3 Statistical Analysis ........................................................................................................................................ 24

3.3 Results ................................................................................................................................................................ 24

3.3.1 Sediment Characteristics .............................................................................................................................. 24
iv

3.3.2 Isotopic composition of primary source pools ............................................................................................... 28

3.3.3 Sediment macrofaunal isotopic composition ................................................................................................ 29

3.3.3.1 Green Canyon-GC 852 ................................................................................................................................. 29

3.3.3.2 Alaminos Canyon-AC 601 ............................................................................................................................ 30

3.3.3.3 Atwater Valley-AT 340 .................................................................................................................................. 30

3.4 Discussion ........................................................................................................................................................... 31

3.5. Acknowledgments .............................................................................................................................................. 34

4. MACROFAUNAL COMMUNITY STRUCTURE AND SEDIMENT ENVIRONMENTAL CHARACTERISTICS IN 

THREE SEEP ECOSYSTEMS ..................................................................................................................................... 35

4.1 Introduction .......................................................................................................................................................... 35

4.2 Methods ............................................................................................................................................................... 36

4.2.1 Sampling Sites .............................................................................................................................................. 36

4.2.2 Lab Processing ............................................................................................................................................. 37

4.3 Results ................................................................................................................................................................ 38

4.3.1 Sediment Properties ..................................................................................................................................... 38

4.3.2 Macrofauna abundance and composition ..................................................................................................... 40

4.4 Discussion ........................................................................................................................................................... 42

4.5 Acknowledgments ............................................................................................................................................... 43

5. PHYLOGEOGRAPHIC AFFINITIES OF SQUAT LOBSTERS (DECAPODA: GALATHEOIDAE) FROM LOWER 

CONTINENTAL SLOPE COLD-SEEP HABITATS IN THE NORTHERN GULF OF MEXICO ..................................... 45

5.1 Introduction .......................................................................................................................................................... 45

5.2 Methods ............................................................................................................................................................... 49

5.2.1 Sample Collections ....................................................................................................................................... 49

5.2.2 DNA extraction, amplification, and sequencing ............................................................................................ 52
v 

5.2.3 Mitochondrial DNA sequence analysis ......................................................................................................... 53

5.3 Results ................................................................................................................................................................ 54

5.3.1 Diversity of Galatheoidea .............................................................................................................................. 54

5.3.2 Munidopsis species ...................................................................................................................................... 55

5.3.3 Munida species ............................................................................................................................................. 59

5.4 Discussion ........................................................................................................................................................... 62

5.5 Acknowledgments ............................................................................................................................................... 64

6. PRELIMINARY MOLECULAR ASSESSMENT OF SCLERACTINIAN CORAL AND OCTOCORAL BIODIVERSITY 

FROM LOWER CONTINENTAL SLOPE HABITATS IN THE NORTHERN GULF OF MEXICO ................................. 66

6.1 Introduction .......................................................................................................................................................... 66

6.2 Methods ............................................................................................................................................................... 69

6.2.1 Sampling sites .............................................................................................................................................. 69

6.2.2 Molecular Methods ....................................................................................................................................... 71

6.2.3 Phylogenetic analyses .................................................................................................................................. 72

6.3 Results ................................................................................................................................................................ 73

6.3.1 Scleractinian coral phylogeny ....................................................................................................................... 73

6.3.2 Octocoral phylogeny ..................................................................................................................................... 78

6.4 Discussion ........................................................................................................................................................... 83

6.5 Acknowledgments ............................................................................................................................................... 85

7. COMMUNITY STRUCTURE OF MESOPELAGIC FISHES OVER THE SLOPE OF THE NORTH-CENTRAL GULF 

OF MEXICO .................................................................................................................................................................. 86

7.1 Introduction .......................................................................................................................................................... 86

7.2 Methods ............................................................................................................................................................... 89

7.2.1 Study Areas .................................................................................................................................................. 91
vi

7.2.2 Tucker trawl .................................................................................................................................................. 96

7.2.3 Data Analysis ................................................................................................................................................ 98

7.3 Results .............................................................................................................................................................. 102

7.3.1 Site Comparisons ....................................................................................................................................... 118

7.3.1.1 Species Richness ......................................................................................................................................... 118

7.3.1.2 Across-Site Comparisons ............................................................................................................................. 120

7.3.1.3 Within-Site Comparisons .............................................................................................................................. 123

7.3.2 Depth, Diel, and Size Distributions ............................................................................................................. 126

7.4 Discussion ......................................................................................................................................................... 135

7.4.1 General ....................................................................................................................................................... 135

7.4.2 Site Comparisons ....................................................................................................................................... 137

7.4.3 Depth, Diel, and Size Distributions ............................................................................................................. 140

7.4.4 Conclusion .................................................................................................................................................. 142

7.5 Acknowledgments ............................................................................................................................................. 143

8. DIETS AND FEEDING BEHAVIOR OF MIDWATER FISHES OVER COLD- SEEP SITES IN THE NORTHCENTRAL GULF OF MEXICO .................................................................................................................................... 144

8.1 Introduction ........................................................................................................................................................ 144

8.2 Methods ............................................................................................................................................................. 148

8.2.1 Study Area .................................................................................................................................................. 148

8.2.2 Sample Collection ....................................................................................................................................... 149

8.2.3 Diet Analyses .............................................................................................................................................. 153

8.2.4 Stable Isotope Analysis (SIA) ..................................................................................................................... 154

8.2.5 Statistical Analyses ..................................................................................................................................... 156

8.3 Results .............................................................................................................................................................. 156
vii

8.3.1 Primary Producers ...................................................................................................................................... 160

8.3.2 Invertebrates ............................................................................................................................................... 160

8.3.3 Fishes ......................................................................................................................................................... 163

8.3.3.1 Gonostomatidae ........................................................................................................................................... 163

8.3.3.2 Myctophidae ................................................................................................................................................. 179

8.3.3.3 Phosichthyidae ............................................................................................................................................. 196

8.3.3.4 Sternoptychidae ............................................................................................................................................ 202

8.3.3.5 Stomiidae ...................................................................................................................................................... 210

8.4 Discussion ......................................................................................................................................................... 212

8.5 Conclusions ....................................................................................................................................................... 218

8.6 Acknowledgments ............................................................................................................................................. 218

9. DISTRIBUTIONS AND COMPOSITION OF THE MESOPELAGIC INVERTEBRATE FAUNA OVER THE SLOPE 

OF THE NORTH-CENTRAL GULF OF MEXICO ....................................................................................................... 220

9.1 Introduction ........................................................................................................................................................ 220

9.2 Methods ............................................................................................................................................................. 221

9.3 Results .............................................................................................................................................................. 223

9.3.1 Species composition and relative abundance among study sites .............................................................. 237

9.3.2 Species composition and relative abundance among zones ...................................................................... 239

9.4 Discussion ......................................................................................................................................................... 256

9.5 Acknowledgements ........................................................................................................................................... 260

10. ANALYSIS OF FUNGAL DIVERSITY IN SEDIMENT FROM A METHANE SEEP, GULF OF MEXICO .............. 261

10.1 Introduction and Rationale .............................................................................................................................. 261

10.2 Methods ........................................................................................................................................................... 262

10.2.1 Recovery ................................................................................................................................................... 262
viii

10.2.2 Extraction and Amplification ..................................................................................................................... 263

10.2.3 Analysis .................................................................................................................................................... 263

10.3 Results ............................................................................................................................................................ 264

10.4 Discussion ....................................................................................................................................................... 266

10.5 Acknowledgments ........................................................................................................................................... 267

References Cited ........................................................................................................................................................ 268

Figures

Figure 1.1. Four major study areas sampled in the Gulf of Mexico during the Chemo III project. (VK, Viosca Knoll; 

AT, Atwater Canyon; GC, Green Canyon; AC, Alaminos Canyon. Insets for each area illustrate sampling stations by 

gear type: BC, box core; OT, otter trawl; NN, neuston net; OD, on deck; PN, plankton net followed by mesh size; 

Phyto, phytoplankton water sample; CTD, conductivity, temperature, depth profiler; TT, Tucker trawl.) ....................... 4

Figure 2.1. Viral lysis of bacteria converts cellular components into dissolved organic matter, transferring nutrients 

away from grazers and stimulating other heterotrophic prokaryotic growth. ................................................................... 7

Figure 3.1. Collection sites in the Gulf of Mexico. (Contour lines represent 1,000-, 2,000-, and 3,000- m 

bathymetry.) ................................................................................................................................................................ 22

Figure 3.2. Dual stable isotope plots of different primary sources (open rectangles), and macrofauna (>300 

micrometers, μm) from Gulf of Mexico seeps: (A) GC852, (B) AC601, and (C) AT340. (Each point represents a 

distinct individual. Ranges in stable carbon and nitrogen isotope values are given for primary sources, including 

particulate organic matter (POM), suspended organic matter (SOM), Beggiatoa bacteria, and sediment.) ................. 27

Figure 4.1. A, Macrofaunal (>300 μm) density (individuals per square meter), and B, taxonomic composition by 

major taxa. ................................................................................................................................................................ 41

Figure 5.1. Multibeam bathymetry map of the northern Gulf of Mexico continental slope. Included on map are 

galatheiod collection localities (yellow dots) and lease blocks established by the Bureau of Ocean Energy 
ix

Management, Regulation and Enforcement for oil and gas activity management. (Map created by Harry Roberts, 

Louisiana State University). .......................................................................................................................................... 52

Figure 5.2. Phylogenetic hypothesis for Munidopsis resulting from Bayesian analysis of mitochondrial cytochrome 

oxidase (COI) DNA sequence data. A and B are clades, or groupings of taxa. ............................................................ 57

Figure 5.3. Phylogenetic hypothesis for Munida resulting from Bayesian analysis of mitochondrial cytochrome 

oxidase I (COI) DNA sequence data. ............................................................................................................................ 61

Figure 6.1. Sampling locations in the northern Gulf of Mexico. ................................................................................. 70

Figure 6.2. Phylogenetic hypothesis for scleractinian corals based upon Bayesian analysis of mitochondrial 16S 

sequences. (Species names in bold represent samples unique to this study, whereas others originate from GenBank 

or Morrison and others (2008). Numbers at nodes represent Bayesian posterior probabilities of node support.) ........ 78

Figure 6.3. Phylogenetic hypothesis for octocorals based upon Bayesian analysis of mitochondrial msh1 

sequences. (Species names in bold represent samples unique to this study, whereas others originate from GenBank. 

Numbers at nodes represent Bayesian posterior probabilities of node support. Vertical bars indicate the following 

families: Ac, Acanthogorgiidae; Go, Gorgoniidae; St, Stenogorgiinae; Pl, Plexauridae; Ch, Chrysogorgiidae; Pr, 

Primnoidae; Is, Isididae; Co, Coralliidae.) ..................................................................................................................... 81

Figure 6.4. Phylogenetic hypothesis for octocorals based upon Bayesian analysis of mitochondrial ND2 sequences.

(Species names in bold represent samples unique to this study, whereas others originate from GenBank. Numbers at 

nodes represent Bayesian posterior probabilities of node support. Vertical bars indicate the following families: Ac, 

Acanthogorgiidae; St, Stenogorgiinae; Ch, Chrysogorgiidae; Pr, Primnoidae; Is, Isididae; Co, Coralliidae.) ............... 83

Figure 7.1. Study area locations in the north-central Gulf of Mexico sampled August 9-29, 2007. Three sites 

(AC601, GC852, and AT340) were over cold-seep habitats, and VK826 was over a coral-carbonate and seep habitat. 

Vector lines represent Tucker trawl tows and boxes are conductivity, temperature, and depth profiler (CTD) stations. .. 

 ................................................................................................................................................................ 91
x 

Figure 7.2. Naval Research Lab Layered Ocean Model (high resolution) assimilating Sea Surface Height (SSH) for 

four dates during our study period. The anomaly SSH satellite maps show the difference in measured sea height 

from the calculated, mean sea level. A +17 cm SSH contour generally tracks the loop current (LC) and loop current 

rings. Reds and yellows represent higher SSH and warmer waters of the LC and LC eddies. Blue to purple colors 

are negative SSH anomalies representing cold-core cyclonic eddies. ......................................................................... 93

Figure 7.3. Conductivity, temperature, depth (CTD) (SeaBird 911plus) casts at the four Gulf of Mexico study sites, 

illustrating dissolved oxygen (milliliters per liter), fluorescence, water temperature (degrees Celsius), and salinity 

profiles (practical salinity units). .................................................................................................................................... 96

Figure 7.4. Tucker trawl being deployed over the stern of the R/V Cape Hatteras on August 13, 2007. .................. 97

Figure 7.5. Species accumulation curves for the four Gulf of Mexico study sites plotted using the Colwell and 

others (2004) analytical method. ................................................................................................................................. 119

Figure 7.6. Multdimensional scaling ordination of 115 stations based on the Bray-Curtis similarity matrix calculated 

from standardized, fourth-root transformed fish abundances (117 species) with superimposed (A) SIMPROF groups 

labeled by day (D) or night (N) and (B) mean depths (in meters) with SIMPROF labels. The embedded dendrogram in 

A is labeled with SIMPROF groups. The table includes sites, number of stations, and sampled mean depth ranges (in 

parentheses) of each SIMPROF group. ...................................................................................................................... 122

Figure 7.7. Multidimensional scaling ordinations for three stations based on Bray-Curtis similarity matrices 

calculated from standardized, fourth-root transformed fish abundances. Each plot, (A) GC852 (50 stations, 91 

species), (B) AT340 (35 stations, 71 species), and (C) VK826 (25 stations, 51 species), has superimposed SIMPROF 

groups labeled by day (D) or night (N). The embedded dendrograms include SIMPROF groups, followed by number of 

stations and sampled mean depth ranges (in parentheses). ...................................................................................... 126

Figure 7.8. Overall (all stations combined) temporal depth distributions of dominant midwater fishes (Cyclothone 

acclinidens, C. alba, C. braueri) by abundance and size class collected in the Gulf of Mexico, August 9-29, 2007. SL 

mm, standard length in millimeters. ............................................................................................................................ 128
xi

Figure 7.9. Overall (all stations combined) temporal depth distributions of dominant midwater fishes (Cyclothone 

pallida, C. pseudopallida, Valenciennellus tripunctulatus) by abundance and size class collected in the Gulf of Mexico, 

August 9-29, 2007. SL mm, standard length in millimeters. ........................................................................................ 129

Figure 7.10. Overall (all stations combined) temporal depth distributions of dominant midwater fishes (Vinciguerria 

poweriae, Benthosema suborblitale, Diaphus dumerilii) by abundance and size class collected in the Gulf of Mexico, 

August 9-29, 2007. ...................................................................................................................................................... 131

Figure 7.11. Overall (all stations combined) temporal depth distributions of dominant midwater fishes 

(Lepidophanes guentheri, Notolychnus valdiviae) by abundance and size class collected in the Gulf of Mexico, August 

9-29, 2007. ............................................................................................................................................................ 132

Figure 8.1. North-central Gulf of Mexico illustrating sampling areas for midwater fauna, August 9-25, 2007, at three 

cold-seep sites (AC601, GC852, and AT340) located on the slope at depths >1,000 meters. Each dot represents one 

station. .............................................................................................................................................................. 149

Figure 8.2. Mean δ13C and δ15N (± 1 SE) stable isotope values for all samples collected. Data from all three sites 

for each species were grouped together. *, Detritus values are not shown. ............................................................... 162

Figure 8.3. The relationships between stomach fullness and depth of capture for 18 midwater fishes. Data from all 

three sites were grouped together to detect diel vertical migrations. .......................................................................... 167

Figure 8.4. The relationship of standard length (SL) to δ15N values in midwater fishes from the families (A) 

Gonostomatidae – Cyclothone spp.; (B) Gonostomatidae – Gonostoma elongatum; (C) Myctophidae; (D) 

Phosichthyidae; (E) Sternoptychidae; and (F) Stomiidae collected at all three sites. ................................................. 179

Figure 9.1. Map of study area in the north-central Gulf of Mexico showing location of sampling sites. Three sites 

(AC601, GC852, and AT340) were over cold-seep habitats and one site (VK826) was over a Lophelia pertusa coral 

habitat. .............................................................................................................................................................. 222
xii

Figure 9.2. Overall (all sampling sites combined) species richness of invertebrates for each major taxon collected by 

zone (surface, midwater, benthic) at three cold-seep sites (AC601, GC852, and AT340) and one Lophelia pertusa site 

(VK826) in the Gulf of Mexico, August 9-29, 2007. ..................................................................................................... 232

Figure 9.3. Overall (all sampling sites combined) species richness of all major invertebrate taxa collected at three 

cold-seep sites (AC601, GC852, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-

29, 2007. ............................................................................................................................................................... 234

Figure 9.4. Overall (all sampling sites combined) species richness and abundance of major invertebrate taxa 

collected at three cold- seep sites (AC601, GC852, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of 

Mexico, August 9-29, 2007. ........................................................................................................................................ 235

Figure 9.5. Species richness (by site) of invertebrates collected at three cold-seep sites (AC601, GC852, and 

AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ........................................ 238

Figure 9.6. Species richness of all major invertebrate taxa collected using surface gear over three cold-seep sites 

(AC601, GC852, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ..... 242

Figure 9.7. Species richness of major invertebrate taxa collected using bottom gear at two cold-seep sites (GC852 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ................................. 247

Figure 9.8. Species richness of major invertebrate taxa collected using midwater gear over three cold-seep sites 

(AC601, GC852, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ..... 255

Figure 10.1. Primers used for amplification of fungal LSU and ITS regions. .......................................................... 263

Figure 10.2. ...Redox profile for the Alaminos Canyon methane seep boxcore, mV, millivolts; cm, 

centimeters.__Courtesy of A.W.J. Demopoulos, USGS. Shaded area is the region dominated by an unidentified 

ascomycete clade. ...................................................................................................................................................... 265

Figure 10.3. Eukaryotic phylotypes recovered from Alaminos Canyon methane seep, 0–2 cm and 2–4 cm. Greater 

depths are not shown due to few sequences recovered below the redox zone. ......................................................... 266
xiii

Tables

Table 2.1 Nine sediment cores were collected from four sites in the Gulf of Mexico between June 21 and July 2, 

2007, utilizing the utilizing the R/V Ronald H. Brown and the remotely operated vehicle (ROV) Jason. [m, meter; C, 

degrees Celsius, ‰, parts per thousand] ........................................................................................................................ 9 

Table 2.2. Microbial abundance numbers from previous studies of sediments below 1,000 m water depth. ......... 14

Table 3.1. Box core locations and depths, northern Gulf of Mexico. ........................................................................ 23

Table 3.2. Redox potential profiles (Eh, in millivolts) in box cores from Green Canyon (GC 852), Alaminos Canyon 

(AC601), and Atwater Valley (AT340). .......................................................................................................................... 27

Table 4.1. Average (± 1 S.E.) sediment particle size, percent organic carbon and nitrogen, δ13C, δ5N, and salinity 

from three seeps in the Gulf of Mexico. [%, percent; cm, centimeter; salinity measured in practical salinity units] ...... 39

Table 5.1. Species list for galatheoid samples examined. ...................................................................................... 51

Table 5.2. Pairwise uncorrected P-distances between mitochondrial cytochrome oxidase I (COI) sequences for 

Munidopsis samples. ..................................................................................................................................................... 58

Table 6.1. Collection and information for scleractinian coral samples. ..................................................................... 74

Table 6.2. Collection and information for octocoral samples. .................................................................................... 78

Table 7.1. Relative abundance of species comprising ~90 percent of total catch at each site. ............................ 101

Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (August 9-29, 2007). ....................... 103

Table 7.3. Total numbers and standard length ranges (millimeters in parentheses) of juvenile and adult fishes 

collected by Tucker trawl over three cold-seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in 

the Gulf of Mexico (August 9-29, 2007). ..................................................................................................................... 110

Table 8.1. Surface stations sampled over three cold-seep sites (AC601, GC852, and AT340) (see fig. 8.1) in the 

Gulf of Mexico (August 9-25, 2007). .......................................................................................................................... 151

Table 8.2. Mean δ15N and δ13C (±1 SE) stable isotope values by species collected at three cold-seep sites (AC601, 

GC852, and AT340) in the Gulf of Mexico, August 9-25, 2007. .................................................................................. 158
xiv

Table 8.3. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone alba collected from 

two sites (AT340, and GC852) in the Gulf of Mexico separated by day and night. Additionally, two C. alba were 

captured at site AC601, both at night with empty stomachs. ...................................................................................... 168

Table 8.4. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone pallida collected 

from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. ............................. 169

Table 8.5. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone braueri collected 

from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night. Additionally, two C. braueri

were captured at site AC601, both at night with empty stomachs. ............................................................................. 170

Table 8.6. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone pseudopallida

collected from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. .............. 171

Table 8.7. Percent volume (%V) and percent frequency (%F) of prey consumed by Gonostoma elongatum

collected from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night. .............................. 173

Table 8.8. Percent volume (%V) and percent frequency (%F) of prey consumed by Hygophum benoiti collected 

from AT340 in the Gulf of Mexico separated by day and night. Additionally, six H. benoiti were collected at AC601 at 

night, all with empty stomachs. At site GC852, 33 H. benoiti were collected during the day and 37 during the night, all 

with empty stomachs. .................................................................................................................................................. 181

Table 8.9. Percent volume (%V) and percent frequency (%F) of prey consumed by Benthosema suborbitale

collected from three sites (AC601, AT340 and GC852) in the Gulf of Mexico separated by day and night. ............... 182

Table 8.10. Percent volume (%V) and percent frequency (%F) of prey consumed by Diaphus mollis collected from 

three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. ..................................... 185

Table 8.11. Percent volume (%V) and percent frequency (%F) of prey consumed by Notolychnus valdiviae 

collected from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. .............. 187

Table 8.12. Percent volume (%V) and percent frequency (%F) of prey consumed by Ceratoscopelus warmingii 

collected from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. .............. 189
xv

Table 8.13. Percent volume (%V) and percent frequency (%F) of prey consumed by Lepidophanes guentheri 

collected from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. .............. 192

Table 8.14. Percent volume (%V) and percent frequency (%F) of prey consumed by Lampanyctus alatus collected 

from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. ............................. 194

Table 8.15. Percent volume (%V) and percent frequency (%F) of prey consumed by Pollichthys mauli collected 

from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night. ............................................. 198

Table 8.16. Percent volume (%V) and percent frequency (%F) of prey consumed by Vinciguerria poweriae 

collected from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. .............. 199

Table 8.17. Percent volume (%V) and percent frequency (%F) of prey consumed by Argyropelecus aculeatus 

collected from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. .............. 204

Table 8.18. Percent volume (%V) and percent frequency (%F) of prey consumed by Argyropelecus hemigymnus 

collected from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night. .............................. 207

Table 8.19. Percent volume (%V) and percent frequency (%F) of prey consumed by Valenciennellus tripunctulatus 

collected from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. .............. 208

Table 8.20. Percent volume (%V) and percent frequency (%F) of prey consumed by Chauliodus sloani collected 

from three sites (AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. ............................. 211

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three 

cold-seep sites (GC852, AC601, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-

29, 2007. .............................................................................................................................................................. 224

Table 9.2. Invertebrate species and number of individuals collected at the surface over two cold-seep sites (GC852 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ................................. 241

Table 9.3. Invertebrate species and number of individuals collected on the bottom at two cold-seep sites (GC852 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ................................. 244
xvi

Table 9.4. Invertebrate species and number of individuals collected in midwater over three cold-seep sites (GC852, 

AC601, and AT340) and at one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ................ 249

Table 10.1. Total sequences recovered, fungal sequences recovered, and sequences recovered from unidentified 

ascomycete clade by 2-cm sediment depth intervals from the Alaminos Canyon methane seep (2,300 m). ............. 264
xvii

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

mile, nautical (nmi) 1.852 kilometer (km)

yard (yd) 0.9144 meter (m)

Area

acre 4,047 square meter 2 (m )

square foot (ft2) 0.09290 square meter 2 (m )

Volume

ounce, fluid (fl. oz) 0.02957 liter (L) 

pint (pt) 0.4732 liter (L) 

quart (qt) 0.9464 liter (L) 

gallon (gal) 3.785 liter (L) 

Mass

ounce, avoirdupois (oz) 28.35 gram (g) 

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

NOTE TO USGS USERS: Use of hectare (ha) as an alternative name for square hectometer (hm2

) is restricted to the measurement 

of small land or water areas. Use of liter (L) as a special name for cubic decimeter (dm3

) is restricted to the measurement of 

liquids and gases. No prefix other than milli should be used with liter. Metric ton (t) as a name for megagram (Mg) should be 

restricted to commercial usage, and no prefixes should be used with it.
1 

1. INTRODUCTION AND PROJECT OVERVIEW

By Steve W. Ross1 

1

University of North Carolina Wilmington, Center for Marine Science, Wilmington, NC

This report summarizes research funded by the U.S. Geological Survey (USGS) in 

collaboration with the University of North Carolina at Wilmington (UNCW) on the ecology of 

deep chemosynthetic communities in the Gulf of Mexico. The research was conducted at the 

request of the U.S. Bureau of Ocean Energy Management, Regulation and Enforcement 

(BOEMRE; formerly Minerals Management Service) to complement a BOEMRE-funded project 

titled “Deepwater Program: Investigations of Chemosynthetic Communities on the Lower 

Continental Slope of the Gulf of Mexico.” The overall research partnership, known as “Chemo 

III,” was initiated to increase understanding of the distribution, structure, function, and 

vulnerabilities of these poorly known associations of animals and microbes for water depths 

>1,000 meters (m) in the Gulf of Mexico. Chemosynthetic communities rely on carbon sources 

that are largely independent of sunlight and photosynthetic food webs. Despite recent research 

directed toward chemosynthetic and deep coral (for example, Lophelia pertusa) based 

ecosystems, these habitats are still poorly studied, especially at depths greater than 1,000 m. 

With the progression into deeper waters by fishing and energy industries, developing sufficient 

knowledge to manage these deep ecosystems is essential. Increased understanding of deep-sea 

communities will enable sound evaluations of potential impacts and appropriate mitigations. 

Cruise reports and preliminary data for the BOEMRE-funded projects are included in 

reports prepared by TDI-Brooks International, Inc. (2006a, b; 2007), and a final report that 
2 

complements this USGS report is near completion. Some USGS objectives were addressed with 

participation in the BOEMRE-supported cruises, while others were addressed through a USGS 

cruise (Ross, 2007). This research is part of a larger, long-term goal of the USGS deep-sea 

studies group to develop, integrate, and synthesize information on deep-sea corals (and 

hardgrounds) and chemosynthetic communities and to compare community composition, 

fauna/habitat linkages, genetic structures, and energetics across latitudes, habitat types, depth 

zones, and regions. A special issue of peer-reviewed papers that stemmed from this Chemo III 

project was recently published in the journal Deep-Sea Research – Part II (Roberts, 2010), and 

some of the data contained in this USGS report are also within the Deep-Sea Research 

publication. 

Deep water (aphotic) coral, hardground, and chemosynthetic systems are important 

habitats for macrofauna, repositories of data on ocean climate and productivity, and hotspots of 

increased biodiversity. Fishes and crustaceans are megafauna of particular interest to decisionmakers, but their abundance, microhabitat affinities, and importance in structuring these biotic 

communities are poorly known. Understanding trophic (food web) linkages between the benthos 

and the overlying waters is fundamental ecological knowledge about how deep ecosystems 

function. Deciphering barriers to gene flow that may isolate populations has been problematic 

for marine species. Even so, some slope species exhibit unexpected population heterogeneity. 

Genetic techniques applied to organisms associated with coral, hardbottom, and chemosynthetic 

habitats from various locations provide insights into species biology, mechanisms regulating 

community structure (dispersal), and information about reproduction and recovery after various 

impacts. Microbes, specifically bacteria, are the foundation of deep-sea chemosynthetic 

communities and may provide vital functions to deep-sea corals. Viruses are the most numerous 
3 

organisms in the ocean, and the majority appears to infect marine bacteria. As such, viruses 

control microbial diversity and carbon cycling. Little is known about viruses in the deep sea, and 

to understand cold seep dynamics, the viral ecology of this ecosystem (water and sediments) 

must be addressed. Sponges, important as deep-reef habitat for macrofauna, are recognized as 

“microbial apartment buildings,” containing a wide variety of commensal and symbiotic bacteria 

and archaea. As with coral-associated microbes, assessing these microorganisms allows a better 

understanding of the biology of the macrofauna they inhabit, increases understanding of 

microbial biodiversity, and reveals species interdependencies. 

The USGS Chemo III effort was composed of five interrelated study components, each 

with separate chapters in this report: Part I, midwater macrofauna (fishes and mobile 

invertebrates) taxonomy and ecology (abundances, habitat associations, behaviors); Part II, 

midwater and benthic trophic connectivity; Part III, crustacean taxonomy and ecology; Part IV, 

microbial ecology (composition, distributions); and Part V, genetics (including community 

genetics, phylogeography). While the above lists the five study parts as funded, actual chapter 

titles in this report are different (see Contents). This research in >1,000-m depths expanded and 

supplemented prior projects that focused on Lophelia pertusa communities (300-900 m) and 

provides comparisons with datasets from different areas/ecosystems (reviewed in Brooke and 

Schroeder, 2007; Ross and Nizinski, 2007). The four study areas and sampling completed in 

each area are illustrated in figure 1.1. Other chapters below may use different figures to 

document their sampling. 

This USGS final report has been prepared, in part, to address time-dependent information 

needs as requested by the BOEMRE. Additional analyses, interpretation, and syntheses of the 

available data are expected to lead to future journal publications. 
Figure 1.1. Four major study areas sampled in the Gulf of Mexico during the Chemo III project. (VK, 

Viosca Knoll; AT, Atwater Canyon; GC, Green Canyon; AC, Alaminos Canyon. Insets for each area 

illustrate sampling stations by gear type: BC, box core; OT, otter trawl; NN, neuston net; OD, on deck; 

PN, plankton net followed by mesh size; Phyto, phytoplankton water sample; CTD, conductivity, 

temperature, depth profiler; TT, Tucker trawl.) 

4 
5 

2. ENUMERATION OF MICROBES IN CHEMOSYNTHETIC COMMUNITY 

SEDIMENTS

An expanded version of this paper was published as 

Kellogg, C.A., 2010, Enumeration of viruses and prokaryotes in deep-sea sediments and cold seeps of the Gulf of 

Mexico, in Roberts, H.H., ed., Gulf of Mexico cold seeps: Deep-Sea Research II, v. 57, p. 2002-2007.

By Christina A. Kellogg

St. Petersburg Coastal and Marine Science Center, U.S. Geological Survey, St. Petersburg, FL

2.1 Introduction

Numerous cold seeps and their associated chemosynthetic communities have been 

documented and studied in the Gulf of Mexico over the past 25 years (for example, Kennicutt 

and others, 1985; Brooks and others, 1987; Cordes and others, 2007). Autotrophic bacteria, 

capable of utilizing hydrogen sulfides and methane, are the primary producers in these 

communities, much like the communities found in hydrothermal vents (Brooks and others, 

1987). The microbiology of these cold seeps also includes heterotrophic bacteria and archaea 

(collectively referred to as prokaryotes) and viruses. 

There are estimated to be 1030 marine viruses in the world oceans (Suttle, 2007), and 

typically the number in the underlying sediments exceeds the water-column abundance by 10 to 

100 times (Middelboe and others, 2006). Bacteriophages, viruses that specifically infect 

bacteria, make up the majority (reviewed by Fuhrman, 2000). As the most numerous organisms, 

these viruses play a major role in the marine environment (Fuhrman, 1999; Wommack and 

Colwell, 2000; Suttle, 2005). Viruses affect bacterial diversity and succession; as a particular 

bacterial species achieves a competitive advantage and grows to higher numbers, the probability 
6 

of encountering a virus capable of lysing that specific strain of bacteria increases. Once a single 

cell is infected, the progeny viruses from that infection proceed to infect additional bacteria, until 

that bacterial ‘bloom’ is depleted. This clears the way for another bacterial species (succession) 

and maintains higher bacterial diversity than if a single species were to dominate. Viruses also 

affect productivity and the flow of carbon. Viral lysis of bacteria converts cellular components 

into dissolved organic matter, transferring nutrients away from grazers and stimulating other 

heterotrophic prokaryotic growth (fig. 2.1). In aquatic environments, mortality of bacteria due to 

viral infection is roughly equal to mortality by bacterivory (Bratbak and others, 1994). 

Additionally, viruses can themselves be a source of carbon; it has been shown that flagellates 

will feed on viral particles (Gonzalez and Suttle, 1993). 
7 

Figure 2.1. Viral lysis of bacteria converts cellular components into dissolved organic matter, 

transferring nutrients away from grazers and stimulating other heterotrophic prokaryotic growth. 

High viral abundance in sediments has been shown to be an indicator of increased 

microbial activity (Middelboe and others, 2003; Glud and Middelboe, 2004). In spite of the 

fundamental role that microorganisms play in chemosynthetic communities, no investigation of 

the viral dynamics in the cold-seep environments of the Gulf of Mexico has been previously 

undertaken. This microbial enumeration component directly complements a bacterial 

biogeochemistry component of the BOEMRE-funded project titled “Deepwater Program:

Investigations of Chemosynthetic Communities on the Lower Continental Slope of the Gulf of 

Mexico” (Chemo III), providing a more complete picture of the microbial dynamics that sustain 

a chemosynthetic community. 

The objective of this study was to produce accurate baseline data on the abundance of 

prokaryotes and viruses in surface sediments below a water depth of 1,000 m. The sites chosen 

included a variety of cold-seep environments in the northern Gulf of Mexico to test the 

hypothesis that chemosynthetic communities are areas of increased viral production. 

2.2 Methods

2.2.1 Sampling sites

Nine individual push cores of sediment were collected from four sites in the Gulf of 

Mexico (table 2.1) between June 21 and July 2, 2007, utilizing the R/V Ronald H. Brown and the 

remotely operated vehicle (ROV) Jason. Atwater Valley 340 is characterized by surface brine 

flows and populated by mussels (Bathymodiolus brooksi) and white bacterial mats (Roberts and 

others, 2007b; Lessard-Pilon and others, 2008). Four push cores were collected at this station: 
8 

AT340-2 was soft brown sediment in an active brine seep with salinity of 50 parts per thousand 

(‰); AT340-7 was black sediment in a less saline brine of 38 ‰; and both AT340-8 and AT340-

9 were taken inside a white bacterial mat, also in a brine of 38 ‰. Green Canyon 852 was the 

shallowest site sampled. Two cores of fine-grained brown reference sediments (GC852-2 and 

GC852-4) were collected near authigenic carbonate boulders hosting azooxanthellate corals. 

However, numerous chemosynthetic communities including pogonophoran tubeworms and 

mussel beds also occur within 80-400 m of these reference sediments (Roberts and others, 

2007b). Alaminos Canyon 645 contains tubeworms and mussels and has been the focus of 

multiple studies (Carney, 1994; Roberts and Aharon, 1994; Cordes and others, 2007). Two cores 

were collected in a pogonophoran tubeworm field at this site (AC645-2 and AC645-4); each was 

brown on the surface but gray underneath. Alaminos Canyon 818 is the deepest site and, unlike 

the other sites, does not occur on a mound-like bathymetric high. The AC818 has small clumps 

of chemosynthetic fauna along a narrow linear fault where seepage is occurring (Roberts and 

others, 2007b). The single core collected at this location (AC818-6) was cored through black 

sediment in an urchin field, away from the active chemosynthetic region of the site. 
9 

Table 2.1. Nine sediment cores were collected from four sites in the Gulf of Mexico between June 21 

and July 2, 2007, utilizing the R/V Ronald H. Brown and the remotely operated vehicle (ROV) Jason.

[m, meter; °C, degrees Celsius, ‰, parts per thousand]

Site Sample

ID Description

Latitude / 

Longitude Depth (m) Temp ( ̊C) Salinity (‰)

Atwater Valley 340 AT340-2 Seep site - brine 27 ̊25.169322’N 2,210 4.26 50

88 ̊21.770082’W

Atwater Valley 340 AT340-7 Seep site – brine, 

reduced sediment

27 ̊25.167810’N

88 ̊21.770286’W

2,211 4.26 38

Atwater Valley 340 AT340-8 Seep site – brine, 

microbial mat

27 ̊25.161312’N

88 ̊21.777882’W

2,209 4.26 38

Atwater Valley 340 AT340-9 Seep site – brine, 

microbial mat

27 ̊25.161390’N

88 ̊21.777966’W

2,209 4.26 38

Green Canyon 852 GC852-2 Reference sediments 27 ̊6.607194’N 1,400 4.27 35

(non-seep) 91 ̊9.976008’W

Green Canyon 852 GC852-4 Reference sediments 27 ̊6.607176’N 1,400 4.27 35

(non-seep) 91 ̊9.975996’W

Alaminos Canyon 645 AC645-2 Seep site – 

pogonophoran

tubeworms

26 ̊21.267198’N

94 ̊29.899938’W

2,213 4.27 36

Alaminos Canyon 645 AC645-4 Seep site – 

pogonophoran 

tubeworms

26 ̊21.267186’N

94 ̊29.896944’W

2,213 4.27 36

Alaminos Canyon 818 AC818-6 Seep site – reduced 

sediments, urchin field

26 ̊10.867842’N

94 ̊37.362474’W

2,742 4.31 35

2.2.2 Sediment Characteristics

Immediately after reaching the ship’s deck, sediment cores were transported to a cold 

room (10 ̊C) and surface sediments (the top 0-2 centimeters (cm) of the core) were collected. 

These sediment samples were transferred to whirlpak bags and frozen at -20 ̊C until analysis. To 

determine grain size, sediments were later thawed, treated with sodium hexametaphosphate, and 

examined using a Beckman Coulter LS 200 particle size analyzer. In addition to determining the 

average grain size, particle size data were then divided into percent sand and percent silt/clay 

based on size limits determined by the traditional dry sieve method. 
10

2.2.3 Enumeration of microbes

Three replicate samples (0.5 cubic centimeters (cm3) each) of surface sediment were 

collected from each sediment core using a sterile spatula for enumeration of prokaryotes and 

viruses. Samples for microscopy were processed immediately on board ship, using a modified 

version of Danovaro and others’ (2001) method. Briefly, sediment was suspended in sterile, 

0.02-micrometer (μm)-filtered Milli-Q water and sonicated to release particle-bound microbes. 

A low-speed centrifugation was used to pellet the sediment particles. The supernatant from this 

centrifugation was then filtered onto membranes, stained with a nucleic-acid specific dye (Sybr 

Gold), mounted on glass microscope slides, treated with an antifade solution, and frozen at -20 ̊C 

(Noble and Fuhrman, 1998). Sybr Gold stains the nucleic acids inside the bacteria and viruses, 

making the particles fluoresce when excited by blue light from the epifluorescence microscope. 

These slides were manually counted within 72 hours; a minimum of 10 fields of view and 400 

particles was examined per slide. Samples were processed immediately without the addition of 

preservatives because it has been shown that rapid and variable viral decay occurs in aldehydefixed samples, resulting in underestimates of viral abundance (Wen and others, 2004). 

2.3 Results

2.3.1 Sediment characteristics

Most sediment cores were dominated by smaller particles (>50 percent silt/clay). The 

average grain size ranged from 29.9 – 170.0 μm. Many of the cores were black or dark gray, 

indicating a reduced environment. 
11

2.3.2 Microbial enumeration

Prokaryote counts were an order of magnitude lower in sediments directly in contact with 

megafauna (urchins, pogonophorans; Alaminos Canyon AC645 and AC818) compared to all 

other samples (107

 versus 108 cells/gram (g) dry weight) and were highest in areas of elevated 

salinity (brine seeps; Atwater Valley AT340). Viral-like particle (VLP) counts were lowest in 

the reference sediments (Green Canyon 852) and pogonophoran cores (Alaminos Canyon 

AC645; 108

 VLP/g dry weight), high in brine seeps (Atwater Valley AT340-2; 109 VLP/g dry 

weight), and highest in the microbial mats (Atwater Valley AT340-8, AT340-9; 1010 VLP/g dry 

weight). Virus-prokaryote ratios (VPR) ranged from <5 in the reference sediment to >30 in the 

microbial mats and >60 in the urchin field. Gulf of Mexico seep sites sampled in this study had 

higher VPRs than the reference sediments, indicating higher production of viruses in these 

environments. High viral numbers may be a result of increased burst sizes, reflecting higher 

rates of cellular activity (Middelboe, 2000), or may indicate a zone of virus accumulation (Suttle, 

2007). 

2.4 Discussion

The number of prokaryotes (bacteria and archaea) in a given sample can be affected by 

environmental factors such as oxygen levels, salinity, and nutrient levels. Higher levels of 

prokaryotes are expected in samples containing microbial mats, since the mats themselves are 

made up of prokaryotes. Higher levels of prokaryotes in brines may be due to the high salinity 

inhibiting protists and other grazers that typically feed on bacteria. Lower levels of prokaryotes 

in samples containing megafauna (urchins, tubeworms) may indicate that these animals (or 

smaller cryptic fauna associated with them) are feeding on bacteria. 
12

At the time of sample collection, this was the first study to enumerate viruses in 

sediments below 1,000 m without preserving the samples in formaldehyde or glutaraldehyde. 

Viruses have been shown to decay rapidly in preserved samples, and the decay is not constant, 

confounding efforts to apply a conversion factor to previous counts (Danovaro and others, 2001; 

Wen and others, 2004). Currently, the most accurate methods to make estimates of viral 

abundance are processing the samples immediately to slides or flash-freezing the samples in 

liquid nitrogen (Wen and others, 2004). Viral abundances and VPRs from Gulf of Mexico coldseep samples in this study are significantly greater than those reported from deep-sea sediments 

in the Mediterranean (Danovaro and Serresi, 2000; Danovaro and others, 2002; Danovaro and 

others, 2005). 

The only published study to specifically enumerate microbes in cold-seep sediments 

examined cores from Sagami Bay, Japan (Middelboe and others, 2006). The Sagami Bay 

samples were preserved with gluaraldehyde and extracted without sonication, both of which are 

known to reduce viral counts (Danovaro and others, 2001; Wen and others, 2004). However, the 

environments sampled are similar to those described here from the Gulf of Mexico, so 

comparisons have been made in spite of these caveats. Prokaryote and viral abundances from 

non-cold-seep reference sediments were similar between the Gulf of Mexico and Sagami Bay at 

the same depth (~1,400 m). While prokaryote counts inside microbial mat samples were on par 

with microbial mat samples from Sagami Bay, Gulf of Mexico viral counts were two orders of 

magnitude higher, resulting in VPRs 10 times higher than in the Japanese samples. Comparing 

reduced (black) sediment samples from cold-seep sites in Sagami Bay and the Gulf of Mexico, 

the Gulf samples had one to two orders of magnitude more prokaryotes and three orders of 
13

magnitude greater viral abundance. It is impossible to determine how much of this difference is 

due to the differences in methodology. 
14

Table 2.2. 

[Note that all 

Microbial 

studies outside 

abundance numbers from previous studies of sediments below 1,000 m 

the Gulf of Mexico employed some type of aldehyde fixative. The symbol ‡ indicates 

water depth. 

an average value; VPR, Virus-prokaryote ratio]

Geographic 

Area Description Sample ID Lat/Long Depth (meters)

Prokaryote 

abundance

(cells per gram) 

Viral 

abundance

(viruses per 

gram)

VPR Reference

Mediterranean Deep-sea sediments Sporades Basin

Cretan Sea

Ierapetra Trench

S1

S2

S3

S4

S5

S6

S7

S8

S10

39°15.50’N

23°42.48’E

35°50.52’N

25°15.99’E

34°25.00’N

26°04.00’E

35°46.29’N

28°43.15’E

33°39.34’N

33°18.34”E

33°23.18’N

28°19.04’E

34°52.91’N

22°31.97’E

35°42.38”N

20°08.80’E

35°37.18’N

17°23.27’E

36°36.66’N

12°14.77’E

38°24.05’N

06°53.72’E

40°33.99’N

04°57.14’E

1,221

1,840

4,260

3,870

2,100

3,055

2,950

3,200

4,000

1,290

2,850

2,755

1.10 x 109‡

4.00 x 108‡

4.90 x 108‡

3.50 x 108

4.20 x 108

2.77 x 108

6.53 x 108

5.66 x 108

1.84 x 108

6.45 x 108

6.54 x 108

2.53 x 108

2.38 x 109‡

2.02 x 109‡

1.21 x 109‡

4.19 x 107

7.91 x 107

3.57 x 107

6.92 x 107

6.62 x 107

8.58 x 107

7.09 x 107

1.20 x 108

5.11 x 107

2.16

0.51

0.25

0.12

0.19

0.13

0.11

0.12

0.47

0.11

0.18

0.2

Danovaro and 

Serresi, 2000

Danovaro and 

Serresi, 2000

Danovaro and 

Serresi, 2000

Danovaro and others,

2002

Danovaro and others,

2002

Danovaro and others,

2002

Danovaro and others,

2002

Danovaro and others,

2002

Danovaro and others,

2002

Danovaro and others,

2002

Danovaro and others,

2002

Danovaro and others,

2002
15

Table 2.2. 

[Note that all 

Microbial 

studies outside 

abundance numbers from previous studies of sediments below 1000 m water depth.—Continued

the Gulf of Mexico employed some type of aldehyde fixative. The symbol ‡ indicates an average value; VPR, Virus-prokaryote ratio]

Geographic 

Area Description Sample ID Lat/Long Depth (meters)

Prokaryote 

abundance

(cells per gram) 

Viral 

abundance

(viruses per 

gram)

VPR Reference

Northeast

Atlantic

Sagami Bay, 

Japan

Gulf of 

Mexico

Deep-sea sediments

Deep-sea sediments

Cold seep;

inside microbial mat

Cold seep; outside 

microbial mat

Cold seep; near 

mussel bed

Cold seep; black 

sediment

Deep-sea sediments 

(reference)

Deep-sea sediments 

(reference)

Cold seep; inside 

microbial mat

Calabrian Rise

Topographic 

Highs

Atalante Basin

Porcupine 

Abyssal Plain

OBB2

Seep 3

Seep 3

Seep 14

Seep 18

GC852-2

GC852-4

AT340-8

38°30.62’N

17°58.87’E

35°11.84’N

21°24.75’E

35°18.20’N

21°23.33’E

48°50’N

16°20’W

35°00.7’N

139°22.5’E

35°00.1’N

139°13.6”E

35°00.1’N

139°13.6”E

35°00.1’N

139°13.6”E

35°00.1’N

139°13.6”E

27 ̊6.61’N

91 ̊9.98’W

27 ̊6.61’N

91 ̊9.98’W

27 ̊25.16’N

88 ̊21.78’W

2,255

3,225

3,363

4,800

1,450

1,200

1,200

1,200

1,200

1,400

1,400

2,209

1.60 x 107‡

3.90 x 107‡

4.60 x 107‡

-

-

2.18 x 108

-

-

5.00 x 106

1.37 x 108

1.21 x 108

3.79 x 108

5.00 x 107‡

6.40 x 107‡

5.20 x 107‡

1.46 x 1010

9.90 x 108‡

6.80 x108

8.80 x 108

2.10 x 108

5.00 x 106

8.20 x 108

5.46 x 108

1.30 x 1010

3.13

1.64

1.13

-

16.8‡

3.12

-

-

1

6.03

4.51

34.30

Danovaro and others,

2005

Danovaro and others,

2005

Danovaro and others,

2005

Danovaro and others,

2001

Middelboe and 

others, 2006

Middelboe and 

others, 2006

Middelboe and 

others, 2006

Middelboe and 

others, 2006

Middelboe and 

others, 2006

This study

This study

This study
16

Table 2.2. Microbial abundance numbers from previous studies of sediments below 1000 m water depth.—Continued

[Note that all studies outside the Gulf of Mexico employed some type of aldehyde fixative. The symbol ‡ indicates an average value; VPR, Virus-prokaryote ratio]

Geographic 

Area Description Sample ID Lat/Long Depth (meters)

Prokaryote 

abundance

(cells per gram) 

Viral 

abundance

(viruses per 

gram)

VPR Reference

Cold seep; inside 

microbial mat AT340-9 27 ̊25.16’N88 ̊21.78’W 2,209 3.59 x 108 1.31 x 1010 36.49 This study

Cold seep; black 

sediment AT340-7 27 ̊25.17’N88 ̊21.77’W 2,211 2.59 x 108 3.49 x109 13.47 This study

Cold seep; black 

sediment AC818-6 26 ̊10.87’N94 ̊37.36’W 2,742 2.20 x 107 1.46 x 109 66.36 This study

Cold seep; 50% 

brine AT340-2 27 ̊25.17’N88 ̊21.77’W 2,210 6.27 x 108 6.86 x 109 10.94 This study

Cold seep; tube 

worm field AC645-2 26 ̊21.27’N94 ̊29.90’W 2,213 4.32 x 107 6.08 x 108 14.07 This study

Cold seep; tube 

worm field AC645-4 26 ̊21.27’N94 ̊29.90’W 2,213 5.24 x 107 7.98 x 108 15.23 This study
17

Viral counts were lowest in the reference sediments (GC852-2, GC852-4) and 

pogonophoran tubeworm cores (AC645-2, AC645-4) and highest in the microbial mats (AT340-

8, AT340-9). The highest viral abundances were at site AT340, which had salinities ranging 

from 38 parts per thousand to 50 parts per thousand. Danovaro and others (2005) have suggested 

that hypersaline conditions may preserve viruses or render them more resistant to decay. 

Additionally, two of the cores at AT340 contained microbial mats, where higher prokaryote host 

abundances contribute to higher viral abundances. Variation in viral abundances did not relate to 

water depth or salinity but was strongly correlated with grain size (viral adsorption to larger 

particles) and prokaryote abundance (host required for reproduction). Virus-prokaryote ratios 

(VPRs) are used as a measure of viral productivity in an environment. 

The VLP and VPR ratios were all significantly greater than those reported from 

sediments in the deep Mediterranean Sea and in most cases were higher than ratios reported from 

recent data from a cold-seep site near Japan. This suggests that viral production is occurring at 

Gulf of Mexico cold-seep sites and that these viruses are mediating prokaryote mortality, thereby 

exerting control over the energy flow to higher trophic levels.

2.5 Acknowledgments

The author wishes to thank TDI-Brooks International, Inc., C. Fisher, and Bureau of 

Ocean Energy Management, Regulation and Enforcement for allowing her to participate in their 

Chemo III research cruise. She also thanks M. Bowles, K. Hunter, V. Samarkin, and K. Segarra 

for assistance in sample collection, as well as the crews of the R/V Ronald H. Brown and ROV 

Jason.
18

3. FOOD-WEB STRUCTURE OF SEEP SEDIMENT MACROBENTHOS FROM 

THE GULF OF MEXICO

An expanded version of this paper was published as 

Demopoulos, A.W.J., Gualtieri, D., and Kovacs, K., 2010, Food-web structure of seep sediment macrobenthos from 

the Gulf of Mexico, in Roberts, H.H., ed., Gulf of Mexico cold seeps: Deep-Sea Research II, v. 57, p. 1972-1981.

By Amanda W.J. Demopoulos,

1 Daniel Gualtieri,2 and Kaitlin Kovacs1 

1

Southeast Ecological Science Center, U.S. Geological Survey, Gainesville, FL 2

Jacobs Technology, Southeast Ecological Science Center, U.S. Geological Survey, Gainesville, FL

3.1 Introduction

Chemosynthetic environments provide a haven for chemoautotrophic bacterial mats and 

megafaunal invertebrates that house endosymbiotic bacteria (Childress and others, 1986; 

MacDonald and others, 1989; Fisher and others, 1993; Sibuet and Olu, 1998). Research 

examining seep food webs has focused primarily on understanding the nutritional modes of the 

larger megafaunal or epifaunal taxa in seeps (Childress and others, 1986; Brooks and others, 

1987; Fisher and others, 1993; Peek and others, 1998). Seeps located in the northern Gulf of 

Mexico slope environments contain tubeworms and clams that harbor symbiotic sulfideoxidizing chemoautolithotrophic bacteria and mussels that contain chemoautolithotrophic sulfuroxidizing symbionts (Brooks and others, 1987; Kennicutt and others, 1992). 

Seep ecosystems also contain abundant heterotrophic species that do not house symbionts 

(MacAvoy and others, 2005), including sediment-associated macrofauna and meiofauna (Levin, 

2005). Food resources for these smaller invertebrates have been examined in the shelf, upper, 

and lower slope in the northeastern Pacific Ocean, the Florida Escarpment (Levin and Mendoza, 
19

2007), Blake Ridge methane seeps in the Atlantic (Van Dover and others, 2003), and the Hakon 

Mosby Mud Volcano in the southwestern Barents Sea (Van Gaever and others, 2006). Potential 

carbon sources (food) available to sediment infauna include photosynthetically fixed material 

raining from surface waters (for example, phytoplankton-derived organic matter), terrestrially 

derived material transported to deep waters, or organic carbon synthesized chemoautotrophically 

from dissolved inorganic carbon (DIC) either by symbiotic or free-living bacteria. Recent 

studies suggest that macrofaunal reliance on chemosynthetically derived material may increase 

with depth (Levin and Michener, 2002; Levin and Mendoza, 2007), because particulate flux from 

surface waters typically decreases with increasing water depth (Turley and others, 1995). The 

hypothesis that decreased particle flux leads to increased dependence on locally produced 

organic carbon has not been tested extensively because food-web studies have not been 

conducted at most deep seep environments (Levin and Mendoza, 2007). 

Because of the remoteness of seep communities, it is challenging to conduct diet studies. 

Stable isotope analysis has proven useful in discerning nutritional modes and can provide basic 

information about primary carbon sources fueling seep communities (see reviews in Conway and 

others, 1994; Van Dover, 2007). Different carbon fixation pathways involve distinct carbon 

isotopic fractionation. Chemoautotrophic organic matter fixed at or near the sediment-seawater 

interface results in heavily depleted δ13C values (-75 to -28 per mil, Paull and others, 1985; 

Brooks and others, 1987). Therefore, heterotrophic fauna with low δ13C values (<-25 per mil) 

are likely dependent in some way on chemoautotrophic bacteria. In contrast, fauna that depend 

on photosynthetically fixed carbon would have tissue δ13C values that are enriched relative to 

these other sources (for example, -25 to -15 per mil, Fry and Sherr, 1984). 
20

Stable nitrogen isotope values (δ15N) can provide information on trophic position and 

sources of nitrogen because animals are expected to be ~3 per mil enriched relative to their diet 

(Minagawa and Wada, 1984; Post, 2002; McCutchan and others, 2003). If animals are using 

deep-sea particulate organic nitrogen (PON), then they should have values enriched in 15N 

relative to deep-water PON sources (for example, 3-6 per mil, Paull and others, 1985). In 

contrast, animals that contain chemoautotrophic symbionts typically have very low, often 

negative, δ15N values (Brooks and others, 1987). Therefore, combined use of δ13C and δ15N 

values of animals can yield information on nitrogen and carbon sources, trophic position, 

fixation pathways, and the possible presence of chemoautotrophic symbioses (Levin and 

Michener, 2002). 

Stable isotope ratios have been used to infer type of nutrition and indicate presence of 

petroleum-derived carbon in the benthic food web (Spies and DesMarais, 1983; Paull and others, 

1985; Kennicutt and others, 1992). Stable isotope analysis has revealed different food resources 

utilized, including chemoautotrophy from bacterial symbioses (Dando and others, 1991; Jensen 

and others, 1992) and local chemosynthetic production (Levin and Michener, 2002; Van Dover 

and others, 2003). For the Gulf of Mexico, results from upper and middle slope seeps indicate 

that heterotrophic megafauna and meiofauna rely on chemautotrophic production for nutrition 

(Powell and others, 1986; Brooks and others, 1987; Kennicutt and others, 1992; MacAvoy and 

others, 2002). However, nutritional relations for seep associates (macrofauna and meiofauna) in 

the lower slope of the northern Gulf of Mexico remain unknown. 

This study investigated the importance of chemosynthesis to macro-infaunal nutrition in 

deep-slope cold seeps and wider regions in the northern Gulf of Mexico. We combined the use 

of δ13C and δ15N data to estimate food-web structure among consumer species. Our specific 
21

question was: to what degree do seep-associated infaunal benthos derive their nutrition from 

chemosynthetic sources? 

3.2 Materials and Methods

3.2.1 Collection Methods

Sampling was conducted at depths of 1,400 to 2,400 m during September 2007 aboard 

the R/V Cape Hatteras. Three seep sampling sites were selected: Atwater Valley (AT340), 

Green Canyon (GC852), and Alaminos Canyon (AC601) (fig. 3.1). At each of these sites, 

transects were established across known seep locations (table 3.1) based on information from 

Brooks and others (2008). Sediment samples for infaunal analysis were collected using an 

Ocean Instruments Mark III (50 cm x 50 cm) box core. Smaller tube cores (32 cm2

 x 10 cm 

depth) were inserted into the box cores to measure redox potential and collect sediments for 

sediment and infaunal isotope analysis. Vertical redox potential (Eh in millivolts, mV) profiles 

(at 0-1, 1-2, 2-3, 3-5, 5-7, and 7-10 cm depth) were obtained from undisturbed cores by inserting 

a combination redox electrode through the sediment surface; redox potential was then read on a 

portable pH-millivolt meter. To collect sediment macrofauna, sediment cores were sectioned (at 

0-1, 1-2, 2-3, 3-5, 5-7, and 7-10 cm depth) after recovery. Sediment fractions were sieved 

through a 300-micrometer (μm) screen, and animals were sorted at sea to collect macrofauna for 

stable isotopic analysis. Living organisms were identified, placed into filtered seawater for 24 

hours (h) to evacuate their guts, washed in Ultrapure water, then placed in preweighed tin boats 

or combusted vials, and frozen at -70oC. 
22

Figure 3.1. Collection sites in the Gulf of Mexico. (Contour lines represent 1,000-, 2,000-, and 3,000- 

m bathymetry.) 
23

Table 3.1. Box core locations and depths, northern Gulf of Mexico. 

Location Date Depth 

(meters) Latitude Longitude Station #

Green Canyon (GC 852)

10-Aug-07 1,431 27° 06.996 91° 09.840 11

10-Aug-07 1,426 27° 07.149 91° 09.961 13

10-Aug-07 1,435 27° 06.978 91° 09.873 14

10-Aug-07 1,449 27° 07.262 91° 09.997 15

10-Aug-07 1,425 27° 07.198 91° 09.905 16

13-Aug-07 1,431 27° 06.68 91° 09.92 55

13-Aug-07 1,406 27° 06.654 91° 09.998 59

13-Aug-07 1,400 27° 06.543 91° 09.953 60

13-Aug-07 1,430 27° 07.112 91° 09.991 61

13-Aug-07 1,425 27° 07.206 91° 09.907 62

Alaminos Canyon (AC 601)

18-Aug-07 2,391 26° 23.408 94° 30.798 130

Atwater Valley (AT 340)

24-Aug-07 2,239 27° 38.774 88° 21.808 193

24-Aug-07 2,222 27° 38.791 88° 21.986 194

24-Aug-07 2,222 27° 38.706 88° 21.686 196

24-Aug-07 2,222 27° 38.679 88° 22.060 197

25-Aug-07 2,227 27° 38.746 88° 21.966 207

25-Aug-07 2,255 27° 38.646 88° 21.828 208

 25-Aug-07 2,222 27° 38.847 88° 22.483 209

Potential food resources, including suspended particulate organic matter (POM), 

sediments, and filamentous bacteria from surface sediments, also were processed for stable 

carbon and nitrogen isotopes. POM was collected by filtering 3 liters (L) of seawater from the 

surface from each site (5-15 stations per site) onto precombusted glass fiber filters (GFF). 

Suspended organic matter (SOM) was collected from box core surface water after push core 

subsamples were inserted. SOM was sieved through 300 μm screen to remove animals and then 

filtered onto pre-combusted GFF filters. SOM represents fine organic matter that was 

resuspended after box core recovery, with isotope values that may differ from bulk sediment 

organic matter. All GFF filters were dried and processed for stable isotope analysis. 
24

3.2.2 Lab Processing

Dried sediments, POM, and SOM filters were acidified with 1 N HCl, dried, and then 

transferred into tin boats. Infaunal samples were dried at 60oC for 1-2 days to a constant weight, 

weighed in tin boats, and acidified with 1 percent PtCl2 to remove inorganic carbon 

(Demopoulos and others, 2007; Levin and Mendoza, 2007). Stable isotope measurements of 

infauna were made on single individuals, parts of individuals, or several small specimens of the 

same species combined. Samples were analyzed for C and N compositions referenced to Vienna 

PeeDee Belemnite (VPDB) and nitrogen gas (atmospheric) (Peterson and Fry, 1987). Analyses 

were performed using a Costech (Valencia, Calif.) elemental analyzer interfaced to a GV 

instruments (Manchester, U.K.) Isoprime isotope ratio mass spectrometer. Reproducibility was 

monitored using several organic reference standards (Fry, 2007). Isotope ratios are expressed as 

δ13C or δ15N in units of per mil. 

3.3.3 Statistical Analysis

All data are expressed as mean ± 1 standard error (SE) unless indicated otherwise. Data 

for multiple individuals of a single species were averaged within each site. Tests of site effects 

then used species as replicates to avoid overrepresentation of the most abundant taxa. All 

statistical analysis was performed using SPSS statistical software. 

3.3 Results

3.3.1 Sediment Characteristics

Box core collections ranged from 15 to 1,000 m away from known seep locations. While 

sampling locations targeted areas of known seep assemblages, only one box core from Alaminos 

Canyon recovered a siboglinid tubeworm, a characteristic fauna from seep environments. The 
25

remaining cores did not contain the typical seep megafauna (clams, mussels, tubeworms), nor 

large bacterial mats. However, bacterial filaments were present in many of the cores, both 

visible on the sediment surface and within the cores sorted for infauna. 

Of the nine successful box cores collected at GC852, four had low redox profiles (below 

0 mV, table 3.2), and six contained bacterial filaments indicative of chemosynthetic communities 

(Stations 13, 15, 55, 59, 61, and 62). The profiles with the lowest redox (Stations 13, 15, 16, and 

62, fig. 3.2) had a shallow redox potential discontinuity (rpd) depth (~ 2 cm), and sediment color 

transitioned from brown on the surface to gray directly below; some of these cores had a 

noticeable sulfide odor. Sediment cores with high redox values (>0 mV, Stations 11, 14, 55, 59, 

and 60, table 3.2) were also brown on the surface and grey in subsurface sediments but generally 

contained a deeper rpd (4-5 cm). 
26

-9

-5

-1

3

7

11

-60 -55 -50 -45 -40 -35 -30 -25 -20 -15

δ 15N (‰)

Beggiatoa

POM

Sediments

SOM

-9

-5

-1

3

7

11

-60 -55 -50 -45 -40 -35 -30 -25 -20 -15

δ 15N (‰)

Beggiatoa

Sediments

POM

-9

-5

-1

3

7

11

-60 -55 -50 -45 -40 -35 -30 -25 -20 -15

δ 15N (‰)

δ 13C (‰)

Sediment

Beggiatoa

SOM

POM

Crustacea

Polychaeta

X Sipunculida

Mollusca

Anthozoa

Echinodermata

Nematoda

A 

B 

C 
27

Figure 3.2. Dual stable isotope plots of different primary sources (open rectangles), and macrofauna 

(>300 micrometers, μm) from Gulf of Mexico seeps: (A) GC852, (B) AC601, and (C) AT340. (Each 

point represents a distinct individual. Ranges in stable carbon and nitrogen isotope values are given for 

primary sources, including particulate organic matter (POM), suspended organic matter (SOM), 

Beggiatoa bacteria, and sediment.) 

Table 3.2. Redox potential profiles (Eh, in millivolts) in box cores from Green Canyon (GC 852), 

Alaminos Canyon (AC601), and Atwater Valley (AT340). 

 Fraction 

(centimeters) 

 Station 0-1 1-2 2-3 3-5 5-7 7-10

GC852 

11 154.9 155.7 167.6 181.7 184.5 196.6

13 - 35 -13.2 -152.8 -189.4 -471

14 90 89.3 91.4 94.8 102.2 110

15 - -70.4 -303 -483 -497 -519

16 38.6 -6.7 -86.1 -421 -447 -442

55 44 47 49 51 35.4 -19.1

59 19.1 25.5 33.6 39.2 48.5 49.2

60 57.2 64.5 68.4 70.6 72.9 59.9

62 24.4 -40.9 -443 -460 -466 -473

AC601

130 58 56 46 -2 -65.1 -120

AT340

193 -396 -397 -402 -409 -418 -425

194 -220 -318 -390 -401 -411 -418

195 76.2 76.6 78.9 78.6 74.5 63.7

196 76.6 76.2 75.5 74.9 28.9 -3.1

 197 73 72.6 70.8 23.3 -31.5 -165.5

A single box core was collected at AC601 near to a known chemosynthetic ecosystem, 

approximately 15 m from a tubeworm assemblage (Brooks and others, 2008). This box core had 

oil visible on the water surface and bacteria were present on the sediment surface. The Eh 
28

profile included a 0-2 cm oxidizing layer followed by reducing conditions below 2 cm (table 

3.2). 

Box cores collected at AT340 were approximately 75-260 m away from known seep 

environments. Of the seven cores collected, two were completely reducing throughout the 

sediment profile (Stations 193, 194, table 3.2). The remaining cores had either oxidizing 

conditions throughout the cores (table 3.2, Stations 195, 196, and 208) or had a 2-4 cm oxidizing 

layer, with reducing conditions below that depth (Stations 197 and 207). Five cores had 

Beggiatoa bacteria present both in the sorted sediments and visible on the sediment surface 

(Stations 193, 194, 196, 197, and 207). 

3.3.2 Isotopic composition of primary source pools

Specific organic matter pools generally had similar isotope values at all three sites (fig. 

3.2). There were no site differences in Beggiatoa, POM, SOM, or sediments between Green 

Canyon and Atwater Valley. This was determined using an analysis of variance (ANOVA) test, 

in which the F statistic is defined as the ratio of the variance calculated among the means to the 

variance within the samples, and the p value indicates the probability of obtaining a value for F 

that is as high as what would be observed by chance; that is, the lower the p value, the more 

significant the difference between the sites (Beggiatoa, ANOVA, F=2.835, p=0.078 for carbon; 

F=1.357, p=0.277 for nitrogen; SOM, Kruskal Wallis, x2

 = 0.593, p=0.441 for carbon, x2 = 

2.370, p=0.124 for nitrogen; and sediments ANOVA, F=0.181, p=0.672 for carbon; F=0.587, 

p=0.448 for nitrogen). Because only one box core was collected from Alaminos Canyon, this 

precluded among-site statistical comparisons of primary source pools. In addition, there was no 

significant difference in POM among the three sites (ANOVA, F=0.093, p=0.912 for carbon, 

F=1.232, p=0.308 for nitrogen). POM was the most enriched in δ13C and δ15N, reflecting its 
29

photosynthetic origin. In contrast, Beggiatoa was the most depleted in 13C and 15N across all 

sites; Beggiatoa δ13C values ranged from -39.4 to -22.9 and δ15N from -6.8 to 5.1 (fig. 3.2), 

reflecting chemosynthetic carbon fixation. SOM and sediment had intermediate isotope values, 

falling between POM and Beggiatoa. 

3.3.3 Sediment macrofaunal isotopic composition

Invertebrates collected from each site included a variety of polychaete annelids, 

nematodes, crustaceans, molluscs, sipunculids, and echinoderms. A total of 240 infaunal 

samples were analyzed for δ13C and δ15N stable isotopes. Stable isotope values of macroinfauna 

across sites exhibited a large range (fig. 3.2, δ13C from -54.7 to -17.9 per mil, δ15N from -8 to 

11.3 per mil), with the lightest values likely reflecting input from methane-derived carbon (δ13C), 

utilization of locally fixed nitrogen, or symbiosis (δ15N). There were no significant differences 

between carbon and nitrogen isotope values among sites (ANOVA, F= 0.636, p = 0.533 for δ13C, 

F = 0.105, p =0.900 for δ15N). 

3.3.3.1$Green$Canyon-GC$852$

Stable isotope values of sediment macrofauna were the most variable at GC852; δ13C 

ranged from -55 to -18 per mil and δ15N ranged from -8 to 11 per mil (fig. 3.2). Animals that 

exhibited the lowest isotope values included nematodes (δ13C = -54.6 ± 0.1 per mil, δ15N = -6.1 ± 

0.2 per mil) and one gastropod (δ13C = -50.4 per mil, δ15N = -1.1 per mil). They were depleted 

in 13C and 15N relative to measured primary sources, indicating that they may be assimilating 

methane oxidizing bacteria; these particular microorganisms typically have very negative carbon 

isotope values. Animals with isotope values consistent with Beggiatoa-derived diet included 

molluscs, nematodes, polychaetes, crustaceans, and ophiuroid echinoderms. Animals with 
30

isotope values consistent with a phytoplankton-derived diet (that is, having δ13C >-25 per mil 

and δ15N >3 per mil) included ophiuroid and crinoid echinoderms, certain cumacean crustaceans, 

dorvilleid polychaetes, copepods, and an unidentified crustacean. 

3.3.3.2$Alaminos$Canyon-AC$601

Stable δ13C values ranged from -36 to -20 per mil and δ15N ranged from -6 to 8 per mil 

(fig. 3.2). Polychaete annelids, bivalve molluscs, and a sipunculid appeared to derive their 

nutrition from photosynthetically produced sources. The remaining fauna were depleted relative 

to POM, indicating that they rely on chemoautotrophically derived organic matter. Other fauna 

that had low δ13C and δ15N values included nematodes and Tanaid sp. A. Ostracods exhibited 

the largest range in 15N values (-4.9 to 5.2 per mil), while Tanaid sp. A had the largest range in 

δ13C (-34.8 to -26.0 per mil). Few taxa had isotope values consistent with a phytoplanktonderived diet, much like the other two sites. 

3.3.3.3$Atwater$Valley-AT$340

Infaunal stable δ13C ranged from -45 to -17 per mil and δ15N ranged from –7 to 12 per 

mil. Animals most enriched in 13C and 15N were an anemone, a maldanid polychaete, a 

cumacean, and a nematode. Infauna collected from the remaining stations were depleted relative 

to sources measured (fig. 3.2). Those most depleted in 15N included other cumaceans, tanaids, 

and gastropod and aplacophoran molluscs. Low 15N values may indicate presence of bacterial 

symbionts within these infauna, utilizing local nitrogen sources that are depleted in 15N. Most of 

the infauna fell between two isotopic endmembers: phytoplankton and methane-derived carbon, 

including paranoid polychaetes, gammarid amphipods, certain nematodes, tanaids, and ostracods. 
31

Intermediate isotope values may indicate that the fauna are relying on either a mixed diet of these 

two sources or on sulfur oxidizing bacteria. 

3.4 Discussion

Stable isotope analysis indicated that infauna from Gulf of Mexico seep environments fell 

into three groups: (1) those that derived carbon from photosynthetic sources (most enriched in 

13C and 15N), (2) consumers of chemosynthetically fixed carbon (possibly sulfide oxidizing 

bacteria), and (3) consumers depleted in13C and 15N relative to the measured bacterial sources, 

indicating possible assimilation of an unmeasured source (for example, methane-derived carbon) 

and (or) translocation from symbionts. Very light δ13C and δ15N values indicate the potential 

presence of symbionts. Light δ15N values between -8 and 0 per mil were measured for multiple 

taxa, including several species of polychaetes, crustaceans, aplacophorans, and nematodes, 

indicating possible reliance on bacterial symbionts. Ectosymbioses have been documented in 

seep nematodes (Dando and others, 1991; Jensen and others, 1992). Light isotope values have 

also been found in polychaete annelids collected from the Gulf of Alaska seeps (Levin and 

Michener, 2002), although symbionts have not been isolated from these animals. Very depleted 

values of gastropods and nematodes at Green Canyon also may represent incorporation of 

methane-oxidizing archaea. Archael lipids in Florida sediments reflect large fractionation of 

carbon to yield δ13C of <-100 per mil (Zhang and others, 2003). These taxa merit further study 

to examine food sources fueling these organisms and potential reliance on symbionts for 

nutrition. 

In addition to bacterial symbionts, invertebrates utilize bacterial production through 

consumption of free-living chemoautotrophs. Chemosynthetic bacterial mats can be extensive in 

the Gulf of Mexico (MacDonald and others, 1989; Sassen and others, 1994) and may be a 
32

significant source of nutrients to benthos in the northern Gulf of Mexico continental slope 

(Kelley and others, 1998). Free-living bacteria (both chemosynthetic and heterotrophic) on 

surfaces or suspended in the water column may be food for grazing and filter-feeding 

invertebrates, as has been suggested for hydrothermal vent fauna (Van Dover and Fry, 1989). 

Filaments present in box core collections were small enough to be grazed by infauna and 

epifauna. In addition, several taxa had δ13C and δ15N values consistent with assimilation of 

bacteria. Not all taxa found at these three seep sites target or assimilate Beggiatoa, but isotopic 

similarities suggest incorporation of chemoautotrophic production into their tissues. While 

sulfide oxidizing Beggiatoa represent one potentially important food source, other bacteria (for 

example, methane oxidizing archaea, methanotrophic bacteria), yet unmeasured isotopically, are 

likely important for infaunal seep associates. 

Despite the large spatial separation among sites (fig. 3.1), there were remarkably similar 

isotopic compositions and ranges among primary producers and secondary consumers (fig. 3.2), 

suggesting possible isotopic uniformity in the diverse biogeochemical processes occurring at 

seeps (for example, Van Dover and Fry, 1994). Diverse patterns in isotope values have also 

been found in sedimented hydrothermal vents in the Gorda Ridge (Van Dover and Fry, 1994). 

Isotope diversity found in vents was attributed to the large diversity in microbial populations 

fueling these food webs (Van Dover and Fry, 1994). The wide range in both carbon and nitrogen 

isotopes found in our study indicates trophic complexity and possibly high microbial diversity 

both on small (within box core) and large (across sites) spatial scales. 

Our results are consistent with isotope ranges published from Florida Escarpment and 

Atwater Valley and are depleted relative to background sediments in the northern Gulf of 

Mexico and Florida Escarpment (Levin, 2005; Levin and Mendoza, 2007; A.W.J. Demopoulos, 
33

USGS, unpub. data, 2011). Seep infauna collected from Gulf of Alaska, Oregon, and Florida 

Escarpment seeps were considered the isotopically lightest known on Earth (Levin and 

Michener, 2002; Levin and Mendoza, 2007). Our data overlap theirs, although results from the 

Florida Escarpment represent the most depleted infauna from seep environments (Levin and 

Mendoza, 2007). Overall, most infauna near seeps apparently derive their nutrition from seep 

production, consistent with other slope studies (Levin and Mendoza, 2007). 

These results represent new information on seep-associated infaunal nutrition. Many 

appear to be heterotrophic and consume free-living bacteria (Levin and Michener, 2002), similar 

to patterns found at hydrothermal vents (Van Dover and Fry, 1994). The diverse nature of our 

stable isotope data reflects upper slope work in the Gulf of Mexico (Brooks and others, 1987; 

Kennicutt and others, 1988; MacAvoy and others, 2002; 2005; 2008a), which has demonstrated 

that seeps are locations where microbial chemoautotrophic primary production can substitute 

photosynthesis as the primary source of ecosystem energy production (Brooks and others, 1987). 

Reliance on chemoautotrophic production fueled by hydrocarbon seepage rather than 

photosynthetically derived carbon may be dictated by differences in fluid flow rates and seepage 

(Van Dover, 2007), as thermogenic hydrocarbons are known to be widespread in the surface 

sediments throughout the continental slope of the Gulf of Mexico (MacDonald and others, 1989). 

Subsequent transport of biological productivity from seeps to surrounding benthos may 

contribute significantly to the ecology of the continental slope (MacDonald and others, 1989). 

However, the degree to which chemosynthetically derived carbon is transferred to surrounding 

ecosystems remains unknown, although transfer via larger, mobile fish and invertebrates has 

been suggested to be quite variable (MacAvoy and others, 2002; 2008b). Based on the great 

spatial separation among the sites sampled in this study and indication that several infauna from 
34

these sites derive their nutrition from seep production, chemoautotrophic production may be 

quite diffuse and widespread over large areas of the Gulf of Mexico. 

3.5. Acknowledgments

We thank the captain and crew of the R/V Cape Hatteras. We also thank the following 

individuals for their help at sea, site selection, and helpful suggestions: J. Gonzalez, Ross Lab, L. 

Levin. E. Cordes, and C. Fisher. Special thanks go to S. Ross for inviting us to participate in this 

cruise and for facilitating the box core sampling. We thank R. Lee (Washington State 

University) for conducting stable isotope analyses. 
35

4. MACROFAUNAL COMMUNITY STRUCTURE AND SEDIMENT 

ENVIRONMENTAL CHARACTERISTICS IN THREE SEEP ECOSYSTEMS 

By Amanda W.J. Demopoulos1 Kaitlin Kovacs1 and Daniel Gualtieri2 

1

Southeast Ecological Science Center, U.S. Geological Survey, Gainesville, FL 2

Jacobs Technology, Southeast Ecological Science Center, U.S. Geological Survey, Gainesville, FL

4.1 Introduction

Descriptions of seep communities and their megafaunal associates have been studied 

extensively in the Gulf of Mexico (Bergquist and others, 2003a; Cordes and others, 2005; Cordes 

and others, 2007). Smaller macrofauna (>300 μm) associated with soft sediment environments 

within seeps in the Gulf of Mexico are not well known (Powell and others, 1986; Robinson and 

others, 2004; Levin and Mendoza, 2007), and few studies have examined these seep associates 

worldwide (see review by Levin, 2005). 

Studies of meiofauna (<300 μm and >42 μm) from upper slope seep environments in the 

Gulf of Mexico (GOM) (Powell and Bright, 1981; Powell and others, 1983; Robinson and 

others, 2004) indicate no consistent patterns in meiofaunal densities. They can either be 

enhanced, depleted, or unchanged relative to background sediments (Levin, 2005). Sediment 

geochemical environment may play a role in controlling infaunal community composition and 

abundance. For example, enhanced densities of sediment infauna relative to background soft 

sediments were observed within the uppermost sediment layers, corresponding to the location of 

minimal porewater methane concentrations (Sergeeva and Gulin, 2007). In contrast, the 

presence of sulfide has been linked to increased abundance of meiofaunal taxa (Powell and 
36

others, 1986), despite the toxicity associated with sulfide, indicating that certain meiofauna may 

be highly tolerant of toxic sediment environments. Thus, the abundance and composition of seep 

infauna may be strongly tied to sediment biogeochemistry, including sulfide concentration 

(Sahling and others, 2002). 

Macro-infauna provide a variety of ecosystem services, including cycling of particulate 

organic matter and serving as food for fish and larger invertebrates for seep associates and 

transients (MacAvoy and others, 2008b; Demopoulos and others, Chapter 3), yet their relative 

abundance and general composition in GOM seeps is not understood, in particular in lower slope 

seep environments. 

This chapter represents a preliminary assessment of the macrofaunal community 

composition and their associated sediment environment for three seep areas located on the deep 

slope of the GOM. We examined whether GOM seep communities were similar in terms of 

major taxonomic groups and how comparable these macrofauna were to seeps located outside of 

the GOM. The description of infaunal densities and composition adds to the existing knowledge 

of small macrofauna from seeps and provides information for future comparisons across 

biogeographical regions. 

4.2 Methods

4.2.1 Sampling Sites

Investigations were conducted in three sites in the GOM: Atwater Valley (AT340), Green 

Canyon (GC852), and Alaminos Canyon (AC601). See Chapter 3 for more detailed site 

descriptions and for the site map. At each site, transects were established across known seep 

locations (Brooks and others, 2008). Sediment samples were collected using an Ocean 
37

Instruments Mark III (50 cm x 50 cm) box core, which was then subsampled on deck using 2 

tube cores (32 cm2

 x 10 cm depth), one each for macrofauna and sediment analysis. The top 10 

cm of each core were sectioned horizontally (0-1, 1-2, 2-3, 3-5, 5-7, and 7-10 cm). Sediment for 

macrofaunal analysis was preserved in 10 percent formalin prior to sieving. Sediment cores 

intended for sediment analysis, for example, particle size and organic carbon and nitrogen 

content, were frozen at -20o

 C. Salinity was measured using a refractometer (± 2 practical 

salinity units, PSU) for porewater extracted from syringe samples taken at each sediment 

fraction. 

4.2.2 Lab Processing

A portion of sediment for grain-size analysis was digested with hydrogen peroxide to 

remove organic material and subsequently wet sieved through 2000-μm (to separate rubble/large 

grain sizes) and 63-μm sieves. Size fractions (>2000 μm, 2000 - 63 μm, and <63μm) were dried 

at 60oC for 1-2 days (d), weighed, and percent rubble/shell (>2000 μm), sand (63 μm ≤ x <2000 

μm), and silt/clay (<63 μm) calculated. Organic carbon and total nitrogen content of the 

sediments were determined using a Costech (Valencia, Calif.) elemental analyzer interfaced to a 

GV instruments (Manchester, U.K.) Isoprime isotope ratio mass spectrometer after carbonate 

material was dissolved using sulfurous acid. 

In order to characterize sediment macrofauna, preserved sediment fractions were washed 

through a 300-μm sieve, and animals retained on the 300-μm sieve were sorted under a 

dissecting scope, identified to major taxonomic group, and transferred to 80 percent ethanol for 

storage. 
38

4.3 Results

4.3.1 Sediment Properties

Results presented here are based on 10 replicate box cores collected from GC852 and 8 

box cores collected from AT340. While only one core was collected from Alaminos Canyon, we 

included the results for general comparative purposes only. Porewater salinity ranged from 36.0 

to 38.0 PSU. Sediment percent organic carbon and organic nitrogen were similar between 

GC852 and AT340 (table 4.1). However, at AC601, percent organic carbon was lower within 

the upper 0-3 cm (0.20-0.29 percent) and increased down core, ranging from 0.74 to 0.93 

percent. Percent organic nitrogen exhibited the same pattern, increasing with depth from 0.02 

percent (0-1 cm) to 0.09 percent (7-10 cm). No major differences in sediment δ13C or δ15N 

values were observed among the three seeps sites (table 4.1)
Table 4.1. Average (± 1 S.E.) sediment particle size, percent organic carbon and nitrogen, δ13C, δ5N, and salinity from three seeps in the Gulf 

of Mexico. [%, percent; cm, centimeter; salinity measured in practical salinity units] 

Fraction % Shell % Sand % Silt/Clay % C % N δ13C δ15N Salinity

GC852 

(N=10)

0-1 cm 18.91 ± 18.8 21.8 ± 5.13 74.41 ± 7.94 0.55 ± 0.09 0.06 ± 0.01 -23.1 ± 0.6 4.4 ± 0.5 37.2 ± 0.1

1-2 cm 0.36 ± 0.08 29.64 ± 6.14 70.29 ± 6.18 0.55 ± 0.1 0.06 ± 0.01 -23 ± 0.7 2.9 ± 0.9 37.3 ± 0.3

2-3 cm 0.18 ± 0 26.31 ± 5.23 73.67 ± 5.23 0.49 ± 0.11 0.05 ± 0.01 -24.1 ± 0.6 4.3 ± 1.7 37.5 ± 0.5

3-5 cm 1.56 ± 1.42 37.34 ± 6.41 62.35 ± 6.57 0.46 ± 0.06 0.05 ± 0.01 -21.6 ± 0.4 3.3 ± 0.4 37.1 ± 0.1

5-7 cm 3.28 ± 3.19 31.54 ± 6.26 67.81 ± 6.39 0.41 ± 0.03 0.04 ± 0 -22.3 ± 0.6 2.6 ± 0.6 37.2 ± 0.2

7-10 cm 0.99 ± 0.85 24.48 ± 3.94 75.22 ± 3.89 0.58 ± 0.11 0.06 ± 0.01 -22.6 ± 0.4 1.6 ± 0.8 37.1 ± 0.2

AT340 

(N=8)

0-1 cm 0.69 ± 0.25 48 ± 3.97 51.09 ± 4.17 0.43 ± 0.1 0.04 ± 0.01 -22.6 ± 1.8 2.7 ± 0.9 37.6 ± 0.2

1-2 cm 0.71 ± 0.2 40.35 ± 6.19 58.77 ± 6.46 0.43 ± 0.09 0.05 ± 0.01 -23.7 ± 0.9 2.4 ± 1.5 37.3 ± 0.2

2-3 cm 1.31 ± 0.62 40.07 ± 9.93 58.94 ± 9.98 0.29 ± 0.09 0.03 ± 0.01 -23.7 ± 0.9 4.3 ± 1.3 37.5 ± 0.3

3-5 cm 11.49 ± 9.96 36.62 ± 8.23 53.33 ± 7.15 0.51 ± 0.11 0.05 ± 0.01 -23.3 ± 0.7 3.5 ± 0.4 37.4 ± 0.2

5-7 cm 0.98 ± 0.41 42.2 ± 9.46 62.33 ± 10.2 0.48 ± 0.1 0.04 ± 0.01 -23 ± 1.1 4.3 ± 1.7 37.4 ± 0.2

7-10 cm 2.36 ± 1.88 42.65 ± 8.15 55.29 ± 7.74 0.5 ± 0.11 0.04 ± 0.01 -23.3 ± 0.8 2.9 ± 0.8 36.7 ± 0.8

AC6011

(N=1)

0-1 cm 0.15 - 52.41 - 47.44 - 0.2 - 0.02 - -22.8 - 4.9 - 37 -

1-2 cm 0.11 - 63.04 - 36.85 - 0.2 - 0.02 - -24 - 1.3 - 38 -

2-3 cm - - 47.54 - 52.46 - 0.29 - 0.03 - -23.4 - 3.5 - 38 -

3-5 cm - - 55.36 - 44.64 - 0.9 - 0.1 - -21.8 - 3.7 - 36 -

5-7 cm - - 54.33 - 45.67 - 0.74 - 0.08 - -21.3 - 4 - 36 -

7-10 cm - - 48.97 - 51.03 - 0.93 - 0.09 - -22.5 - 4.2 - 37 -

1

 Only one core was collected from Alaminos Canyon.

39
40

Particle size varied across sites. GC852 sediments were composed of generally finer 

material; more silt/clay particles were present (62.33-75.22 percent) relative to percent sand 

(21.80-37.34 percent) and shell (0.36-18.91 percent). In contrast, both AT340 and AC601 

sediments had a sandier composition, ranging from 36.62 to 63.04 percent sand.

4.3.2 Macrofauna abundance and composition

Total macrofaunal densities were the highest at GC852 (16,174 ± 4,357 individuals per 

square meter, ind m-2), while AT340 and AC601 had similar densities (11,348 ± 2,532 ind m-2

and 12,131 ind m-2) of infauna, respectively (fig. 4.1). Several phyla were represented in the 

sediments: annelids, crustaceans, molluscs and ‘other,’ which included hydroids, sipunculids, 

and porifera. Slight differences in macrofaunal composition were observed among the sites as 

follows. GC852 had an even mix of polychaete annelids (48 percent) and crustaceans (48

percent) with tanaids dominating the crustacean assemblage. Isopod and amphipod crustaceans 

were also present, in lower densities. In contrast, sediment macrofauna from AC601 was 

dominated by crustaceans (77 percent), mostly tanaids (64 percent), followed by polychaete 

annelids (21 percent). There was a notable absence of amphipod crustaceans from this single 

core. Lastly, AT340 sediments were composed of polychaetes (57 percent), followed by 

crustaceans (22 percent), mostly tanaids, and other taxa (15 percent) including hydrozoa. Other 

crustaceans observed at AT340 included cumaceans, isopods, and amphipods.
41

Figure 4.1. A, Macrofaunal (>300 μm) density (individuals per square meter), and B, taxonomic 

composition by major taxa.

A

B
42

Across the three sites, macrofauna were most abundant in the uppermost sediment 

fractions, with 72-80 percent found within the top 0-3 cm. Crustaceans declined dramatically 

with depth and were most abundant in the 0-1 cm fraction, while polychaetes had similar 

densities within each fraction from 0-3 cm, then declined with depth thereafter. 

4.4 Discussion

Macrofaunal densities in deep-sea environments found outside the influence of seeps 

typically only reach a few thousand individuals per square meter (for example, 1,000-2,000 ind 

m

2

); this pattern has been suggested to be a function of food availability (Levin and Gooday, 

2003). In addition, the GOM is generally defined as a low productivity water mass, with low 

densities recorded for deep-sea benthic infauna (Tyler, 2003). For example, low infaunal 

densities have been observed from background sediments in the Florida Escarpment (254 ± 152 

ind m2, Levin and Mendoza, 2007), and infauna were composed of amphipod crustaceans 

followed by both polychaete and oligochaete annelids. In contrast, enhanced infaunal densities 

were recorded from microbial mat sediments in the Florida Escarpment (20,961 ± 11,618 ind m2

, 

Levin and Mendoza, 2007), comparable to those found within Green Canyon sediments in this 

study (19,160 ± 5288 ind m-2), and higher than infaunal densities at Alaminos Canyon and 

Atwater Valley (fig. 4.1). Macrofaunal densities from the three GOM seeps also are comparable 

to densities found in shallower seeps off Eel River, Calif. (13,500 ± 4,770 ind m-2, Levin and 

others, 2003), East Flower Garden brine seep, GOM (for polychaetes, 0-58,360 ind m-2, Powell 

and others, 1986) and at Atwater Valley (13,906 ind m-2, Robinson and others, 2004). In 

addition, seep infaunal communities are typically composed of polychaete and oligochaete 

annelids, gastropods, and gammarid amphipods (Powell and others, 1983; Levin, 2005). Our 
43

results indicate that these major taxonomic groups were also present at the northern Gulf of 

Mexico seeps described here. 

In general, sediment macrofauna from seeps worldwide exhibit high dominance and low 

diversity (Levin, 2005). For example, macrofauna from the Florida Escarpment seeps contained 

a high proportion of a single annelid taxa (Levin and Mendoza, 2007). Future species level 

identification will enable determination of whether northern GOM seeps exhibit the same 

patterns in species dominance observed in other seeps. 

A vast majority of the fauna were found in the upper 3 cm of sediment. In microbial mat 

sediments, 91percent of the infauna occurred within the top 2 cm at Eel River Seeps (Levin and 

others, 2003), possibly a consequence of enhanced food availability near the sediment surface. 

Alternatively, avoidance of toxic sulfides can also affect the vertical distribution and 

composition of infauna (Levin and others, 2003). 

This study represents the first preliminary analysis of seep sediment macrofauna from 

three deep-slope environments in the GOM. Because macrofaunal densities were comparable to 

microbial mat sediments found elsewhere in the GOM, the availability of bacteria as a food 

source may be promoting high densities of infauna (Powell and others, 1986). Food-web studies 

using stable isotopes indicate that sediment-associated bacteria may be fueling some of these 

organisms (Demopoulos and others, Chapter 3). Thus, enhanced densities of infauna may 

ultimately be a function of food supply and availability in these remote seep environments on the 

lower slope (>1,200 m). 

4.5 Acknowledgments

We thank the captain and crew of the R/V Cape Hatteras. We also thank the following 

individuals for their help at sea, site selection, and helpful suggestions: J. Gonzalez, Ross Lab, L. 
44

Levin. E. Cordes, and C. Fisher. Special thanks go to S. Ross for inviting us to participate in this 

cruise and for facilitating the box core sampling. We thank R. Lee (Washington State 

University) for conducting sediment organic carbon and nitrogen analyses. 
45

5. PHYLOGEOGRAPHIC AFFINITIES OF SQUAT LOBSTERS (DECAPODA: 

GALATHEOIDAE) FROM LOWER CONTINENTAL SLOPE COLD-SEEP 

HABITATS IN THE NORTHERN GULF OF MEXICO

By Cheryl L. Morrison1 and Martha S. Nizinski2 

1

Leetown Science Center, Aquatic Ecology Branch, U.S. Geological Survey, Kearneysville, WV 2

NMFS National Systematics Laboratory, Smithsonian Institution, Washington, DC

5.1 Introduction

Squat lobsters (Chirostyloidea: Chirostylidae, Eumunididae, Kiwaidae; Galatheoidea: 

Galatheidae, Munididae, Munidopsidae) are a diverse group of crustaceans comprising over 870 

recognized species worldwide (Baba and others, 2008), with several hundred additional species 

recognized by taxonomic experts as new to science. Collectively, the galatheoids and 

chirostyloids are considered to be ubiquitous members of the deep-sea fauna. Within the 

Galatheoidae, the genera Munida and Munidopsis are the most diverse, with 243 and 224 

species, respectively. Most members of these genera occur in deep waters, with the majority of 

species of Munida found at shelf and slope depths and species of Munidopsis found mainly on 

continental slopes and abyssal plains (Baba and others, 2008). In the western North Atlantic, 

approximately 35 species of Munida are recognized (Baba and others, 2008), of which 20 have 

been reported from the Gulf of Mexico (Felder and others, 2009). Forty-eight species of 

Munidopsis also occur in the western North Atlantic (Baba and others, 2008), with 36 reported 

from the Gulf of Mexico (GOM; Felder and others, 2009). 
46

Anomurans, which include the galatheoids, are particularly well represented at 

chemosynthetically based ecosystems (Chevaldonné and Olu, 1996; Martin and Haney, 2005). 

Anomurans in general, and galatheoids in particular, are the dominant top predator/scavengers 

found at these reducing habitats (Chevaldonné and Olu, 1996). Members of Munidopsis are 

frequently reported as part of faunal assemblages found associated with extreme environments, 

including hydrothermal vents and cold seeps (Martin and Haney, 2005). In fact, Munidopsis is 

the most speciose and widespread of all hydrothermal vent-associated taxa (Martin and Haney, 

2005), and Munidopsis species have been reported from these habitats since their discovery in 

the late 1970s (Chevaldonné and Olu, 1996). Galatheoids were also recorded from cold-seep 

environments when these reducing habitats were first discovered in the GOM during the mid1980s (Paull and others, 1984). 

Although recent investigations conducted in the GOM involving quantitative surveys of 

mega- and macro-invertebrates (for example, Macdonald and others, 1989; Carney, 1994; 

Bergquist and others, 2003b; Cordes and others, 2006; 2007; 2009) report galatheids as being an 

important, and sometimes dominant, member of the seep-associated fauna, specific 

identifications of galatheids have been lacking. Galatheids are often collected opportunistically 

or photographed in lieu of samples. Many species and even genera of galatheids are 

morphologically similar, which makes identifications from photographs extremely problematic 

(Chevaldonné and Olu, 1996; C.L. Morrison, unpub. data, 2011). The lack of specific 

identification has led to vague general references to these decapods at vents and seeps (see 

Chevaldonné and Olu, 1996; Martin and Haney, 2005), thus hindering our ability to estimate 

galatheid species diversity at these sites. In situ photographs taken during recent expeditions to 

seep sites in the GOM illustrate live coloration; however, often no information from earlier 
47

literature exists to compare with observations. The majority of galatheid species were described 

in the 18th and early 19th century. At this time, color patterns were often unknown or considered 

to be unimportant as diagnostic characters. Thus, the use of color characteristics to identify 

species potentially or to narrow the field of possible species is not practical currently. Additional 

uncertainty to our present level of knowledge regarding diversity estimates of galatheoids at 

cold-seep sites is caused by the lack of ecological information incorporated in taxonomic 

literature and the vague taxonomic accounts generally reported in ecological literature 

(Chevaldonné and Olu, 1996). As a result, it is difficult to assess and compare information from 

these two different but equally important references describing associated fauna found in and 

around cold-seep areas. Thus, the total diversity of galatheoids at cold-seep sites remains 

unresolved. 

In recent studies (Chevaldonné and Olu, 1996; Martin and Haney, 2005; Macpherson and 

Segonzac, 2005) investigators surveyed published literature and examined additional material to 

assess the diversity of galatheoids associated with hydrothermal vents and cold seeps. The 

species list is not extensive for either of these reducing environments, yet confirmed 

identifications of galatheids at cold seeps are minimal. For example, Martin and Haney (2005) 

list a total of 2 species of Munida and 13 species of Munidopsis (counting Munidopsis sp. as one 

species) from known vent and seep sites, and of these, only Munidopsis sp. has been recorded 

from cold-seep sites in the GOM. Three unidentified species of Munidopsis along with Munida 

microphthalma are reported by Chevaldonné and Olu (1996) to occur in reducing environments 

in the western Atlantic, including the GOM. Macpherson and Segonzac (2005) record two 

species of Munidopsis occurring at Mid-Atlantic Ridge hydrothermal vent sites and five species 

at Atlantic seeps sites. 
48

Molecular approaches, when used together with morphology data, have proven 

increasingly useful in species identifications. Genetic approaches provide an independent 

assessment of species diversity from that of morphology and may reveal underlying diversity not 

evident in taxa featuring morphological conservatism. For example, combined morphological 

and molecular approaches confirmed the existence of sibling species of Mundia from off New 

Caledonia (Macpherson and Machordom, 2005) and Munidopsis in the East Pacific (Jones and 

Macpherson, 2007). Macpherson and Machordom (2005) and Cabezas and others (2009) 

highlighted the fact that molecular data supported designation of new species when only subtle 

morphological differences were observed. In contrast, molecular analyses questioned the 

taxonomic validity of two sympatric species of Munida occurring off southern South America 

(Pérez-Barros and others, 2008). The authors of that study suggested that although 

morphological differences were apparent, the genetic divergence between the putative species 

was not substantial enough to warrant recognition of two species. Overall, species diversity 

estimates of the Pacific galatheoid fauna have increased with discovery of cryptic species due to 

increased sampling and better defined taxonomy (incorporating both morphological and 

molecular data). Application of similar approaches is expected to increase estimates of 

galatheoid diversity in the western Atlantic. 

Phylogenetic relationships of squat lobsters are poorly understood, and there is still much 

to learn about the evolutionary history of these crustaceans. Recent work (Machordom and 

Macpherson, 2004; Macpherson and Machordom, 2005; Jones and Macpherson, 2007; Cabezas 

and others, 2009) has explored and attempted to clarify some of these relationships; however, 

molecular data are lacking for many species, particularly those in the western Atlantic, making 

construction of phylogenies difficult and incomplete. Machordom and Macpherson (2004) had 
49

good support for most groups identified in their phylogenetic analyses; however, certain 

intrageneric relationships were not highly supported. They concluded that this low support was 

indicative of a rapid radiation event followed by stasis or constraints in morphological evolution 

of the taxa studied. Jones and Macpherson (2007) suggested that low-level genetic divergence 

observed among morphologically differentiated species of Munidopsis collected on the East 

Pacific Rise could suggest a recent and (or) rapid diversification. Cabezas and others (2009) also 

found minimal support for intrageneric relationships within their phylogeny of galatheoids from 

the South-West Pacific. Their results concur with those of previous works (Machordom and 

Macpherson, 2004; Jones and Macpherson, 2007) and thus they suggested that this observed 

pattern may be indicative of a rapid diversification and radiation events that appear to be 

fundamental to structuring the evolutionary history of this group. 

Recent expeditions to cold-seep sites in the GOM collected several individuals of 

multiple species of galatheoids that were made available for study. Morphological and 

molecular analyses were conducted on these specimens to provide an initial assessment of the 

species composition of squat lobsters present at cold-seep habitats on the lower continental slope 

in the GOM and to examine species diversity in an evolutionary and phylogenetic context 

through comparisons with other species in the genera Munidopsis and Munida. 

5.2 Methods

5.2.1 Sample Collections

Twenty-five galatheoid samples, some including multiple individuals (table 5.1), were 

collected from eight chemosynthetic and (or) deep-sea coral sites (AC818, AT340, GC234, 

GC354, GC600, GC852, VK826, WR269) between September 2003 and August 2007 from 
50

depths between 1,188 and 2,746 m. Of these, 13 galatheoid samples, collected at 5 

chemosynthetic sites (AT340, GC600, GC852, AC818, WR269) on the lower continental slope 

in the northern GOM (fig. 5.1), were used for molecular analysis. Additional information 

regarding sample sites can be found in Roberts and others (2007b). Samples were collected by 

manned submersible DSV Alvin, ROV Jason2, and otter trawl deployed near hydrocarbon seep 

sites (see table 5.1). After capture, specimens were sorted and preserved in 70 percent ETOH. A 

small portion of tissue (leg, abdomen, or egg) was placed in 95 percent ETOH for subsequent 

DNA analysis. In the laboratory, samples were examined and identified using authoritative keys, 

taxonomic literature, and comparative material housed at the National Museum of Natural 

History, Smithsonian Institution (USNM). Vouchers will be deposited at the USNM. 
51

Table 5.1. Species list for chirostyloid and galatheoid samples examined.

Species Site Station1 Date Depth 

(meters)

Collection

Method

No. Ind. Used in 

Phylogeny

Family Chirostylidae

Gastroptychus affinis

Family Eumunididae

Eumunida picta

Family Munididae

Munida microphthalma

Munida sanctipauli

Family Munidopsidae

Leiogalathea agassizii

Munidopsis bermudezi

Munidopsis curvirostra

Munidopsis glabra

Munidopsis livida

Munidopsis similis

Munidopsis penescabra

Munidopsis n. sp.

Munidopsis sp. A.

GC852

VK826

GC600

GC600

GC852

GC852

GC852

VK826

VK826

VK826

GC354

AC818

WR269

AT340

GC234

AC818

AT340

AT340

GC852

AT340

AT340

VK826

GC600

GC234

AC818

AC818

AD-4185

JSL-4733

AD-4174

AD-4184

AD-4186

CH-07-027

CH-07-042

CH-07-237

CH-07-238

CH-07-245

JSL-4741

J2-282

J2-275

AD-4173

JSL-4587

J2-282

J2-270

AD-4179

CH-07-042

AD-4180

AD-4173

CH-07-226

AD-4174

JSL-4587

AD-4195

J2-282

5/21/2006

7/22/2004

5/10/2006

5/20/2006

5/22/2006

8/11/2007

8/12/2007

8/27/2007

8/27/2007

8/27/2007

7/26/2004

7/01/2007

6/18/2007

5/09/2006

9/05/2003

7/01/2007

6/9/2007

5/15/2006

8/12/2007

5/16/2006

5/09/2006

8/26/2007

5/10/2006

9/05/2003

5/30/2006

7/01/2007

1,398

462

1,188

1,200

1,410

1,426-1,564

1,478-1,574

550

482

476

563

2,746

1,919

1,139 

534

2,746

2,192

2,184 

1,478-1,574

2,184

1,139 

477

1,188

534

2,744

2,746

On bamboo coral

Bushmaster

Suction, carbonate

Suction

Suction, bushmaster scar

Otter Trawl

Otter Trawl

Box Core

Box Core

Box Core

Bushmaster

Bushmaster, Escarpia

Suction, tubeworm

Bushmaster, tubeworms

Bushmaster 

Bushmaster, Escarpia

Bushmaster, tubeworms

Bushmaster

Otter Trawl

Bushmaster 

Bushmaster, tubeworms

Tucker Trawl

Suction

Bushmaster

Suction

Bushmaster, Escarpia

1

1

2

3

1

3

1

1

1

1

1

2

1

1

26

1

1

1

1

1

1

2

1

168

1

1

N

N

Y

Y

Y

Y

Y

N

N

N

N

Y

Y

N

N

Y

Y

N

Y

N

N

N

Y

N

Y

Y

1

AD= DSV Alvin; J2= ROV Jason2; JSL= Johnson-Sea-Link submersible; CH= R/V Cape Hatteras, trawl. 
52

Figure 5.1. Multibeam bathymetry map of the northern Gulf of Mexico continental slope. Included on 

map are galatheiod collection localities (yellow dots) and lease blocks established by the Bureau of 

Ocean Energy Management, Regulation and Enforcement for oil and gas activity management. (Map 

created by Harry Roberts, Louisiana State University). 

5.2.2 DNA extraction, amplification, and sequencing

Total DNA was isolated from ethanol-preserved tissue using the tissue protocol from the 

PureGene DNA extraction kit (Gentra Systems Inc., Minneapolis, Minn.). The following 

primers were used to amplify a 650 base pair (bp) portion of the mitochondrial cytochrome 

oxidase I gene (COI): 

LCO1490 (5’ – GGTCAACAAATCATAAAGATATTGG – 3’) and HCO2198 (5’ - 

TAAACTTCAGGGTGACCAAAAAATCA) (Folmer and others, 1994); gala-COIF (5’ – 

CATCACTWAGWTTRATYATTCGAGCAGAA – 3’) and gala-COIR (5’ – 

GAAYAGGRTCTCCTCCTCCTAC – 3’) (Jones and Macpherson, 2007); CrustF2 (5’ – 
53

GGTTCTTCTCCACCAACCACAARGAYATHGG – 3’) (Costa and others, 2007) and COI-H 

(5’ – TCAGGGTGACCAAAAAATCA – 3’) (Machordom and Macpherson, 2004). Forward 

primers LCO1490 or gala-COIF paired with COI-H produced most of the sequences for this 

study. PCR reactions were carried out using 1X PCR buffer (10 millimoles (mM) Tris-HCl, pH 

8.3, 20 mM KCl), 2 mM MgCl2, 0.2 mM of dNTPs, 0.375 micromoles (μM) of each primer, 0.01 

milligrams per milliliter (mg/mL) bovine serum albumin, 2.5 units of Taq polymerase, and 

approximately 100 nanograms (ng) of template DNA in a 20 microliter (μL) reaction volume. 

Thermal cycling was performed using an MJ-Research (Watertown, Mass.) PTC-200 

thermocycler and the following cycle parameters: initial denaturing at 94°C for 2 min; followed 

by 35 cycles of 94 °C denaturing (1 min), 52–56 °C annealing (1 min), 72 °C extension (1 min), 

ending with a 5-min extension at 72 °C. PCR products were purified with Exonuclease I and 

Shrimp Alkaline Phosphatase (Promega Corp., Madison, Wisc.) and then used as templates in 

sequencing reactions with the ABI Prism BigDye Terminator Cycle Sequencing Ready Reaction 

Kit v. 3.1 (Applied Biosystems, Foster City, Calif.). Sequencing reactions were analyzed by 

capillary electrophoresis using the ABI PRISM 3100TM Genetic Analyzer and DNA Sequencing 

Analysis Software (Applied Biosystems, Foster City, Calif.). 

5.2.3 Mitochondrial DNA sequence analysis

Forward and reverse sequences were assembled for each individual using Sequencher v. 

4.0 (Gene Codes Corporation, Ann Arbor, Mich.). Multiple sequence alignments for Munida

and Munidopsis species were carried out using Clustal X v. 1.4b (Thompson and others, 1997) 

with default gap opening/extension penalties. For both genera, most of the comparative 

sequence data available are from Pacific Ocean taxa. For the Munida analysis, comparative 

sequences from GenBank were included from the following studies: Machordom and 
54

Macpherson (2004); Costa and others (2007), and Perez-Barros and others (2008). The majority 

of comparative Munidopsis sequences were from Jones and Macpherson (2007); several 

sequences from Cubelio and others (2007) were also included. 

Phylogenetic trees were estimated via Bayesian analysis using MrBayes v. 3.1.2 

(Huelsenbeck and Ronquist, 2001). For each dataset, two simultaneous Bayesian runs were 

completed for 8 X 106 generations with random starting trees, default priors, four Markov chains, 

and sampling every 100 generations. Stationarity of the Markov chain Monte Carlo (MCMC) 

analyses was determined by plotting negative log-likelihood values and parameter estimates 

against generation times. Trees from the burn-in (24,000 trees) were discarded before clade 

posterior probabilities were calculated from their frequencies. 

5.3 Results

5.3.1 Diversity of Galatheoidea

Two hundred and twenty-six individuals were collected in 25 samples taken at 20 stations 

(table 5.1). Individuals in these samples represented two families (Chirostylidae, Galatheidae) 

and 13 species (2 chirostyliods, 11 galatheiods; table 5.1); two of these species are new to 

science. Seven species (Eumunida picta, Munida sanctipauli, Munidopsis bermudezi, M. glabra, 

M. livida, M. penescabra, Munidopsis n.sp.) have been previously reported from the GOM. 

Only three species (Eumunida picta, Munida microphthalma and Munidopsis livida) were 

recorded previously from cold seeps (Martin and Haney, 2005; Macpherson and Segonzac, 

2005). Of these species, E. picta is the only species previously reported from cold seeps in the 

GOM (Martin and Haney, 2005). 
55

At the majority of stations (N = 15) only one species was collected. Two species were 

collected at four stations, three of which were located at GC and one at AT. Three species were 

collected only once at a station located at AC818. Also of interest is that the combination of 

species collected at a station was never the same. 

Most samples comprised one to a few individuals. However, two large collections were 

made at GC234, consisting of 26 individuals of Munidopsis glabra and 168 individuals of 

Munidopsis n. sp. These samples were collected using the JSL submersible and the Bushmaster 

tubeworm community collection device as part of a study of fauna associated with 

chemosynthetic communities (Cordes and others, 2005). These Munidopsis species, labeled 

Munidopsis sp. nov. 1 and 2 for Munidopsis n. sp. and M. glabra, respectively, were among the 

most abundant tubeworm-associated fauna in collections of Lamellibrachia luymesi at GC234 

(Cordes and others, 2005). Although Munidopsis species are fairly inconspicuous in video data, 

collections of entire tubeworm communities allow a perspective on their abundances in these 

long-lived habitats. 

Overall, Munida microphthalma and Munidopsis similis were collected most frequently; 

each species was captured in five samples. Four samples of M. similis were taken at AT340; one 

sample at GC852. Munida microphthalma was collected only at GC. With regard to species 

diversity by site, VK826 and AC818 were the most diverse with three species collected at each 

site. Two species were collected at AT340, GC234, GC600, and GC852, and one species at 

GC852, GC354, and WR269. 

5.3.2 Munidopsis species

Eight individuals collected at four deep chemo sites in the northern GOM were included 

in the phylogenetic analysis. Six species of Munidopsis (M. bermudezi, M. curvirostra, M. 
56

livida, M. similis, Munidopsis n. sp., and Munidopsis sp. A) were represented in the samples 

(table 5.1; fig. 5.2). 
57

Figure 5.2. Phylogenetic hypothesis for Munidopsis resulting from Bayesian analysis of mitochondrial 

cytochrome oxidase (COI) DNA sequence data. A and B are clades, or groupings of taxa. 

Partial mitochondrial COI sequences from the Munidopsis samples were determined and 

aligned with 45 additional sequences representing 18 Munidopsis taxa. Eumunida 

sternomaculata, a chirostyloid, was designated as an outgroup. The alignment contained 566 bp 

of sequence data; 233 sites were variable, 199 sites were parsimony-informative, and no gaps 

were present. 

Results of the Bayesian phylogenetic analysis are shown in figure 5.2. Munidopsis

samples from GOM cold-seep sites are taxonomically and phylogenetically diverse. Two 

distinct, well supported clades or groupings of taxa (clades A and B, fig. 5.2) were produced in 

the analysis. Cold-seep species collected in the GOM were not clustered together in the 

phylogeny. Rather, these species were placed in multiple locations throughout the phylogenetic 

tree with inclusion of some species from these samples in each of the major clades. Divergence 

between taxa from the two major clades was high, with an average uncorrected P-distance of 

approximately 20 percent (table 5.2 for Munidopsis n. sp. and M. curvirostra, other distances not 

shown). 
58

Table 5.2. Pairwise uncorrected P-distances between mitochondrial cytochrome oxidase I (COI) sequences for Munidopsis samples.

M. sp. A. M. sp. A. livida similis similis bermudezi M. n. sp. M. curvirostra

Individual

AD4195-01 J2282-03 J2282-02 J2270-01 CH07-042-02 J2282-01 AD4174-01 J2275-01

M. sp. A. AD4195-01 -

M. sp. A. J2282-03 0.37 -

M. livida J2282-02 10.64 10.78 -

M. similis J2270-01 9.58 9.95 11.97 -

M. similis CH07-042-02 9.91 10.25 12.72 0.55 -

M. bermudezi J2282-01 11.01 11.31 12.01 11.6 12.54 -

M. n. sp. AD4174-01 22.57 22.44 21.38 21.73 22.79 22.57 -

M. curvirostra J2275-01 19.27 19.05 19.73 17.69 17.91 19.5 17.23 -
59

Clade A (fig. 5.2) included four species, two species from GOM seeps (Munidopsis 

curvirostra and Munidopsis n.sp.), one from the eastern Pacific (M. quadrata), and one from the 

eastern North Atlantic (M. polymorpha). Within this clade the GOM species grouped with 

species from other oceans or regions instead of together. Interestingly, M. quadrata is the sister 

taxon to Munidopsis n.sp. 

The remaining four GOM Munidopsis species included in the phylogenetic analysis were 

placed in the distinct and well-supported Clade B (fig. 5.2). Concordant with morphology, 

sequences from multiple individuals of the same taxon grouped together in the phylogeny and 

were minimally divergent (Munidopsis sp. A, uncorrected P-distance=0.37 percent 

substitutions/site; M. similis P-distance=0.55 percent; fig. 5.2; table 5.2). Munidopsis cascadia

(eastern Pacific) and M. bermudezi were sister taxa and basal to this clade (fig. 5.2). Corrected 

sequence divergence between these taxa was 3.9 percent. Of particular interest was the clade 

containing GOM Munidopsis sp. A individuals (this study) and M. bracteosa individuals from 

the eastern Pacific Ocean (Jones and Macpherson, 2007). These two species were approximately 

1 percent divergent. 

5.3.3 Munida species

Munida microphthalma was the only species of Munida from these collections included 

in this analysis. This species occurred at relatively high densities at two different Green Canyon 

sampling locations, GC852 (N=4) and GC600 (N=5). 

Partial mitochondrial COI sequences from these nine M. microphthalma individuals were 

determined and aligned with 56 additional sequences representing 35 Munida taxa. Eumunida 

sternomaculata, a chirostyloid, was designated as an outgroup. The alignment contained 657 bp 
60

of sequence data; 262 sites were variable, 246 sites were parsimony-informative, and no gaps 

were present. 

Results of the Bayesian phylogenetic analysis are shown in figure 5.3. Multiple 

groupings of Munida taxa were supported by high posterior probabilities, yet resolution of 

relationships among these major groupings was poor. Sequences from all individuals of GOM 

M. microphthalma were included in one grouping. These sequences differed little from each 

other as illustrated by short branch lengths (fig. 5.3). In this analysis, the closest relative to 

GOM M. microphthalma was M. tiresias from New Caledonia. However, these species were 

quite differentiated with an average Tamura-Nei sequence divergence of 15 percent.
61

Figure 5.3. Phylogenetic hypothesis for Munida resulting from Bayesian analysis of mitochondrial 

cytochrome oxidase I (COI) DNA sequence data. 
62

5.4 Discussion

Galatheoid crabs from the genera Munida and Munidopsis have been reported from coldseep sites in the GOM, yet species accounts have been vague (Martin and Haney, 2005). Here 

we report eight species of Munidopsis and two species of Munida collected near chemosynthetic 

habitats in the northern Gulf of Mexico. Of these species, we examined the phylogenetic 

placement of six species of Munidopsis and one species of Munida relative to other species 

within each genus. Other species examined but not included in phylogenetic analysis were either 

not preserved correctly for DNA analysis or did not amplify for sequencing. 

In this initial assessment of deep chemosynthetic sites in the northern GOM, high 

taxonomic diversity was found in the genus Munidopsis. This is not surprising given that this 

genus is extremely diverse, particularly in deep-sea environments. Additionally, species of 

Munidopsis are the most frequently encountered decapod crustaceans at hydrothermal vent and 

seep sites (Chevaldonné and Olu, 1996; Martin and Haney, 2005). The GOM species of 

Munidopsis included in our analysis represent divergent evolutionary lineages as illustrated by 

their placements throughout the phylogenetic tree. These species usually grouped with species 

from either the eastern Pacific or North Atlantic Oceans. 

Two of the GOM seep species examined, Munidopsis n.sp. (GC600) and M. curvirostra 

(WR269), were members of a well-supported basal clade that also included M. quadrata (eastern 

Pacific Ocean) and M. polymorpha (eastern North Atlantic Ocean). Munidopsis species that fell 

into Clade A (fig. 5.2) were substantially differentiated from the other Munidopsis species 

examined. 

At the base of the second major clade of Munidopsis taxa (Clade B, fig. 5.2), Munidopsis 

cascadia from the Pacific Ocean (off the coast of Oregon) formed a sister relationship with M. 
63

bermudezi from the GOM. A molecular clock calibrated for other decapod crustacean taxa 

(sister species of snapping shrimps) separated by the Isthmus of Panama can be used to estimate 

the approximate timing of lineage divergence (1.5 percent, Morrison and others, 2004). Based 

on these calculations, divergence of these taxa is estimated to be slightly less than 3 million years 

ago, which is in accordance with the final closing of the Panamanian Seaway. 

Our phylogenetic analysis corroborates the results presented by Jones and Macpherson 

(2007). Munidopsis bracteosa belongs to a species complex that includes M. recta, the most 

common species from the vast East Pacific Rise, M. scotti from the Juan de Fuca vent system, 

and M. exuta from the Mid-Atlantic Ridge. This species complex now also includes Munidopsis

sp. A from the GOM. In fact, a close phylogenetic relationship was found between Munidopsis

sp. A from GOM seeps and the recently described M. bracteosa (Jones and Macpherson, 2007) 

from the Juan de Fuca hydrothermal vent system and whalefall in Monterey Bay in the eastern 

Pacific Ocean. Sequence divergence of approximately 1 percent suggests that these individuals 

may have relatively recent faunal connections (less than a million years, applying the same rate 

calibration as above). These lineages may be in the process of speciating, since several 

distinctive morphological differences were identified. 

Although the species belonging to the closely related clade mentioned above (M. 

bracteosa/ M. sp. A., M. recta, M. scotti, and M. exuta) can be identified morphologically, they 

differ by less than 2 percent mitochondrial sequence divergence. This value is close to the value 

of 1.6 percent suggested by Lefébure and others (2006) as the minimum amount of divergence 

needed between crustacean species to support recognition of distinct species. Jones and 

Macpherson (2007) hypothesize that species belonging to this clade have recently diverged or 

have undergone a rapid radiation. It is especially interesting that M. exuta and Munidopsis sp. A. 
64

have such close molecular ties to the eastern Pacific species group, since they are distributed in 

different ocean basins and more recent pathways for larval dispersal between these ocean basins 

are not obvious. Additional sampling, as well as taxonomic and DNA sequence analyses, will be 

necessary to unravel this unexpected evolutionary pattern. 

From these initial collections, it appears that the genus Munida is not as taxonomically 

diverse as Munidopsis at GOM deep chemosynthetic habitats. This is not surprising since only 

two Munida species have been reported from seep or vent habitats previously (Martin and 

Haney, 2005). The single species collected at GOM deep chemosynthetic sites included in the 

analysis, Munida microphthalma, is known from cold-seep sites in the Barbados Accretionary 

Prism, as well as throughout the North Atlantic Ocean (Martin and Haney, 2005). 

The diversity of galatheoid crabs is high at these extreme deep-sea environments in the 

GOM. We are just beginning to recognize this diversity. High quality collections are key to our 

understanding of the morphology and taxonomy of this group. Most of these species cannot be 

identified from photographs or videos. Once we are able to positively identify the galatheoid 

fauna associated with cold-seep environments, we can utilize this information to make progress 

on the systematics, phylogenetics, phylogeography, and connectivity of the members of this 

group. We have made significant progress toward this goal, but more intensive sampling is 

needed to determine the total diversity and evolutionary relationships of the galtheoid crabs 

associated with GOM cold-seep habitats. 

5.5 Acknowledgments

This investigation was financially supported by the USGS Outer Continental Shelf 

Ecosystem Program and was sponsored by the Bureau of Ocean Energy Management, 

Regulation and Enforcement. The USGS-BRD Leetown Science Center, Aquatic Ecology 
65

Branch, provided partial funding. The following individuals kindly donated crab samples: E. 

Cordes and C. Fisher. The authors would like to thank TDI-Brooks International, Inc., C. Fisher, 

and H. Roberts for allowing C. Morrison to participate in a research cruise. Additionally, the 

authors thank the crew members of the R/V Atlantis, R/V Ronald H. Brown, and the R/V Cape 

Hatteras, as well as the crews for DSV Alvin and ROV Jason2, who made this research possible. 
66

6. PRELIMINARY MOLECULAR ASSESSMENT OF SCLERACTINIAN 

CORAL AND OCTOCORAL BIODIVERSITY FROM LOWER CONTINENTAL 

SLOPE HABITATS IN THE NORTHERN GULF OF MEXICO

By Cheryl L. Morrison 

Leetown Science Center, Aquatic Ecology Branch, U.S. Geological Survey, Kearneysville, WV

6.1 Introduction

Hydrocarbon seeps and their associated chemosynthetic communities are widespread in 

the Gulf of Mexico (GOM; Fisher and others, 2007). Over the past two decades, studies of the 

physiology of symbiont-containing megafauna and the ecology of the chemosynthetic 

communities occurring on the GOM upper continental slope have made these habitats model 

systems for the study of seep communities (reviewed by Fisher and others, 2007; Cordes and 

others, 2009). Typical seep chemosynthetic communities in the GOM are dominated by five 

species of bathymodiolin mussel species with methane- or sulfide-oxidizing symbionts, six 

vestimentiferan polychaete (tubeworm) species and (or) two species of vesicomyid clams that 

harbor sulfide-oxidizing symbionts (Cordes and others, 2009). For tubeworm species, a strong 

temporal component, or community succession, has been documented, where young, fluid-prone 

habitats consisting of seep endemics eventually transition as seepage subsides to older, mineralprone habitats with lower biomass but higher non-endemic diversity (Bergquist and others, 

2003a; Cordes and others, 2005; Fisher and others, 2007; Cordes and others, 2009). At this latter 
67

stage in community succession, when fluid-gas expulsion has subsided, relict seeps are often 

represented by authigenic carbonates produced during active seepage. In some areas, these 

exposed carbonates may be colonized by deep-sea scleractinian corals, octocorals, and black 

corals, providing a direct link between cold seeps and coral communities in the deep GOM 

(Fisher and others, 2007; Cordes and others, 2009). 

Azooxanthellate scleractinian corals are fairly well characterized and diverse in the 

GOM, with 94 species recorded, and a large percentage of these, 82 species, or 87 percent, 

occurring in deep water (>200 m; Cairns and others, 2009). Only 23 of these GOM scleractinian 

species occur at depths greater than 1,000 m (Cairns and others, 2009). The scleractinian coral 

Lophelia pertusa forms extensive reef structures on the upper continental slope (Schroeder and 

others, 2005). Madrepora oculata also occurs on the upper continental slope in the GOM 

(Cairns and others, 2009). The depth range of both of these species exceeds 1,000 m (Cairns, 

1979; Cairns and others, 2009), yet there are no known reef areas at such depths in the GOM. 

Scleractinian taxonomy and phylogeny are in a transition in which traditional skeletal 

characters are being supplemented with characters from microstructures, reproduction, and 

frequently, molecular genetics (Cairns and others, 2009). In particular, analyses of both 

mitochondrial and nuclear sequence data have established two ancient clades, or groupings, of 

scleractinian coral species, the “complex” and “robust” clades (Romano and Palumbi, 1996; see 

Romano and Cairns, 2000, and Kitahara and others, 2010a, for discussion). From 16S 

mitochondrial ribosomal RNA sequences, the two clades are easily distinguishable by sequence 

length: the “robust” corals have a short 16S sequence relative to the “complex” corals (Romano 

and Palumbi, 1997). Such molecular studies have also revealed that morphologically defined 

families often do not represent “natural” families that share a common ancestry (Fukami and 
68

others, 2004; 2008). Based on a recent analysis including many deep-water, azooxanthellate 

species, and unlike shallow-water zooxanthellate species, the majority of azooxanthellate coral 

families do appear to be natural groupings, with the exception of the Caryophylliidae and the 

Oculiniidae (Kitahara and others, 2010a). In fact, the Caryophylliidae, which includes Lophelia 

pertusa and many solitary corals in the genus Caryophyllia plus other genera, is the least 

cohesive of extant coral families, with representatives falling into both the “complex” and 

“robust” sections of the scleractinian phylogeny (Le Goff-Vitry and others, 2004; Kitahara and 

others, 2010a). 

Octocoral biodiversity is still poorly known in the GOM, yet diversity appears high, with 

162 species recorded (Cairns and Bayer, 2009). About half of these GOM octocoral species (77 

species) occur in deep water (>200 m), and 15 species have depth ranges greater than 1,000 m 

(Cairns and Bayer, 2009). Considering the entire GOM basin divided into four approximately 

equal quadrants at 900W. latitude and 250N. longitude for biogeographic comparisons (Felder 

and others, 2009), the highest biodiversity of both scleractinian and octocoral species has been 

recorded in the southeastern quadrant of the GOM, with numbers of species decreasing 

considering quadrants in a counterclockwise fashion (Cairns and others, 2009; Cairns and Bayer, 

2009). 

Although chemosynthetic communities occurring on the GOM upper continental slope 

(water depths <1,000 m) have been well characterized (for example, Kennicutt and others, 1985; 

Brooks and others, 1987; Cordes and others, 2007), few are known from the middle and lower 

continental slope, and they remain poorly studied. The objective of this study was to produce a 

preliminary genetic assessment of scleractinian coral and octocoral species diversity associated 

with chemosynthetic habitats at water depths of 1,000 m or greater in the northern GOM. 
69

6.2 Methods

6.2.1 Sampling sites

Azooxanthellate scleractinian corals and octocorals associated with chemosynthetic 

habitats in the northern GOM were collected from five sites at depths ranging from 942 to 2,240 

m (fig 6.1). The westernmost site, Alaminos Canyon 645 (AC645), was characterized by 

tubeworms and mussels and has been the focus of multiple studies (Carney, 1994; Roberts and 

Aharon, 1994; Cordes and others, 2007). The Alaminos Canyon site was also the deepest site 

where corals were collected for this study. Octocoral samples were obtained from two sites in 

the Garden Banks (GB), GB647 and GB697. Both of these sites were salt ridges with 

chemosynthetic communities and seep-associated carbonates where octocorals were found. 

Chemosynthetic communities including tubeworms and mussel beds occur near (80-400 m) to 

authigenic carbonate boulders hosting octocorals and scleractinian corals at Green Canyon 852 

(GC852). This area is now referred to as the ‘coral gardens’ (Roberts and others, 2007a). Unlike 

other coral sites that were generally topographic highs, Mississippi Canyon 462 (MC462) was a 

depression in the continental slope and represents the most eastern coral collection site. Small 

carbonates at the bottom of the depression hosted scleractinian and octocorals. 
70

Figure 6.1. Sampling locations in the northern Gulf of Mexico. 

Sampling occurred during May of 2006 aboard the R/V Atlantis using the Deep 

Submergence Vehicle (DSV) Alvin and June 2007 aboard the R/V Ronald H. Brown using the 

remotely operated vehicle (ROV) Jason2. Small pieces of scleractinian corals or octocorals were 

collected using the Alvin or Jason2. Once on board the vessel, a small piece of tissue was 

excised from each coral and preserved in 95-percent ETOH. Additionally, a larger piece of the 

skeleton was placed in 70-percent ETOH to serve as a voucher. Voucher specimens were 

identified by Dr. Stephen Cairns, Curator and Chair in the Department of Invertebrate Zoology 

and the National Museum of Natural History, Smithsonian Institution. 
71

6.2.2 Molecular Methods

Total DNA was isolated from preserved coral tissue using the tissue protocol from the 

PureGene DNA extraction kit (Gentra Systems Inc., Minneapolis, Minn.). DNA concentrations 

were determined by fluorescence assay (Labarca and Paigen, 1980) and integrity of the DNA 

was visualized on 1-percent agarose gels (Sambrook and others, 1989). 

For scleractinian corals, DNA sequences were obtained for a portion of the 16S 

mitochondrial DNA (mtDNA) gene region, allowing for comparisons with large number of 

scleractinian coral sequences available in GenBank from coral phylogenetic studies by Romano 

and Cairns (2000), Le Goff-Vitry and others (2004), and Kitahara and others (2010a; b). PCR 

primers for the 16S mtDNA gene region included universal primers 16Sar and 16Sbr of Palumbi 

and others (1991). 

For octocorals, mitochondrial DNA sequences were obtained for portions of the msh1

and ND2 genes, allowing for comparisons with GenBank sequence data from major works by 

Wirshing and others (2005), McFadden and others (2006), and France (2007). The 5’ end of the 

msh1 gene was amplified with the primers ND42599F (France and Hoover, 2001) and mut3458R 

(Sánchez and others, 2003). For bamboo corals (isidids), the forward primer msh5p8f (France, 

2007) was paired with mut3458R. The primers 16S-647F and ND21418R (McFadden and 

others, 2006) were used to amplify the ND2 gene region. 

PCR reactions were carried out using 1X PCR buffer (10 mM Tris-HCl, pH 8.3, 20 mM 

KCl), 2 mM MgCl2, 0.2 mM of dNTPs, 0.375 μM of each primer, 0.01 mg/mL bovine serum 

albumin, 2.5 U of Taq polymerase, and approximately 100 ng of template DNA in a 20 μL 

reaction volume. Thermal cycling used an MJ-Research (Watertown, Mass.) PTC-200 

thermocycler using the following cycle parameters: initial denaturing at 94°C for 2 min; 
72

followed by 35 cycles of 94 °C denaturing (1 min), 52–56 °C annealing (1 min), 72 °C extension 

(1 min), ending with a 5-min extension at 72 °C. PCR products were purified with Exonuclease 

I and Shrimp Alkaline Phosphatase (Promega Corp., Madison, Wisc.) and then used as templates 

in sequencing reactions with the ABI Prism BigDye Terminator Cycle Sequencing Ready 

Reaction Kit v3.1 (Applied Biosystems, Foster City, Calif.). Sequencing reactions were 

analyzed by capillary electrophoresis using the ABI PRISM 3100TM Genetic Analyzer and DNA 

Sequencing Analysis Software (Applied Biosystems, Foster City, Calif.). Sequence traces were 

edited, and forward and reverse sequences for each samples were assembled using Sequencher 

version 4.10 (Gene Codes Corporation, Ann Arbor, Mich.). 

6.2.3 Phylogenetic analyses

New sequences were aligned with select sequences available in GenBank for 

representative species belonging to the families represented by samples from this study. 

Multiple sequence alignment was carried out using Clustal X v. 1.4b (Thompson and others, 

1997), with default gap opening/extension penalties. The resulting alignment was checked by 

eye using MacClade v. 4.08 for OS X (Maddison and Maddison, 2005). 

Phylogenetic analyses of DNA sequences were carried out using PAUP* 4.0b10 

(Swofford, 2002) and MrBayes v. 3.04 (Bayesian analysis; Huelsenbeck and Ronquist, 2001). 

Pairwise genetic distances plus the neighbor-joining tree reconstruction method were calculated 

in PAUP, and nodal support was assessed using 1,000 bootstrap replicates (Felsenstein, 1985). 

The MrBayes analysis was run for 1,000,000 generations with random starting trees, default 

priors, two Markov chains, and sampling every 1,000 generations. Stationarity of the MCMC 

analyses was determined by plotting negative log likelihood values and parameter estimates 
73

against generation times. Trees from the burn-in (300 trees) were discarded before posterior 

probabilities were calculated. 

6.3 Results

6.3.1 Scleractinian coral phylogeny

Six scleractinian coral samples representing three families (Dendrophyliidae, Oculinidae 

and Caryophylliidae) were obtained from two sites (GC-852, northwest GOM, and MC-462, 

northeast GOM) for this study (table 6.1). Two of the species sampled at GC-852 were 

previously known only from the southeastern GOM: Enallopsammia rostrata and Solenosmilia 

variabilis (Cairns and others, 2009). 
74

Table 6.1. Collection and information for scleractinian coral samples. 

[Species identifications by Dr. Stephen Cairns, USNM] 

Species Identification USNM # Dive # ID # Date Site Depth 

(m) Family

Enallopsammia rostrata (Pourtalés, 1878)

Madrepora oculata (Linnaeus, 1758)

Caryophyllia polygona (Pourtalés, 1878)

Solenosmilia variabilis (Duncan, 1873)

Madrepora oculata (Linnaeus, 1758)

Madrepora oculata (Linnaeus, 1758)

1100985

1110233

1110967

1110364

1110362

1110363

AD-4190

J2-271

J2-271

J2-278

J2-278

J2-278

01

01

04

10

13

14

25-May-06

12-Jun-07

12-Jun-07

23-Jun-07

23-Jun-07

23-Jun-07

GC-852

MC-462

MC-462

GC-852

GC-852

GC-852

1,347

954

954

1,396

1,396

1,396

Dendrophyliidae

Oculinidae

Caryophylliidae

Caryophylliidae

Oculinidae

Oculinidae
75

The only “complex” coral sampled for this study, Enallopsammia rostrata, was included 

in an analysis in the Lophelia I final report (Morrison and others, 2008). The E. rostrata sample 

from GC-852 differed by one base from the 16S sequence for this species in GenBank (France 

and others, 1996), and differed by 2-3 bases from the congeneric species E. profunda from the 

northwestern Atlantic Ocean (fig. 4.5, Morrison and others, 2008). 

Four of five “robust” scleractinian corals were successfully amplified at the mtDNA 16S 

gene and were aligned with other “robust” coral sequences from GenBank. The coral 

Solenosmilia variabilis collected from GC-852 did not amplify, nor did a comparative sample 

from the northwestern Atlantic Ocean. Two new sequences for Madrepora oculata samples J2-

278-11 and J2-278-12 were identical, and only the latter was included in the phylogenetic 

analysis. The Bayesian analysis included 54 species belonging to 35 genera of “robust” corals. 

Based upon the well-established sister relationship between hexacorallians (scleractinians, 

anemones, zoanthids, and corallimorphs) and octocorallians (France and others, 1996; Berntson 

and others, 1999), two octocoral species, Briareum and Pseudopterogorgia, were designated as 

outgroups. Both the Madrepora sequences as well as the Caryophyllia polygona sequence fell 

within a well-supported clade containing species belonging to the families Oculinidae, 

Pocilloporidae, and Caryophylliidae (fig. 6.2, posterior probability 0.97). The Oculinidae clade 

comprised seven sequences of Madrepora oculata collected from the eastern and western North 

Atlantic Ocean and Gulf of Mexico. The two new samples from this study differed by 1 percent 

sequence divergence from an M. oculata sequence from the upper continental slope (M. oculata

4738-2B from MC-885, fig. 6.2). As in previous analyses (Le Goff-Vitry and others, 2004; 

Morrison and others, 2008), Caryophyllia solitary corals were closely allied with Lophelia 

pertusa (fig. 6.2). The Caryophyllia polygona sample from MC-461 was 3 percent divergent 
76

from a sample of C. polygona from the upper continental slope (C. polygona 4738-04, fig. 6.2), 

and these sequences did not group together, yet both fell within the clade containing other 

Caryophyllia species and L. pertusa. A second major grouping was composed of mostly 

shallow-water species in the families Meandrinidae, Faviidae, Mussidae, Pectinidae, 

Merulinidae, Fungiidae, and Siderastreidae, and also several species belonging to the family 

Caryophylliidae (fig. 6.2, posterior probability 0.93). Most of the families within this grouping 

were not monophyletic, as has been seen in previous analyses (Fukami and others, 2004; 2008; 

Kitahara and others, 2010a). 
77
78

Figure 6.2. Phylogenetic hypothesis for scleractinian corals based upon Bayesian analysis of 

mitochondrial 16S sequences. (Species names in bold represent samples unique to this study, 

whereas others originate from GenBank or Morrison and others (2008). Numbers at nodes represent 

Bayesian posterior probabilities of node support.) 

6.3.2 Octocoral phylogeny

Twelve octocoral samples were collected for this study (table 6.2). Samples were 

representative of three octocorallian sub-orders (Holaxonia, Calcaxonia, and Scleraxonia) and 

five families (Plexauridae, Isididae, Acanthogorgiidae, Chrysogorgiidae and Coralliidae; table 

6.2). 

Table 6.2. Collection 

[Species identifications by 

and information for octocoral

Dr. Stephen Cairns, USNM] 

samples.

Species Identification USNM # Dive # ID # Date Site Depth 

(meters) Sub-order Family

Paramuricea?

Bamboo coral

Paramuricea?

Stenogorgiinae

Acanthogorgoria armata

(Verrill, 1878)

Keratoisis sp. 

Iridogorgia pourtalesii 

(Verrill, 1883)

Paramuricea sp. 

Chrysogorgia fewkesii 

(Verrill, 1883)

Corallium medea 

(Bayer, 1964)

Villogorgia sp.

cf. Placogorgia sp. 

1100983

1099767

1100984

1110234

1110361

1110367

1110366

1110368

1110371

1110365

1110369

1110370

AD4190

AD4194

AD4194

J2-271

J2-271

J2-273

J2-273

J2-273

J2-274

J2-278

J2-280

J2-280

02

01

03

02

03

05

06

07

08

09

13

14

25-May-06

29-May-06

29-May-06

12-Jun-07

12-Jun-07

14-Jun-07

14-Jun-07

14-Jun-07

17-Jun-07

23-Jun-07

26-Jun-07

26-Jun-07

GC-852

AC-645

AC-645

MC-462

MC-462

GC-852

GC-852

GC-852

GB-697

GC-852

GB-647

GB-647

1,410

2,240

2,240

954

954

1,422

1,422

1,422

1,003

1,397

942

959

Holaxonia

Calcaxonia

Holaxonia

Holaxonia

Holaxonia

Calcaxonia

Calcaxonia

Holaxonia

Calcaxonia

Scleraxonia

Holaxonia

Holaxonia

Plexauridae

Isididae

Plexauridae

Plexauridae

Acanthogoriidae

Isididae

Chrysogorgiidae

Plexauridae

Chrysogorgiidae

Coralliidae

Plexauridae

Plexauridae
79

Six octocoral samples were successfully amplified and sequenced at the 5’ msh1 gene 

region. New sequences were aligned with others from GenBank for an alignment of 901 base 

pairs in length, including 69 ingroup taxa and Telestula, a stoloniferan, as the outgroup. Both 

Bayesian and neighbor-joining analyses produced trees with similar topologies, and the Bayesian 

cladogram is shown in figure 6.3. The three sub-orders represented in our samples (Holaxonia, 

Calaxonia, and Scleraxonia) were well supported in the analysis (fig. 6.3). Corallium medea, 

collected from GC-852, clustered with other Corallium species included in the analysis (C. niobe

and C. ducale; sub-order Scleraxonia). Pairwise sequence divergence among these Corallium

samples averaged 3.6 percent. Both Keratoisis sp. from GC852 and Isidella sp. from AC645 

were members of a well-supported clade containing mostly Isidella and Lepidisis species from 

both the Atlantic and Pacific Oceans and corresponding to haplotype I1/2 of France (2007). The 

Isidella sp. from AC645 was the most divergent sequence of this isidid clade, averaging 2.8 

percent sequence divergence, whereas others in the clade were minimally divergent, differing by 

less than 1 percent. Iridogorgia pourtalesii from GC852 clustered with other species belonging 

to the family Chrysogorgiidae, and differed from Iridogorgia sp. from GenBank by less than 1 

percent. 
80
81

Figure 6.3. Phylogenetic hypothesis for octocorals based upon Bayesian analysis of mitochondrial 

msh1 sequences. (Species names in bold represent samples unique to this study, whereas others 

originate from GenBank. Numbers at nodes represent Bayesian posterior probabilities of node support. 

Vertical bars indicate the following families: Ac, Acanthogorgiidae; Go, Gorgoniidae; St, 

Stenogorgiinae; Pl, Plexauridae; Ch, Chrysogorgiidae; Pr, Primnoidae; Is, Isididae; Co, Coralliidae.) 

Six octocoral samples were successfully sequenced at the ND2 gene region. Although 

fewer ND2 gene region sequences were available in GenBank relative to the msh1 gene region, 

representatives from each of the three sub-orders mentioned above were included. As with the 

analysis of the msh1 gene region, the three sub-orders fell into separate, well-supported clades 

(fig. 6.4). Similar to the msh1 results, Corallium medea clustered with C. ducale. The two 

Corallium sequences differed by 3.2 percent, whereas other sequences discussed below had 

closest matches that differed by less than 1 percent. Iridogorgia pourtalesii and another 

Iridogorgia sequence from GenBank fell within a clade containing members of the 

Chrysogorgiidae. Isidella sp. from AC645 clustered with a congener from GenBank and formed 

a well-supported clade with Lepidisis, also an isidid. Acanthogorgia armata from the MC462 

clustered with an Acanthogorgia species, but Acanthogorgia angustiflora fell outside of this 

clade, as it did in the analysis of McFadden and others (2006). The Stenogorgiinae sample from 

MC462 clustered with Paramuricea multispina, and these sequences varied little (0.22 percent 

sequence divergence). 
82
83

Figure 6.4. Phylogenetic hypothesis for octocorals based upon Bayesian analysis of mitochondrial 

ND2 sequences. (Species names in bold represent samples unique to this study, whereas others 

originate from GenBank. Numbers at nodes represent Bayesian posterior probabilities of node support. 

Vertical bars indicate the following families: Ac, Acanthogorgiidae; St, Stenogorgiinae; Ch, 

Chrysogorgiidae; Pr, Primnoidae; Is, Isididae; Co, Coralliidae.) 

6.4 Discussion

The deep sea has long been looked to for important clues to anthozoan evolution (Lindler 

and others, 2008; Kitahara and others, 2010a). Collections made as part of this project add to our 

knowledge of diversity of corals in the deep GOM and confirm the presence of deep corals in 

proximity to chemosynthetic sites. In many cases, the scleractinian and octocoral species 

collected were attached to exposed authigenic carbonates, concordant with the idea that such 

carbonates provide a direct link between cold seeps and coral communities (Fisher and others, 

2007; Cordes and others, 2009). 

Our analysis of the “robust” scleractinian corals included species belonging to families 

that typically do not form monophyletic groups: the Oculinidae and the Caryophylliidae 

(Romano and Cairns, 2000; Le Goff-Vitry and others, 2004; Kitahara and others, 2010a; b). 

Confirming previous phylogenetic analyses (Romano and Cairns, 2000; Le Goff-Vitry and 

others, 2004; Kitahara and others, 2010a; b), the Caryophyllidae appears to be an unnatural 

grouping given the scattered placement of species, even among the “robust” corals. However, 

results of phylogenetic analyses using different mitochondrial gene regions and different taxa 

sets support consistent grouping of Caryophyllia and L. pertusa, and several other species. 

Similar to findings of Kitahara and others (2010b), all Caryophyllia species appeared 

monophyletic, but this grouping was not exclusive, as Lophelia pertusa, Desmophyllum 
84

dianthus, Cyathoceras squiresi, and Dasmosmilia lymani were included in this clade as well. 

Although members of this clade occur in both Atlantic and Pacific oceans, these taxa appear 

closely related according to the 16S phylogeny. As has been noted previously in the literature 

(for example, Shearer and others, 2002), scleractinian mitochondrial DNA evolves slowly. 

Therefore, the application of additional polymorphic markers is necessary for a better 

understanding of the relationships among the genera and species within this diverse clade of 

deep-sea corals. 

Although similar types of species comprise chemosynthetic communities on the upper 

and lower continental slope in the GOM, little species overlap has been found (Cordes and 

others, 2007), with Madrepora oculata now being an exception to this observation. Similarly, it 

is intriguing that the two Caryophyllia polygona sequences representing samples from the upper 

continental slope and a deeper chemosynthetic site (MC-462) did not cluster together and were 

fairly divergent. This result was surprising, given the lack of species-level variability in coral 

mitochondrial DNA (Shearer and others, 2002), yet could be indicative of a cryptic species. 

However, Madrepora oculata from upper and lower continental slope sites differed little at the 

16S gene and clustered together. Based upon the depth range of L. pertusa (146-1,200 m, Cairns 

and others, 2009), its presence was anticipated at depths investigated in this study, yet it was not 

found. Whether a species changeover occurs between upper and lower continental slope habitats 

for scleractinian coral species requires further investigation. 

Octocorals from the GOM remain poorly known (Cairns and Bayer, 2009). The diverse 

octocoral collections made from five sites on the lower continental slope of the GOM add to our 

knowledge of this important faunal group. These collections contained at least 10 species from 3 

alcyonacean sub-orders. Three of these octocoral samples have not been collected in the GOM 
85

previously; Acanthogorgia armata, Iridogorgia pourtalesii, and Corallium medea (Cairns and 

Bayer, 2009). All of these species appeared closely related to congeners in our analysis, but the 

latter species, C. medea, was quite divergent from a congener C. ducale. Bamboo coral samples 

from the GOM were related to other corals in the family Isididae, and an Isidella sample from 

AC645 was the most genetically unique of the GOM bamboo corals. Molecular data confirmed 

the morphologically based taxonomic identifications and, as such, may be useful in guiding 

identification in the future when necessary. Although this survey increases our knowledge of 

octocoral biodiversity in the deep GOM, much taxonomic and systematic work remains before 

this GOM octocoral biodiversity inventory is complete. 

6.5 Acknowledgments

The author wishes to thank TDI-Brooks International, Inc., C. Fisher, H. Roberts, the 

Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE), and the 

National Oceanic and Atmospheric Administration (NOAA) for allowing her to participate in 

their DSV Alvin Chemo III research cruise. She also thanks E. Cordes and C. Kellogg for 

assistance in sample collection on the ROV Jason2 research cruise, Dr. Stephen Cairns for 

specimen identification, R. Johnson for laboratory work, M. Springmann for creating sampling 

map, as well as the crews of the R/V Atlantis, the R/V Ronald H. Brown, the DSV Alvin and 

ROV Jason2. 
86

7. COMMUNITY STRUCTURE OF MESOPELAGIC FISHES OVER THE 

SLOPE OF THE NORTH-CENTRAL GULF OF MEXICO

An expanded version of this paper was published as

Ross, S.W., Quattrini, A.M., Roa-Varón, A.Y., and McClain, J.P., 2010, Species composition and distributions of 

mesopelagic fishes over the slope of the north-central Gulf of Mexico, in Roberts, H.H., ed., Gulf of Mexico cold 

seeps: Deep-Sea Research II, v. 57, no. 21-23, p. 1926-1956. 

By Steve W. Ross, Andrea M. Quattrini, Adela Y. Roa-Varón, and Jennifer P. McClain

University of North Carolina Wilmington, Center for Marine Science, Wilmington, NC

7.1 Introduction

The Gulf of Mexico (GOM) is a large, semi-enclosed, warm-temperate to subtropical 

marine system. Its maximum depth is around 3,700 m, and its bathymetry is quite complicated, 

exhibiting numerous canyons, escarpments, and topographic features (Bryant and others, 1990; 

Roberts and Aharon, 1994). GOM circulation is dominated by the Loop Current (LC), which 

originates at the Yucatan Channel, flows northward into the GOM, and exits via the Straits of 

Florida (Oey and others, 2005). Large, warm-core LC eddies periodically detach from the LC 

and propagate northwest or west, impinging on the slope (for example, Smith, 1986; Oey and 

others, 2005). Numerous cold-core eddies often form adjacent to the LC and warm-core LC 

eddies (Oey and others, 2005). The cyclonic and anti-cyclonic eddies may produce conditions 

that move nutrient-rich deep waters into the upper water column as they move along or across 

the slope (Biggs and others, 2005; Jochens and DiMarco, 2008). In addition to the complexities 

of the LC and its eddy fields, wind-induced currents play a role over deep GOM waters (Carnes 

and others, 2008), and riverine discharge can bring lower salinities and nutrients to deep areas 

(Morey and others, 2003; Hamilton and Lee, 2005). Variability in water properties is negligible 
87

at depths greater than 800 m (Jochens and DiMarco, 2008). Thus, the complicated interactions 

between topography and currents probably impact species distributions and community 

composition of the slope mesopelagic fauna. In turn, the vertically migrating and possibly 

horizontally displaced mesopelagic fishes play a major role in moving energy through the water 

column, even from surface to bottom (Angel and Pugh, 2000; Gartner and others, 2008).

Since their recent discovery in the northern GOM (Paull and others, 1984; Kennicutt and 

others, 1985), the importance of cold seep (chemosynthetic) communities has been increasingly 

recognized. Benthic water chemistry at these sites is characterized by hydrocarbon (for example, 

methane) or sulfide seepage, presence of gas hydrates, and hypersaline water (Paull and others, 

1984; Sibuet and Olu, 1998; Van Dover, 2000). This unusual water chemistry and associated 

substrata, including carbonate buildups (Roberts and Aharon, 1994), support unique biota 

dominated by sulfide-oxidizing or methanotrophic endosymbiotic organisms (Hecker, 1985; 

MacDonald and others, 1990). Various studies have concentrated on the chemosynthetic and 

associated seep or vent fauna (typically siboglinid tubeworms, mytilidid and vesicomyid 

bivalves, and hosionid polychaetes) (for example, Van Dover, 2000); however, data on the 

larger, surrounding fauna, especially the midwater fauna that occur over these areas, are usually 

lacking. Herring (1998; 2006) listed some of the micronekton, especially young bresiliid and 

alvinocaridid shrimps, captured over hydrothermal vents. At least in the GOM, hydrocarbon 

(liquid and gaseous) seepage reaches to the surface (MacDonald and others, 2002) and thus, has 

an opportunity to impact midwater fauna. Whether such deep benthic seeps or vents influence 

fishes or other fauna that occur above them is unknown. 

Hydrocarbon seeps often co-occur with cold-water coral mounds, and the seeps have 

been implicated in coral mound formation (Hovland and others, 1998; Hovland and Risk, 2003). 
88

However, there appears to be little evidence that seeps cause coral mound formation or attract L. 

pertusa (Duineveld and others, 2004; Williams and others, 2006). Nevertheless, there is usually 

massive carbonate deposition in cold-seep areas (Aharon, 1994) that, along with corals, results in 

two different types of carbonate substrata from different processes (Roberts and Aharon, 1994). 

Both habitats influence local communities by providing physical structure and trophic inputs. 

Cold-water corals are widely distributed on a variety of hard substrata in the GOM but are only 

densely developed at a few sites (Brooke and Schroeder, 2007). 

Considering the size and importance of the GOM, research on the overall midwater fauna 

has been relatively restricted. The most expansive survey of GOM midwater fishes resulted 

from 35 stations (R/V Alaminos, 1965-1973), most over water depths >1,500 m, sampled from 

the surface to depth with nonclosing nets (Murdy and others, 1983). Murdy and others (1983) 

indicated that relatively few fish taxa dominated the GOM midwater fauna; however, one of their 

most abundant taxa (Cyclothone spp.) was not identified to species level. Bright and Pequegnat 

(1969) reviewed the Sternoptychidae from a portion of the Alaminos stations (see Murdy and 

others, 1983) and reported that the family was concentrated between 250 and 1,500 m. Backus 

and others (1970; 1977) did not provide explicit data for the GOM stations (all with nonclosing 

nets) used (along with other Atlantic data) to characterize Atlantic basin mesopelagic fish 

distribution patterns and myctophid zoogeography, respectively. Bangma and Haedrich (2008) 

reanalyzed 27 GOM stations (1961-1969) from the same archive used by Backus and others 

(1970; 1977), concluding that the GOM mesopelagic fish community contained more species 

than neighboring regions and defined a unique ecotone. Neither Murdy and others (1983), 

Backus and others (1970; 1977), nor Bangma and Haedrich (2008) presented diel or vertical 

distribution data for the GOM mesopelagic fishes. Most GOM studies on midwater fishes were 
89

concentrated in the eastern Gulf of Mexico, especially around one station (off west-central 

Florida), and resulted in treatments of selected fish taxa (for example, gonostomatids: Lancraft 

and others, 1988; myctophids: Gartner and others, 1987; Hopkins and Baird, 1985a; 

sternoptychids: Hopkins and Baird, 1985b; stomiids: Sutton and Hopkins, 1996a). These studies 

mostly relied upon opening-closing Tucker trawls similar to the net used in our study, which 

allowed analyses of vertical distributions. 

Most previous research on seep and deep-coral sites in the GOM was focused in depths 

<1,000 m. The first sampling of GOM chemosynthetic communities in waters >1,000 m 

revealed that the benthic invertebrate fauna differed from that of the shallower Louisiana upper 

slope (Cordes and others, 2007). No such depth-related comparisons are available for the overall 

GOM midwater fish fauna, and the only regional comparative treatment (Bangma and Haedrich, 

2008) did not provide specific data on species composition or distributions. In collaboration 

with ongoing benthic studies (see Roberts and others, 2007a), we sampled the midwater fauna 

over three cold-seep habitats >1,000 m and a comparative area over a cold-water coral bank 

(<1,000 m) in the north-central GOM. Our goal was to intensively sample a few widely 

separated sites, covering most of the water column at each site over the 24-hour (h) period. Our 

objectives for this project were to (1) characterize the vertical distributions of the mesopelagic 

fishes, (2) describe diel migration patterns of the fishes, (3) describe size composition of the 

midwater fish fauna, and (4) compare ichthyofaunal composition and behavior among the three 

offshore, deeper sites and the inshore (coral bank) study site. 

7.2 Methods

The study areas were over three lower slope cold-seep sites and one upper slope deep-sea 

coral site in the north-central to western GOM (fig. 7.1). As part of a larger multidisciplinary 
90

project, these sites were also visited in companion study cruises and were sampled with a variety 

of methods (Roberts and others, 2007a; see other chapters in this report). Sampling for this study 

was accomplished August 9-29, 2007, using the R/V Cape Hatteras (Duke-UNC Oceanographic 

Consortium). New moon occurred on August 12, and full moon occurred on August 28. 
91

Figure 7.1. Study area locations in the north-central Gulf of Mexico sampled August 9-29, 2007. 

Three sites (AC601, GC852, and AT340) were over cold-seep habitats, and VK826 was over a coralcarbonate and seep habitat. Vector lines represent Tucker trawl tows and boxes are conductivity, 

temperature, and depth profiler (CTD) stations. 

7.2.1 Study Areas

The three offshore seep sites were mapped, named, and described by Roberts and others 

(2007b). The easternmost study area in Atwater Valley Lease Block 340 (AT340) contained 

several mounds on a topographic high, and we sampled here over bottom depths of 2,001 to 

2,397 m. The bottom in this area contained authigenic carbonate substrata, soft sediments, a 

brine seep, and chemosynthetic communities (Roberts and others, 2007b). The dominant bottom 

feature of the central study site (278 km west of AT340) in Green Canyon Lease Block 852 

(GC852) was a north-south oriented ridge about 2 km long whose crest contained carbonate hard 

substrata, exhibited oil seepage, and was colonized by corals and chemosynthetic communities 

(Roberts and others, 2007b). The bottom around this ridge was composed of dense muddy 

sediments. Our samples at GC852 ranged over bottom depths of 1,301 to 1,785 m. The 

westernmost seep study area (328 km west of GC852) was located in Alaminos Canyon Lease 

Block 601 (AC601) and exhibited relatively low topography compared with the above sites. The 

bottom was characterized by a large brine lake, carbonate hard substrata, and chemosynthetic 

communities (Roberts and others, 2007b). This site had high methane concentrations in the 

water column. Our few samples in this area were over bottom depths of 2,306-2,523 m. 

The inshore study area was over a well known deep-sea coral site named Vioska Knoll 

826 (VK826, 156 km north of AT340). This site has two mound areas and represents the best 

developed Lophelia pertusa community in the GOM (Brooke and Schroeder, 2007). The bottom 
92

was characterized by carbonate blocks, extensive scleractinian and antipatharian corals, 

hydrocarbon seeps, and chemosynthetic communities surrounded by soft substrata. Our 

sampling was conducted over bottom depths of 448 to 645 m. 

During the study period the LC and associated rings may have impacted the midwater 

region of only one (AT340) of the four sampling sites (fig. 7.2). The Naval Research Laboratory 

Layered Ocean Model showed the LC extending to ~ 175 km south of AT340 and a large (~200 

km diameter), warm-core LC ring to the west of AT340 that was present during the entire 

sampling period. In the beginning of the sampling period, the eastern edge of the LC ring 

overlaid AT340; the ring then moved west (up to 20 km) from AT340, but later reattached to the 

LC on August 23, 2008, as the LC extended ~100 km northward into the GOM. AT340 was 

between the edge of this LC ring and a cold core ring to the east during the time this site was 

sampled (August 20-25). Cyclonic cold-core eddies (~50-150 km diameter) present during this 

period were usually distant (~20 –100 km) from our sampling sites. 
93

Figure 7.2. Naval Research Lab Layered Ocean Model (high resolution) assimilating Sea Surface 

Height (SSH) for four dates during our study period. The anomaly SSH satellite maps show the 

difference in measured sea height from the calculated, mean sea level. A +17 cm SSH contour 

generally tracks the loop current (LC) and loop current rings. Reds and yellows represent higher SSH 

and warmer waters of the LC and LC eddies. Blue to purple colors are negative SSH anomalies 

representing cold-core cyclonic eddies. 

Periodically, one (AC601) to seven (GC852) conductivity, temperature, and depth (CTD) 

(SeaBird 911plus) casts were made in each study area to record profiles of temperature (oC), 

salinity, dissolved oxygen (ml/L), and fluorescence (μg/L) through the water column (fig. 7.3). 

Fluorescence data exhibited typical similar patterns at all sites, with peak fluorescence levels in 
94

the upper 120 m range. Higher fluorescence levels (up to 2.5 μg/L ) in shallower waters (~35-65 

m) were exhibited at the inshore VK826 site compared to the three offshore sites (up to 1.2 μg/L, 

~80-120 m), suggesting higher primary productivity likely related to increased nutrient input 

from Mississippi River outflow. The AT340 site appeared most different in water column 

profiles compared with the other sites, perhaps due to influence of a nearby warm-core LC ring 

(fig. 7.2). While all sites exhibited the high salinity Subtropical Underwater signature (Jochens 

and DiMarco, 2008) in the upper 200 m (fig. 7.3), this indicator of LC water was strongest and 

occurred deeper at AT340. The oxygen minimum layer reached a similar minimum value at all 

sites; however, it was deeper (~160-720 m) and more variable at AT340, compared with AC601 

(~100-600 m), GC852 (~120-680 m), and VK826 (~80-640 m). Warm water also persisted 

deeper at AT340, with a temperature of ~20o C at 200 m, versus ~13-16o C at 200 m at the other 

sites (fig. 7.3). 
95
96

Figure 7.3. Conductivity, temperature, depth (CTD) (SeaBird 911plus) casts at the four Gulf of Mexico 

study sites, illustrating dissolved oxygen (milliliters per liter), fluorescence, water temperature (degrees 

Celsius), and salinity profiles (practical salinity units). 

7.2.2 Tucker trawl

Discrete depth Tucker trawling was conducted from the surface to 1,377 m. A plankton 

net (0.5 m diameter, 335 μm mesh) was suspended in the center mouth opening of the Tucker 

trawl (TT, 2 x 2 m, 1.59 mm mesh), providing two separate samples per deployment. Catches of 

juvenile and adult fishes from both of these nets were combined to give one sample per tow. The 

TT was deployed in an open position (fig. 7.4). Because of the rapid lowering, steep wire angle, 

and minimal forward movement, we assumed there was little fishing as the net was deployed. 

When it reached the target depth, it was towed for 30 min at about 2 km (3.71 km/h) ground 

speed, usually against the current. A weighted messenger was then sent down the ship’s wire to 

trigger the net closed, after which it was retrieved. This was repeated as many times as possible 

throughout the day and night to cover most of the water column during the time the ship 

occupied the sampling area. A temperature-depth recorder (TDR, SeaBird SBE39) was attached 

to the upper net bar to record time, depth, and temperature every 5 seconds (s) during each tow. 

Actual fishing depth was determined after each trawl from the TDR data and was used to adjust 

fishing methods to achieve desired sampling depths. 
97

Figure 7.4. Tucker trawl being deployed over the stern of the R/V Cape Hatteras on August 13, 2007.

All fishes were fixed in 10-percent formalin seawater solution, and after the cruise were 

transferred to 50-percent isopropanol. Juvenile and adult specimens were identified to the lowest 

possible taxa and were measured to the nearest millimeter standard length (SL). Species 

captured (for example, monacanthids, carangids, exocoetids) that were exclusive to surface 

waters were eliminated from analyses. 
98

7.2.3 Data Analysis

Data were analyzed to examine differences in species composition and distribution 

among sites, depths, and time of day. Time of day was divided into four categories: day (0730 to 

1830 h CDT), night (2030 to 0530 h CDT), dawn (0530 to 0730 h CDT, 1 h on either side of 

average sunrise) and dusk (1830 to 2030 h CDT, 1 h on either side of average sunset). Mean 

fished depths per TT tow were calculated by averaging all depths recorded by the TDR from tow 

start to end time, and these were used in depth analyses and for depth ranges of each species. 

Samples from TTs which failed to close properly were excluded from most statistical analyses 

but were included in the overall species list and the relative abundance table. Because only a few 

night samples were taken at AC601, this site was excluded from univariate statistical analyses. 

Multivariate analyses were used to examine differences in mesopelagic fish assemblages 

throughout the study area. All analyses were conducted in PRIMER 6.1 based on Clarke and 

Warwick (2001) and Clarke and Gorley (2006). Species’ abundances were standardized per 

sample by dividing the number of individuals per species by the total number of fishes per 

sample. Next, standardized abundances were fourth-root transformed to down weight the 

common species relative to the rare species. Third, similarities between samples were calculated 

using a Bray-Curtis similarity coefficient. Hierarchical clustering with group average linking 

and nonmetric multidimensional scaling (MDS) analyses were then performed on the resulting 

Bray-Curtis similarity matrix; these analyses were performed on all samples combined (115 

stations, 117 species) and then only for samples from each site (GC852=50 stations, 91 species; 

AT340=35 stations, 71 species; VK826=25 stations, 51 species). A one-way analysis of 

similarities (ANOSIM) was used to test if fish assemblages were significantly different (R=0 

when groups are similar; R=1 when groups are different, Clarke and Warwick, 2001) among the 
99

study sites. Similarity profile (SIMPROF) tests run during the hierarchical clustering analyses 

determined if there were significant groupings among the samples in each dendrogram, allowing 

us to determine patterns in mesopelagic fish assemblages among depths, time of day, and sites 

without assigning a priori factors to the dataset. Samples on the MDS plots were then coded for 

their respective SIMPROF groups assigned by PRIMER. Samples on each dendrogram were 

also labeled with SIMPROF codes and embedded within the respective MDS plot; the 

dendrograms were configured to save space by collapsing higher order clusters that were not 

significant into the level at which they were significant. In addition, mean depths of each sample 

were superimposed as bubbles onto the original MDS plots. If significant differences were 

found using ANOSIM or SIMPROF, the similarity percentages routine (SIMPER) was used to 

determine which species contributed to assemblage dissimilarities. SIMPER determines the 

contribution of particular species to the average dissimilarities among groups and to the average 

similarities of samples within each group. Because mesopelagic fishes often move vertically 

during dawn and dusk, including these data in the ANOSIM and SIMPROF analyses may 

obscure patterns. Thus, we omitted twilight stations (n=35) from these analyses. 

Species richness and relative abundances were examined among sites. Species 

accumulation curves illustrated how thoroughly the mesopelagic fish fauna was sampled at each 

site and were used to compare species richness among sites. Curves were calculated with species 

collected in discrete depth TTs using the Colwell and others (2004) analytical method in 

EstimateS (ver. 8.0). Analysis of covariance (ANCOVA), followed by a Tukey post-hoc 

multiple comparison test (SPSS ver. 17) on log transformed species richness, was used to 

determine whether species accumulations were significantly different between GC852, AT340 

and VK826. Relative abundances were calculated for most taxa (excluding genera groupings of 
100

multiple species) collected at all sites (percent total catch per taxon) and at each site (percent 

total catch of each taxon per site). Frequencies of occurrence were calculated for each taxon 

collected at all sites (number of samples in which species occurred / total number of samples) 

and at each site (number of samples in which species occurred per site / total number of samples 

per site). Depth and temporal distributions of the dominant species (n = 11 species, bold in table 

7.1) collected at GC852, AT340, and VK826 were examined in further detail. 
101

Table 7.1. Relative abundance of species comprising ~90 percent of total catch at each site. 

[Top 11 species in bold. Species are listed in order of overall percent relative abundance. Numbers in parentheses 

are frequencies of occurrence. n = number of stations, * = species presence <0.8 percent of total catch per site] 

AC601 GC852 AT340 VK826 Total

Species n=5 n=69 n=49 n=36 n=159

Notolychnus valdiviae * 20.0 (0.6) 11.5 (0.6) 5.0 (0.3) 15.4 (0.5)

Cyclothone pallida 18.2 (0.2) 16.1 (0.6) 6.0 (0.3) * 11.5 (0.3)

Cyclothone pseudopallida 10.0 (0.2) 13.5 (0.6) 5.5 (0.3) 3.0 (0.2) 10.1 (0.4)

Cyclothone braueri 1.2 (0.4) 11.0 (0.5) 8.3 (0.4) 9.9 (0.3) 10.0 (0.4)

Cyclothone alba 1.2 (0.4) 10.7 (0.5) 6.2 (0.3) 12.4 (0.4) 9.6 (0.4)

Valenciennellus 

tripunctulatus 15.3 (0.6) 1.9 (0.4) 7.0 (0.6) 17.0 (0.5) 5.4 (0.5)

Vinciguerria poweriae 1.2 (0.4) 5.6 (0.5) 3.7 (0.5) 3.6 (0.4) 4.8 (0.5)

Lepidophanes guentheri 8.8 (0.4) 1.0 (0.4) 12.1 (0.7) * 3.9 (0.4)

Benthosema suborbitale 9.4 (0.6) 1.7 (0.4) 7.6 (0.7) 2.6 (0.3) 3.5 (0.5)

Cyclothone acclinidens * 3.3 (0.4) 0.8 (0.1) 2.2 (0.2)

Hygophum benoiti 3.5 (0.2) 1.5 (0.2) 1.8 (0.4) 3.8 (0.4) 1.9 (0.3)

Diaphus dumerilii 1.8 (0.2) * * 11.5 (0.6) 1.7 (0.2)

Myctophum affine * 1.3 (0.4) * 5.7 (0.4) 1.6 (0.3)

Pollichthys mauli * 3.6 (0.4) 4.3 (0.3) 1.5 (0.2)

Gonostoma elongatum * 3.0 (0.5) * 1.3 (0.3)

Ceratoscopelus warmingii 4.1 (0.4) * 2.5 (0.5) 1.2 (0.3)

Chauliodus sloani 1.2 (0.2) 1.1 (0.3) * 1.2 (0.3) 1.0 (0.3)

Lampanyctus alatus 3.5 (0.6) 0.9 (0.3) 1.5 (0.3) 1.0 (0.3)

Vinciguerria nimbaria * * 1.2 (0.2) 1.8 (0.2) 0.9 (0.2)

Hygophum taaningi * * 2.0 (0.4) 2.1 (0.3) 0.8 (0.2)

Argyropelecus aculeatus 1.8 (0.4) * 0.9 (0.2) 1.5 (0.3) 0.8 (0.2)

Diaphus mollis * * 0.8 (0.3) 1.3 (0.3) 0.6 (0.2)

Argyropelecus hemigymnus 1.2 (0.2) * 0.8 (0.2) * 0.6 (0.2)

Diaphus splendidus 2.2 (0.3) * 0.6 (0.1)

Bregmaceros atlanticus * 0.9 (0.2) 1.4 (0.2) 0.5 (0.2)

Vinciguerria attenuata 1.8 (0.2) * * * 0.5 (0.2)

Melamphaes simus 4.1 (0.6) * * * 0.4 (0.2)

Diogenichthys atlanticus 4.1 (0.2) * * 0.2 (0.1)

Synagrops spinosus * 0.8 (0.1) 0.2 (0.1)

Bathophilus pawneei * 1.0 (0.3) 0.1 (0.1)

Diaphus perspicillatus 0.8 (0.1) 0.1 (0.03)
102

7.3 Results

The 159 Tucker trawl stations (table 7.2, fig. 7.1) yielded 9,802 individuals, representing at least 

126 species (30 families) of juvenile and adult midwater fishes (table 7.3). In terms of species richness, 

the collections at all sites were dominated by Myctophidae (lanternfishes, 38 species), Stomiidae 

(dragonfishes, 17 species), Gonostomatidae (lightfishes, 12 species), and Sternoptychidae 

(hatchetfishes, 10 species) (table 7.3). The Gonostomatidae dominated in overall relative abundance (56 

percent of the total catch), followed by the Myctophidae (28 percent), Phosichthyidae (lightfishes, 6 

percent), and Sternoptychidae (6 percent), all four families accounting for about 96 percent of the 

individuals collected. 

One species, Sphyraenops bairdianus, a deepwater cardinalfish, Epigonidae (3 from VK826), 

appears to be a new record for the Gulf of Mexico. Two forms of Cyclothone, sp. 1 and sp. 2, did not 

match known species descriptions. Additional investigation may prove these to be undescribed species. 

Current data on the family Howellidae did not allow a generic or species level classification, and it is 

possible that we collected more than one species. One species, Stemonosudis bullisi, a barracudina, 

Paralepididae, considered to be endemic to the GOM, was collected at VK826 (table 7.3). 
Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (August 9-29, 2007).

[D, day (0630 to 1920 h CDT); N, night (1920 to 0630 h CDT); N/D, samples covering both day and night; CTD, Seabird SBE 911+; TT, Tucker trawl; m, 

meters; *, net did not close; ^, net fished on bottom for portion of tow; NR, not recorded]

Min Max 

Start Start Sample Sample Station # Gear Date Location Time End Latitude End Longitude Latitude Longitude Depth Depth 

(m) (m)

CH-2007-001 CTD 9-Aug-07 GC852 N 27° 06.505 91° 09.964 27° 06.659 91° 09.893 Surface 1,406

CH-2007-002 TT 9-Aug-07 GC852 N 27° 07.200 91° 09.769 27° 06.278 91° 09.945 561 705

CH-2007-007* TT 10-Aug-07 GC852 N 27° 07.318 91° 09.736 27° 08.244 91° 09.480 Surface 296

CH-2007-008 TT 10-Aug-07 GC852 N 27° 06.984 91° 09.844 27° 06.034 91° 10.025 272 39 8

CH-2007-010 CTD 10-Aug-07 GC852 N/D 27° 07.023 91° 09.863 27° 06.802 91° 09.058 Surface 1,551

CH-2007-017 TT 10-Aug-07 GC852 N 27° 07.407 91° 09.878 27° 06.436 91° 09.948 594 655

CH-2007-018* TT 10-Aug-07 GC852 N 27° 06.354 91° 09.929 27° 07.386 91° 09.858 Surface 486

CH-2007-019 TT 10-Aug-07 GC852 N 27° 07.823 91° 09.780 27° 06.975 91° 09.917 392 426

CH-2007-020 TT 11-Aug-07 GC852 N 27° 05.979 91° 09.940 27° 07.053 91° 09.864 194 210

CH-2007-021 TT 11-Aug-07 GC852 N 27° 07.074 91° 09.893 27° 06.278 91° 09.982 232 292

CH-2007-022 TT 11-Aug-07 GC852 N 27° 06.550 91° 09.957 27° 07.604 91° 09.886 316 441

CH-2007-023* TT 11-Aug-07 GC852 N 27° 07.715 91° 09.851 27° 06.680 91° 09.963 Surface 712

CH-2007-025 CTD 11-Aug-07 GC852 N/D 27° 07.080 91° 09.868 27° 06.878 91° 10.230 Surface 1,466

CH-2007-029 TT 11-Aug-07 GC852 D 27° 10.481 91° 09.684 27° 09.381 91° 09.547 630 836

CH-2007-030 TT 11-Aug-07 GC852 N 27° 07.591 91° 09.272 27° 06.815 91° 09.939 373 403

CH-2007-031* TT 11-Aug-07 GC852 N 27° 06.280 91° 10.229 27° 07.036 91° 09.676 Surface 382

CH-2007-032 TT 11-Aug-07 GC852 N 27° 07.289 91° 09.857 27° 06.706 91° 10.685 468 558

CH-2007-033 TT 12-Aug-07 GC852 N 27° 06.204 91° 10.505 27° 07.071 91° 09.742 237 304

CH-2007-035 TT 12-Aug-07 GC852 N 27° 07.282 91° 09.630 27° 06.444 91° 10.342 146 181

CH-2007-036 TT 12-Aug-07 GC852 N 27° 06.467 91° 10.403 27° 07.270 91° 09.604 144 174

CH-2007-037 TT 12-Aug-07 GC852 N 27° 07.284 91° 09.637 27° 06.455 91° 10.320 172 212

CH-2007-038 TT 12-Aug-07 GC852 N 27° 06.779 91° 10.077 27° 08.391 91° 08.713 455 467

CH-2007-044 TT 12-Aug-07 GC852 D 27° 12.181 91° 09.454 27° 10.146 91° 09.474 745 895

CH-2007-045 TT 12-Aug-07 GC852 N 27° 08.756 91° 09.574 27° 07.816 91° 09.565 538 592

103
104

Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (9-29 August 2007).—Continued

[D, day (0630 to 1920 h CDT); N, night (1920 to 0630 h CDT); N/D, samples covering both day and night; CTD, Seabird SBE 911+; TT, Tucker trawl; m, 

meters; *, net did not close; ^, net fished on bottom for portion of tow; NR, not recorded] 

Min Max 

Start Start Sample Sample Station # Gear Date Location Time End Latitude End Longitude Latitude Longitude Depth Depth 

(m) (m)

CH-2007-046* TT 12-Aug-07 GC852 N 27° 06.034 91° 09.704 27° 05.290 91° 09.704 Surface 325

CH-2007-047 TT 12-Aug-07 GC852 N 27° 05.665 91° 09.647 27° 06.713 91° 09.744 245 361

CH-2007-048 TT 12-Aug-07 GC852 N 27° 07.203 91° 09.795 27° 06.338 91° 09.781 170 210

CH-2007-049 TT 13-Aug-07 GC852 N 27° 06.454 91° 09.621 27° 07.493 91° 09.626 425 537

CH-2007-050 TT 13-Aug-07 GC852 N 27° 07.626 91° 09.789 27° 06.726 91° 09.752 626 757

CH-2007-053 TT 13-Aug-07 GC852 N 27° 06.415 91° 09.700 27° 05.454 91° 09.695 466 539

CH-2007-054 TT 13-Aug-07 GC852 N 27° 08.270 91° 09.827 27° 07.304 91° 09.805 236 248

CH-2007-056 CTD 13-Aug-07 GC852 D 27° 06.697 91° 09.993 27° 06.559 91° 10.018 Surface 1,438

CH-2007-063 TT 13-Aug-07 GC852 N 27° 07.349 91° 10.193 27° 06.229 91° 10.163 388 447

CH-2007-064 TT 13-Aug-07 GC852 N 27° 05.002 91° 10.098 27° 06.993 91° 10.152 187 224

CH-2007-065 TT 13-Aug-07 GC852 N 27° 07.318 91° 10.205 27° 06.339 91° 10.338 146 178

CH-2007-066 TT 13-Aug-07 GC852 N 27° 06.364 91° 10.472 27° 07.361 91° 10.404 591 732

CH-2007-068 TT 14-Aug-07 GC852 N 27° 07.655 91° 10.406 27° 06.498 91° 10.396 608 739

CH-2007-070 TT 14-Aug-07 GC852 N 27° 06.208 91° 10.393 27° 07.194 91° 10.422 472 531

CH-2007-071 TT 14-Aug-07 GC852 N 27° 07.462 91° 10.356 27° 06.522 91° 10.354 187 267

CH-2007-072 TT 14-Aug-07 GC852 N 27° 06.686 91° 10.480 27° 07.828 91° 10.481 334 460

CH-2007-073 CTD 14-Aug-07 GC852 N/D 27° 08.739 91° 10.685 27° 09.180 91° 11.330 Surface 1,711

CH-2007-080 TT 14-Aug-07 GC852 D 27° 10.379 91° 09.659 27° 09.372 91° 09.736 847 1,027

CH-2007-082 TT 14-Aug-07 GC852 D 27° 07.841 91° 09.948 27° 06.897 91° 09.925 191 232

CH-2007-083 TT 14-Aug-07 GC852 D 27° 05.076 91° 09.857 27° 04.136 91° 09.852 737 842

CH-2007-084 TT 14-Aug-07 GC852 N 27° 05.194 91° 09.691 27° 06.258 91° 09.810 432 565

CH-2007-085 TT 14-Aug-07 GC852 N 27° 07.000 91° 09.830 27° 06.055 91° 09.802 332 391

CH-2007-086 TT 14-Aug-07 GC852 N 27° 06.133 91° 09.832 27° 07.162 91° 09.915 689 972

CH-2007-087 TT 15-Aug-07 GC852 N 27° 07.043 91° 09.791 27° 06.157 91° 09.875 948 1,017

CH-2007-088 TT 15-Aug-07 GC852 N 27° 05.024 91° 09.692 27° 06.632 91° 09.703 501 572
105

Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (9-29 August 2007).—Continued

[D, day (0630 to 1920 h CDT); N, night (1920 to 0630 h CDT); N/D, samples covering both day and night; CTD, Seabird SBE 911+; TT, Tucker trawl; m, 

meters; *, net did not close; ^, net fished on bottom for portion of tow; NR, not recorded] 

Min Max 

Start Start Sample Sample Station # Gear Date Location Time End Latitude End Longitude Latitude Longitude Depth Depth 

(m) (m)

CH-2007-089 TT 15-Aug-07 GC852 N 27° 07.452 91° 09.710 27° 06.456 91° 09.731 150 150

CH-2007-090 TT 15-Aug-07 GC852 N 27° 06.872 91° 10.013 27° 07.949 91° 10.191 412 472

CH-2007-091 CTD 15-Aug-07 GC852 D 27° 08.915 91° 10.371 27° 08.768 91° 09.104 Surface 1,793

CH-2007-092 TT 15-Aug-07 GC852 D 27° 08.468 91° 07.273 27° 07.702 91° 06.813 951 1,044

CH-2007-093 TT 15-Aug-07 GC852 D 27° 09.883 91° 09.198 27° 09.065 91° 08.610 790 1,035

CH-2007-094 TT 15-Aug-07 GC852 D 27° 09.020 91° 09.419 27° 08.421 91° 08.831 NR NR

CH-2007-095 TT 15-Aug-07 GC852 D 27° 08.001 91° 09.940 27° 07.224 91° 09.176 551 664

CH-2007-096* TT 15-Aug-07 GC852 D 27° 06.985 91° 10.006 27° 07.324 91° 09.216 Surface 569

CH-2007-097 TT 15-Aug-07 GC852 D 27° 06.474 91° 10.045 27° 06.090 91° 09.078 289 401

CH-2007-098 TT 15-Aug-07 GC852 N 27° 05.122 91° 10.161 27° 04.635 91° 09.361 693 756

CH-2007-099 TT 15-Aug-07 GC852 N 27° 06.869 91° 09.295 27° 04.437 91° 08.386 561 635

CH-2007-101 TT 16-Aug-07 GC852 D 27° 06.882 91° 09.207 27° 06.447 91° 08.140 443 569

CH-2007-102 CTD 16-Aug-07 GC852 D 27° 06.944 91° 09.769 27° 11.322 91° 14.384 S 1,554

CH-2007-103 TT 16-Aug-07 GC852 D 27° 07.981 91° 10.268 27° 07.663 91° 09.187 520 625

CH-2007-104 TT 16-Aug-07 GC852 D 27° 06.933 91° 10.182 27° 06.401 91° 09.166 NR NR

CH-2007-105 TT 16-Aug-07 GC852 D 27° 06.146 91° 10.299 27° 05.025 91° 10.148 886 1,016

CH-2007-106 TT 16-Aug-07 GC852 D 27° 05.257 91° 10.480 27° 06.145 91° 10.673 1,004 1,144

CH-2007-107 TT 16-Aug-07 GC852 D 27° 07.714 91° 10.575 27° 06.697 91° 10.493 291 319

CH-2007-108 TT 16-Aug-07 GC852 N 27° 05.657 91° 09.916 27° 04.715 91° 09.464 130 149

CH-2007-110 TT 16-Aug-07 GC852 N 27° 05.265 91° 09.515 27° 06.212 91° 09.680 446 532

CH-2007-111 TT 16-Aug-07 GC852 N 27° 07.135 91° 09.955 27° 06.190 91° 10.241 81 110

CH-2007-112 TT 16-Aug-07 GC852 N 27° 06.082 91° 10.482 27° 06.929 91° 10.661 136 145

CH-2007-113 TT 17-Aug-07 GC852 N 27° 06.958 91° 10.845 27° 06.001 91° 10.946 53 87

CH-2007-114 TT 17-Aug-07 GC852 N 27° 05.795 91° 10.799 27° 06.978 91° 10.690 49 58

CH-2007-115 TT 17-Aug-07 GC852 N 27° 07.113 91° 10.611 27° 06.010 91° 10.542 77 86
106

Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (9-29 August 2007).—Continued

[D, day (0630 to 1920 h CDT); N, night (1920 to 0630 h CDT); N/D, samples covering both day and night; CTD, Seabird SBE 911+; TT, Tucker trawl; m, 

meters; *, net did not close; ^, net fished on bottom for portion of tow; NR, not recorded] 

Min Max 

Start Start Sample Sample Station # Gear Date Location Time End Latitude End Longitude Latitude Longitude Depth Depth 

(m) (m)

CH-2007-116 TT 17-Aug-07 GC852 N 27° 05.701 91° 10.320 27° 07.004 91° 10.227 18 30

CH-2007-117 TT 17-Aug-07 GC852 N 27° 06.340 91° 10.268 27° 05.345 91° 10.336 516 611

CH-2007-118 TT 17-Aug-07 AC601 N 26° 23.314 94° 30.559 26° 22.580 94° 31.020 244 268

CH-2007-119 TT 18-Aug-07 AC601 N 26° 23.215 94° 30.841 26° 24.247 94° 30.814 165 178

CH-2007-122 TT 18-Aug-07 AC601 N 26° 23.450 94° 30.771 26° 22.905 94° 30.832 518 700

CH-2007-124 TT 18-Aug-07 AC601 N 26° 22.962 94° 30.903 26° 24.152 94° 31.038 311 372

CH-2007-126 TT 18-Aug-07 AC601 N 26° 24.786 94° 31.143 26° 23.872 94° 31.135 38 57

CH-2007-134 CTD 18-Aug-07 AC601 D 26° 22.185 94° 31.077 26° 21.821 94° 30.335 Surface 2,278

CH-2007-136 TT 20-Aug-07 AT340 N 27° 38.175 88° 21.014 27° 38.083 88° 21.956 317 465

CH-2007-137 TT 20-Aug-07 AT340 N 27° 38.258 88° 21.699 27° 38.066 88° 22.702 255 352

CH-2007-138 TT 20-Aug-07 AT340 N 27° 38.876 88° 21.910 27° 38.752 88° 22.889 206 228

CH-2007-139 TT 21-Aug-07 AT340 N 27° 38.685 88° 22.052 27° 38.593 88° 23.286 113 126

CH-2007-140* TT 21-Aug-07 AT340 N 27° 38.659 88° 22.195 27° 38.642 88° 23.122 Surface 425

CH-2007-141* TT 21-Aug-07 AT340 N 27° 38.733 88° 22.647 27° 38.862 88° 23.578 Surface 586

CH-2007-143 CTD 21-Aug-07 AT340 N/D 27° 39.122 88° 23.084 27° 38.277 88° 20.382 Surface 2,198

CH-2007-151 TT 21-Aug-07 AT340 N 27° 38.083 88° 21.521 27° 38.751 88° 21.994 169 301

CH-2007-152 TT 22-Aug-07 AT340 D 27° 38.319 88° 21.485 27° 38.875 88° 22.066 407 763

CH-2007-153 CTD 22-Aug-07 AT340 D 27° 38.663 88° 21.469 27° 37.855 88° 19.026 Surface 2,304

CH-2007-154 TT 22-Aug-07 AT340 D 27° 37.987 88° 21.708 27° 38.762 88° 22.018 481 666

CH-2007-156 TT 22-Aug-07 AT340 D 27° 38.326 88° 21.637 27° 38.811 88° 21.935 818 935

CH-2007-157 TT 22-Aug-07 AT340 D 27° 38.400 88° 21.294 27° 38.740 88° 21.934 938 1,059

CH-2007-159 TT 22-Aug-07 AT340 D 27° 38.516 88° 21.610 27° 38.970 88° 22.381 310 437

CH-2007-160* TT 22-Aug-07 AT340 N 27° 38.589 88° 21.721 27° 39.007 88° 22.591 Surface 627

CH-2007-161 TT 22-Aug-07 AT340 N 27° 38.343 88° 21.277 27° 38.667 88° 22.243 187 403

CH-2007-163 TT 22-Aug-07 AT340 N 27° 38.353 88° 21.046 27° 38.676 88° 21.893 135 301
107

Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (9-29 August 2007).—Continued

[D, day (0630 to 1920 h CDT); N, night (1920 to 0630 h CDT); N/D, samples covering both day and night; CTD, Seabird SBE 911+; TT, Tucker trawl; m, 

meters; *, net did not close; ^, net fished on bottom for portion of tow; NR, not recorded] 

Min Max 

Start Start Sample Sample Station # Gear Date Location Time End Latitude End Longitude Latitude Longitude Depth Depth 

(m) (m)

CH-2007-164* TT 22-Aug-07 AT340 N 27° 38.392 88° 21.217 27° 39.118 88° 22.124 Surface 421

CH-2007-165 TT 23-Aug-07 AT340 N 27° 38.166 88° 20.877 27° 38.715 88° 21.805 168 217

CH-2007-166 TT 23-Aug-07 AT340 N 27° 38.339 88° 21.034 27° 38.768 88° 21.906 131 220

CH-2007-168 TT 23-Aug-07 AT340 N 27° 38.544 88° 21.363 27° 38.880 88° 22.181 59 89

CH-2007-169 TT 23-Aug-07 AT340 N 27° 38.481 88° 21.438 27° 38.924 88° 22.252 152 212

CH-2007-171 TT 23-Aug-07 AT340 D 27° 39.344 88° 22.858 27° 39.795 88° 23.663 120 164

CH-2007-172 TT 23-Aug-07 AT340 D 27° 38.466 88° 21.212 27° 38.755 88° 21.748 279 494

CH-2007-173 TT 23-Aug-07 AT340 D 27° 39.085 88° 21.980 27° 39.430 88° 22.802 302 702

CH-2007-175 TT 23-Aug-07 AT340 D 27° 38.006 88° 20.645 27° 38.178 88° 21.475 359 827

CH-2007-176 TT 23-Aug-07 AT340 D 27° 38.657 88° 21.842 27° 38.890 88° 22.623 232 311

CH-2007-178 TT 23-Aug-07 AT340 D 27° 38.400 88° 21.216 27° 38.765 88° 22.082 297 391

CH-2007-180 TT 23-Aug-07 AT340 D 27° 39.436 88° 23.669 27° 39.813 88° 24.614 403 602

CH-2007-182 TT 23-Aug-07 AT340 D 27° 38.522 88° 21.466 27° 38.879 88° 22.379 533 892

CH-2007-183 TT 23-Aug-07 AT340 N 27° 38.343 88° 21.041 27° 38.728 88° 21.036 124 183

CH-2007-184 TT 23-Aug-07 AT340 N 27° 38.169 88° 20.947 27° 38.559 88° 21.804 473 959

CH-2007-186 TT 23-Aug-07 AT340 N 27° 38.280 88° 21.203 27° 38.819 88° 22.169 330 478

CH-2007-188 TT 24-Aug-07 AT340 N 27° 38.566 88° 21.511 27° 38.941 88° 22.385 275 300

CH-2007-189 TT 24-Aug-07 AT340 N 27° 38.460 88° 21.314 27° 38.848 88° 22.197 264 328

CH-2007-191 TT 24-Aug-07 AT340 N 27° 38.463 88° 21.357 27° 38.837 88° 22.285 251 297

CH-2007-192 TT 24-Aug-07 AT340 N 27° 38.832 88° 22.322 27° 39.206 88° 23.222 232 349

CH-2007-198 TT 24-Aug-07 AT340 N 27° 38.767 88° 21.397 27° 39.120 88° 22.339 277 344

CH-2007-199 TT 24-Aug-07 AT340 N 27° 38.718 88° 21.795 27° 39.237 88° 22.684 104 146

CH-2007-200 TT 24-Aug-07 AT340 N 27° 38.611 88° 21.584 27° 39.101 88° 22.504 465 750

CH-2007-202 TT 24-Aug-07 AT340 N 27° 38.640 88° 21.675 27° 39.095 88° 22.586 379 481
108

Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (9-29 August 2007).—Continued

[D, day (0630 to 1920 h CDT); N, night (1920 to 0630 h CDT); N/D, samples covering both day and night; CTD, Seabird SBE 911+; TT, Tucker trawl; m, 

meters; *, net did not close; ^, net fished on bottom for portion of tow; NR, not recorded] 

Min Max 

Start Start Sample Sample Station # Gear Date Location Time End Latitude End Longitude Latitude Longitude Depth Depth 

(m) (m)

CH-2007-204 TT 24-Aug-07 AT340 N 27° 38.644 88° 21.662 27° 39.110 88° 22.691 499 704

CH-2007-205 TT 24-Aug-07 AT340 N 27° 38.706 88° 21.715 27° 39.100 88° 22.662 367 467

CH-2007-210* TT 25-Aug-07 AT340 D 27° 38.651 88° 21.414 27° 38.828 88° 22.558 Surface 142

CH-2007-211 TT 25-Aug-07 AT340 D 27° 39.026 88° 24.074 27° 39.195 88° 25.116 743 1,025

CH-2007-212 CTD 25-Aug-07 AT340 D 27° 38.699 88° 22.354 27° 38.517 88° 20.747 S 2,212

CH-2007-213 TT 25-Aug-07 AT340 D 27° 38.782 88° 21.433 27° 38.881 88° 22.279 329 370

CH-2007-214 TT 25-Aug-07 AT340 N 27° 38.600 88° 21.459 27° 38.857 88° 22.587 290 360

CH-2007-216 TT 25-Aug-07 AT340 N 27° 38.573 88° 21.399 27° 38.848 88° 22.497 452 708

CH-2007-218 TT 25-Aug-07 AT340 N 27° 38.649 88° 21.746 27° 38.834 88° 22.774 540 605

CH-2007-219 TT 25-Aug-07 AT340 N 27° 38.777 88° 21.981 27° 39.923 88° 23.041 74 94

CH-2007-220 TT 25-Aug-07 AT340 N 27° 38.802 88° 22.198 27° 38.998 88° 23.552 1,019 1,377

CH-2007-222 CTD 26-Aug-07 VK826 D 29° 08.974 88° 01.244 29° 08.508 88° 01.634 Surface 631

CH-2007-223 TT 26-Aug-07 VK826 D 29° 10.204 88° 00.750 29° 11.049 88° 00.118 296 440

CH-2007-224* TT 26-Aug-07 VK826 D 29° 09.957 88° 01.033 29° 10.688 88° 00.197 Surface 446

CH-2007-225 TT 26-Aug-07 VK826 N 29° 10.140 88° 00.823 29° 10.843 88° 00.101 360 462

CH-2007-226^ TT 26-Aug-07 VK826 N 29° 09.703 88° 01.112 29° 10.621 88° 00.548 350 477

CH-2007-227 TT 26-Aug-07 VK826 N 29° 09.583 88° 01.141 29° 10.396 88° 00.700 295 364

CH-2007-228 TT 27-Aug-07 VK826 N 29° 09.557 88° 01.221 29° 10.393 88° 00.692 88 135

CH-2007-229 TT 27-Aug-07 VK826 N 29° 09.424 88° 01.405 29° 10.158 88° 00.528 200 278

CH-2007-230 TT 27-Aug-07 VK826 N 29° 10.025 88° 00.689 29° 09.383 88° 01.487 238 324

CH-2007-232 TT 27-Aug-07 VK826 N 29° 09.581 88° 01.224 29° 10.452 88° 00.548 310 419

CH-2007-233 TT 27-Aug-07 VK826 N 29° 10.613 88° 00.346 29° 10.027 88° 00.909 222 267

CH-2007-234 TT 27-Aug-07 VK826 N 29° 09.781 88° 01.025 29° 10.514 88° 00.440 121 139

CH-2007-246 CTD 27-Aug-07 VK826 D 29° 10.135 88° 00.879 29° 10.080 88° 00.863 Surface 494

CH-2007-249 TT 27-Aug-07 VK826 D 29° 09.532 88° 01.743 29° 08.554 88° 01.883 361 442
109

Table 7.2. Stations sampled at four sites (see fig. 7.1) in the Gulf of Mexico (9-29 August 2007).—Continued

[D, day (0630 to 1920 h CDT); N, night (1920 to 0630 h CDT); N/D, samples covering both day and night; CTD, Seabird SBE 911+; TT, Tucker trawl; m, 

meters; *, net did not close; ^, net fished on bottom for portion of tow; NR, not recorded] 

Min Max 

Start Start Sample Sample Station # Gear Date Location Time End Latitude End Longitude Latitude Longitude Depth Depth 

(m) (m)

CH-2007-250 TT 27-Aug-07 VK826 N 29° 08.738 88° 01.418 29° 09.589 88° 01.027 201 233

CH-2007-252 TT 27-Aug-07 VK826 N 29° 09.940 88° 01.004 29° 10.705 88° 00.452 116 156

CH-2007-253 TT 27-Aug-07 VK826 N 29° 10.321 88° 00.641 29° 09.399 88° 00.981 366 465

CH-2007-254 TT 27-Aug-07 VK826 N 29° 08.944 88° 01.243 29° 09.837 88° 00.928 222 239

CH-2007-256*^ TT 28-Aug-07 VK826 N 29° 09.769 88° 00.524 29° 08.884 88° 00.979 Surface 488

CH-2007-257 TT 28-Aug-07 VK826 N 29° 08.936 88° 00.968 29° 09.939 88° 00.433 269 361

CH-2007-259 TT 28-Aug-07 VK826 N 29° 10.075 88° 00.401 29° 09.280 88° 00.769 198 260

CH-2007-260 TT 28-Aug-07 VK826 N 29° 08.947 88° 00.949 29° 09.729 88° 00.502 139 166

CH-2007-262 TT 28-Aug-07 VK826 N 29° 10.048 88° 00.419 29° 09.152 88° 00.821 119 165

CH-2007-263 TT 28-Aug-07 VK826 N 29° 09.318 88° 00.754 29° 10.219 88° 00.266 306 332

CH-2007-264 TT 28-Aug-07 VK826 D 29° 10.480 88° 00.789 29° 10.008 88° 01.672 297 405

CH-2007-265 CTD 28-Aug-07 VK826 D 29° 09.430 88° 02.174 29° 09.340 88° 02.284 Surface 541

CH-2007-266 TT 28-Aug-07 VK826 D 29° 09.296 88° 01.252 29° 09.809 88° 00.348 359 442

CH-2007-267 TT 28-Aug-07 VK826 D 29° 09.623 88° 00.373 29° 09.095 88° 01.242 446 507

CH-2007-268 TT 28-Aug-07 VK826 D 29° 08.479 88° 02.019 29° 09.024 88° 01.021 369 534

CH-2007-276 TT 28-Aug-07 VK826 D 29° 10.164 88° 00.554 29° 10.283 87° 59.531 185 228

CH-2007-277 TT 28-Aug-07 VK826 N 29° 10.303 87° 59.495 29° 10.230 88° 00.712 151 203

CH-2007-278 TT 28-Aug-07 VK826 N 29° 09.857 88° 00.894 29° 09.160 88° 01.725 273 370

CH-2007-279 TT 28-Aug-07 VK826 N 29° 09.206 88° 02.009 29° 09.668 88° 01.113 221 287

CH-2007-281 TT 28-Aug-07 VK826 N 29° 09.890 88° 00.836 29° 09.266 88° 01.844 83 138

CH-2007-282 TT 28-Aug-07 VK826 N 29° 09.495 88° 01.692 29° 10.360 88° 01.012 301 370

CH-2007-286 TT 29-Aug-07 VK826 N 29° 09.268 88° 02.083 29° 10.060 88° 01.281 95 120

CH-2007-287 TT 29-Aug-07 VK826 N 29° 10.169 88° 01.191 29° 09.253 88° 02.043 342 516

CH-2007-289 TT 29-Aug-07 VK826 N 29° 09.181 88° 02.242 29° 09.884 88° 01.503 314 392

CH-2007-290 TT 29-Aug-07 VK826 N 29° 10.653 88° 00.560 29° 11.412 87° 59.879 26 47
110

Table 7.3. Total numbers and standard length ranges (millimeters in parentheses) of juvenile and adult fishes collected by Tucker trawl 

over three cold-seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (August 9-29, 2007).

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a, damaged specimens not measured; m, meters]

Species

Depth 

Range

(m)

AC601 GC852 AT340 VK826

N

n=5

D

n=17

N

n=52

D

n=16

N

n=33

D

n=8

N

n=28

Microstomatidae

 Dolicholagus longirostris

Gonostomatidae

113-1377 4 (26-50) 3 (22-23) 2 (29, 40)

 Bonapartia pedaliota

 Cyclothone acclinidens

 Cyclothone alba

 Cyclothone braueri

 Cyclothone obscura

 Cyclothone pallida

 Cyclothone pseudopallida

 Cyclothone sp. 1

 Cyclothone sp. 2

 Cyclothone spp.

 Gonostoma atlanticum

 Gonostoma elongatum

 Margrethia obtusirostra

Sternoptychidae

 Argyropelecus aculeatus

 Argyropelecus affinis

 Argyropelecus gigas

222-460

359-1144

150-1144

121-1144

1019-1377

150-1377

150-1377

369-935

443-836

131-1144

53-507

49-1377

144-239 

170-935

*

372-757

1 (21)

2 (26, 27)

2 (16.5, 24)

31 (14-49)

17 (20-36)

23

3 (13-30)

1 (40)

103 (14-52)

66 (13-27)

96 (12.5-27)

173 (15-50)

139 (12-43)

5 (15-18)

3 (19-32)

503 (12-42)

2 (28, 90)

1 (27)

1 (40)

47 (12-46)

426 (10-29)

409 (11-28)

564 (13-51)

48 (11-45)

5 (12-36)

1064 (12-35)

12 (21-27)

31 (21-180)

6 (16-28)

22 (15-45)

1 (27)

5 (17-78)

8 (31-34)

59 (13-27)

62 (12-26)

71 (12-50)

51 (15-40)

2 (15-17)

140 (12-

53)

1 (27)

4 (21-38)

6 (13-42)

1 (n/a)

3 (21-32)

52 (11-28)

100 (13-25)

9 (16-55)

46 (15-49)

40 (14-30)

156 (12-38)

3 (25-30)

54 (21-158)

3 (14-18)

12 (13-43)

1 (26)

58 (12-28)

47 (12-25)

20 (13-29)

6 (16-17)

51 (12-20)

1 (44)

3 (25-27)

6 (n/a)

3 (18-25)

67 (11-28)

53 (11-25)

2 (19)

10 (11-28)

37 (12-20)

1 (22)

4 (21-34)

1 (14)

9 (16-50)

2 (16, 17)
111

Table 7.3. Total numbers and standard length ranges (mm in parenthesis) of juvenile and adult fishes collected by Tucker trawl over 

three cold seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (9-29 Aug 2007). —Continued

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a, damaged specimens not measured; m, meters]

Species

Depth 

Range

(m)

AC601 GC852 AT340 VK826

N

n=5

D

n=17

N

n=52

D

n=16

N

n=33

D

n=8

N

n=28

 Argyropelecus spp.

 Maurolicus weitzmani

 Polyipnus clarus

 Polyipnus spp.

 Sternoptyx diaphana

 Sternoptyx pseudobscura

 Sternoptyx spp.

 Valenciennellus tripunctulatus

432-531

1019-1377

295-1144

329-1377

302-1027

737-1044

745-865

165-1035

1 (18)

26 (13-30)

1 (25)

10 (13-23)

9 (13-45)

3 (11)

13 (14-27)

4 (10-12)

1 (27)

1 (17)

5 (13-35)

1 (44)

72 (13-30)

1 (19)

2 (15)

1 (30)

19 (17-30)

1 (15)

1 (n/a)

1 (17)

117 (13-30)

1 (19)

29 (14-29)

3 (26-34)

142 (13-30)

 Undetermined

Phosichthyidae

 Ichthyococcus ovatus

 Pollichthys mauli

 Vinciguerria attenuata

 Vinciguerria nimbaria

 Vinciguerria poweriae

 Vinciguerria spp.

Stomiidae

187-267

306-625

59-739

165-625

49-666

49-1377

113-605

3 (14-18)

1 (16)

2 (18, 29)

2 (14, 15)

1 (16)

3 (14-22)

2 (18, 22)

21 (13-20)

1 (16)

3 (12-14)

3 (33-37)

18 (13-20)

26 (12-30)

237 (12-35)

3 (13)

1 (22)

19 (15-32)

4 (14-18)

13 (12-22)

10 (12-24)

1 (15)

51 (14-51)

4 (16-38)

11 (12-26)

62 (12-30)

8 (12-17)

1 (19)

2 (13, 25)

 9 (12-18)

4 (11-24)

42 (17-39)

4 (13.5-23)

16 (17-39)

27 (12-29)

 Aristostomias tittmanni

 Astronesthes macropogon

 Astronesthes niger

 Astronesthes similus

626-757

206-228

373-403

77-625

1 (34)

1 (21)

1 (35)

1 (27)

1 (20)

1 (21)

1 (31) 1 (26)
112

Table 7.3. Total numbers and standard length ranges (mm in parenthesis) of juvenile and adult fishes collected by Tucker trawl over 

three cold seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (9-29 Aug 2007). —Continued

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a

Species

 Bathophilus longipinnis

 Bathophilus nigerrimus

 Bathophilus pawneei

 Chauliodus sloani

 Chauliodus spp.

 Eustomias lipochirus

 Eustomias schmidti

 Leptostomias bilobulatus

 Melanostomias biseriatus

 Melanostomias valdiviae

 Photonectes margarita

 Photonectes sp.

 Photostomias guernei

 Stomias affinis

 Stomias longibarbatus

, damaged specim

Depth 

Range

(m)

53-149

*

121-442

53-1377

551-757

144-174

144-217

*

172-212

236-248

255-352

540-605

136-895

77-836

150

ens not measu

AC601

N

n=5

2 (23, 24)

red; m, meters]

GC

D

n=17

9 (21-132)

1 (30)

2 (104, 

120)

2 (29,90)

852

N

n=52

2 (41-65)

1 (31)

40 (20-80)

2 (30, 32)

1 (80)

1 (82)

1 (40)

1 (31)

5 (49-75)

3 (28-50)

1 (86)

AT

D

n=16

5 (20-41)

340

N

n=33

10 (20-210)

1 (80)

1 (105)

1 (260)

1 (32)

1 (100)

9 (23-55)

V

D

n=8

1 (20)

4 (29-39)

4 (23-56)

2 (26,49)

K826

N

n=28

6 (28-57)

8 (23-170)

1 (94)

 Undetermined

Chlorophthalmidae

 Chlorophthalmus agassizi

Notosudidae

168-531

165-1377 1 (27)

1 (n/a) 1 (60)

1 (45)

1 (46)

1 (26)

 Scopelosaurus mauli

Evermannellidae

630-836 1 (65)

 Coccorella atlantica 104-210 1 (48) 1 (31)
113

Table 7.3. Total numbers and standard length ranges (mm in parenthesis) of juvenile and adult fishes collected by Tucker trawl over 

three cold seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (9-29 Aug 2007). —Continued

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a, damaged specimens not measured; m, meters]

Depth AC601 GC852 AT340 VK826

Range N D N D N D N

Species (m) n=5 n=17 n=52 n=16 n=33 n=8 n=28

Alepisauridae-Omosudidae

 Omosudis lowii 847-1027 6 (20-30)

Paralepididae

 Lestidiops affinis 135-664 2 (50, 54) 1 (55)

 Lestrolepis intermedia 95-516 5 (45-60)

 Stemonosudis bullisi 88-135 2 (55, 57)

 Sudis atrox 135-605 4 (24-46) 2 (24, 27)

 Uncisudis advena 119-203 2 (37, 40)

Myctophidae

 Benthosema suborbitale 38-1044 16 (10-31) 10 (10-27) 70 (10-29) 23 (11-23) 125 (10-30) 16 (12-16) 10 (11-16)

 Bolinichthys photothorax 104-664 2 (14, 15) 4 (20-32) 1 (15) 6 (15-25) 3 (15-17)

 Bolinichthys supralateralis 150-392 2 (14, 17) 3 (15-18) 3 (14-17)

 Centrobranchus nigroocellatus 81-666 2 (14, 17) 1 (16.5) 1 (17) 2 (15, 24)

 Ceratoscopelus warmingii 49-1144 7 (17-40) 8 (15-32) 31 (16-42) 6 (15-40) 43 (17-45)

 Diaphus brachycephalus 38-558 1 (13) 2 (38, 43) 6 (13-27)

 Diaphus dumerilii 38-739 3 (13-16) 3 (17-31) 2 (13, 17) 5 (12-19) 68 (12-27) 48 (12-23)

 Diaphus fragilis 53-827 1 (16) 2 (13)

 Diaphus lucidus 104-447 1 (80) 2 (25, 65) 4 (19-70)

 Diaphus mollis 49-666 1 (30) 2 (12, 16) 17 (12-55) 3 (12-17) 13 (12-31) 3 (12-16) 10 (14-50)

 Diaphus perspicillatus 121-405 5 (14-22) 3 (14-18)

 Diaphus problematicus 49-1017 2 (12) 5 (12-70) 1 (43) 10 (14-66) 1 (15)

 Diaphus spp. 18-1025 4 (12-15) 2 (14) 2 (13, 15) 3 (16-18)

 Diaphus splendidus 59-605 7 (12-35) 34 (12-32) 1 (20)
114

Table 7.3. Total numbers and standard length ranges (mm in parenthesis) of juvenile and adult fishes collected by Tucker trawl over 

three cold seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (9-29 Aug 2007). —Continued

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a, damaged specimens not measured; m, meters]

Depth AC601 GC852 AT340 VK826

Range N D N D Range N

Species (m) n=5 n=17 n=52 n=16 Species (m) n=5

 Diaphus subtilis 144-370 3 (14-56) 1 (14)

 Diaphus taaningi 144-398 2 (12, 32)

 Diaphus termophilus 359-827 1 (12)

 Diogenichthys atlanticus 38-1016 7 (16-18.5) 1 (n/a) 3 (16-18) 1 (18) 6 (14-17)

 Gonichthys cocco 74-895 3 (17-28) 2 (19, 22) 1 (20)

 Hygophum benoiti 83-1144 6 (12-14) 33 (12-18) 36 (12-16) 8 (12-22) 27 (12-19) 5 (12-13) 33 (12-18)

 Hygophum macrochir 187-655 3 (12-15) 2 (12, 19) 1 (n/a)

 Hygophum reinhardtii 314-1027 2 (15) 1 (14) 1 (15) 1 (15)

 Hygophum sp. 113-126 1 (n/a)

 Hygophum taaningi 59-1027 1 (12) 2 (17) 2 (12) 6 (12-25) 32 (12-40) 3 (12-14) 18 (12-17)

 Lampadena luminosa 77-750 3 (20) 3 (22-46)

 Lampanyctus alatus 53-836 5 (15-45) 5 (14-40) 38 (14-45) 6 (19-30) 21 (17-55)

 Lampanyctus nobilis 113-301 3 (20-25)

 Lampanyctus spp. 77-220 1 (30) 1 (21.5)

 Lampanyctus tenuiformis 77-349 2 (24, 50) 2 (23, 28)

 Lepidophanes guentheri 18-1377 16 (16-24) 4 (15-27) 40 (15-57) 28 (15-40) 205 (14-65) 2 (17, 33)

 Lobianchia gemellarii 104-352 1 (18) 9 (16-26) 1 (15)

 Myctophum affine 49-1377 1 (15) 10 (13-15) 48 (13-45) 4 (13-16) 14 (15-30) 43 (15-40)

 Myctophum asperum 49-1017 1 (15) 3 (16-18)

 Myctophum nitidulum 113-732 1 (16) 1 (18)

2 (15, 

 Myctophum obtusirostre 95-625 1 (14) 1 (14) 20) 1 (18)

 Myctophum selenops 130-150 2 (12, 14)
115

Table 7.3. Total numbers and standard length ranges (mm in parenthesis) of juvenile and adult fishes collected by Tucker trawl over 

three cold seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (9-29 Aug 2007). —Continued

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a, damaged specimens not measured; m, meters]

Depth AC601 GC852 AT340 VK826

Range N D N D Range N

Species (m) n=5 n=17 n=52 n=16 Species (m) n=5

 Nannobrachium atrum * 1 (65)

 Nannobrachium lineatum 272-1035 3 (66-85) 2 (28) 1 (26)

 Notolychnus valdiviae 49-1377 1 (14) 29 (11-21) 886 (11-22) 79 (11-19) 125 (16-21) 33 (11-20) 17 (11-18)

 Notoscopelus resplendens 150-1035 2 (22, 45) 1 (56)

 Symbolophorus rufinus 886-1016 1 (21)

 Undetermined 49-1377 1 (n/a) 13 (12-31) 21 (12-24) 11 (12-22) 26 (13-28) 1 (n/a) 4 (12)

Polymixiidae

 Polymixia lowei 136-460 1 (25) 2 (25, 30)

Bregmacerotidae

 Bregmaceros atlanticus 53-1059 1 (17) 9 (14-26) 3 (12-33) 14 (16-34) 1 (13) 13 (11-36)

 Bregmaceros cantori 198-260 2 (29, 36)

 Bregmaceros mcclellandii 49-328 2 (18, 20) 2 (17, 18)

 Bregmaceros spp. 77-447 3 (12) 1 (19)

Moridae

 Physiculus fulvus 273-370 1 (42)

Melanonidae

 Melanonus zugmayeri 538-592 1 (55) 2 (63, 71)

Ceratiidae

 Ceratias holboelli 382-426 1 (15)

 Ceratias uranoscopus 194-210 1 (35)

 Cryptopsaras couesii 146-935 1 (15) 2 (13, 15) 2 (8)

Melamphaidae

 Melamphaes pumilus 136-1016 1 (16) 2 (22) 5 (12-17) 1 (13)
116

Table 7.3. Total numbers and standard length ranges (mm in parenthesis) of juvenile and adult fishes collected by Tucker trawl over 

three cold seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (9-29 Aug 2007). —Continued

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a,

Species

 Melamphaes simus

 Melamphaes typhlops

 Scopeloberyx opisthopterus

 Scopeloberyx robustus

 Scopelogadus mizolepis

 damaged specim

Depth 

Range

(m)

116-1044

245-531

146-1027

689-1377

*

ens not measu

AC601

N

n=5

7 (20-28)

red; m, meters]

GC

D

n=17

4 (14-19)

2 (19, 24)

1 (21)

852

N

n=52

12 (12-23)

2 (22, 25)

4 (12-14)

2 (14, 15)

AT

D

n=16

4 (23-27)

1 (23)

340

Ra

Species (m)

4 (13-25)

1 (21)

1 (23)

VK826

nge N

n=5

3 (12-13)

 Undetermined

Cetomimidae

311-372 1 (26)

 Cetostoma regani

Anoplogasteridae

 Anoplogaster cornuta

Berycidae

 Beryx splendens

Zenionidae

359-827

446-532

81-110

1 (85)

1 (18)

1 (74)

 Zenion hololepis

Caproidae

 Antigonia combatia

Scorpaenidae

 Setarches guentheri

Peristediidae

472-531

*

221-935

1 (21)

2 (13, 14)

1 (19) 1 (15)

 Peristedion sp.

Acropomatidae

 Synagrops bellus

 Synagrops sp.

144-174

83-1377

53-87

1 (19)

1 (40)

3 (11-12)

1 (12)

3 (11.5-21) 12 (12-22) 2 (11, 13)
117

Table 7.3. Total numbers and standard length ranges (mm in parenthesis) of juvenile and adult fishes collected by Tucker trawl over 

three cold seep sites (AC601, GC852, AT340) and one deep-sea coral site (VK826) in the Gulf of Mexico (9-29 Aug 2007). —Continued

[Depth ranges are minimum and maximum depths from properly working Tucker trawls; *, no depth because net did not close; n, number of stations 

sampled; D, day; N, night; n/a, damaged specimens not measured; m, meters]

Depth AC601 GC852 AT340 VK826

Range N D N D Range N

Species (m) n=5 n=17 n=52 n=16 Species (m) n=5

 Synagrops spinosus 81-739 7 (19-23) 1 (20) 7 (12-24)

 Synagrops trispinosus 245-1027 3 (11-18)

Howellidae

 Undetermined 77-248 1 (48) 8 (9-25) 5 (13-20)

Epigonidae

 Epigonus pectinifer 198-260 1 (21)

 Sphyraenops bairdianus 121-364 3 (16-17)

Chiasmodontidae

 Pseudoscopelus altipinnis 472-531 1 (95)

 Pseudoscopelus scriptus 412-472 2 (49, 62)

Percophidae

 Bembrops sp. 361-442 1 (17)

Gempylidae

 Diplospinus multistriatus 222-447 1 (95) 1 (66)

 Gempylus serpens * 1 (30)

 Nesiarchus nasutus 130-149 1 (77)

Total 18-1377 197 1334 4860 693 1544 404 696
118

7.3.1 Site Comparisons

7.3.1.1%Species%Richness

Mesopelagic fish assemblages were generally comparable among sites. As a result of 

adverse weather, the AC601 site was only sampled on one night (5 stations). Thus, this station 

was represented by the least number of individuals (n=197) and fish species (n=31), none of 

which were unique to this site (table 7.3). The species-accumulation curve at this site did not 

approach an asymptote (fig. 7.5). The 69 tows at GC852 and the 49 tows at AT340 produced 99 

species (6,193 individuals) and 80 species (2,312 individuals), respectively (table 7.3). Thirtysix Tucker trawl tows at the inshore station, VK826, yielded 58 species and 1,100 individuals 

(table 7.3). All three species accumulation curves (GC852, AT340, VK826, fig. 7.5) approached 

an asymptote, and species accumulation at each of the two offshore sites was significantly 

greater than that at VK826 (ANCOVA, p<0.01). Thirty fish species were collected only at 

GC852, while 10 species each were unique to AT340 and VK826. For the top four families 

(Myctophidae, Stomiidae, Gonostomatidae, Sternoptychidae), the offshore sites GC852 and 

AT340 yielded comparable numbers of species; however, except for the Gonostomatidae, 

families collected at VK826 were represented by fewer species than at the other two sites (table 

7.3). 
119

Figure 7.5. Species accumulation curves for the four Gulf of Mexico study sites plotted using the 

Colwell and others (2004) analytical method.

Thirty-one species (8 families) comprised about 90 percent of the overall abundance of 

fishes across the four sites (table 7.1). Eighteen species composed 92.4 percent of the fish fauna 

at AC601, dominated by Cyclothone pallida, C. pseudopallida, Valenciennellus tripunctulatus, 

Lepidophanes guentheri, and Benthosema suborbitale. At GC852, 14 species accounted for 89.6 

percent of the fauna, and the dominant fishes were mostly gonostomatids (C. pallida, C. 

pseudopallida, C. braueri, C. alba) and a myctophid, Notolychnus valdiviae. AT340 yielded 22 

species that accounted for 89.9 percent of its fauna, dominated by N. valdiviae, C. braueri, and 

L. guentheri. At the inshore VK826, 20 species composed 90.7 percent of the fauna, and the 

most abundant species were C. braueri, C. alba, V. tripunctulatus, and Diaphus dumerilii. The 

most abundant fishes were also generally the most frequently collected (table 7.1).
120

7.3.1.2%Across3Site%Comparisons

Geographic and temporal patterns in mesopelagic fish assemblages were also not evident 

in multivariate analyses of the 115 day and night stations from the four study sites (ANOSIM, 

Global R = 0.20, p=0.1 percent, pairwise R values <0.3). There were significant station 

groupings at moderate levels of similarity (SIMPROF, p <1.5 percent fig. 7.6), but these 

exhibited little fidelity to geographic locations or time of day. Instead, station groupings 

appeared to be more related to similarities in sampled depths (see fig. 7.6B). Overall, the 

average similarity percentages within each SIMPROF group were fairly low (30-47 percent 

average similarity per group), revealing the variability in mesopelagic sampling and the diversity 

in the catches. 
121

A 

B 
122

Figure 7.6. Multdimensional scaling ordination of 115 stations based on the Bray-Curtis similarity 

matrix calculated from standardized, fourth-root transformed fish abundances (117 species) with 

superimposed (A) SIMPROF groups labeled by day (D) or night (N) and (B) mean depths (in meters) 

with SIMPROF labels. The embedded dendrogram in A is labeled with SIMPROF groups. The table 

includes sites, number of stations, and sampled mean depth ranges (in parentheses) of each 

SIMPROF group. 

Upper water column stations (<400 m) grouped together. SIMPROF groups a, b, c, and g 

(fig. 7.6A) were composed of stations with a mean depth of 214 m. Group a consisted of the two 

shallowest stations (21 and 45 m, both night) sampled in this study, and L. guentheri typified this 

group. Group b included four stations from VK826 with a mean depth of 343 m, and Diaphus 

dumerilii and Vinciguerria nimbaria typified this group and distinguished it from other groups. 

Valenciennellus tripunctulatus and Argyropelecus aculeatus typified group c (mean depth = 275 

m) and distinguished this group from others. Species that dominated group g (mean depth = 156 

m) included N. valdiviae, V. poweriae, B. suborbitale, L. guentheri, Gonostoma elongatum, and 

Hygophum taaningi. 

Deeper stations also grouped together (station groups d, e, and f, fig. 7.6A) at a similarity 

level of 28 percent, and, except for one station at 150 m, generally these groups were composed 

of deep water stations >300 m (mean depth of the three groups = 609 m). Species that typified 

(SIMPER) group e (mean depth = 486 m) and distinguished it from others included (in order of 

percent contribution to average similarity within group) Cyclothone alba, C. braueri, C. 

pseudopallida, C. pallida, and V. tripunctulatus. Species that typified group f (mean depth = 778 

m), distinguishing this group from others, included C. pallida, C. acclinidens, C. pseudopallida, 
123

and Hygophum benoiti. Group d consisted of only one night station (mean depth=1,149 m) 

where C. obscura and C. pallida were the most abundant species collected. 

7.3.1.3%Within3Site%Comparisons

Although strong geographic differences among mesopelagic fish assemblages were 

lacking, depth patterns were apparent (see above). Therefore, we examined station relationships 

within each of the three well-sampled study areas (fig. 7.7), where, despite overlap, there were 

general depth-related station groupings (SIMPROF, p <5 percent). At the two deeper, offshore 

sites (fig. 7.7A, B), the species typifying the shallow station groupings were similar within sites. 

At GC852, shallow station group a (2 stations, 21 and 273 m) was typified by Lepidophanes 

guentheri, while Notolychnus valdiviae, V. poweriae, B. suborbitale, and L. guentheri 

distinguished group b (12 stations, mean depth = 139 m). The shallower stations at AT340 were 

within groups b (mean depth = 370 m) and c (mean depth = 340 m). Group b was represented by 

a diversity of taxa, but L. guentheri, N. valdiviae, and B. suborbitale were the main 

discriminating species. The two stations of AT340 group c were dominated by V. tripunctulatus. 

Low percent average similarities (27-37 percent) in the shallow station groupings at both 

offshore sites reflected the high diversity in the catches. The species dominating the deeper 

station groups were also comparable at the two offshore sites. At GC852, the mostly deeper 

station groups c through h (mean depths per group ranged from 227 m to 1,002 m) were typified 

by Cyclothone acclinidens (groups c, d, and e), C. alba (groups f, g, and h), C. braueri (groups f, 

g, and h), C. pallida (groups c, d, e, f, and g), and C. pseudopallida (groups c, d, e, and g). In 

addition, Sternoptyx pseudobscura, H. benoiti, and V. tripunctulatus distinguished SIMPROF 

GC852 groups c, d, and h from others, respectively. Although Cyclothone spp. were the most 

abundant species in group f, additional taxa distinguished this group, including Synagrops 
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spinosus, Ceratoscopelus warmingii, and Gonostoma elongatum. Three deep stations comprised 

group a (mean depth = 898 m) at AT340, and C. pallida, C. acclinidens, C. warmingii, and C. 

pseudopallida dominated this station group. Somewhat higher values of percent average 

similarity (37-58 percent) within these deeper groups indicated more consistency in the catches. 
125
126

Figure 7.7. Multidimensional scaling ordinations for three stations based on Bray-Curtis similarity 

matrices calculated from standardized, fourth-root transformed fish abundances. Each plot, (A) GC852 

(50 stations, 91 species), (B) AT340 (35 stations, 71 species), and (C) VK826 (25 stations, 51 species), 

has superimposed SIMPROF groups labeled by day (D) or night (N). The embedded dendrograms 

include SIMPROF groups, followed by number of stations and sampled mean depth ranges (in 

parentheses).

SIMPROF station groups at VK826 were more variable in depth-related patterns (fig. 

7.7C). Group a (mean depth = 271 m) was most distinct from the other groups and was 

distinguished by V. tripunctulatus and A. aculeatus. Group b (mean depth = 343 m) was typified 

by D. dumerilii and V. nimbaria. Although group d consisted of mostly shallow water stations 

(mean depth = 176 m) sampled at night, it was most similar to group c (mean depth = 402 m) 

(fig. 7.7C). The abundance of V. poweriae in both groups c and d probably influenced their 

similarity. Hygophum benoiti, D. dumerilii, and Mycophum affine were also distinguishing 

species in group d, whereas C. alba, C. braueri, and C. pseudopallida typified group c. VK826 

station groups exhibited moderate percent average similarities (30-43 percent). 

7.3.2 Depth, Diel, and Size Distributions

Depth, size, and time of capture distributions revealed a variety of patterns for the 

dominant species. Details of depth distributions by size and general time of sampling are 

provided for each study site (except AC601) for 11 of the most abundant species (figs. 7.8-7.11). 
127
128

Figure 7.8. Overall (all stations combined) temporal depth distributions of dominant midwater fishes 

(Cyclothone acclinidens, C. alba, C. braueri) by abundance and size class collected in the Gulf of 

Mexico, August 9-29, 2007. SL mm, standard length in millimeters. 
129

Figure 7.9. Overall (all stations combined) temporal depth distributions of dominant midwater fishes 

(Cyclothone pallida, C. pseudopallida, Valenciennellus tripunctulatus) by abundance and size class 

collected in the Gulf of Mexico, August 9-29, 2007. SL mm, standard length in millimeters. 

Cyclothone spp., abundant at all sites except VK826 (figs. 7.8, 7.9), usually occurred in 

deeper waters (>130 m), especially during the day (>335 m). Most individuals were captured at 

night at GC852, with catches being more evenly distributed across times at AT340 and VK826. 

The two most abundant Cyclothone spp., C. pallida and C. pseudopallida, had the largest overall 

depth ranges (150-1,377 m, fig. 7.9) and exhibited similar diel distribution trends at the two 

offshore sites, remaining around 400-1,050 m during the day and shifting to 150-1,100 m (most 

around 450-750 m) at night. The few dawn samples of these species were toward the shallower 

depths of their ranges, while dusk samples tended toward the center of the ranges. Cyclothone 

alba and C. braueri did not exhibit any clear size related trends with depth or time (fig. 7.8). 

Both species were spread over a similar large depth range (150-1,144 m and 121-1,144 m, 

respectively) and were most abundant in about 300-600 m at all times. Although the bulk of 

these species did not exhibit much difference in diel depth distribution, a few individuals were 

captured in shallower depths (as shallow as 150 m) at night at GC852. Cyclothone acclinidens

was only captured at the offshore sites, mostly at GC852 during the day. This species ranged 

from 480 to 1,067 m (fig. 7.8) but were most common at depths >500 m at all times. 

Most Valenciennellus tripunctulatus were captured at night, and they tended to have 

larger mean sizes in the deeper parts of the range (fig. 7.9). This species did not exhibit strong 

diel patterns of vertical distribution. Night and day depth ranges covered about 150-450 m versus 

750 and 1,000 m, respectively, at GC852, 200-600 m (most at 250-400 m) versus 300-500 m at 

AT340, and 200-350 m versus 350-450 m at VK826. Shallower depths were occupied at night 
130

by some individuals at all sites, and substantial captures during dusk were in the upper depths 

(fig. 7.9). 

Nearly all Vinciguerria poweriae were caught at night but did not exhibit a clear trend of 

size with depth (fig. 7.10). Where diel comparisons were possible, V. poweriae occupied a wider 

depth range at night, and most were in the upper 200 m at night. More individuals were caught 

during dusk, most in the upper 300 m, compared with dawn samples. 
131

Figure 7.10. Overall (all stations combined) temporal depth distributions of dominant midwater fishes 

(Vinciguerria poweriae, Benthosema suborblitale, Diaphus dumerilii) by abundance and size class 

collected in the Gulf of Mexico, August 9-29, 2007.
132

Figure 7.11. Overall (all stations combined) temporal depth distributions of dominant midwater fishes 

(Lepidophanes guentheri, Notolychnus valdiviae) by abundance and size class collected in the Gulf of 

Mexico, August 9-29, 2007.

Most myctophids, the strongest diel migrators we collected, were captured at night and at 

the offshore stations (figs. 7.9, 7.10). The dominant myctophid, Notolychnus valdiviae, was 

most abundant at GC852, where it occupied 550, 750, and 1,050 m depths by day and 50-750 m 

(most <100 m) at night (fig. 7.11). At AT340, N. valdiviae was most common in the upper 200 
133

m (50-500 m) at night and occurred from 350 to 500 m during the day (fig. 7.11), but diel 

movement seemed less distinct than at GC852. This species occurred around 400-450 m during 

the day and around 50-200 m at night. No size related trends with depth were apparent for N. 

valdiviae. Lepidophanes guentheri were common only at the offshore sites. At GC852, this 

species was widely scattered in the water column at night (near surface to 650 m) with no clear 

trend, but at AT340 they were most common above 150 m at night and occurred in 400-650 m 

during the day. Most individuals collected during twilight were between 100 and 150 m with 

another small group between 250 and 350 m (fig. 7.11). Size differences with depth were not 

apparent for L. guentheri. Benthosema suborbitale was least abundant at VK826 and occurred in 

similar abundances at the two offshore sites. The relatively few individuals captured during the 

day at GC852 and AT340 occurred at 550 and 1,000 m and 400-650 m, respectively (fig. 7.10). 

At both of these sites, most B. suborbitale occurred above 150 m at night, although a few 

remained deep, >400 m. Dawn and dusk captures at AT340 were generally <150 m, while at 

GC852 they were more widely spread through the water column. At VK826, B. suborbitale

individuals occurred around 400-450 m during the day and around 50-200 m (few at 300 m) at 

night. Diaphus dumerilii were most common at the inshore VK826 site (table 7.3). At VK826, 

they were captured during the day around 400-450 m, but most were above 200 m at night, and 

dawn/dusk captures were in the upper part of the depth range (fig. 7.10). Too few D. dumerilii

were captured at GC852 or AT340 to discern any clear diel pattern, and they ranged over a mean 

depth of 150 to 657 m (table 7.3). No size trends with depth were observed for D. dumerilii. 

Other important but less abundant species also exhibited diel variability by site. Gonostoma 

elongatum was most abundant at the offshore sites and was mostly collected at night at all sites 

where it often occurred at shallower depths than during the day (table 7.3). The two most 
134

common sternoptychids (Argyropelecus aculeatus and A. hemigymnus), after V. tripunctulatus, 

exhibited a wide depth range (185-842 m and 150-1,149 m, respectively), were also mostly 

collected at night, and occurred in shallower water at night (table 7.3). These two species, 

especially A. hemigymnus, occupied deeper depths at night at VK826 and AT340 compared with 

GC852. Diel comparisons were possible for the phosichthyids Pollichthys mauli and 

Vinciguerria nimbaria only at AT340 and VK826, where they occupied an overall depth range 

of 98-511 m and 98-539 m, respectively (table 7.3). Some P. mauli and V. nimbaria occurred in 

the upper 100 m at night. Chauliodus sloani was the most abundant stomiid, occurring at all 

sites, and exhibited an expanded depth range at night (table 7.3). Although all myctophid 

individuals did not exhibit diel vertical movements, many moved from lower depths into the 

upper 100 m at night (table 7.3). Hygophum benoiti, common at all sites, remained in deep water 

(>586 m) at all times at GC852, while at AT340 and VK826 it ranged into shallower depths at 

night than during the day. Myctophum affine was also common in the upper 100 m at night and 

occurred below 500 m at the only site (GC852) where it was collected during the day (table 7.3). 

Ceratoscopelus warmingii and Lampanyctus alatus (only collected at offshore sites) exhibited 

larger depth ranges at night, were common above 100-170 m at night, but were deeper than 500 

m during the day (table 7.3). H. taaningi occurred at all sites but was only common at AT340 

and VK826, where it moved into the upper 100 m at night and was deeper than 400 m during the 

day (table 7.3). Diaphus mollis and D. splendidus also exhibited expanded depth ranges at night 

and occurred in the upper 100 m at night but were all deeper than 350 m during the day (table 

7.3). 
135

7.4 Discussion

7.4.1 General

In most large scale analyses of mesopelagic fishes, the GOM stands out as a discrete 

region. Backus and others (1970) defined the GOM as 1 of 10 pelagic regions in the Western 

North Atlantic Ocean, dominated by generally tropical to subtropically distributed fishes. The 

GOM persisted as a discrete region in a broader analysis of the Myctophidae over the whole 

Atlantic Ocean (Backus and others, 1977). Similar results were obtained by Bangma and 

Haedrich (2008), who reported the GOM mesopelagic fishes constituted an ecotone between 

Sargasso Sea and Caribbean Sea faunas. We note that the above three studies dealt in different 

ways with essentially the same Woods Hole Oceanographic Institution database. 

Despite high species richness, the Gulf of Mexico is no exception to the rule that 

mesopelagic fish assemblages are generally dominated by relatively few families and species. 

Numerically, the top two families in our samples, Gonostomatidae (principally Cyclothone spp.) 

and Myctophidae, also dominated the collections of Murdy and others (1983) and Hopkins and 

Lancraft (1984). While the Sternoptychidae were important in the above studies and ranked 

fourth in abundance in our study, the Phosichthyidae were more abundant in our samples than in 

those of Murdy and others (1983) or Hopkins and Lancraft (1984). This general mesopelagic 

ichthyofaunal structure was similar in the North Atlantic, where the most abundant fishes were 

consistently in the families Gonostomatidae, Myctophidae, Sternoptychidae and Melamphaidae 

(Backus and others, 1969; Badcock and Merrett, 1976; Howell and Krueger, 1987; Keene and 

others, 1987). The lack of consistency in sampling methods (notably discrete depth versus 

oblique sampling) and data treatment (omission of certain taxa) across studies impedes more 

detailed comparisons. 
136

There is considerable similarity in dominant mesopelagic fishes among the GOM studies 

that treated the whole midwater ichthyofauna; however, there were also major differences. 

Aside from the overwhelming abundance of Cyclothone spp., the most abundant species varied 

somewhat among studies. While our top five non-Cyclothone species were, in decreasing order, 

Notolychnus valdiviae, Valenciennellus tripunctulatus, Vinciguerria poweriae, Lepidophanes 

guentheri, and Benthosema suborbitale, the most abundant non-Cyclothone in Murdy and others 

(1983) were Sternoptyx pseudobscura, L. guentheri, Gonostoma elongatum, Ceratoscopelus 

warmingii, and B. suborbitale. Hopkins and Lancraft (1984) reported V. tripunctulatus, C. 

warmingii, Diaphus dumerilii, Lampanyctus alatus, and L. guentheri as the dominant nonCyclothone species in the eastern GOM. In a much greater sampling effort in the same area as 

that of Hopkins and Lancraft (1984), Hopkins and others (1996) reported the myctophids N. 

valdiviae, D. dumerilii, L. guentheri, B. suborbitale, and L. alatus to be most abundant 

(excluding Cyclothone). Backus and others (1970), also excluding Cyclothone, reported N. 

valdiviae, L. alatus, B. suborbitale, V. poweriae, and Melamphaes pumilus to be the dominant 

species in the upper 200 m at night in the GOM. The fifth most abundant species (Melamphaes 

pumilus) of Backus and others (1970) was not common in our samples, and several species (for 

example, V. tripunctulatus, L. guentheri, Pollichthys mauli) that ranked highly in our samples 

were uncommon or missing in Backus and others (1970). Treatments of only the myctophid 

fauna across the GOM (Backus and others, 1977) and in the eastern GOM (Gartner and others, 

1987) confirmed the persistence of N. valdiviae, C. warmingii, L. guentheri, L. alatus, and B. 

suborbitale as abundant species. The most abundant stomiid fishes were the same three species 

(Photostomias guernei, Chauliodus sloani, Stomias affinis) in our samples and in the eastern 

GOM (Sutton and Hopkins, 1996a). The general similarities of dominant mesopelagic fishes 
137

across the above studies, including our study, is evidence that this fauna is spatially and 

temporally stable, considering that the above collections were widely separated in time (1961 to 

2007), that sampling and analysis methods varied, and that the samples were from different areas 

of the GOM. 

The Cyclothone spp. are the most abundant member of the mesopelagic micronekton 

worldwide (Maynard and others, 1975; Badcock and Merrett, 1976; Miya and Nemoto, 1991; 

Gartner and others, 2008). Most of the species of this small-sized, generally nonmigrating genus 

are characteristic of the deeper depths (Maynard and others, 1975; De Forest and Drazen, 2009). 

This genus (at least 6 spp.) alone represented 50 percent of the numerical abundance in our 

overall fish catches, compared with 65 percent of all fishes in stations across the GOM (Murdy 

and others, 1983) and 34.1 percent of the overall micronekton (fishes and invertebrates) at an 

eastern GOM study area (Hopkins and Lancraft, 1984). In a longer term sampling of the same 

area as Hopkins and Lancraft (1984), Hopkins and others (1996) also reported that Cyclothone

spp. dominated fish abundance. As in the eastern GOM (Hopkins and Lancraft, 1984; Hopkins 

and others, 1996) and off the Bahamas (McClain and others, 2001), C. pallida was the most 

abundant species (of all fishes) in our offshore GOM sites, closely followed by C. pseudopallida, 

C. braueri, and C. alba. The tendency for Cyclothone spp. to occupy deeper depths probably 

explained its rarity at the shallower VK826 site.

7.4.2 Site Comparisons

Our data suggested a fairly homogeneous mesopelagic fish fauna across the GOM with 

no clear geographic station groupings. Although our inshore study area yielded noticeable 

differences in fish composition compared with the offshore study areas, these were not 

statistically significant. Transitions from offshore to inshore were reported for the eastern GOM 
138

with an abrupt change between bottom depths of 275-400 m (Hopkins and others, 1981), but 

VK826 (450-650 m) was well within the zone of typical deep-sea fishes. The lack of horizontal 

station groupings in the GOM supports the paradigm of faunal patterns being determined by 

large-scale water mass characteristics (Badcock and Merrett, 1976; Jahn and Backus, 1976; 

Sutton and others, 2008); thus, small-scale mesopelagic fish communities would not be expected. 

However, this lack of pattern in our statistical analyses was also influenced by the high catch 

variability, which is common in midwater samples. Although Backus and others (1970; 1977) 

and Bangma and Haedrich (2008) considered the GOM as a separate mesopelagic faunal region, 

we caution that this hypothesis was based on analysis of few samples that did not represent the 

whole GOM and analysis of only one fish family in one study (Backus and others, 1977). Most 

GOM studies did not sample the mesopelagic fauna in relation to the various water masses, 

which could influence geographic community patterns. The eastern and western basins of the 

GOM deeper than 900 m may be isolated (Weatherly and others, 2005), and a permanent 

cyclonic circulation in the upper 800 m of the Bay of Campeche may isolate that basin (Vázquez 

and others, 2005). Until more ubiquitous and synoptic data that better represent the upper 1,000 

m of the GOM are available, existing data argue for a singular mesopelagic, tropical to 

subtropical ichthyofauna in the GOM. 

Deep-sea bottom topography can influence distribution patterns of midwater pelagic 

fauna, perhaps indirectly at times through its influence on hydrography (Fock and others, 2004; 

Sutton and others, 2008; De Forest and Drazen, 2009). We are not aware of any data suggesting 

that the offshore ridges and seep sites over which we sampled modified local currents or other 

upper water-column parameters. Also, our sampling was usually well above the bottom. Pusch 

and others (2004) noted reduced species richness and abundances and truncated migration depth 
139

ranges of mesopelagic fishes over North Atlantic seamounts. We also observed fewer species 

and lower abundances at the VK826 site; however, this is more likely related to the winnowing 

of oceanic species as one moves inshore (Hopkins and others, 1981). While the Vioska Knoll 

mounds are significant topographic highs, they are relatively small in area, and our Tucker trawl 

tows were not concentrated just over the high mounds but represented a larger area surrounding 

the mounds. Because of its shallower depth, mesopelagic fishes at VK826 by necessity had a 

truncated depth range available. Even though less water column was available at VK826, the 

fishes did not seem to take full advantage of the available range, since they were rarely seen on 

or near the bottom at VK826 (Sulak and others, 2007; S.W. Ross, UNCW, unpub. data, 2011). 

Some species may remain elevated off bottom over VK826 because of increased benthic 

predation around the coral and carbonate block habitats, as suggested for seamounts (Pusch and 

others, 2004). Although we have observed benthic predators eating mesopelagic fauna, this does 

not seem a likely explanation since midwater fishes were commonly observed all the way to the 

bottom at similar sites in similar depths off North Carolina (Gartner and others, 2008). 

The strongest station cohesion was related to depth. Fishes composed a shallower group, 

including many diel vertical migrators, and a deeper group, including many species that did not 

migrate, with the boundary between these around 300-400 m depth. Baird and Wilson (1977) 

noted a persistent deep scattering layer (around 400-500 m) in the eastern GOM, containing 

largely nonmigrating species. Data are lacking from across the GOM to explore whether depth 

was consistently a major structuring factor in groups of mesopelagic fishes. Over the MidAtlantic Ridge, depth was also the major factor determining assemblage composition of deeppelagic fishes (Sutton and others, 2008). 
140

The potential impact of seasonal differences in interpreting GOM mesopelagic fish 

occurrence patterns is unclear. Large seasonal changes in micronekton fauna, probably in 

response to changing upper water column primary productivity, have been reported in other 

places (Maynard and others, 1975). But, most midwater fish datasets from the GOM resulted 

from sampling concentrated in the summer to fall months, and data were not examined for 

temporal patterns. Lancraft and others (1988) speculated that seasonal changes in the GOM 

(supposedly in the midwater community) might be small or nonexistent and that these might be 

masked by the patchy nature of the data. Just as more widespread sampling would help elucidate 

mesopelagic community structure (see above), synoptic sampling across all seasons is also 

needed to determine how mesopelagic fauna respond to seasonally changing oceanographic 

conditions. 

7.4.3 Depth, Diel, and Size Distributions

Overall, our data compared with other studies illustrate considerable diversity in depth 

distributions and migratory behavior expressed by individual mesopelagic species. Most species 

of the genus Cyclothone were consistently reported not to undergo diel migrations (Badcock and 

Merrett, 1977; Miya and Nemoto, 1991; Kashkin, 1995; McClain and others, 2001) and were 

characterized as lethargic swimmers (McKelvie, 1989). While our two most abundant species in 

this genus, C. pallida and C. pseudopallida, exhibited the trend reported for the larger 

individuals to occur in deeper depths (Badcock and Merrett, 1976; Miya and Nemoto, 1991; 

McClain and others, 2001), diel depth distributions and overall ranges of our GOM samples 

deviated considerably, mostly at GC852, from those reported elsewhere. Although all 

individuals do not migrate, a substantial number of both species at GC852 shifted upward by 300 

to 400 m at night. In most locations, C. pallida and C. pseudopallida usually occupied depths of 
141

400-1,500 m and 400-800 m, respectively, at all times (Badcock and Merrett, 1976; Hopkins and 

others, 1981; Miya and Nemoto, 1986; Kashkin, 1995). Our data document the shallowest 

captures for these fishes as well as the first occurrences of what seem to be diel migrations. Diel 

migration was less clear for C. alba and C. braueri; however, both species exhibited upward 

shifts at night at GC852 that appear to be a diel migration. Although we are not aware of 

literature indicating a lunar effect on Cyclothone, GC852 was sampled during the new moon, and 

some mesopelagic fauna do move closer to the surface during the new moon (Clarke, 1973; 

Horning and Trillmich, 1999). We did not detect the layering of C. braueri, C. alba, and C. 

pallida (in descending depth order) as reported by Miya and Nemoto (1987), these species being 

comparable in depth ranges in our samples. In keeping with other reports (DeWitt, 1972; 

Hopkins and others, 1981; Kashkin, 1995), C. acclinidens occurred deeper than other Cyclothone

at all times. 

As reported elsewhere (Badcock and Merrett, 1976), most Valenciennellus tripunctulatus

were captured at night. Lack of diel migration seems to be consistent behavior for this species 

(Badcock and Merrett, 1976; Hopkins and Baird, 1981); however, we captured it over a larger 

depth range than usually reported. Badcock and Merrett (1976) hypothesized that the difference 

in day/night captures was related to net avoidance during the day, when this species was most 

active. 

The dominant Myctophidae in our samples exhibited typical diel migrations, but these 

varied with location and varied in some respects from other studies. The day and night depth 

ranges for Notolychnus valdiviae were similar to those reported elsewhere and suggested a 

definite upward migration at night (Badcock and Merrett, 1976; Gartner and others, 1987). 

Although Gartner and others (1987) indicated that the whole population of N. valdiviae at his 
142

eastern GOM study area migrated, our data agreed more with Clarke (1973) and Badcock and 

Merrett (1976), indicating that some individuals remained at depth at night. We did not observe 

a clear trend of smaller individuals of N. valdiviae being shallower (Clarke, 1973; Gartner and 

others, 1987), nor did there seem to be a depression of the migrants to lower depths during the 

full moon (station VK826), as noted by Clarke (1973). Diel patterns of Lepidophanes guentheri

in our GOM stations generally agreed with those from the eastern GOM (Gartner and others, 

1987), except our depth ranges were somewhat shallower. Although all individuals do not 

migrate, many move all the way to the surface at night, and during the new moon they may 

occupy the shallowest parts of their range (Gartner and others, 1987). Benthosema suborbitale

may exhibit ontogenetic diel movements, with juveniles (< approximately12 mm) reportedly not 

migrating (Clarke, 1973; Gartner and others, 1987). Juveniles of this species <12 mm SL 

occupied both deep and shallow zones at night in our collections. Their movements may be 

more complex, being tied more to coloration changes than absolute sizes (Badcock and Merrett, 

1976). Diaphus dumerilii seems to be more affiliated with the upper slope to outer shelf 

interface (Hopkins and others, 1981; this study) and exhibits a shallower depth range than other 

myctophids (Gartner and others, 1987). While all individuals did not appear to exhibit diel 

migration, a substantial number moved toward the surface at night. 

7.4.4 Conclusion

Our general conclusions are that (1) the mesopelagic realm of the GOM is represented by 

a species-rich fauna whose basic structure varies little over large distances and is perhaps similar 

over the whole GOM, (2) abundance and distribution patterns are related to depth, (3) a 

significant component of the fishes exhibit diurnal migrations and these may vary among 

different locations, and (4) a number of fishes expand their ranges at night but typically remain 
143

in deeper depths at all times. These conclusions agree with most of the literature available for 

the GOM (see above). However, despite decades of sampling the midwater GOM fauna and a 

large number of papers published on this topic, this water body is still poorly known for deepwater fauna, and only one relatively small area in the eastern GOM is well studied for 

mesopelagic fauna. As noted above, many of the historical datasets did not have large sample 

sizes, were used in several different analyses from the GOM, and did not contain depth-discrete 

sampling. We propose that a better understanding of GOM midwater communities would be 

achieved by intense depth-discrete sampling (as in the eastern GOM) in strategic locations 

designed to represent different hydrographic and depth regimes, as well as different seasons. 

7.5 Acknowledgments

Funding for this project was largely provided by the Department of the Interior U.S. 

Geological Survey under Cooperative Agreement No. 05HQAG0009, subagreement 

05099HS004, and we especially thank Dr. Gary Brewer (USGS) for his support of our work. 

We are grateful to the crew of the R/V Cape Hatteras and all scientific staff for helping with 

fishing operations and sample processing. S. Artabane assisted with sampling and identification 

of fishes and C. Ames assisted with various aspects of the cruise. H. Roberts and C. Fisher 

provided multibeam maps of the seep sites to assist sample location. We thank G. Boland 

(BOEMRE), S.D. Brooke (MCI), and J. Sinclair (BOEMRE) for helpful comments on this 

chapter and J.H. Caruso for examining Ceratias spp. specimens. 
144

8. DIETS AND FEEDING BEHAVIOR OF MIDWATER FISHES OVER COLDSEEP SITES IN THE NORTH-CENTRAL GULF OF MEXICO

An expanded version of this paper was completed as a master’s thesis:

McClain-Counts, J.P., 2010, Trophic structure of midwater fishes over cold seeps in the north-central Gulf of 

Mexico, M.S. thesis, University of North Carolina Wilmington.

By Jennifer P. McClain, Adela Y. Roa-Varón, Steve W. Ross, and Tara L. Casazza

University of North Carolina Wilmington, Center for Marine Science, Wilmington, NC

8.1 Introduction

Midwater fishes are an important component of the pelagic food web due to their high 

abundance and global distribution (Gjøsaeter and Kawaguchi, 1980; Cornejo and Koppelmann, 

2006). These unique fishes inhabit the mesopelagic zone (200 to 1,000 m), and although 

midwater fishes are consumed by a variety of marine fauna, such as penguins (Adams and 

others, 2004), tuna (Potier and others, 2007), and grenadiers (Laptikhovsky, 2005), they are also 

important consumers of zooplankton. In low-latitude midwater fish assemblages, midwater 

fishes consumed 5-10 percent of the zooplankton production in the epipelagic zone (<200 m), 

with myctophids, sternoptychids, and stomiids consuming 31, 27, and 20 percent, respectively, 

of the zooplankton biomass per day (Hopkins and others, 1996). The ability of midwater fishes 

to affect both surface and benthic communities results from diel vertical migrations (DVMs). 

DVMs are migratory patterns documented in many midwater fishes. During DVMs, 

midwater fishes migrate from the mesopelagic zone to the epipelagic zone (surface to 200 m) at 

night, primarily at sunset, and return to the mesopelagic zone at approximately sunrise. Dietz 

(1962) suggested DVMs occurred for feeding purposes due to the correlation between migrations 
145

of mesopelagic fishes and their zooplankton prey (Merrett and Roe, 1974; Kinzer, 1977; 

Beamish and others, 1999; Yatsu and others, 2005). Additionally, increased densities of 

zooplankton and increased stomach fullness of midwater fishes collected in the epipelagic zone 

at night indicated midwater fishes primarily fed at night in the epipelagic zone (Backus and 

others, 1969; Kinzer, 1977; Williams and others, 2001; Pusch and others, 2004). Through 

DVMs, midwater fishes, particularly myctophids (Kinzer, 1977; Hidaka and others, 2001; 

Cornejo and Koppelmann, 2006), contributed significantly to the vertical transportation of 

organic matter from the epipelagic zone to the mesopelagic zone (Ashjian and others, 2002; 

Brodeur and Yamamura, 2005), thus impacting the trophic structure of the entire water column. 

Previous dietary studies on midwater fishes utilized gut content analyses (GCA) to 

determine prey composition and trophic relationships. Midwater fishes were classified into three 

major feeding guilds: zooplanktivores, which consume planktonic organisms such as copepods, 

amphipods, and euphausiids; micronektonivores, which consume fishes and cephalopods; and 

generalists, which consumed a variety of unrelated taxa (Gartner and others, 1997). Placement 

into these guilds may be variable, with changes in feeding strategies possibly related to food 

availability (Kawaguchi and Mauchline, 1982). Variations within the diets of midwater fishes 

also occurred with changing seasons (Kawaguchi and Mauchline, 1982) and predator ontogeny 

(Kawaguchi and Mauchline, 1982; Young and Blaber, 1986; Hopkins and others, 1996; Beamish 

and others, 1999; Williams and others, 2001; Butler and others, 2001). Although GCA provides 

detailed diet data, this method produces little data when stomachs are empty, a common 

occurrence in midwater fishes. Additionally, these GCA only represent a short time frame (<24 

h), and the cumulative feeding habits of the midwater fauna cannot be determined except through 

intensive temporal sampling. 
146

Stable isotope analyses (SIA) can complement GCA and are becoming increasingly more 

important in ecological and biological fields. Although SIA cannot provide detailed diet data 

(for example, species-level identifications of prey), general information on the cumulative 

feeding habits of an organism (Fry, 2006) and trophic positions within a food web (Paradis and 

others, 2008) can be determined using SIA. Trophic studies utilizing SIA examined carbon and 

nitrogen signatures to elucidate relationships between predator and prey. The separation of 

heavy and light isotopes (termed fractionation) occurs during biological processes, such as 

photosynthesis, respiration, and digestion, because lighter isotopes require less energy to create 

or break bonds compared to heavier isotopes (Van Dover, 2000; Fry, 2006). Trophic 

fractionation, the shift in isotope ratios due to a change in trophic levels, can range from 1 to 5 

per mil for nitrogen and 0 to 1 per mil for carbon (Lajtha and Michener, 1994); however, the 

majority of studies apply a shift of 3.4 per mil for nitrogen and 1 per mil for carbon (Minagawa 

and Wada, 1984; MacAvoy and others, 2002). Nitrogen isotopes are ideal for determining 

trophic relations in a food web, due to the high fractionation between trophic levels (Fry, 1988; 

Thomas and Cahoon, 1993; Van Dover, 2000; Hobson and others, 2002; Behringer and Butler, 

2006; Fry, 2006), whereas carbon isotopes, with low trophic fractionation, are useful in 

determining carbon sources because fractionation during carbon fixation varies between primary 

producers (Lajtha and Michener, 1994; Fry, 2006). These differences in carbon fixation result in 

distinct ratios for different producers: -22 to -16 per mil for marine phytoplankton, -18 to -15 per 

mil for Sargassum spp., -16 to -5 per mil for turtlegrass, and –75 to -28 per mil for 

chemosynthetic material (Kennicutt and others, 1992; Hemminga and Mateo, 1996; Aharon and 

Fu, 2000; Post, 2002; Fry, 2006; Rooker and others, 2006). 
147

In the Gulf of Mexico (GOM), the trophic structure of midwater fishes may be influenced 

by the presence of chemosynthetic cold seeps, but the extent of these effects (if any) is unknown. 

While a chemosynthetic trophic pathway provides a nutritional basis to support components of 

benthic cold-seep communities (Brooks and others, 1987), recent studies documented higher 

abundances of nonseep, benthic species in the vicinity of seeps (Levin, 2005) and some benthic 

species consuming chemosynthetic material (MacAvoy and others, 2002; 2008b). However, 

whether the trophic structure of midwater fishes is influenced by chemosynthetic energetic 

pathways, either in the water column above the seep or in the benthic communities through 

interaction, has not been examined. 

Understanding the trophic relationships of midwater fishes provides necessary 

information regarding energy flow through the water column, particularly as midwater fishes that 

undergo DVMs can provide a link between surface and benthic communities. While previous 

dietary studies on midwater fish in the GOM only focused on a few species from the eastern 

GOM (Hopkins and Baird, 1985a; 1985b; Lancraft and others, 1988; Sutton and Hopkins, 

1996b) and did not utilize SIA, this study incorporated multiple midwater fish species collected 

over three cold-seep habitats (>1,000 m) in the north-central GOM. The objectives were to 

utilize GCA and SIA to (1) determine basic feeding patterns of the dominant midwater fish 

species collected, (2) document feeding changes, if any, that occurred due to spatial, temporal, or 

size variations, (3) examine the relationship between feeding and DVM in midwater fishes, (4) 

document differences in feeding based on GCA and SIA, and (5) determine to what extent, if 

any, the midwater community utilized chemosynthetic energy sources from cold seeps in the 

GOM.
148

8.2 Methods

8.2.1 Study Area

Three cold-seep sites in the GOM were selected for sampling, based on previous data 

collected by TDI-Brooks International, Inc.: Green Canyon 852 (GC852), Atwater Valley 340 

(AT340), and Alaminos Canyon 601 (AC601). The sites were located on the middle to lower 

slope in the north-central GOM, and each contained benthic chemosynthetic communities (fig. 

8.1). AT340 (2,216 m) contained a topographic high topped with multiple mounds. The area 

had extensive carbonate substrata, large mussel beds, clumps of tubeworms, and a few soft 

corals. GC852 (1,450 m) was characterized by an elongated mound approximately 2 km long 

running north to south, with vast amounts of carbonate substrata and numerous corals on the 

crest. This area also contained tubeworms and mussel beds. AC601 (2,340 m) differed from the 

other two sites, having low relief and a large brine pool. Some carbonate substrata and a few 

isolated aggregations of tubeworms were present, none of which were near the brine pool. High 

methane concentrations were recorded in the water column over this site. See Ross and others 

(Chapter 7, this volume) for additional details of these sites. 
149

Figure 8.1. North-central Gulf of Mexico illustrating sampling areas for midwater fauna, August 9-25, 

2007, at three cold-seep sites (AC601, GC852, and AT340) located on the slope at depths >1,000

meters. Each dot represents one station. 

8.2.2 Sample Collection

Sampling was conducted during 24-h operations in the GOM August 9-25, 2007; 

however, due to inclement weather, only minimal night sampling was conducted at AC601. A 

total of 173 stations (45 day, 108 night, and 20 twilight) were sampled (table 8.1). Midwater 

fauna were collected using a discrete-depth Tucker trawl (2 x 2 m) with a plankton net (0.5 m 

diameter, 335 μm mesh) placed inside the Tucker trawl to simultaneously sample the smaller 
150

components of the midwater community. The trawl was deployed open, and it was assumed no 

significant fishing occurred during deployment due to the rapid lowering, steep wire angle, and 

minimal forward movement of the vessel (Gartner and others, 2008; Ross and others, Chapter 7, 

this volume). Upon reaching the designated depth, the trawl fished for approximately 30 min at 

a 2-knot ground speed and was triggered closed using a double trip mechanism. All trawls were 

equipped with a Sea-Bird SBE39 temperature-depth recorder (TDR) attached to the upper frame 

bar to record time, depth, and temperature during deployment. Actual time and depth fished for 

each trawl were determined post-trawl using data from the TDR, and these data were used 

throughout the cruise to adjust fishing strategies to achieve desired sampling depths. 
151

Table 8.1. Surface stations sampled over three cold-seep sites (AC601, GC852, and AT340) (see fig. 8.1) in the Gulf of Mexico (August 

9-25, 2007).

[PN, plankton net; NN, Neuston net; 5 GB, 5-gallon bucket for POM samples; D, day (0630 to 1930 h CDT); N, night (1930 to 0630 h CDT)]

Station #

CH-2007-004

Gear

5 GB

Date

10-Aug-07

Location

GC852

Time

N

Start 

27° 

Latitude

07.979

Start L

91° 

ongitude

09.028

End 

27° 

Latitude

07.979

End L

91° 

ongitude

09.028

CH-2007-006 5 GB 10-Aug-07 GC852 N 27° 07.288 91° 09.771 27° 07.288 91° 09.771

CH-2007-009 PN - 0.5m 10-Aug-07 GC852 N 27° 07.042 91° 09.829 27° 06.048 91° 10.025

CH-2007-024 PN - 0.5m 11-Aug-07 GC852 N 27° 08.093 91° 09.807 27° 07.078 91° 09.925

CH-2007-028 PN - 0.5m 11-Aug-07 GC852 D 27° 07.769 91° 09.810 27° 08.269 91° 09.817

CH-2007-034 5 GB 12-Aug-07 GC852 N 27° 06.928 91° 09.881 27° 06.928 91° 09.881

CH-2007-039 PN - 0.5m 12-Aug-07 GC852 N 27° 08.036 91° 08.901 27° 08.138 91° 08.817

CH-2007-041 PN - 1m 12-Aug-07 GC852 D 27° 02.139 91° 09.618 27° 01.057 91° 09.738

CH-2007-043 NN 12-Aug-07 GC852 D 27° 10.116 91° 09.910 27° 10.824 91° 09.867

CH-2007-051 5 GB 13-Aug-07 GC852 N 27° 07.516 91° 09.790 27° 07.516 91° 09.790

CH-2007-052 PN - 0.5m 13-Aug-07 GC852 N 27° 07.274 91° 09.786 27° 06.794 91° 09.760

CH-2007-067 5 GB 13-Aug-07 GC852 N 27° 07.166 91° 10.418 27° 07.166 91° 10.418

CH-2007-069 PN - 0.5m 14-Aug-07 GC852 N 27° 07.505 91° 10.418 27° 07.015 91° 10.406

CH-2007-075 NN 14-Aug-07 GC852 D 27° 08.616 91° 10.180 27° 08.149 91° 10.169

CH-2007-076 5 GB 14-Aug-07 GC852 D 27° 06.656 91° 10.079 27° 06.656 91° 10.079

CH-2007-079 5 GB 14-Aug-07 GC852 D 27° 09.388 91° 09.765 27° 09.388 91° 09.765

CH-2007-081 5 GB 14-Aug-07 GC852 D 27° 09.660 91° 09.695 27° 09.660 91° 09.695

CH-2007-120 PN - 0.5m 18-Aug-07 AC601 N 26° 22.991 94° 30.838 26° 23.584 94° 30.851

CH-2007-121 5 GB 18-Aug-07 AC601 N 26° 24.247 94° 30.814 26° 24.247 94° 30.814

CH-2007-123 5 GB 18-Aug-07 AC601 N 26° 22.941 94° 30.823 26° 22.941 94° 30.823

CH-2007-125 5 GB 18-Aug-07 AC601 N 26° 23.705 94° 30.996 26° 23.705 94° 30.996

CH-2007-129 5 GB 18-Aug-07 AC601 D 26° 23.683 94° 30.923 26° 23.683 94° 30.923

CH-2007-133 5 GB 18-Aug-07 AC601 D 26° 22.504 94° 31.365 26° 22.504 94° 31.365

CH-2007-142 5 GB 21-Aug-07 AT340 N 27° 39.388 88° 24.022 27° 39.388 88° 24.022

CH-2007-146 5 GB 21-Aug-07 AT340 D 27° 38.812 88° 21.766 27° 38.812 88° 21.766

CH-2007-148 5 GB 21-Aug-07 AT340 D 27° 38.905 88° 21.766 27° 38.905 88° 21.766
152

Table 8.1. Surface stations sampled over three cold seep sites (AC601, GC852, and AT340) (see fig. 8.1) in the Gulf of Mexico (9-25 

August 2007).—Continued

[PN, plankton net; NN, Neuston net; 5 GB, 5-gallon bucket for POM samples; D, day (0630 to 1930 h CDT); N, night (1930 to 0630 h CDT)]

Station # Gear Date Location Time Start Latitude Start Longitude End Latitude End Longitude

CH-2007-150 5 GB 21-Aug-07 AT340 N 27° 38.770 88° 21.118 27° 38.770 88° 21.118

CH-2007-155 PN - 0.5m 22-Aug-07 AT340 D 27° 37.933 88° 21.129 27° 37.921 88° 21.422

CH-2007-158 PN - 0.5m 22-Aug-07 AT340 D 27° 38.470 88° 21.414 27° 38.460 88° 21.402

CH-2007-162 5 GB 22-Aug-07 AT340 N 27° 38.607 88° 22.151 27° 38.607 88° 22.151

CH-2007-167 5 GB 23-Aug-07 AT340 N 27° 38.412 88° 21.200 27° 38.412 88° 21.200

CH-2007-170 PN - 0.5m 23-Aug-07 AT340 N 27° 38.396 88° 21.268 27° 38.578 88° 21.641

CH-2007-174 5 GB 23-Aug-07 AT340 D 27° 39.034 88° 21.969 27° 39.034 88° 21.969

CH-2007-177 PN - 1m 23-Aug-07 AT340 D 27° 38.640 88° 21.781 27° 38.872 88° 22.582

CH-2007-179 5 GB 23-Aug-07 AT340 D 27° 38.383 88° 21.177 27° 38.383 88° 21.177

CH-2007-181 PN - 1m 23-Aug-07 AT340 D 27° 39.326 88° 23.419 27° 39.653 88° 24.196

CH-2007-185 PN - 1m 23-Aug-07 AT340 N 27° 38.183 88° 20.712 27° 38.226 88° 20.129

CH-2007-187 PN - 1m 23-Aug-07 AT340 N 27° 38.235 88° 20.784 27° 38.434 88° 21.485

CH-2007-190 5 GB 24-Aug-07 AT340 N 27° 38.291 88° 20.933 27° 38.291 88° 20.933

CH-2007-201 PN - 1m 24-Aug-07 AT340 N 27° 38.335 88° 21.133 27° 38.665 88° 21.757

CH-2007-203 PN - 1m 24-Aug-07 AT340 N 27° 38.387 88° 21.184 27° 38.757 88° 21.929

CH-2007-206 PN - 1m 24-Aug-07 AT340 N 27° 38.415 88° 21.190 27° 38.819 88° 21.964

CH-2007-215 PN - 1m 25-Aug-07 AT340 N 27° 38.479 88° 21.082 27° 38.785 88° 22.031

CH-2007-217 PN - 1m 25-Aug-07 AT340 N 27° 38.577 88° 21.421 27° 38.838 88° 22.485

CH-2007-221 PN - 1m 25-Aug-07 AT340 N 27° 38.565 88° 20.778 27° 38.698 88° 21.596
153

Additional sampling was conducted to collect potential zooplankton and phytoplankton 

for stable isotope analysis (SIA, table 8.1). A 1.1 x 2.4-m Neuston net (6.4-mm mesh body and 

3.2-mm tail bag) and plankton nets (335 μm and 505 μm mesh) were deployed at the surface and 

towed for 15-30 min to obtain zooplankton samples. Particulate organic matter (POM) was 

collected by filtering seawater through a 125-μm precombusted glass filter, and it was assumed 

that the majority of POM was phytoplankton (Kling and others, 1992). The POM and 

zooplankton samples provided a trophic baseline for SIA. 

All fishes collected were preserved in 10-percent seawater-formalin solution and later 

transferred to 50-percent isopropyl for storage until dietary analyses. Invertebrates were 

preserved in 70-percent ethanol, with the exception of jelly and salp specimens that were 

preserved in 10-percent seawater-formalin solution. All specimens were sorted, identified to the 

lowest possible taxa, and measured to the nearest millimeter standard length (SL, fishes) or total 

length (TL, invertebrates). The life history stage of fishes was also recorded based on the 

presence or absence of gonads. A fish was classified as juvenile when either no gonads or 

immature gonads were documented. 

8.2.3 Diet Analyses

Gut content analysis (GCA) was conducted for the 18 most abundant species using 

methods outlined in Ross and Moser (1995). Fish specimens were subsampled from each site to 

include all sizes ranges and depths sampled. Fishes were dissected and the stomachs were 

removed for GCA. Stomach fullness was estimated as 0, 5, 25, 50, 75, or 100 percent. Empty 

stomachs were documented and the percent number of empty stomachs was calculated for day 

and night samples at all sites; however, data on empty stomachs were not included in most 

analyses. Stomach contents were placed on a Petri dish and identified to the lowest possible 
154

taxa. Similar prey items were then piled together on a grid of 1 mm squares and flattened to a 

uniform height, which was measured. The height multiplied by the number of squares occupied 

by the food item yielded volume in cubic millimeters. The sum of all prey volumes equaled the 

total volume of the stomach, and the volume of each prey item was converted to a percentage of 

the total prey volume (%V). The frequency of occurrence for a prey item equaled the number of 

times a prey item occurred in the fish species examined divided by the total number of stomachs 

analyzed for that species. 

The relationship between DVMs and stomach fullness was examined by plotting stomach 

fullness as a function of time of day and mean depth sampled for each Tucker trawl. Time of 

day was divided into three categories: day (0730 to 1830 CDT), night (2030 to 0530 CDT), and 

twilight (0530 to 0730 and 1830 to 2030 CDT, 1 h on either side of the average sunrise and 

sunset). The mean depth for each Tucker trawl tow was calculated by averaging all depths 

recorded by the TDR from the start to the end of each tow, similar to Ross and others (Chapter 7, 

this volume). Trawls with no mean sampling depth were excluded. 

8.2.4 Stable Isotope Analysis (SIA)

Before specimens were preserved in formalin or ethanol, samples of white muscle tissue 

were dissected from fishes and invertebrates and frozen for later SIA. For consistency, tissue 

was taken from similar areas based on the type of specimen (that is, muscle tissue was removed 

from the dorsal region of fishes, the caudal region of shrimps, the legs for crabs, and the mantle 

for mollusks). When specimens were too small to dissect tissue from, the entire specimen was 

utilized. Contamination from other tissue types was minimized by removing the head, tail, 

entrails, scales, and photophores prior to obtaining the tissue sample. For specimens taken 

whole, identification occurred either prior to sampling or a similar specimen was saved as a 
155

reference for future identification. Collected isotope samples were dried and crushed into a 

powder. The majority of samples were dried to a constant weight in a convection oven at 50-

60 ̊C. Additional samples were frozen at -80 ̊C for a minimum of 24 h and freeze dried in a 

VirTis Benchtop 3.3 Vac-Freeze. It was assumed no significant differences occurred in isotopic 

ratios as a result of different drying techniques (Bosley and Wainright, 1999). 

Tissue samples were analyzed for carbon and nitrogen isotope ratios. For each sample, 

approximately 500 μg were placed into a tin capsule and combusted in an Elemental Combustion 

System Model 4010 coupled to a Delta V Plus Isotope Ratio Mass Spectrometer (IRMS) via 

Conflo II interface at the University of North Carolina Wilmington (UNCW). POM samples 

(provided by A. Demopoulos, USGS) were analyzed at Washington State University (WSU) 

using a Costech (Valencia, Calif.) elemental analyzer interfaced to a GV instruments 

(Manchester, U.K.) Isoprime IRMS. Precision of the IRMS was verified by repeated analysis of 

standards USGS 40 and USGS 41, which were incorporated into each sample run. Raw delta 

values were corrected for linearity and normalized to known reference materials USGS 40 and 

USGS 41. A similar procedure was utilized at WSU using egg albumin powder calibrated 

against National Institute of Standards reference materials. Reproducibility was monitored using 

several organic reference standards (Fry, 2007). 

Isotope ratios were expressed in the standard delta (δ) notation as parts per thousand (‰) 

according to the following equation: 

*1000

R

(R )R - X

standard

sample standard δ = (1) 

where X is 13C or 15N and R is the corresponding ratio 13C/12C or 15N/14N. The global standards 

for δ13C and δ15N are Vienna PeeDee Belemnite and atmospheric nitrogen (air). A minimum of 
156

five samples were analyzed per fish species, with the exception of Photostomias guernei (n = 4). 

In order to increase sample size, Diaphus mollis, D. lucidus, and D. problematicus were grouped 

together and referred to as Diaphus spp., and Sternoptyx diaphana and S. pseudobscura were 

grouped together and referred to as Sternoptyx spp. 

8.2.5 Statistical Analyses

Statistical analyses were conducted on isotope ratios using SigmaStat 3.4. Data were 

analyzed for normality and homogeneity of variance using Kolmogorov-Smirnov and Levene 

Median tests. One way analysis of variance (ANOVA) was used to determine significant 

differences in isotopic values for primary producers, invertebrates, and fishes. A post-hoc Tukey 

test was used for pairwise comparisons of statistical differences among groups. Data that failed 

normality or equal variance tests were analyzed with ANOVA on the Ranks and the post-hoc 

Dunn’s test. Species with low sample sizes (n <5) were not analyzed statistically. Species 

comparisons between sites AT340 and GC852 were analyzed using a two-way ANOVA and 

post-hoc Holm-Sidak test. Regressions of δ15N against fish SL were conducted to determine 

whether ontogenetic shifts in diet occurred. Statistical significance was determined when p was 

<0.05. Isotope data were reported with the mean ±1 standard error. 

8.3 Results

Tucker trawling resulted in a total of 123 tows (33 day and 90 night) from three sites 

(AC601, GC852, and AT340); however, AC601 consisted of only minimal sampling at night (n 

= 5). The mean sampled depth ranges for each site were 63 to 1,503 m for AT340, 21 to 1,067 m 

for GC852, and 45 to 584 m for AC601. A total of 8,716 fishes (30 families) were collected, but 

97.7 percent of these fishes were from five families, Gonostomatidae (58.8 percent), 
157

Myctophidae (27.4 percent), Phosichthyidae (5.8 percent), Sternoptychidae (4.4 percent) and 

Stomiidae (1.3 percent) (see Ross and others, Chapter 7, this volume). 

The GCA was conducted on the 18 most abundant species within these 5 families (in 

order of decreasing abundance): Notolychnus valdiviae, Cyclothone pallida, C. pseudopallida, C. 

braueri, C. alba, Valenciennellus tripunctulatus, Vinciguerria poweriae, Lepidophanes 

guentheri, Benthosema suborbitale, Hygophum benoiti, Pollichthys mauli, Gonostoma 

elongatum, Ceratoscopelus warmingii, Chauliodus sloani, Lampanyctus alatus, Argyropelecus 

aculeatus, Diaphus mollis, and A. hemigymnus. Gut contents were analyzed for 2,925 stomachs, 

of which 1,636 (56 percent) were empty. A total of 119 food items (# species, # families) were 

identified and grouped into 16 general prey categories: Amphipoda, Annelida, Cephalopoda, 

Chaetognatha, Cnidaria, Copepoda, Crustacea, Decapoda, Euphausiacea, Fish, Gastropoda, 

Mollusca, Nematoda, Ostracoda, Salpida, and Other. Copepods were the dominant prey, 

documented in the stomachs of all midwater fish species except C. sloani, which was a piscivore. 

SIA was conducted on 246 samples, collected from the Neuston net (n = 2), plankton nets 

(n =21), Tucker trawl (n = 123), other gear, and filtered seawater (n= 22). These samples 

represented 19 fish species (5 families), 15 invertebrate taxa, and three potential carbon sources 

(detritus, Sargassum sp., and POM, table 8.2). 
158

Table 8.2. Mean δ15N and δ13C (±1 SE) stable isotope values by species collected at three cold-seep sites (AC601, GC852, and AT340) in the 

Gulf of Mexico, August 9-25, 2007.

[(n), the number of samples averaged for each taxon; SE, standard error; POM, particulate organic matter]

mean δ15N ±1 SE (n) mean δ13C ±1 SE (n)

Species AC601 AT340 GC852 AC601 AT340 GC852

Fish

Argyropelecus aculeatus 8.68 ± 0.24 (5) 7.90 ± 0.44 (5) -17.94 ± 0.41 (5) -18.83 ± 0.10 (5)

Ceratoscopelus warmingii 6.36 ± 0.29 (3) 6.43 ± 0.63 (4) 7.21 ± 0.33 (5) -19.6 ± 0.26 (3) -18.98 ± 0.35 (4) -19.34 ± 0.21 (5)

Chauliodus sloani 8.03 ± 0.24 (5) -19.95 ± 0.54 (5)

Diaphus spp. 8.84 ± 0.27 (6) -19.32 ± 0.23 (6)

Cyclothone acclinidens 9.52 (1) -18.45 (1)

Cyclothone alba 7.32 ± 0.32 (5) -19.53 ± 0.12 (5)

Cyclothone pallida 8.44 ± 0.28 (5) 8.56 ± 0.63 (4) -19.22 ± 0.12 (5) -18.82 ± 0.13 (4)

Gonostoma elongatum 7.28 ± 0.27 (5) 8.90 ± 0.32 (5) -18.90 ± 0.11 (5) -18.87 ± 0.39 (5)

Lampanyctus alatus 7.91 ± 0.22 (3) 7.49 ± 0.29 (5) 8.47 ± 0.27 (5) -19.52 ± 0.22 (3) -18.95 ± 0.19 (5) -19.55 ± 0.18 (5)

Lepidophanes guentheri 6.75 ± 0.28 (5) 7.94 ± 0.25 (4) -18.42 ± 0.05 (5) -19.22 ± 0.10 (4)

Myctophum affine 5.63 ± 0.28 (5) -21.52 ± 0.27 (5)

Photostomias guernei 8.96 ± 0.40 (4) -18.49 ± 0.14 (4)

Pollichthys mauli 6.67 ± 0.25 (5) -18.50 ± 0.13 (5)

Sternoptyx diaphana 8.52 ± 0.07 (3) -19.48 ± 0.14 (3)

Sternoptyx pseudobscura 8.67 ± 0.17 (4) -19.96 ± 0.10 (4)

Valenciennellus tripunctulatus 9.15 ± 0.09 (5) 8.57 ± 0.28 (5) 9.06 ± 0.21 (5) -19.97 ± 0.14 (5) -18.76 ± 0.41 (5) -19.73 ± 0.16 (5)

Vinciguerria poweriae 7.59 ± 0.32 (5) 7.94 ± 0.10 (10) -18.98 ± 0.09 (5) -19.60 ± 0.09 (10)

Invertebrate

Acanthephyra purpurea 6.98 (1) 8.85 ± 0.24 (2) -18.41 (1) -17.41 ± 0.09 (2)

Ancistrocheirus lesuerii 6.19 (1) -19.25 (1)

Chaetognatha 8.84 ± 1.24 (5) -19.98 ± 0.19 (5)

Copepoda 7.00 ± 1.53 (5) 6.21 ± 1.56 (5) -19.77 ± 0.43 (5) -19.91 ± 0.61 (5)

Euphausiacea 5.97 ± 0.66 (4) 4.98 ± 0.23 (5) 6.65 ± 0.25 (2) -19.57 ± 0.31 (4) -19.33 ± 0.08 (5) -19.67 ± 0.02 (2)

Gennadas valens 6.83 ± 0.12 (4) 6.49 ± 0.10 (4) 7.50 ± 0.32 (6) -19.16 ± 0.39 (4) -18.26 ± 0.14 (4) -18.47 ± 0.31 (6)
159

Table 8.2. Mean δ15N and δ13C (±1 SE) stable isotope values by species collected at three cold-seep sites (AC601, GC852, and AT340) in the 

Gulf of Mexico, August 9-25, 2007.

[(n), the number of samples averaged for each taxon; SE, standard error; POM, particulate organic matter] 

mean δ15N ± 1 SE (n) mean δ13C ±1 SE (n)

Species AC601 AT340 GC852 AC601 AT340 GC852

Japetella diaphana

Nematoscelis megalops 

5.67 (1)

6.60 ± 0.33 (3)

-19.55 (1)

-19.89 ± 0.08 (3)

Salpida

Sergia sp.

0.95 ± 0.14 (5)

7.79 (1)

-17.92 ± 0.27 (5)

-19.10 (1)

Stigmatoteuthis arcturi 

Systellaspis debilis 5.93 ± 0.29 (6)

10.39 ± 1.04 (3)

6.30 (1) -17.84 ± 0.07 (6)

-20.71 ± 0.10 (3)

-17.17 (1)

Zooplankton

Plant

5.96 ± 2.17 (2) 5.69 ± 0.16 (3) 6.92 ± 1.09 (5) -19.67 ± 0.41 (2) -24.65 ± 4.65 (3) -20.37 ± 0.93 (5)

Detritus 3.60 ± 2.08 (5) -9.95 ± 0.92 (5)

POM 3.82 ± 0.57 (5) 5.25 ± 0.35 (8) 2.13 ± 0.64 (9) -20.01 ± 0.78 (5) -19.36 ± 0.69 (8) -19.64 ± 0.74 (9)

Sargassum spp. 1.40 ± 0.33 (3) 0.84 (1) 1.88 ± 1.00 (5) -17.71 ± 0.51 (3) -18.48 ± 0.29 (1) -18.33 ± 1.11 (5)
160

8.3.1 Primary Producers

Spatial variations in δ13C and δ15N were examined in the three potential carbon sources 

(detritus, Sargassum sp., and POM, table 8.2). No statistical comparisons were conducted on 

detritus (only collected at site AT340), or Sargassum spp. (n <5 at AT340 and AC601). 

Statistical comparisons conducted on POM documented no significant differences in δ13C among 

sites; however, POM samples collected at GC852 were depleted in 15N compared to samples 

collected at AT340 (post-hoc Tukey test, p = 0.003). 

Species variations in δ13C and δ15N were also examined among the three potential carbon 

sources by combining data from all sites. Although a chemosynthetic signature was not detected 

in isotope samples for any carbon source, there was a clear distinction in δ13C for each carbon 

source. Detritus was significantly enriched in 13C compared to Sargassum spp. (Tukey, p 

<0.001) and POM (Tukey, p <0.001), while Sargassum spp. was significantly enriched in 13C 

compared to POM (Tukey, p = 0.031, table 8.2). There were no significant differences in δ15N 

between detritus and POM or detritus and Sargassum spp.; however, Sargassum spp. was 

significantly depleted in 15N compared to POM (Dunn’s, p <0.05). 

8.3.2 Invertebrates

Although no GCA was conducted on invertebrate specimens, SIA was conducted on 15 

invertebrate species (7 orders) from all 3 sites combined (table 8.2). Due to the small sample 

sizes, spatial variations among invertebrate taxa were only conducted for Copepoda collected at 

GC852 and AT340 (table 8.2). There were no significant differences in δ13C or δ15N for 

Copepoda between GC852 and AT340. Small sample sizes also prevented statistical species 

comparisons for all invertebrates except Decapoda. Comparisons between two decapod species, 
161

Gennadas valens and Systellaspis debilis, documented significantly depleted 13C but 

significantly enriched 15N in G. valens compared to S. debilis (post-hoc Tukey, p = 0.034, p = 

0.007). Although no chemosynthetic signature was detected in any invertebrates, a trophic shift 

of approximately 2 per mil in nitrogen was documented in invertebrate specimens with 

increasing trophic levels at all three sites (fig. 8.2).

163

8.3.3 Fishes

8.3.3.1%Gonostomatidae

GCA were conducted on five gonostomatid species: C. alba, C. braueri, C. pallida, C. 

pseudopallida, and G. elongatum. A high percentage of empty stomachs (>65 percent at all 

sites) occurred in all Cyclothone spp., with empty stomachs occurring more frequently in 

specimens collected during the day. In contrast, empty stomachs occurred less frequently in G. 

elongatum than Cyclothone spp. (22 percent at AT340 and 48 percent at GC852); however, 

empty stomachs only occurred in specimens collected at night. Migration patterns were 

examined to document general trends in feeding. No DVMs were apparent for C. alba and C. 

braueri (fig. 8.3A, B), with more full stomachs documented at night. Slight DVMs were evident 

for C. pallida and C. pseudopallida, with more full stomachs documented during the day for C. 

pallida (fig. 8.3C) and full stomachs occurring throughout a 24-h period for C. pseudopallida 

(fig. 8.3D). In contrast, G. elongatum exhibited a strong DVM pattern associated with more full 

stomachs in the epipelagic at night (fig. 8.3E). 

Diet comparisons were examined to document differences among gonostomatid species. 

A similar diet composition was documented in all Cyclothone spp., with Copepoda and 

Ostracoda documented as the most important prey in both overall percent volume and percent 

frequency (tables 8.3-8.6). Despite these diet similarities, the species of Copepoda consumed 

varied among Cyclothone spp. Pleuromamma spp. was the dominant copepod consumed by C. 

alba (table 8.3), whereas Aegisthus mucronatus was more important in the diets of C. braueri 

(table 8.5). Valdiviella minor was volumetrically more important in the stomachs of C. 

pseudopallida, though Lubbockia sp. occurred more frequently (table 8.6). This diet 
164

composition remained similar at all sites with one exception. At GC852, Amphipoda was 

volumetrically more important than Copepoda in the diet of C. pallida collected at night (table 

8.4). Compared with Cyclothone spp., Gonostoma elongatum consumed a higher diversity of 

prey items, which included non-crustacean prey items such as Chaetognatha (table 8.7). 

Euphausiids and decapods were volumetrically more important in G. elongatum, whereas 

copepods occurred more frequently in the stomachs. Examination of the diets on a spatial scale 

revealed euphausiids were more important volumetrically for G. elongatum at GC852, whereas 

decapods were more important volumetrically at AT340 (table 8.7). 
165

A B 

C D 

E F 
166

G H 

I J 

K L 
167

M N 

O P 

Q R 

Figure 8.3. The relationships between stomach fullness and depth of capture for 18 midwater fishes. 

Data from all three sites were grouped together to detect diel vertical migrations. 
168

Table 8.3. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone alba collected 

from two sites (AT340, and GC852) in the Gulf of Mexico separated by day and night. Additionally, two C. alba

were captured at site AC601, both at night with empty stomachs. 

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AT340 GC852

Day Night Day Night

(n=21) (n=16) (n=19) (n=36)

(E=46) (E=30) (E=43) (E=77)

Food Item % V % F % V % F % V % F % V % F

OSTRACODA – – – – 3.6 5.3 0.2 2.8

Halocyprididae – – – – 3.6 5.3 – – 

Myodocopida – – – – – – 0.2 2.8

COPEPODA 95 66.7 78.5 50 29.9 36.8 75.4 47.2

Aetideidae – – 1.3 6.3 – – – – 

Calanoida 20.9 14.3 15.7 18.8 5.4 5.3 29.5 22.2

Copepoda 0.2 4.8 – – – – – – 

Cyclopoida – – – – 0.1 5.3 – – 

Euchirella curticauda 43.5 9.5 – – – – – – 

Euchirella sp. – – – – – – 9.2 2.8

Heterorhabdidae – – – – – – 3.9 2.8

Lubbockia aculeata 1.5 4.8 – – – – – – 

Pleuromamma robusta 6.7 4.8 – – – – – – 

Pleuromamma sp. – – 4 6.3 – – 14.7 5.6

Pleuromamma xiphias 17.3 9.5 53.1 6.3 18.6 5.3 14.7 5.6

Poecilostomatoida – – – – 0.8 15.8 – – 

Unidentified copepod parts 4.9 19 4.4 18.8 5.1 10.5 3.2 11.1

CRUSTACEA 2.3 19 2.2 12.5 60.6 42.1 14 27.8

Unidentified crustacean parts 2.3 19 2.2 12.5 60.6 42.1 14 27.8

DECAPODA – – – – – – 7.4 2.8

Decapoda – – – – – – 7.4 2.8

OTHER 2.8 19 19.3 43.8 5.9 36.8 3 25

Organic material 2.8 19 9.2 37.5 5.9 31.6 3 22.2

Unidentified animal parts – – 10.1 37.5 <0.1 5.3 <0.1 5.6
169

Table 8.4. Percent volume (%V) and percent frequency (%F) of prey 

and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

consumed by Cyclothone pallida collected from three sites (AC601, AT340, 

AC601 AT340 GC852

Night Day Night Day Night

(n=3) (n=0) (n=1) (n=6) (n=11)

(E=15) (E=58) (E=43) (E=134) (E=91)

Food Item % V % F % V % F % V % F % V % F % V % F

OSTRACODA 23.1 33.3 – – – – 9.4 33.3 24.9 18.2

Conchoecinae – – – – – – 5.7 16.7 – –

Halocyprididae 23.1 33.3 – – – – – – – –

Halocypridinae – – – – – – 3.8 16.7 – –

Myodocopida – – – – – – – – 10 9.1

Unidentified ostracod parts – – – – – – – – 14.9 9.1

COPEPODA 68.4 33.3 – – – – 71.6 16.7 3.1 9.1

Aetideidae – – – – – – 22.6 16.7 – –

Haloptilus oxycephalus – – – – – – – – 3.1 9.1

Unidentified copepod parts 68.4 33.3 – – – – 49 16.7 – –

AMPHIPODA – – – – – – – – 29.9 9.1

Unidentified amphipod parts – – – – – – – – 29.9 9.1

CRUSTACEA – – – – – – 9.4 16.7 – –

Unidentified crustacean parts – – – – – – 9.4 16.7 – –

OTHER 8.5 33.3 – – 100 100 9.5 33.3 42.1 63.6

Organic material 8.5 33.3 – – 100 100 9.5 33.3 42.1 63.6
170

Table 8.5. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone braueri collected 

from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night. Additionally, two C. 

braueri were captured at site AC601, both at night with empty stomachs.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AT340 GC852

Day Night Day Night

(n=8) (n=19) (n=18) (n=24)

(E=48) (E=75) (E=40) (E=85)

Food Item % V % F % V % F % V % F % V % F

OSTRACODA 57.6 25 – – 23.7 16.7 1.2 4.2

Conchoecinae 54.2 12.5 – – – – – –

Ostracoda 3.4 12.5 – – 23.7 16.7 – –

Unidentified ostracod parts – – – – – – 1.2 4.2

COPEPODA 42.4 87.5 68.1 52.6 68.4 72.2 64.4 41.7

Aegisthus mucronatus 16.2 25 – – 32.5 16.7 – –

Calanoida 5.3 25 36.1 21.1 1.8 5.6 10.9 8.3

Copepoda – – – – – – <0.1 4.2

Corycaeus sp. – – – – 1.2 5.6 – –

Cyclopoida – – 0.4 5.3 – – 0.2 4.2

Lubbockia aculeata – – – – 1.8 5.6 – –

Miracia efferata 1.2 12.5 – – – – – –

Pleuromamma sp. – – – – – – 34.9 8.3

Unidentified copepod parts 19.7 25 31.6 26.3 31.1 72.2 18.3 16.7

CRUSTACEA – – 27.1 52.6 – – 22.9 41.7

Unidentified crustacean parts – – 27.1 52.6 – – 22.9 41.7

OTHER – – 4.8 31.6 7.9 16.7 11.5 37.5

Organic material – – 4.8 31.6 5.1 11.1 11.5 37.5

Unidentified animal parts – – – – 2.8 5.6 – –
171

Table 8.6. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone pseudopallida collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=9) (n=13) (n=24) (n=29)

(E=11) (E=54) (E=25) (E=90) (E=76)

Food Item % V % F % V % F % V % F % V % F % V % F

OSTRACODA – – 8.7 11.1 5.3 7.7 3.9 8.3 0.1 3.4

Conchoecinae – – – – 5.3 7.7 0.8 4.2 – –

Myodocopida – – – – – – 3.2 4.2 – –

Ostracoda – – 8.7 11.1 – – – – 0.1 3.4

COPEPODA 100 100 86.3 77.8 92.8 76.9 85.7 54.2 60.8 48.3

Aegisthus mucronatus – – 9.1 11.1 – – – – 0.5 3.4

Aetideidae – – – – 3 7.7 – – – –

Calanoida – – 77.3 66.7 49.7 38.5 12.3 29.2 9.5 17.2

cf. Mormonilla phasma – – – – – – 20.5 4.2 – –

Chiridus sp. – – – – – – 1.7 4.2 – –

Copepoda – – – – – – 31.6 4.2 0.6 3.4

Harpacticoida – – – – 0.3 7.7 – – – –

Lubbockia aculeata – – – – – – 0.8 4.2 – –

Lubbockia sp. – – – – – – 0.2 4.2 – –

Lubbockia squillimana – – – – – – – – 0.9 3.4

Lucicutia sp. – – – – – – – – <0.1 3.4

Oithona sp. – – – – – – 0.3 4.2 – –

Pleuromamma sp. – – – – – – – – 17 3.4

Pleuromamma xiphias – – – – – – 15.2 4.2 – –

Rhincalanus sp. – – – – – – – – 0.4 3.4

Valdiviella minor – – – – 24.8 7.7 – – – –

Unidentified copepod parts 100 100 – – 15.1 23.1 3 8.3 31.9 13.8
172

Table 8.6. Percent volume (%V) and percent frequency (%F) of prey consumed by Cyclothone pseudopallida collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=9) (n=13) (n=24) (n=29)

(E=11) (E=54) (E=25) (E=90) (E=76)

Food Item % V % F % V % F % V % F % V % F % V % F

CRUSTACEA – – – – 1.8 15.4

Unidentified crustacean 

parts – – – – 1.8 15.4

OTHER – – 5 22.2 <0.1 7.7

7.3 12.5 12.6 24.1

7.3 12.5 12.6 24.1

3 37.5 26.4 27.6

Animalia – – 2.7 11.1 – – – – – –

Organic material – – 2.3 11.1 <0.1 7.7 3 29.2 26.3 24.1

Unidentified animal parts – – – – – <0.1 8.3 0.1 3.4
173

Table 8.7. Percent volume (%V) and percent frequency (%F) of prey consumed by Gonostoma 

collected from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

elongatum

AT340 GC852

Day

(n=4)

(E=0)

Night

(n=41)

(E=10)

Day

(n=3)

(E=0)

Night

(n=20)

(E=11)

Food Item % V % F % V % F % V % F % V % F

CNIDARIA

Cnidaria

OSTRACODA

Halocyprididae

Myodocopida

Ostracoda

COPEPODA

Aetideus acutus

Calanoida

Candacia longimana

Copepoda

Corycaeus (Urocorycaeus) 

furcifer

Corycaeus sp.

Eucalanidae

Gaetanus pileatus

Haloptilus sp.

Pareucalanus attenuatus

Pleuromamma xiphias

Rhincalanus cornutus

Temora stylifera

Unidentified copepod parts

AMPHIPODA

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

0.1

<0.1

0.1

–

1.7

0.1

0.1

0.3

–

<0.1

<0.1

0.4

–

0.1

0.4

–

–

0.3

0.3

–

–

4.9

2.4

2.4

–

31.7

2.4

2.4

9.8

–

2.4

2.4

2.4

–

2.4

2.4

–

–

9.8

2.4

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

0.2

0.2

<0.1

<0.1

<0.1

1.3

<0.1

0.2

0.1

<0.1

<0.1

0.3

0.3

0.2

<0.1

0.1

0.4

5

5

15

10

5

35

5

15

10

5

5

5

10

5

5

10

10
174

Table 8.7. Percent volume (%V) and percent frequency (%F) of prey consumed by Gonostoma 

from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night. —Continued

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

elongatum collected 

AT340 GC852

Day

(n=4)

(E=0)

Night

(n=41)

(E=10)

Day

(n=3)

(E=0)

Night

(n=20)

(E=11)

Food Item % V % F % V % F % V % F % V % F

Amphipoda

Scina pusilla

EUPHAUSIACEA

Euphausiidae

Thysanoessa sp.

Thysanopoda sp.

Unidentified euphausiid parts

CRUSTACEA

Unidentified crustacean parts

DECAPODA

Decapoda

Lophogastridae

CHAETOGNATHA

Heterokrohnia sp.

OTHER

Organic material

Unidentified animal parts

– 

– 

– 

– 

– 

– 

– 

45.8

45.8

– 

– 

– 

– 

– 

54.2

54.2

– 

– 

– 

– 

– 

– 

– 

– 

50

50

– 

– 

– 

– 

– 

75

75

– 

– 

0.3

3.8

2.1

1.7

– 

– 

3.5

3.5

86.2

86.2

– 

– 

– 

4.4

3.9

0.5

– 

2.4

7.3

7.3

2.4

– 

– 

43.9

43.9

4.9

4.9

– 

– 

– 

70.7

70.7

2.4

– 

– 

1.7

– 

– 

– 

1.7

13.3

13.3

– 

– 

– 

– 

– 

85

85

– 

– 

– 

33.3

– 

– 

– 

33.3

33.3

33.3

– 

– 

– 

– 

– 

100

100

– 

0.4

– 

40.4

16.2

– 

24.2

– 

10.7

10.7

1.3

0.3

1 

1.6

1.6

44

42.9

1.1

10

– 

15

15

– 

5 

– 

50

50

15

5 

10

5 

5 

70

60

10
175

SIA was conducted on C. alba, C. acclinidens, C. pallida and G. elongatum. Cyclothone 

acclinidens was excluded from statistical analyses due to the small sample size (n = 1). 

Cyclothone alba was significantly depleted in 15N compared to C. pallida (Dunn’s, p = 0.021), 

but no differences in δ13C values were documented. Additionally, no significant differences 

were documented in δ13C or δ15N between Cyclothone spp. and G. elongatum. No dietary 

ontogenetic shifts were documented for Cyclothone spp. (fig. 8.4A); however, a significant 

positive relationship between SL and δ15N was indentified for G. elongatum (R2=0.888, p 

<0.001, fig. 8.4B). No site comparisons were conducted between Cyclothone spp.; however, G. 

elongatum was significantly enriched in 15N values at GC852 compared to AT340 (Dunn’s, p = 

0.006). Although no chemosynthetic signature was detected in any gonostomatid, a trophic shift 

of approximately 2 per mil in nitrogen and <1 per mil in carbon was documented with increasing 

trophic levels (fig. 8.2). 
176

A

R2 = 0.0757

R2

 = 0.2818

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35 40 45 50 55 60

SL (mm)

δ15

N

C.alba

C.pallida

B

R2 = 0.8883

3

4

5

6

7

8

9

10

0 20 40 60 80 100 120 140 160 180 200

SL (mm)

δ15

N

G.elongatum

A 

B 

Linear (C.alba)

Linear

(C.pallida)
177

C

R2 = 0.0796

R2

 = 0.0606

R2

 = 0.0524

R2

 = 0.3096

R2

 = 0.7509

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60 70 80

SL (mm)

δ15

N

C.warmingii

Diaphus spp.

L.alatus

L.guentheri

M.affine

D

R2 = 0.6144

R2

 = 0.0127

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30 35 40

SL (mm)

δ15

N

P.mauli

V.poweriae

C 

D 
178

E

R2 = 0.087

R2

 = 0.0007

R2

 = 0.0167

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60

SL (mm)

δ15

N

A.aculeatus

Sternoptyx spp.

V.tripunctulatus

F

R2 = 0.9939

R2

 = 0.9203

3

4

5

6

7

8

9

10

0 20 40 60 80 100 120 140

SL (mm)

δ15

N

C.sloani

P.guernei

E 

F 
179

Figure 8.4. The relationship of standard length (SL) to δ15N values in midwater fishes from the families 

(A) Gonostomatidae – Cyclothone spp.; (B) Gonostomatidae – Gonostoma elongatum; (C) 

Myctophidae; (D) Phosichthyidae; (E) Sternoptychidae; and (F) Stomiidae collected at all three sites. 

8.3.3.2%Myctophidae

Seven species of Myctophidae (B. suborbitale, C. warmingii, D. mollis, H. benoiti, L. 

alatus, L. guentheri, and N. valdiviae) were analyzed for diet composition from the three sites. 

Empty stomachs occurred more frequently in H. benoiti than any other species collected (table 

8.8). Generally, empty stomachs occurred more frequently during the day than at night and more 

frequently at GC852 than any other site for myctophids (tables 8.8-8.14). Additionally, DVMs 

were evident for all myctophids, with more full stomachs documented in specimens collected in 

the epipelagic zone at night (fig. 8.3F-L). 

Diets of myctophids were diverse, ranging from 7 prey categories (H. benoiti and N. 

valdiviae) to 15 prey categories (C. warmingii). Crustaceans were the dominant prey in the diets 

of all myctophids; however, noncrustacean prey were documented in the stomachs of all 

myctophid species. Pleuromamma spp. (Copepoda) was the most abundant species identified in 

stomachs, occurring in all myctophid species, except C. warmingii and H. benoiti, and accounted 

for 44 percent of all identified copepod species. Prey preferences were variable in Myctophidae 

based on time of day and sites. Copepoda were the dominant prey for H. benoiti (table 8.8), B. 

suborbitale (table 8.9), D. mollis (table 8.10), and N. valdiviae (table 8.11) regardless of time or 

sites. Although copepods occurred more frequently in the diets of C. warmingii (table 8.12), L. 

guentheri (table 8.13), and L. alatus (table 8.14), other prey items were more important 

volumetrically. In C. warmingii, amphipods were volumetrically more in the diets of specimens 

collected during the night at AC601 and GC852, while fish were volumetrically more important 
180

in specimens collected during the day samples at AT340. In L. guentheri, copepods were 

volumetrically more important in specimens collected during the night at AC601 and AT340, 

whereas euphausiids were volumetrically more important in specimens collected during the day 

at AT340, ostracods in specimens collected during the day at GC852, and amphipods in 

specimens collected during the night at GC852 (table 8.13). In L. alatus, copepods were 

volumetrically more important in specimens collected during the night at AC601, and during the 

day at AT340 and GC852, whereas amphipods were more important in specimens collected 

during the night at GC852, and euphausiids in specimens collected during the night at AT340 

(table 8.14). 
181

Table 8.8. Percent volume (%V) and percent frequency (%F) of prey consumed by Hygophum benoiti collected 

from AT340 in the Gulf of Mexico separated by day and night. Additionally, six H. benoiti were collected at 

AC601 at night, all with empty stomachs. At site GC852, 33 H. benoiti were collected during the day and 37 

during the night, all with empty stomachs. 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AT340

Day Night

(n=1) (n=16)

(E=7) (E=11)

Food Item % V % F % V % F

MOLLUSCA – – 0.2 18.8

Bivalvia – – 0.2 18.8

OSTRACODA – – 0.6 12.5

Myodocopida – – 0.1 6.3

Ostracoda – – 0.5 6.3

COPEPODA – – 52 81.3

Calanoida – – 15.7 50

Candacia curta – – 1.4 6.3

Candacia pachydactyla – – 2.8 6.3

Cyclopoida – – 5.8 62.5

Farranula gracilis – – 0.9 25

Unidentified copepod parts – – 25.4 68.8

AMPHIPODA – – 0.2 6.3

Amphipoda – – 0.2 6.3

CRUSTACEA 100 100 9.2 25

Unidentified crustacean parts 100 100 9.2 25

DECAPODA – – 3.8 6.3

Decapoda – – 3.8 6.3

OTHER – – 34 75

Organic material – – 34 75
Table 8.9. Percent volume (%V) and percent frequency (%F) of prey consumed by Benthosema suborbitale collected from three sites (AC601, 

AT340 and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Day Night

(n=9) (n=13) (n=71) (n=2) (n=34)

(E=4) (E=9) (E=48) (E=8) (E=36)

Food Item % V % F % V % F % V % F % V % F % V % F

– – – MOLLUSCA – <0.1 1.4 – – – –

– – – Unidentified mollusk parts – <0.1 1.4 – – – –

OSTRACODA 2.7 33.3 3 15.4 4.4 18.3 – – 7 23.5

– – – – Archiconchoecinae 1.8 1.4 – – – –

– – – – Conchoecinae – – 2 5.9

– – – – Halocyprididae – – 1.7 2.9

– – – – Halocypris sp. – – 1.7 2.9

Myodocopida – – 1.8 22.2 0.3 4.2 – – 0.8 8.8

Ostracoda 0.9 11.1 3 15.4 0.4 4.2 – – – –

– – – – Unidentified ostracod parts 1.9 11.3 – – 0.8 5.9

COPEPODA 51.9 77.8 76.1 38.5 24.5 50.7 100 100 30.2 44.1

– – Calanoida 13.1 44.4 0.2 5.6 44.4 50 8.1 11.8

– – – – Candacia bipinnata 1.4 1.4 – – – –

– – – – Candaciidae 0.4 1.4 – – – –

Copepoda 0.4 22.2 51.9 7.7 6 22.5 – – 2.7 26.5

Corycaeus (Urocorycaeus) furcifer – – – – 0.2 1.4 – – –

Corycaeus sp. 11 22.2 – – 0.9 4.2 – – 0.8 2.9

Cyclopoida 0.1 22.2 – – – – – –

– – Euchaetidae – – – – – – 6.8 2.9

Harpacticoida 0.3 11.1 – – <0.1 2.8 – – <0.1 2.9

– – Labidocera sp. – – 0.1 1.4 – – – –

Pleuromamma abdominalis 2.6 11.1 – – – – – – 2.5 2.9

182
183

Table 8.9. Percent volume (%V) and percent frequency (%F) of prey consumed by Benthosema

AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued

[n, number of full stomachs; E, number of empty stomachs; –, no value]

suborbitale collected from three sites (AC601, 

AC601 AT340 GC852

Night Day Night Day Night

(n=9) (n=13) (n=71) (n=2) (n=34)

(E=4) (E=9) (E=48) (E=8) (E=36)

Food Item % V % F % V % F % V % F % V % F % V % F

– – Pleuromamma borealis – – 2.9 2.8 – – – –

– – – – Pleuromamma piseki 10.3 22.2 – – – –

– – – – Pleuromamma sp. 2.4 2.8 55.6 50 6.8 2.9

– – – – Sapphirina metallina 2.1 11.1 – – – –

– – – – Temora stylifera 3.4 11.1 – – – –

Unidentified copepod parts 8.6 33.3 24.1 30.8 9.9 31 – – 2.4 14.7

– – AMPHIPODA 5.8 11.1 4.7 5.6 – – 4.4 2.9

– – – – Anchylomera blossevillei 1.8 1.4 – – – –

– – Hyperiidea 5.8 11.1 1.8 1.4 – – 4.4 2.9

– – – – Platysceloidea 0.9 1.4 – – – –

– – – – Unidentified amphipod parts 0.2 1.4 – – – –

– – – – EUPHAUSIACEA 12.8 5.6 – – 1.8 5.9

– – – – Euphausiidae 10 2.8 – – 0.1 2.9

– – – – Unidentified euphausiid parts 2.7 2.8 – – 1.7 2.9

CRUSTACEA 24.3 44.4 11.1 7.7 18 46.5 – – 17.5 41.2

– – – – – – Crustacea – – 0.2 2.9

Unidentified crustacean parts 24.3 44.1 11.1 7.7 18 46.5 – – 17.3 41.2

– – – – DECAPODA 4.4 4.2 – – 20.9 2.9

– – – – Decapoda 2.4 1.4 – – 20.9 2.9

– – – – Unidentified decapod parts 2 2.8 – – – –

– – – – ANNELIDA 2 2.8 – – – –

– – – – Polychaeta 2 2.8 – – – –
184

Table 8.9. Percent volume (%V) and percent frequency (%F) of prey consumed by Benthosema suborbitale collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night

(n=9) (n=13) (n=71)

(E=4) (E=9) (E=48)

Day Night

(n=2) (n=34)

(E=8) (E=36)

Food Item % V % F % V % F % V % F % V % F % V % F

CHAETOGNATHA – – 1.1 7.7 – – – – – – 

Unidentified chaetognath parts – – 1.1 7.7 – – – – – – 

FISH – – – – 7.3 1.4 – – – – 

Myctophidae – – – – 7.3 1.4 – – – – 

OTHER 15.4 55.6 8.7 30.8 22 66.2 – – 18.2 47.1

Organic material 15.4 55.6 7.8 23.1 22 64.8 – – 18.2 47.1

Unidentified animal parts – – 0.9 7.7 <0.1 1.4 – – <0.1 2.9
185

Table 8.10. Percent volume (%V) and percent frequency (%F) of prey consumed by Diaphus mollis collected from three sites (AC601, AT340, and 

GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=4) (n=11) (n=0) (n=15)

(E=0) (E=0) (E=1) (E=2) (E=0)

Food Item % V % F % V % F % V % F % V % F % V % F

GASTROPODA – – – – <0.1 9.1 – – – – 

Gastropoda – – – – <0.1 9.1 – – – – 

OSTRACODA – – – – 1 18.2 – – 1.5 53.3

Conchoecinae – – – – 1 9.1 – – 

Myodocopida – – – – – – – – 0.2 20

Ostracoda – – – – – – – – 0.4 13.3

Unidentified ostracod parts – – – – <0.1 9.1 – – 0.9 26.7

COPEPODA 63.3 100 12.5 25 26.4 81.8 – – 15.2 60

Calanoida – – 12.5 25 <0.1 9.1 – – – – 

Copepoda 0.5 100 – – 1.3 18.2 – – 1 20

Cyclopoida 0.5 100 – – 0.2 27.3 – – 1.2 6.7

Farranula gracilis – – – – 0.1 9.1 – – – – 

Pleuromamma sp. 62.3 100 – – 18.1 27.3 – – 9 6.7

Unidentified copepod parts – – – – 6.7 45.5 – – 4 26.7

EUPHAUSIACEA – – 34.4 25 <0.1 9.1 – – <0.1 13.3

Euphausiidae – – 34.4 25 – – – – <0.1 13.3

Unidentified euphausiid parts – – – – <0.1 9.1 – – – – 

CRUSTACEA 36.6 100 – – 16.3 54.5 – – 5 53.3

Unidentified crustacean parts 36.6 100 – – 16.3 54.5 – – 5 53.3

DECAPODA – – – – 0.1 9.1 – – <0.1 6.7

Decapoda – – – – 0.1 9.1 – – <0.1 6.7

– – – – – – – – – – 
186

Table 8.10. Percent volume (%V) and percent frequency (%F) of prey consumed by Diaphus mollis collected from three sites (AC601, AT340, and 

GC852) in the Gulf of Mexico separated by day and night. —Continued 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=4) (n=11) (n=0) (n=15)

(E=0) (E=0) (E=1) (E=2) (E=0)

Food Item % V % F % V % F % V % F % V % F % V % F 

CHAETOGNATHA – – 28.1 25 7.6 9.1 – – – – 

Sagittoidea – – 28.1 25 7.6 9.1 – – – – 

Unidentified chaetognath parts – – – – – – – – – – 

FISH – – – – – – – – <0.1 20

Unidentified fish parts – – – – – – – – <0.1 20

OTHER <0.1 100 25 25 48.4 81.8 – – 78.1 86.7

Organic material – – 25 25 48.4 81.8 – – 78.1 86.7

Unidentified animal parts <0.1 100 – – <0.1 9.1 – – <0.1 33.3
187

Table 8.11. Percent volume (%V) and percent frequency (%F) of prey consumed by Notolychnus valdiviae collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=52) (n=66) (n=22) (n=77)

(E=0) (E=44) (E=44) (E=7) (E=31)

Food Item % V % F % V % F % V % F % V % F % V % F

OSTRACODA 100 100 4.6 5.8 7.7 25.8 1.2 18.2 4.1 24.7

Conchoecinae – – – – 0.1 1.5 0.1 4.5 0.5 2.6

Halocyprididae – – – – 5.2 6.1 <0.1 4.5 1.5 3.9

Halocypridinae – – 0.4 1.9 – – – – <0.1 1.3

Myodocopida – – – – 0.6 6.1 1 9.1 0.7 2.6

Myodocopina – – 0.4 1.9 0.4 1.5 – – <0.1 2.6

Ostracoda 100 100 3.5 1.9 0.9 7.6 – – 0.9 7.8

Unidentified ostracod parts – – 0.3 1.9 0.4 4.5 – – 0.5 5.2

COPEPODA – – 68.9 63.5 55.3 63.6 16.6 31.8 40.3 51.9

Calanoida – – 3.4 7.7 7.1 13.6 1.6 9.1 16.9 18.2

Candaciidae – – 1.2 1.9 – – – – 0.1 1.3

Copepoda – – 3.3 1.9 – – 0.1 4.5 – – 

Corycaeidae – – – – 0.1 3 – – – – 

Cyclopoida – – – – 1.1 16.7 – – <0.1 5.2

Euchaeta sp. – – – – – – 9 4.5 – – 

Harpacticoida – – <0.1 1.9 – – – – – – 

Lubbockia squillimana – – – – – – – – <0.1 1.3

Oncaea sp. – – 0.2 1.9 0.2 3 – – 0.1 2.6

Paracandacia simplex – – 2.1 1.9 – – – – – – 

Pleuromamma gracilis – – – – – – – – 0.4 1.3

Pleuromamma piseki – – 0.7 1.9 – – – – 2.8 1.3

Pleuromamma sp. – – 39 13.5 4.7 4.5 – – 0.8 2.6
188

Table 8.11. Percent volume (%V) and percent frequency (%F) of prey consumed by Notolychnus valdiviae collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=52) (n=66) (n=22) (n=77)

(E=0) (E=44) (E=44) (E=7) (E=31)

Food Item % V % F % V % F % V % F % V % F % V % F

Pleuromamma xiphias – – 4.3 1.9 15.9 4.5 – – 11.7 3.9

Poecilostomatoida – – – – 0.5 1.5 0.3 4.5 – – 

Unidentified copepod parts – – 14.7 30.8 25.6 22.7 5.8 13.6 7.4 26

EUPHAUSIACEA – – – – 8.4 1.5 16.2 13.6 22 6.5

Euphausiidae – – – – 8.4 1.5 – – 21.9 5.2

Unidentified euphausiid parts – – – – – – 16.2 13.6 0.1 1.3

CRUSTACEA – – 0.1 1.9 22.9 37.9 48.5 68.2 19.7 41.6

Unidentified crustacean parts – – 0.1 1.9 22.9 37.9 48.5 68.2 19.7 41.6

DECAPODA – – – – 0.1 3 – – <0.1 1.3

Unidentified decapod parts – – – – 0.1 3 – – <0.1 1.3

CHAETOGNATHA – – – – – – <0.1 4.5 – – 

Unidentified chaetognath parts – – – – – – <0.1 4.5 – – 

OTHER – – 26.4 40.4 5.5 12.1 17.5 18.2 13.8 27.3

Organic material – – 26.2 34.6 5.5 10.6 17.5 18.2 13.8 27.3

Unidentified animal parts – – 0.2 5.8 <0.1 3 – – – 1.3
189

Table 8.12. Percent volume (%V) and percent frequency (%F) of prey consumed by Ceratoscopelus warmingii collected from three sites 

(AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=4) (n=3) (n=41) (n=3) (n=21)

(E=1) (E=3) (E=2) (E=4) (E=6)

Food Item % V % F % V % F % V % F % V % F % V % F

CNIDARIA – – – – 1.7 2.4 – – – – 

Hydrozoa – – – – 1.7 2.4 – – – – 

MOLLUSCA 0.1 25 – – 0.5 12.2 – – 0.4 9.5

Bivalvia – – – – 0.1 2.4 – – – – 

Mollusca – – – – – – – – 0.4 4.8

Unidentified mollusk parts 0.1 25 – – 0.4 9.8 – – <0.1 4.8

CEPHALOPODA – – – – – – – – 6.2 4.8

Cephalopoda – – – – – – – – 6.2 4.8

GASTROPODA – – – – 4.4 9.8 – – – – 

Gastropoda – – – – 4.4 9.8 – – – – 

OSTRACODA 1.4 50 – – 2.3 31.7 – – 4 33.3

Conchoecinae – – – – 0.3 2.4 – – – – 

Halocyprididae – – – – 0.2 2.4 – – – – 

Myodocopida 1.4 50 – – 0.6 14.6 – – 0.7 23.8

Ostracoda – – – – 0.9 9.8 – – 0.1 9.5

Platycopida – – – – 0.1 2.4 – – – – 

Unidentified ostracod parts – – – – 0.2 7.3 – – 3.1 9.5

COPEPODA 8.4 100 13.4 100 9.1 65.9 1.2 33.3 3.5 47.6

Calanoida 0.6 25 0.7 33.3 1 4.9 1.2 33.3 2.5 4.8

Candacia sp. – – 3.5 33.3 – – – – – – 

Copepoda 3.1 75 – – 2.7 56.1 – – 0.8 28.6

Corycaeidae – – 0.6 33.3 – – – – – – 
190

Table 8.12. Percent volume (%V) and percent frequency (%F) of prey consumed by Ceratoscopelus warmingii collected from three sites 

(AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=4) (n=3) (n=41) (n=3) (n=21)

(E=1) (E=3) (E=2) (E=4) (E=6)

Food Item % V % F % V % F % V % F % V % F % V % F

Corycaeus sp. – – – – 0.2 4.9 – – 0.2 4.8

Cyclopoida – – – – <0.1 2.4 – – <0.1 4.8

Harpacticoida – – – – <0.1 2.4 – – – – 

Microsetella rosea – – – – – – – – <0.1 4.8

Miracia efferata – – 1.1 33.3 – – – – – – 

Miraciidae – – – – <0.1 2.4 – – – – 

Temora stylifera – – 0.4 33.3 – – – – – – 

Unidentified copepod parts 4.7 25 7.1 33.3 5.1 19.5 – – <0.1 9.5

AMPHIPODA 13.2 50 0.4 33.3 0.8 12.2 – – 8.4 28.6

Amphipoda 13.2 50 – – 0.6 12.2 – – 0.7 9.5

Hyperiidea – – 0.4 33.3 0.2 2.4 – – 1.7 9.5

Phronima stebbingii – – – – – – – – 4.6 4.8

Unidentified amphipod parts – – – – – – – – 1.4 14.3

EUPHAUSIACEA 1.2 25 – – 0.4 4.9 – – – – 

Euphausiidae 1.2 25 – – 0.4 4.9 – – – – 

CRUSTACEA 13.5 50 8.4 33.3 5.1 34.1 44.4 33.3 4.2 42.9

Crustacea – – – – 0.1 2.4 – – 0.3 4.8

Unidentified crustacean parts 13.5 50 8.4 33.3 5 31.7 44.4 33.3 3.9 38.1

DECAPODA – – – – 0.5 7.3 – – – – 

Caridea – – – – 0.1 2.4 – – – – 

Decapoda – – – – 0.2 2.4 – – – – 

Unidentified decapod parts – – – – 0.2 2.4 – – – – 
191

Table 8.12. Percent volume (%V) and percent frequency (%F) of prey consumed by Ceratoscopelus warmingii collected from three sites 

(AC601, AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=4) (n=3) (n=41) (n=3) (n=41)

(E=1) (E=3) (E=2) (E=3) (E=2)

Food Item % V % F % V % F % V % F % V % F % V % F

ANNELIDA – – – – 1.4 7.3 – – 1.6 19

Unidentified polychaete parts – – – – 1.4 7.3 – – 1.6 19

CHAETOGNATHA – – – – – – – – <0.1 4.8

Unidentified chaetognath parts – – – – – – – – <0.1 4.8

FISH – – 77 33.3 0.2 4.9 – – 0.1 4.8

Fish – – 77 33.3 – – – – – – 

Unidentified fish parts – – – – 0.2 4.9 – – 0.1 4.8

SALPIDA – – – – – – – – 3.1 4.8

Salpidae – – – – – – – – 3.1 4.8

OTHER 62.3 75 0.9 33.3 73.7 92.7 54.3 66.7 68.6 81

Organic material 43.4 75 0.9 33.3 68.5 87.8 54.3 66.7 65.5 76.2

Unidentified animal parts 18.9 25 – – 5.5 12.2 – – 3.1 9.5
192

Table 8.13. Percent volume (%V) and percent frequency (%F) of prey consumed by Lepidophanes guentheri collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=15) (n=20) (n=52) (n=3) (n=30)

(E=0) (E=12) (E=12) (E=1) (E=13)

Food Item % V % F % V % F % V % F % V % F % V % F

GASTROPODA – – – – 0.8 1.9 – – – – 

Gastropoda – – – – 0.8 1.9 – – – – 

OSTRACODA 8.3 60 6.6 5 1.6 19.2 71.1 33.3 8.6 30

Conchoecinae 0.2 13.3 – – 0.5 1.9 71.1 33.3 6.8 13.3

Halocyprididae 2.4 6.7 – – – – – – – – 

Myodocopida 0.5 20 6.6 5 – – – – 1.1 10

Ostracoda – – – – 0.1 7.7 – – 0.2 3.3

Unidentified ostracod parts 5.2 40 – – 1 9.6 – – 0.5 10

COPEPODA 75.9 86.7 11.9 50 21.6 59.6 12.1 66.7 25.6 66.7

Calanoida 27.6 20 2 10 5.8 17.3 3.7 33.3 9 10

Candacia curta – – – – 0.5 1.9 – – – – 

Candacia sp. – – – – – – – – 3.5 3.3

Copepoda 2.2 26.7 – – 0.8 11.5 – – 0.3 10

Corycaeus sp. – – – – – – – – 0.2 3.3

Cyclopoida 0.2 33.3 – – <0.1 5.8 – – 0.5 23.3

Farranula gracilis – – – – <0.1 1.9 – – 

Harpacticoida – – 0.5 5 – – – – 0.1 3.3

Pleuromamma gracilis – – – – – – – – 0.3 3.3

Pleuromamma piseki 14.2 6.7 – – 8.1 11.5 – – 2.9 3.3

Pleuromamma sp. 7.3 26.7 – – 5.4 9.6 – – – – 

Unidentified copepod parts 24.4 53.3 9.4 35 1 15.4 8.5 33.3 8.8 33.3
193

Table 8.13. Percent volume (%V) and percent frequency (%F) of prey consumed by Lepidophanes guentheri collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=15) (n=20) (n=52) (n=3) (n=30)

(E=0) (E=12) (E=12) (E=1) (E=13)

Food Item % V % F % V % F % V % F % V % F % V % F

AMPHIPODA – – 9.9 5 0.2 1.9 – – 35.3 6.7

Hyperiidea – – – – – – – – 5.9 3.3

Phronima sp. – – – – – – – – 29.4 3.3

Unidentified amphipod parts – – 9.9 5 0.2 1.9 – – – – 

EUPHAUSIACEA – – 25.7 10 20.2 13.5 14.9 33.3 0.1 3.3

Euphausiidae – – 25.7 10 8.1 1.9 14.9 33.3 – – 

Thysanopoda sp. – – – – 1.5 1.9 – – – – 

Unidentified euphausiid parts – – – – 10.5 9.6 – – 0.1 3.3

CRUSTACEA 6.2 13.3 33.2 15 48.4 46.2 – – 23.9 30

Unidentified crustacean parts 6.2 13.3 33.2 15 48.4 46.2 – – 23.9 30

DECAPODA – – – – 0.3 9.6 – – 0.2 3.3

Decapoda – – – – – – – – 0.2 3.3

Unidentified decapod parts – – – – 0.3 9.6 – – – – 

FISH – – – – <0.1 1.9 – – <0.1 3.3

Unidentified fish parts – – – – <0.1 1.9 – – <0.1 3.3

OTHER 9.6 53.3 12.8 35 7 36.5 1.9 33.3 6.2 53.3

Inorganic material – – – – – – – – <0.1 3.3

Organic material 9.6 46.7 12.8 35 7 36.5 1.9 33.3 6.2 43.3

Unidentified animal parts <0.1 6.7 – – – – – – <0.1 13.3
194

Table 8.14. Percent volume (%V) and percent frequency (%F) of prey consumed by Lampanyctus alatus collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=6) (n=7) (n=12) (n=2) (n=29)

(E=0) (E=0) (E=4) (E=3) (E=8)

Food Item % V % F % V % F % V % F % V % F % V % F

OSTRACODA 7.6 33.3 – – 1.3 25 – – 4.3 34.5

Conchoecinae 6.8 16.7 – – – – – – 3.1 6.9

Halocyprididae – – – – – – – – 0.3 3.4

Myodocopida 0.8 33.3 – – 1.2 16.7 – – <0.1 3.4

Ostracoda – – – – – – – – 0.4 6.9

Unidentified ostracod parts – – – – <0.1 8.3 – – 0.6 13.8

COPEPODA 34.9 83.3 45.4 71.4 21.9 66.7 28.3 100 18.4 48.3

Calanoida 10.9 33.3 42.7 57.1 0.5 16.7 26.1 100 0.6 6.9

Copepoda – – – – 7.9 33.3 – – 0.5 17.2

Corycaeus sp. – – – – – – – – 0.4 3.4

Eucalanus sp. – – – – – – – – 5 3.4

Oncaea sp. – – – – – – 2.2 50 – – 

Paracandacia simplex – – 2.7 14.3 – – – – – – 

Pleuromamma piseki – – – – 8.2 8.3 – – – – 

Pleuromamma sp. 6.2 16.7 – – 2.6 8.3 – – 0.7 6.9

Unidentified copepod parts 17.8 50 – – 2.6 28.6 – – 11.1 27.6

AMPHIPODA 30.4 33.3 – – – – – – 21.3 20.7

Amphipoda – – – – – – – – 1.6 10.3

Gammaridea – – – – – – – – 0.1 3.4

Hyperiidea 27.2 16.7 – – – – – – – – 

Lestrigonus sp. – – – – – – – – 2.8 3.4

Unidentified amphipod parts 3.1 16.7 – – – – – – 16.9 6.9
195

Table 8.14. Percent volume (%V) and percent frequency (%F) of prey consumed by Lampanyctus alatus collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night. —Continued 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AC601 AT340 GC852

Night Day Night Day Night

(n=6) (n=7) (n=12) (n=2) (n=29)

(E=0) (E=0) (E=4) (E=3) (E=8)

Food Item % V % F % V % F % V % F % V % F % V % F

EUPHAUSIACEA – – – – 23.9 16.7 – – 5 6.9

Euphausiidae – – – – 21.3 8.3 – – 0.1 3.4

Nematoscelis sp. – – – – – – – – 4.9 3.4

Unidentified euphausiid parts – – – – 2.6 8.3 – – – – 

CRUSTACEA 22.4 33.3 25.5 14.3 27.7 83.3 60.9 50 43.1 48.3

Crustacea – – – – – – – – 0.1 3.4

Unidentified crustacean parts 22.4 33.3 25.5 14.3 27.7 83.3 60.9 50 43 44.8

DECAPODA – – – – – – – – 3.9 3.4

Decapoda – – – – – – – – 3.9 3.4

FISH – – – – – – – – <0.1 3.4

Unidentified fish parts – – – – – – – – <0.1 3.4

SALPIDA – – – – – – 10.9 50 – – 

Salpidae – – – – – – 10.9 50 – – 

OTHER 4.7 16.7 29.1 28.6 25.2 50 – – 4 31

Organic material 4.7 16.7 29.1 28.6 25.2 50 – – 3.7 27.6

Unidentified animal parts – – – – – – – – 0.3 3.4
196

SIA was conducted on five species of Myctophidae, C. warmingii, D. lucidus, D. mollis, 

D. problematicus, L. alatus, L. guentheri, and Myctophum affine. Significant spatial variations 

for δ13C and δ15N were not documented for any myctophid; however, significant differences 

were documented among myctophid species. Myctophum affine was significantly depleted in 

13C and 15N compared to Diaphus spp. (Tukey, p <0.001), L. alatus (Tukey, p <0.001), and L. 

guentheri (Tukey, p <0.001, p = 0.001). Myctophum affine was also depleted in 13C compared to 

C. warmingii (Tukey, p <0.001). Diaphus spp. was significantly enriched in 15N compared to C. 

warmingii (Tukey, p <0.001) and L. guentheri (Tukey, p = 0.001). Lampanyctus alatus was 

significantly enriched in 15N compared to C. warmingii (Tukey, p <0.001). A dietary 

ontogenetic shift was evident in all myctophid species; however, a significant positive 

relationship between 15N and SL was only documented for Diaphus spp. (R2=0.751, p = 0.03, 

fig. 8.4C). An enrichment in 15N was also documented with increasing trophic levels but was 

less evident in 13C (fig. 8.2). Although no chemosynthetic signature was reported for any 

myctophid, M. affine was depleted in 13C compared to POM samples (fig. 8.2) but was within the 

range of previously reported values for photosynthetic material. 

8.3.3.3 Phosichthyidae

Two species of Phosichthyidae, P. mauli and V. poweriae, were analyzed for dietary 

composition at the three sites. Empty stomachs occurred less frequently in P. mauli (maximum 

of 44 percent) compared to V. poweriae (maximum of 72 percent), and more frequently in 

specimens collected during the day than at night (tables 8.15 and 8.16). DVMs were evident for 

P. mauli and V. poweriae, with full stomachs occurring more frequently in specimens collected 

in the epipelagic at night (fig. 8.3M, N). 
197

Diet comparisons were conducted on both phosichthyid species. Overall, the diets of P. 

mauli were less diverse (seven prey categories; table 8.15) than for V. poweriae, (ten categories; 

table 8.16) and did not include any noncrustacean prey. Spatial variations were also evident for 

both species. At GC852, P. mauli primarily consumed amphipods; however, at AT340, 

euphausiids were volumetrically more important for P. mauli, though copepods occurred more 

frequently (table 8.15). In contrast, for V. poweriae collected at GC852, myctophids were the 

most important prey item in terms of volume and frequency, whereas at AT340 ostracods, 

particularly halocyprids, were volumetrically more important in specimens collected during the 

day and copepods for specimens collected at night (table 8.16). 
198

Table 8.15. Percent volume (%V) and percent frequency (%F) of prey consumed by Pollichthys mauli

collected from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night. 

[n, number of full stomachs; E, number of empty stomachs; –, no value] 

AT340 GC852

Day Night Night

(n=9) (n=37) (n=2)

(E=7) (E=8) (E=0)

Food Item % V % F % V % F % V % F

OSTRACODA 17.9 11.1 21.3 32.4 27.8 50

Conchoecinae – – 14.1 13.5 11.9 50

Halocyprididae – – 2.1 5.4 – – 

Myodocopida – – <0.1 5.4 – – 

Ostracoda 17.9 11.1 3.4 16.2 – – 

Unidentified ostracod parts – – 1.5 13.5 15.9 50

COPEPODA 79.8 77.8 14.2 37.8 8.7 50

Calanoida 40.4 11.1 1.6 5.4 – – 

Copepoda – – 0.7 8.1 0.8 50

Corycaeus sp. – – 0.5 2.7 – – 

Cyclopoida – – 2.7 5.4 – – 

Harpacticoida – – 0.2 2.7 – – 

Pleuromamma borealis – – 3.3 2.7 – – 

Pleuromamma piseki – – 0.8 2.7 – – 

Pleuromamma sp. – – 3.8 10.8 – – 

Unidentified copepod parts 39.5 66.7 0.6 10.8 7.9 50

AMPHIPODA – – 4.4 2.7 63.5 50

Amphipoda – – 4.4 2.7 – – 

Unidentified amphipod parts – – – – 63.5 50

EUPHAUSIACEA – – 44.9 8.1 – – 

Euphausiidae – – 0.1 2.7 – – 

Nyctiphanes capensis – – 17.5 2.7 – – 

Stylocheiron sp. – – 6.6 2.7 – – 

Thysanopoda sp. – – 20.7 2.7 – – 

CRUSTACEA – – 11.4 56.8 – – 

Unidentified crustacean parts – – 11.4 56.8 – – 

DECAPODA – – <0.1 2.7 – – 

Unidentified decapod parts – – <0.1 2.7 – – 

OTHER 2.2 11.1 3.9 18.9 – – 

Organic material 2.2 11.1 3.9 18.9 – – 
199

Table 8.16. Percent volume (%V) and percent frequency (%F) of prey consumed by Vinciguerria

AT340, and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

poweriae collected from three sites (AC601, 

AC601 AT340 GC852

Night Day Night Day Night

(n=2) (n=3) (n=39) (n=6) (n=51)

(E=0) (E=4) (E=9) (E=15) (E=24)

Food Item % V % F % V % F % V % F % V % F % V % F

MOLLUSCA – – – – <0.1 5.1 – – <0.1 5.9

Unidentified mollusk parts – – – – <0.1 5.1 – – <0.1 5.9

GASTROPODA – – – – – – – – <0.1 2

Gastropoda – – – – – – – – <0.1 2

OSTRACODA – – 93.7 66.7 16.8 30.8 8.8 33 12.2 43.1

Archiconchoecinae – – – – 1.6 5.1 2.4 16.7 0.7 2

Conchoecinae – – 10 33.3 6.8 7.7 6.4 16.7 6.5 15.7

Halocyprididae – – 83.7 33.3 2.2 7.7 – – 1.2 3.9

Halocypridinae – – – – – – – – 0.6 5.9

Halocypris sp. – – – – – – – – 0.6 3.9

Myodocopida – – – – 0.4 7.7 – – 0.8 11.8

Myodocopina – – – – 1 5.1 – – – –

Sarsiellidae – – – – 0.2 2.6 – – – –

Unidentified ostracod parts – – – – 4.6 20.5 – – 1.8 13.7

COPEPODA – – 6.3 33.3 19.3 64.1 10.9 50 12.3 39.2

Calanoida – – – – 2.9 15.4 – – 4.4 11.8

Candacia bipinnata – – – – 0.4 2.6 – – – –

Candacia varicans – – – – 0.4 2.6 – – – –

Candaciidae – – – – 4 16.7 – –

Copepoda – – – – 0.1 2.6 3 16.7 0.5 9.8

Corycaeus sp. – – – – 3.8 15.4 4 16.7 0.3 9.8

Cyclopoida – – – – 0.7 20.5 – – 0.5 7.8

Farranula gracilis – – – – 0.2 2.6 – – – –
200

Table 8.16. Percent volume (%V) and percent frequency (%F) of prey consumed by Vinciguerria

AT340, and GC852) in the Gulf of Mexico separated by day and night.—Continued

[n, number of full stomachs; E, number of empty stomachs; –, no value]

poweriae collected from three sites (AC601, 

AC601 AT340 GC852

Night Day Night Day Night

(n=2) (n=3) (n=39) (n=6) (n=51)

(E=0) (E=4) (E=9) (E=15) (E=24)

Food Item % V % F % V % F % V % F % V % F % V % F

Lubbockia sp. – – – – – – – – <0.1 2

Paracandacia bispinosa – – – – – – – – 2.2 2

Paracandacia simplex – – – – 0.5 2.6 – – – –

Pleuromamma sp. – – – – – – – – 0.5 2

Sapphirina sp. – – – – – – – – 0.1 2

Temora sp. – – – – <0.1 2.6 – – – –

Undinula vulgaris – – – – 0.5 2.6 – – – –

Unidentified copepod parts – – 6.3 33.3 9.9 51.3 – – 3.8 21.6

AMPHIPODA – – – – 1.6 5.1 – – 12.8 17.6

Brachyscelus crusculum – – – – – – – – 4.2 2

Brachyscelus sp. – – – – – – – – 0.2 2

Eupronoe armata – – – – – – – – 1.5 2

Hyperiidea – – – – – – – – 1 5.9

Primno latreillei – – – – – – – – 2 2

Themistella fusca – – – – 1.2 2.6 – – – –

Tryphana malmi – – – – 0.4 2.6 – – – –

Unidentified amphipod parts – – – – – – – – 4 11.8

EUPHAUSIACEA – – – – 10 7.7 – – – –

Euphausiidae – – – – 5.1 5.1 – – – –

Unidentified euphausiid parts – – – – 5 2.6 – – – –

CRUSTACEA 100 100 – – 43.7 69.2 – – 20.2 60.8

Unidentified crustacean parts 100 100 – – 43.7 69.2 – – 20.2 60.8
201

Table 8.16. Percent volume (%V) and percent frequency (%F) of prey consumed by Vinciguerria poweriae collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.—Continued

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Day Night

(n=2) (n=3) (n=39) (n=6) (n=51)

(E=0) (E=4) (E=9) (E=15) (E=24)

Food Item % V % F % V % F % V % F % V % F % V % F

DECAPODA – – – – 0.6 2.6 – – 11.3 2

Decapoda – – – – – – 11.3 2

Unidentified decapod parts – – – – 0.6 2.6 – – – –

FISH – – – – 0.1 2.6 72.3 50 17.8 5.9

Myctophidae – – – – – – 72.3 50 17.7 3.9

Unidentified fish parts – – – – 0.1 2.6 – – 0.1 2

OTHER – – – – 7.9 23.1 8 16.7 13.3 33.3

Organic material – – – – 7.9 20.5 8 16.7 13.3 31.4

Unidentified animal parts – – – – <0.1 2.6 – – <0.1 7.8
202

SIA was conducted on P. mauli and V. poweriae (table 8.2). No spatial comparisons 

were conducted on P. mauli, and no significant differences were documented in δ13C or δ15N for

V. poweriae. Despite no spatial variation, P. mauli was significantly enriched in 13C (t-test, p 

<0.001) but depleted in 15N (t-test, p = 0.002) compared to V. poweriae. Additionally, a positive 

relationship between SL and δ15N was identified for P. mauli and V. poweriae; however, this 

relationship was only significant for the latter (R2=0.614, p<0.01, fig. 8.4D). A trophic shift of 

approximately 2 per mil in nitrogen and <1 per mil in carbon was documented for both 

phosichthyids, although no chemosynthetic signature was detected in either species (fig. 8.2). 

8.3.3.4%Sternoptychidae

Three species of Sternoptychidae, A. aculeatus, A. hemigymnus, and V. tripunctulatus, 

were analyzed for diet composition. Empty stomachs occurred less frequently in V. 

tripunctulatus (maximum of 30 percent) compared to A. aculeatus (maximum of 32 percent) or 

A. hemigymnus (maximum of 89 percent), with empty stomachs occurring more frequently 

during the day than night. DVMs were evident for all sternoptychids. Although more full 

stomachs were documented at night in the epipelagic for A. aculeatus (fig. 8.3O), both A. 

hemigymnus and V. tripunctulatus had more full stomachs documented at night in the 

mesopelagic (fig. 8.3P, Q). 

Diet comparisons were conducted on A. aculeatus, A. hemigymnus, and V. tripunctulatus. 

Copepoda and Ostracoda, particularly Conchoecinae, were the dominant prey items for 

Argyropelecus spp.; however, spatial variations were documented. Euphausiacea was 

volumetrically important in the stomachs of Argyropelecus spp. collected at GC852, although 

ostracods occurred more frequently in the stomachs of A. aculeatus (table 8.17) and copepods in 

the stomachs of A. hemigymnus (table 8.18). Ostracods were the most important prey in terms of 
203

volume and frequency for A. aculeatus collected at AT340 and AC601, whereas copepods were 

more important for A. hemigymnus. In contrast, no spatial differences were documented for V. 

tripunctulatus, and Copepoda, particularly Pleuromamma spp., was the most important prey 

consumed in terms of volume and frequency (table 8.19). 
204

Table 8.17. Percent volume (%V) and percent frequency (%F) of prey consumed by Argyropelecus aculeatus collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Night

(n=3) (n=5) (n=7) (n=15)

(E=0) (E=2) (E=2) (E=7)

Food Item % V % F % V % F % V % F % V % F

MOLLUSCA – – – – 0.3 14.3 – –

Unidentified mollusk parts – – – – 0.3 14.3 – –

CEPHALOPODA – – 9.7 20 – – – –

Unidentified cephalopod parts – – 9.7 20 – – – –

GASTROPODA – – 1.9 40 3.6 14.3 0.1 6.7

Gastropoda – – 1.9 40 3.6 14.3 0.1 6.7

OSTRACODA 42.1 100 23.3 80 26.4 57.1 9.4 53.3

Archiconchoecinae – – – – – – 0.2 6.7

Conchoecinae 25.1 66.7 12.6 60 18.6 28.6 3.5 20

Halocypridinae – – 6.8 20 – – – –

Halocypris sp. 4.6 33.3 – – – – – –

Myodocopida 12.4 33.3 3.4 20 7.1 28.6 2.4 26.7

Ostracoda – – – – – – 2.7 6.7

Unidentified ostracod parts – – 0.5 20 0.7 14.3 0.6 20

COPEPODA 31.1 100 10.8 80 14.4 42.9 2.6 46.7

Calanoida 9.4 33.3 3.3 40 2.3 14.3 0.5 6.7

Copepoda 10.6 33.3 1.5 20 5.7 42.9 1.1 33.3

Corycaeus sp. 0.2 33.3 – – – – – –

Cyclopoida 1.5 66.7 0.2 20 – –

Lubbockia aculeata – – – – 0.1 14.3 <0.1 6.7

Paracalanidae 9.4 33.3 – – – – – –

Paracalanus aculeatus – – – – – – 0.5 6.7

Pleuromamma robusta – – 1.9 20 – – – –
205

Table 8.17. Percent volume (%V) and percent frequency (%F) of prey consumed by Argyropelecus aculeatus collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.—Continued

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Night

(n=3) (n=5) (n=7) (n=15)

(E=0) (E=2) (E=2) (E=7)

Food Item % V % F % V % F % V % F % V % F

Pleuromamma xiphias – – – – 6.3 14.3 – –

Poecilostomatoida – – 1.5 20 – – 0.3 6.7

Unidentified copepod parts – – 2.4 40 – – 0.1 13.3

AMPHIPODA 0.4 33.3 24.8 60 6 42.9 7.2 26.7

Amphipoda 0.4 33.3 2.9 20 0.1 14.3 1.5 6.7

Anchylomera blossevillei – – – – – – 3.2 6.7

Eusiridae – – – – – – 0.5 13.3

Gammaridea – – – – – – 0.7 6.7

Hyperiidea – – – – 0.2 14.3 1.4 6.7

Phronima sp. – – 5.8 20 – – – –

Primno evansi – – 8.8 20 – – – –

Primno sp. – – – – 5.7 14.3 – –

Scina oedicarpus – – 1.5 20 – – – –

Unidentified amphipod parts – – 5.8 20 – – – –

EUPHAUSIACEA – – – – – – 14.2 13.3

Euphausiidae – – – – – – 14.2 13.3

DECAPODA – – – – – – 0.1 6.7

Unidentified decapod parts – – – – – – 0.1 6.7

CRUSTACEA 1.8 33.3 17.7 60 20.6 85.7 33.4 80

Crustacea – – – – 0.2 14.3 1.9 13.3

Unidentified crustacean parts 1.8 33.3 17.7 60 20.4 85.7 31.5 80

CHAETOGNATHA – – – – – – 1.6 20

Sagittoidea – – – – – – 1.6 20
206

Table 8.17. Percent volume (%V) and percent frequency (%F) of prey consumed by Argyropelecus aculeatus collected from three sites (AC601, 

AT340, and GC852) in the Gulf of Mexico separated by day and night.—Continued

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Night

(n=3) (n=5) (n=7) (n=15)

(E=0) (E=2) (E=2) (E=7)

Food Item % V % F % V % F % V % F % V % F

OTHER 24.7 33.3 11.7 40 28.8 85.7 31.5 60

Organic material 24.7 33.3 11.7 40 28.6 85.7 25.6 60

Unidentified animal parts – – – – 0.2 14.3 5.9 6.7
207

Table 8.18. Percent volume (%V) and percent frequency (%F) of prey consumed by Argyropelecus hemigymnus 

collected from two sites (AT340 and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AT340 GC852

Day Night Day Night

(n=2) (n=1) (n=2) (n=6)

(E=2) (E=8) (E=1) (E=8)

Food Item % V % F % V % F % V % F % V % F

OSTRACODA 1.2 100 – – 47.7 50 8.6 33.3

Conchoecinae – – – – 47.7 50 – –

Myodocopida – – – – – – 5.7 16.7

Ostracoda 0.6 50 – – – – 1.9 16.7

Unidentified ostracod parts 0.6 50 – – – – 1 33.3

COPEPODA 52.3 100 25.9 100 38.8 100 23.5 100

Calanoida 3.3 100 18.5 100 11.9 50 20.8 66.7

Copepoda 48.6 50 – – 26.8 50 0.2 50

Lubbockia aculeata – – 4.9 100 – – – –

Lubbockia sp. – – – – – – 0.1 16.7

Pleuromamma abdominalis – – – – – – 0.9 16.7

Unidentified copepod parts 0.3 50 2.5 100 – – 1.4 16.7

AMPHIPODA 0.9 50 – – – – – –

Unidentified amphipod parts 0.9 50 – – – – – –

EUPHAUSIACEA – – – – – – 47.3 16.7

Nematoscelis microps – – – – – – 47.3 16.7

CRUSTACEA 3 50 – – 0.1 50 4.9 66.7

Crustacea – – – – 0.1 50 <0.1 16.7

Unidentified crustacean parts 3 50 – – – – 4.9 66.7

OTHER 42.6 100 74.1 100 13.4 100 15.7 100

Organic material 42.6 100 74.1 100 13.4 100 15.7 100
208

Table 8.19.

(AC601, 

[n, number of 

Percent volume (%V) and percent frequency (%F) of prey consumed by Valenciennellus tripunctulatus collected from 

AT340, and GC852) in the Gulf of Mexico separated by day and night.

full stomachs; E, number of empty stomachs; –, no value]

three sites 

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=12) (n=50) (n=13) (n=44)

(E=0) (E=5) (E=13) (E=0) (E=7)

Food Item % V % F % V % F % V % F % V % F % V % F

OSTRACODA – – 1 25 1.4 16 0.6 38.5 1.7 20.5

Archiconchoecinae – – – – – – – – 0.4 2.3

Conchoecinae – – 0.9 16.7 0.6 4 0.5 30.8 0.2 4.5

Halocyprididae – – – – – – 0.1 7.7 – –

Myodocopida – – – – 0.1 2 – – 0.2 2.3

Myodocopina – – – – 0.1 2 – – – –

Ostracoda – – – – 0.2 4 – – <0.1 2.3

Unidentified ostracod parts – – 0.1 16.7 0.3 6 – – 1 11.4

COPEPODA 1.2 100 72.9 91.7 46.4 68 48.1 84.6 45.6 56.8

Aegisthus mucronatus – – – – – – – – 0.1 2.3

Aetideidae – – – – 0.1 2 0.4 7.7 – –

Calanoida – – 12 41.7 7 18 28.8 76.9 3.2 9.1

Candacia curta – – – – 0.3 2 – – – –

Copepoda – – 6.8 33.3 0.5 2 – – 2.1 9.1

Corycaeus sp. – – 0.3 8.3 – – – – – –

Cyclopoida 1.2 100 0.8 16.7 0.7 8 <0.1 15.4 0.9 9.1

Euchaeta sp. – – – – – – – – 1.5 2.3

Lubbockia aculeata – – – – – – – – 0.4 6.8

Lubbockia sp. – – 0.1 8.3 0.7 8 – – – –

Lubbockia squillimana – – 0.3 8.3 0.2 2 – – – –

Oithonidae – – 0.1 8.3 – – – – – –

Pleuromamma abdominalis – – 3.3 16.7 – – – – 0.3 2.3

Pleuromamma piseki – – – – – – – – 6.8 4.5
209

Table 8.19.

(AC601, 

[n, number of 

Percent volume (%V) and percent frequency (%F) of prey consumed by Valenciennellus tripunctulatus collected from 

AT340, and GC852) in the Gulf of Mexico separated by day and night.—Continued

full stomachs; E, number of empty stomachs; –, no value]

three sites 

AC601 AT340 GC852

Night Day Night Day Night

(n=1) (n=12) (n=50) (n=13) (n=44)

(E=0) (E=5) (E=13) (E=0) (E=7)

Food Item % V % F % V % F % V % F % V % F % V % F

Pleuromamma robusta – – – – – – – – 1.5 2.3

Pleuromamma sp. – – 11.7 58.3 6 14 6.4 23.1 3.4 6.8

Pleuromamma xiphias – – 12.2 33.3 – – 6.3 15.4 – –

Poecilostomatoida – – – – – – 0.7 15.4 – –

Rhincalanus cornutus – – 6.4 33.3 4.1 8 – – 0.4 4.5

Rhincalanus sp. – – 1.2 8.3 0.8 2 – – – –

Unidentified copepod parts – – 17.7 41.7 26 44 5.4 15.4 25.2 47.7

AMPHIPODA – – – – – – <0.1 7.7 0.3 2.3

Amphipoda – – – – – – <0.1 7.7 – –

Unidentified amphipod parts – – – – – – – – 0.3 2.3

EUPHAUSIACEA – – – – – – 12.2 7.7 <0.1 2.3

Euphausiidae – – – – – – 12.2 7.7 – –

Unidentified euphausiid parts – – – – – – – – <0.1 2.3

CRUSTACEA 74.1 100 9.2 41.7 31.3 62 22.1 61.5 49.7 79.5

Unidentified crustacean parts 74.1 100 9.2 41.7 31.3 62 22.1 61.5 49.7 79.5

DECAPODA – – – – – – – – – –

Unidentified decapod parts – – – – – – – – – –

OTHER 24.7 100 16.8 50 21 50 17 53.8 2.7 31.8

Organic material 24.7 100 16.8 50 20.9 46 17 53.8 2.6 25

Unidentified animal parts – – – – 0.1 4 – – 0.1 9.1
210

SIA was conducted on four sternoptychids, A. aculeatus, Sternoptyx diaphana, S. 

pseudobscura, and V. tripunctulatus (table 8.2). Although A. aculeatus was significantly 

enriched in δ13C compared to Sternoptyx spp. (Tukey, p = 0.001) and V. tripunctulatus (Tukey, p

= 0.002), there was no significant difference in δ15N. Spatial variations were not conducted for 

Sternoptyx spp. and no variations were documented in δ13C or δ15N for A. aculeatus. However,

V. tripunctulatus was significantly depleted in 13C at AC601 compared to AT340 (p = 0.018), but

no differences were detected in δ15N. Although no dietary ontogenetic shifts were documented 

for Sternoptychidae (fig. 8.4E), there was trophic shift of approximately 2 per mil in nitrogen and 

<1 per mil in carbon with increasing trophic levels for sternoptychids (fig. 8.2), and no

chemosynthetic signature was documented.

8.3.3.5%Stomiidae

Chauliodus sloani was the only stomiid species analyzed for diet composition. A high 

frequency (>75 percent) of empty stomachs occurred in C. sloani, with empty stomachs 

occurring more frequently during the day. A DVM was also documented for C. sloani, with 

more full stomachs documented at night in the mesopelagic (fig. 8.3R). Using GCA, fish, 

particularly Bregmaceros spp. and Myctophidae, were documented as the dominant prey in 

volume and frequency (table 8.20) and no spatial variations were recorded.
211

Table 8.20. Percent volume (%V) and percent frequency (%F) of prey consumed by Chauliodus sloani collected from three sites (AC601, AT340, 

and GC852) in the Gulf of Mexico separated by day and night.

[n, number of full stomachs; E, number of empty stomachs; –, no value]

AC601 AT340 GC852

Night Day Night Day Night

(n=0) (n=0) (n=2) (n=1) (n=8)

(E=2) (E=5) (E=7) (E=8) (E=30)

% % F Food Item V % V % F % V % F % V % F % V % F

CRUSTACEA – – – – – – – – <0.1 12.5

Unidentified crustacean parts – – – – – – – – <0.1 12.5

FISH – – – – 99.7 50 100 100 87.5 37.5

Bregmaceros sp. – – – – – – 100 100 – –

Myctophidae – – – – – – – – 62.2 12.5

Unidentified fish parts – – – – 99.7 50 – – 25.3 25

OTHER – – – – 0.3 50 – – 12.5 62.5

Organic material – – – – 0.3 50 – – 12 50

Unidentified animal parts – – – – – – – – 0.5 12.5
212

SIA was conducted on two stomiid species, C. sloani and Photostomias guernei (table 

8.2). Although C. sloani was depleted in 13C and 15N compared to P. guernei, small sample sizes 

prevented statistical comparisons. Spatial variations were also not statistically analyzed due to 

small sample sizes. The stomiids exhibited enrichment in δ15N values with increasing trophic 

levels; however, enrichment in δ13C values was less evident (fig. 8.2). A significant positive 

relationship between δ15N values and SL was identified for C. sloani (R2=0.920, p = 0.01) and P. 

guernei, (R2

=0.994, p = 0.003, fig. 8.4F). In addition to dietary ontogenetic shifts for C. sloani

and P. guernei, there was trophic shift of approximately 2 per mil in nitrogen and <1 per mil in 

carbon with increasing trophic levels and no chemosynthetic signature was documented. 

8.4 Discussion

Zooplankton was documented as the dominant prey for midwater fishes using both GCA 

and SIA. Crustaceans, particularly the copepod Pleuromamma, were consumed by all midwater 

fishes except C. sloani. Additionally, GCA documented three general feeding guilds similar to 

the findings of Gartner and others (1997). Although trophic enrichment in 13C and 15N with 

increasing trophic levels was lower than the average 3-4 per mil documented in previous studies 

(Roelke and Cifuentes, 1997; Post, 2002; Rybczynski and others, 2008), the enrichment was 

within reported ranges and may result from variation in the nitrogen source and metabolic 

processes (Minagawa and Wada, 1984); however, further investigation was required. 

Additionally, chemosynthetically derived carbon did not significantly contribute to the diets of 

midwater fauna, as evident by the lack of depleted 13C, suggesting photosynthetic material, such 

as POM, supported the base of the midwater food web. 

POM was the main carbon source for both invertebrate and fish fauna. Spatial variations 

documented in POM may result from changes in productivity and species composition. 
213

Trichodesmium, a cyanobacterium, had extensive blooms documented in the GOM, which 

supply new nitrogen to the surrounding area (Holl and others, 2007). Additionally, previous 

literature reported Trichodesmium depleting 15N in POM (Montoya and others, 2002). The 

presence of different water masses can also account for spatial variations in POM. A warm core 

eddy was documented at AT340 during sampling and can encourage diatom production and alter 

the phytoplankton composition (Thompson and others, 2007). 

General trophic relationships documented using SIA for invertebrate species supported 

previous literature based on GCA. Zooplankton, euphausiids, and copepods occupied one 

trophic level above POM, with previous GCA for copepods (Dagg and others, 1989; Olson and 

others, 2006) and euphausiids (Kinsey and Hopkins, 1994) documenting POM-based diets. 

Larger crustaceans, such as S. debilis and A. lesuerii, were reported as trophically similar to 

zooplankton; however, previous studies reported crustaceans, fishes, and chaetognaths as the 

dominant prey consumed (Hopkins and others, 1994). Previous diet studies on Chaetognatha 

(Kehayias and others, 1996), Stigmatoteuthis arcturi (Cherel and Hobson, 2005), G. valens 

(Hopkins and others, 1994), and A. purpurea (Hopkins and others, 1994) were also supported by 

SIA. 

Species composition may also contribute to variations between decapod species. 

Although G. valens and S. debilis consumed similar prey (Hopkins and others, 1994; Hopkins 

and Sutton 1998), isotopic variations in prey species may alter the isotopic signatures of G. 

valens and S. debilis. Prey, such as the commonly consumed euphausiids, can have different 

feeding strategies, as documented in Thysanopoda spp., which consumed ostracods, and 

Euphausia spp., which consumed noncrustacean prey (Kinsey and Hopkins, 1994). Diet 
214

variations in prey alter δ15N (Fry, 1988; Post, 2002) and can be documented on higher trophic 

levels within the food web. 

Cyclothone spp. were classified as zooplanktivores. Similar feeding was documented for 

all Cyclothone spp. using GCA and SIA, supporting previous studies (Hopkins and others, 1996; 

Sutton and others, 1998). Variations in the species of zooplankton prey consumed suggested low 

competition for prey among species, as the dominant copepods consumed by each Cyclothone 

species inhabited different vertical distributions. Cyclothone braueri consumed the copepod 

Aegisthus mucronatus, which was documented from 300 to 500 m (Padmavati and others, 1998), 

whereas C. pseudopallida consumed Valdiviella minor, a mesopelagic/bathypelagic copepod 

documented at depths >500 m (Owre and Foyo, 1964), suggesting C. pseudopallida fed at deeper 

depths than C. braueri. The relationship between stomach fullness and DVMs also supported 

limited competition, as C. braueri occupied shallower depths and did not migrate. Variations in 

the isotopic signatures of Cyclothone spp. also suggested that Cyclothone spp. feed on different, 

but trophically similar, prey. 

Gonostoma elongatum was classified as a large crustacean consumer; however, 

zooplankton was frequently documented in GCA as well. This was similar to previous studies in 

the eastern GOM (Lancraft and others, 1988; Hopkins and others, 1996) and was supported by 

SIA. Preference for euphausiids may be evident in the DVM documented in G. elongatum, as 

euphausiids undergo similar migration patterns (Brinton, 1967). However, prey preferences in 

G. elongatum can be variable. Ontogenetic effects were previously documented for G. 

elongatum, with zooplankton consumed until G. elongatum could consume large crustaceans

(Clarke, 1982). Ontogenetic diet shifts were documented with SIA, with larger specimens 

consuming more euphausiids and less copepods and ostracods (Lancraft and others, 1988). 
215

Myctophids had the most diverse diets of all midwater fishes analyzed and were 

classified as zooplanktivores, using GCA and SIA. Copepods, amphipods, euphausiids, and 

ostracods were the dominant prey items, supporting previous literature (Hopkins and Baird, 

1985b; Hopkins and others, 1996; Sutton and others, 1998; Pusch and others, 2004). Although 

previous studies documented euphausiids as the dominant prey for L. alatus and L. guentheri

(Hopkins and Baird, 1985b, Hopkins and others, 1996), copepods were more important to the 

diet in this study. This diet variation may be attributed to ontogeny, as the majority of specimens 

analyzed were juveniles and larger myctophids consume larger crustacean prey (Hopkins and 

Baird, 1985b). Ontogeny may also contribute to variability in isotopic signatures. Although this 

study only documented ontogenetic diet shifts in Diaphus spp., previous studies have 

documented ontogenetic diet shifts in other myctophid species (Hopkins and Baird, 1985b; 

Hopkins and others, 1996; Sutton and others, 1998; Pusch and others, 2004). Comparisons 

between data from GCA and SIA also suggested variations in diet. Although not evident in 

GCA, depleted 15N in M. affine and C. warmingii may result from omnivory, previously 

documented in C. warmingii (Robinson, 1984). Additionally, the consumption of nitrogendepleted prey, such as salps, was previously documented in the stomachs of C. warmingii

(Sutton and others, 1998) and may contribute to depleted 15N in M. affine and C. warmingii. 

Both phosichthyid species were also classified as zooplanktivores. Pollichthys mauli 

primarily consumed zooplankton and euphausiids; this finding was similar to previous reports 

(Sutton and others, 1998). In contrast, V. poweriae consumed fish in addition to zooplankton, 

which, though not previously reported for V. poweriae (Hopkins and others, 1996), was similar 

to previously dietary studies on V. nimbaria (Hopkins and others, 1996; Champalbert and others, 

2008). As both P. mauli and V. poweriae exhibit similar DVM patterns, the incorporation of 
216

non-zooplankton prey may reduce competition for zooplankton prey between these species. SIA 

supports GCA, with enriched 15N documented in V. poweriae compared to P. mauli. It was also 

possible that P. mauli may have targeted 15N-depleted prey items, such as salps, as evident by the 

depleted isotopic signature. Size may also be a contribution to trophic differences between these 

phosichthyids, as ontogenetic diet shifts were documented for Vinciguerria spp. (Champalbert 

and others, 2008; this study). 

All sternoptychids were classified as zooplanktivores. Valenciennellus tripunctulatus fed 

almost exclusively on copepods, with ostracods, amphipods, and euphausiids also being 

important foods, supporting previous literature (Hopkins and Baird, 1981; Hopkins and others, 

1996; Sutton and others, 1998). Although Argyropelecus spp. ate a mixture of copepods, 

ostracods, amphipods, and euphausiids, which also supported previous studies (Hopkins and 

Baird, 1981; Hopkins and Baird, 1985a; Sutton and others, 1998), A. hemigymnus consumed 

only crustaceans, while A. aculeatus incorporated noncrustacean prey, like mollusks, into its diet. 

Previous studies reported mollusks as a rare prey item for A. aculeatus (Hopkins and Baird, 

1981; Hopkins and Baird, 1985a); however, enriched δ15N documented in SIA for A. aculeatus

implies mollusks, such as cephalopods, which are enriched in 15N compared to zooplankton, may 

be more common prey than originally documented. The incorporation of noncrustacean prey 

suggests A. aculeatus may adapt a more generalist feeding strategy, which reduces its 

dependence on zooplankton and competition for zooplankton with other midwater fishes. Prey 

competition may also be reduced through the utilization of vertical space. While DVMs were 

documented for Argyropelecus spp., with feeding documented at night (Hopkins and Baird, 

1985a; this study), A. aculeatus may be feeding at shallower depths than A. hemigymnus, based 

on the presence of more full stomachs in the epipelagic for A. aculeatus. Interestingly, the 
217

relationship between DVMs and stomach fullness for V. tripunctulatus was similar to A. 

hemigymnus, which contradicts previous literature that documented V. tripunctulatus as a 

nonmigratory species feeding actively during the day (Hopkins and Baird, 1981). This 

contradiction in time of feeding may be due to size differences, with larger specimens not 

migrating (Hopkins and Sutton, 1998). 

Chauliodus sloani was classified as a piscivore. The presence of fishes, particularly 

myctophids, was also previously documented in the literature (Hopkins and others, 1996). In 

contrast to GCA, results from SIA classified C. sloani at a trophic level similar to 

zooplanktivores, which suggests C. sloani consumed zooplankton more frequently than 

previously reported. DVMs of C. sloani reflected migrational patterns of zooplankton, with C. 

sloani migrating to the epipelagic at night. Previous literature reported asynchronous migrations 

in C. sloani (Sutton and Hopkins, 1996b), and variations in diet composition may result from 

ontogeny. Juvenile C. sloani may consume zooplankton prey and incorporate more fish prey 

with increasing size, as documented for G. elongatum (Clarke, 1982). Additional specimens were 

needed to further investigate ontogenetic effects on diet. 

Although GCA were not performed on other stomiids, SIA provided data to support 

Stomiidae as a tertiary consumer. Photostomias guernei occupied a slightly higher trophic 

position than C. sloani, as evident by the enriched 15N. Previous literature documented P. 

guernei as a large crustacean consumer, with the decapod G. valens reported as the dominant 

prey (Hopkins and others, 1996). Gennadas valens is a carnivorous decapod (Hopkins and 

others, 1994) and was documented on the same trophic level as zooplanktivorous fish, and 

consumption by P. guernei would enrich 15N in P. guernei. Consumption of carnivorous prey, 

whether fish or decapod, places the family Stomiidae at the top of the midwater food web. 
218

8.5 Conclusions 

1. The 18 fish species analyzed formed 3 major feeding guilds: zooplanktivore (consuming 

copepods, amphipods, and ostracods), consumers (consuming decapods and euphausiids) 

of larger sized crustaceans, and piscivores. 

2. Stomiidae were the dominant piscivores, with the majority of their prey being 

myctophids and bregmacerotids. 

3. Diel vertical migrations were documented in the majority of midwater fishes, with 

species migrating to the epipelagic at night; however, feeding was not limited to the 

epipelagic or to the night-time period. 

4. Significant shifts in diet composition with ontogeny were documented in stomiids, G. 

elongatum, V. poweriae, and Diaphus spp. 

5. Generally, GCA and SIA complemented each other, and differences between data 

highlighted the importance of utilizing both methods to discern trophic structure. 

6. Photosynthetic material provided the base for the midwater food; however, 

chemosynthetic cold seeps may have minor influences that went undetected using the 

above methodology. 

8.6 Acknowledgments

This project was largely funded by the U.S. Geological Survey under Cooperative 

Agreement No. 05HQAG0009, subagreement 05099HS004. We thank the crew of the R/V Cape 

Hatteras and all scientific personal for assisting with fishing operations and sample processing. 

S. Artabane assisted with sampling and fish identification, and C. Ames assisted with various 

aspects of the cruise and invertebrate identifications. C. Tobias, K. Duernberger, and A. 
219

Demopoulos provided guidance and support for stable isotope analysis. We thank G. Boland 

(BOEMRE), S.D. Brooke (MCI), and J. Sinclair (BOEMRE) for helpful comments on this 

chapter. We would also like to thank M. Rhode for his suggestions and edits to this manuscript. 
220

9. DISTRIBUTIONS AND COMPOSITION OF THE MESOPELAGIC 

INVERTEBRATE FAUNA OVER THE SLOPE OF THE NORTH-CENTRAL 

GULF OF MEXICO

By Martha S. Nizinski1 and Cheryl L. Ames2

1

NOAA, National Marine Fisheries Service, National Systematics Laboratory, Smithsonian Institution, Washington, 

DC 

2

University of North Carolina Wilmington, Center for Marine Science, Wilmington, NC

9.1 Introduction

Cold-seep habitats in the Gulf of Mexico are numerous, widespread, and the most 

thoroughly explored and investigated of any cold-seep habitats in the world (Fisher and others, 

2007). Recent explorations (Roberts and others, 2007b) to some of the deeper seep sites within 

this region have revealed new findings (for example, new species, new assemblages of 

organisms, a variety of new features such as mud volcanoes and brine pools, shifts in community 

structure with depth) and added to our knowledge of the species diversity, community 

composition, and ecology of these reducing environments. Thus, even though these are some of 

the best known chemosynthetic sites, much remains to be learned about these environments. 

The epibenthic megafaunal invertebrate assemblages associated with these reducing 

environments have been studied extensively (for example, MacDonald and others, 1990; 

Bergquist and others, 2003b; Fisher and others, 2007; Cordes and others, 2007; 2009). However, 

relationships between midwater assemblages and the seep benthic assemblages remain unknown. 

A few studies examined the species composition and ecology of the mesopelagic invertebrate 
221

assemblages, in particular, the crustaceans and cephalopods, in the eastern Gulf of Mexico (for 

example, Heffernan and Hopkins, 1981; Hopkins and others, 1989; Passarella and Hopkins, 

1991; Flock and Hopkins, 1992; Hopkins and others, 1994). These previous studies were part of 

an extensive oceanic ecology project designed to characterize and examine the fauna typical of 

low latitude oligotrophic regions (Hopkins and others, 1989). Whether mesopelagic invertebrate 

assemblages are connected in some manner to benthic seep habitats has not been investigated. 

In collaboration with the mesopelagic fish investigation described in Chapter 7 and in 

cooperation with ongoing benthic studies (see Roberts and others, 2007b), we sampled the 

midwater invertebrate fauna at a variety of depths over three cold-seep habitats >1,000 m and 

one deepwater coral bank (<1,000 m) in the north-central GOM. Our goals were to characterize 

the invertebrate fauna collected throughout the water column at each site. Secondly, we 

compared the composition of invertebrate faunal assemblages among the three offshore, deeper 

chemosynthetic sites with that from the inshore, shallower coral site. Thirdly, we compared the 

invertebrate assemblages collected in different zones (surface, midwater, benthic) at all sites 

sampled. 

9.2 Methods

Samples were collected at 290 stations located over and around four study sites in the 

north-central to western GOM: three lower slope (>1,000 m) cold-seep sites (GC852, AT340, 

and AC601) and one upper slope (<1,000 m) deep-sea coral site (VK826; fig. 9.1). Sampling for 

this study was conducted August 9-29, 2007, using the R/V Cape Hatteras (Duke-UNC 

Oceanographic Consortium). The majority of invertebrate samples reported here were captured 

in conjunction with sampling for midwater fishes. See Chapter 7 for a more detailed description 

of study sites and sampling techniques using a Tucker trawl. 
222

Figure 9.1. Map of study area in the north-central Gulf of Mexico showing location of sampling sites. 

Three sites (AC601, GC852, and AT340) were over cold-seep habitats, and one site (VK826) was over 

a Lophelia pertusa coral habitat.

Although the focus of this portion of the study was to characterize the mesopelagic 

invertebrate fauna, several individuals (n = 113) were collected in surface samples taken with 1-

m diameter plankton nets (505-μm and 202-μm mesh) that were towed for 30 min on the surface 

in all study areas. Additionally, 160 epibenthic megafaunal invertebrates were captured with a 

variety of bottom gear (for example, otter trawl, box core, Tucker trawl). A 4.88-m otter trawl 

was towed on the seafloor for 30 min; box core sampling is described in Chapter 3. These data 

are reported here for completeness. 

The majority of invertebrates were fixed and maintained in 75-percent ethanol. 

Cephalopods were fixed in a 10-percent formalin seawater solution and after the cruise were 

transferred to 50-percent isopropanol. Jellyfishes also were fixed in a 10-percent formalin 

seawater solution and maintained in formalin for long-term storage. In the laboratory, all 

collections were sorted and curated. Individuals were identified to the lowest possible taxon 

using historical literature, authoritative keys, and comparative material housed in the National 
223

Museum of Natural History, Smithsonian Institution, Washington, D.C. Some material was 

either identified, or identifications were confirmed, by taxonomic experts at the Smithsonian 

Institution.

9.3 Results

Overall, 912 individuals representing at least 9 phyla, 23 classes, 86 families, and 188 

species of larval, juvenile, and adult invertebrates were collected at 141 of the 290 stations 

sampled (fig. 9.1, table 9.1). These specimens were taken in 14 surface, 116 midwater, and 11 

benthic collections. The majority of species were collected in midwater trawls. Among major 

taxa only four (Cnidaria, Mollusca, Crustacea, Chaetognatha) had species that were collected in 

all three zones sampled (fig. 9.2). 
224

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007.

[n, number of stations where invertebrate specimens were collected; – , no value]

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds.

n=141

Porifera Demospongiae Demospongiae spp. larvae (4) 4 – 6 4 14

Cnidaria Anthozoa cf. Hormathiidae cf. Hormathiidae sp. – – 1 – 1

Umbellulidae Umbellula sp. 13 – – – 13

Cubozoa Alatinidae Alatina sp. – – 1 1 2

Tamoyidae Tamoya haplonema – – – 1 1

Hydrozoa Hydrozoa sp. – – 1 – 1

Aequoreidae Aequorea macrodactyla – – 6 – 6

Aequorea sp. – – 2 – 2

Zygocanna vagans 4 – – 4 8

Aglaopheniidae Aglaophenia sp. – – 1 – 1

Eirenidae Tima sp. 1 – – – 1

Geryoniidae Geryonia probascidalis – – – 1 1

Halicreatidae Halicreas minimum 1 – – – 1

Hippopodiidae Hippopodius hippopus 5 – – – 5

Vogtia cf. serrata 1 – – – 1

Vogtia spinosa 1 – – – 1

Pandeidae Campaniclava clionis(on Clio recurva) 4 – 2 2 8

Scyphozoa Scyphozoa sp. – – – 1 1

Atollidae Atolla sp. 3 – 2 – 5

Atolla vanhoeffeni 4 – – – 4

Atolla wyvelli 5 – – – 5

Nausithoidae Nausithoe cf. aurea 1 – – – 1
225

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds 

n=141

Nausithoe punctata – – – 1 1 

Nausithoe sp. 2 – – – 2 

Pelagiidae Pelagia noctiluca – – 3 17 20

Periphyllidae Periphylla periphylla 11 – 2 – 13

Rhopalonematidae Colobonema sericeum 1 – – – 1 

Ulmaridae Aurelia aurita – – 1 1 2 

Ctenophora Cydippida Pleurobrachiidae Pleurobrachiidae sp. – – – 3 3 

Mollusca Bivalvia Mytilidae Bathymodiolus brooksii 2 – – – 2 

Cephalopoda Chtenopterygidae Chtenopteryx sepioloides 1 – – – 1 

Cranchiidae Bathothauma lyromma – 1 – – 1 

Cranchia scabra 1 – – – 1 

Helicocranchia pfefferi 2 – – – 2 

Liguriella podophthalma 1 – – – 1 

Sandalops melancholius – – 1 – 1 

Cycloteuthidae Cycloteuthis serventyi 1 – – – 1 

Enoploteuthidae Abralia redfieldi 1 – 2 1 4 

Abraliopsis atlantica 1 – 2 – 3 

Abraliopsis sp. 1 – – – 1 

Ancistrocheirus lesueurii 3 – – – 3 

Enoploteuthis anapsi 1 – – – 1 

Enoploteuthis sp. – – – 1 1 

Selenoteuthis scintillans 1 – 2 – 3 

Histioteuthidae Histioteuthidae sp. – – 1 – 1 

Stigmatateuthis arcturi 17 1 – – 18

Lycoteuthidae Lycoteuthis springeri 1 – – – 1 
226

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds 

n=141

Selenoteuthis scintillans 1 – – – 1 

Neoteuthidae Neoteuthis thielei 1 – – – 1 

Octopoteuthidae Octopoteuthis cf. megaptera 1 – – 1 2 

Ommastrephidae Ommastrephes bartramii – – – 1 1 

Onychoteuthidae Onykia carriboea 1 – 1 – 2 

Pyroteuthidae cf. Pterygioteuthis giardi 7 – 12 7 26

Pyroteuthidae sp. – – 1 – 1 

Pyroteuthis magaritifera – 1 2 1 4 

Sepiolidae Heteroteuthis dispar 3 – – 1 4 

Bolitaenidae Bolitaena pygmaea – – 1 – 1 

Japetella diaphana 8 – 2 – 10

Octopodidae Macrotritopus defilippi 1 – 1 1 3 

Tremoctopodidae Tremoctopus violaceus – – 8 – 8 

Vampyroteuthidae Vampyroteuthis infernalis 2 – – – 2 

Gastropoda Turridae Leucosyrinx verrilli 1 – – – 1 

Gastropoda/ 

Heterobranchia Atlantidae cf. Atlanta sp. 4 – – – 4 

Carinariidae Carinaria lamarcki 1 – 1 – 2 

Cavoliniidae Cavolinia tridentata 1 – 4 – 5 

Cavolinia uncinata 1 – – – 1 

Clio recurva 6 – 2 2 10

Cliopsis krohnii 3 – – 1 4 

Diacavolinia cf. elegans 5 – 9 – 14

Diacria cf. rampali 5 – – – 5 

Peraclididae cf. Peracle sp. 7 – – – 7 
227

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds 

n=141

Pterotracheidae Pterotrachea cf. coronata 12 – 2 2 16

Annelida Polychaeta Alciopidae Alciopidae sp. 1 – – – 1 

Arthropoda/ 

Crustacea Amphipoda Cystisomatidae Cystisoma cf. latipes 3 – – – 3 

Lanceolidae Lanceola sp. 2 – – – 2 

Oxycephalidae Rhabdosoma whitei 2 – – – 2 

Streetsia challengeri – – – 1 1 

Phronimidae Phronima sedentaria 10 – 6 – 16

Phrosinidae Anchylomera blossevillei 8 – – – 8 

Phrosina semilunata 2 – – – 2 

Platyscelidae Platyscelus sp. 2 – – – 2 

Platysceloidea sp. 1 – 28 – 29

Pronoidae Parapronoe spp. 3 – 1 – 4 

Pronoidae sp. 1 – – – 1 

Vibiliidae Vibilia sp. 2 – – – 2 

Copepoda Megacalanidae Bathycalanus princeps 6 – 1 – 7 

Decapoda/Anomura Chirostylidae Eumunida picta – – – 3 3 

Galatheidae Munida microphthalma 4 – – – 4 

Munida sanctipauli – – – 3 3 

Munidopsis cf. bermudezi (molt) 1 – – – 1 

Munidopsis n.sp. – – – 1 1 

Munidopsis penescabra – – – 2 2 

Munidopsis similis 1 – – – 1 

Parapaguridae Parapagurus sp. 8 – – – 8 

Decapoda/Astacidea Nephropidae Nephropsis aculeata – – – 2 2 

Nephropsis agassizii 1 – – – 1 
228

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds 

n=141

Decapoda/Brachyura

Decapoda/Caridea

Calappidae

Majidae 

Portunidae 

Glyphocrangonidae

Nematocarcinidae

Oplophoridae

Palaemonidae 

Pandalidae 

Pasiphaeidae 

Brachyura sp.

Calappa cf. tortugae megalopa

Majidae sp.

Portunus sp. 

Glyphocrangon aculeata

Glyphocrangon cf. nobilis

Glyphocrangon longirostris 

Nematocarcinus ensifer 

Nematocarcinus rotundus

Acanthephyra cf. brevirostris 

Acanthephyra curtirostris 

Acanthephyra eximia

Acanthephyra pelagica

Acanthephyra purpurea 

Janicella spinicauda 

Meningodora vesca 

Notostomus elegans 

Oplophorus gracilirostris

Systellaspis debilis 

Systellaspis sp. 

Leander tenuicornis 

Heterocarpus oryx 

Plesionika acanthonotus 

Stylopandalus richardi 

Pasiphaea merriami 

– 

– 

4 

– 

3 

1 

1 

3 

20

2 

2 

4 

1 

15

2 

2 

3 

2 

8 

4 

1 

6 

– 

18

7 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

1 

– 

– 

2 

– 

– 

– 

– 

– 

– 

1 

– 

– 

1 

1 

– 

– 

4 

7 

– 

– 

– 

– 

– 

– 

– 

2 

– 

10

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

3 

– 

– 

– 

– 

1 

– 

3 

1 

2 

4 

12

3 

1 

1 

3 

20

2 

3 

4 

1 

16

3 

2 

3 

9 

15

4 

1 

6 

1 

18

10

 
229

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds 

n=141

Decapoda/ 

Dendrobranchiata

Decapoda/Palinura

Euphausiacea 

Aristeidae

Benthesicymidae

Penaeidae

Sergestidae

Solenoceridae

Polychelidae 

Scyllaridae 

Euphausiidae

Hemipenaeus carpenteri 

Hepomadus tener 

Gennadas elegans 

Gennadas sp. 

Gennadas valens

Funchalia villosa 

Deoergestes curvatus

Deoergestes henseni 

Parasergestes armatus 

Sergestes atlanticus 

Sergestidae sp.

Sergia grandis

Sergia hansjacobi 

Sergia mollis 

Sergia regalis 

Sergia robusta

Sergia splendens

Sergia talismani 

Sergia wolffi 

Pleoticus robustus 

Polycheles sculptus

Polycheles sculptus larva

Scyllaridae sp. larva

cf. Thysanopoda sp.

Euphausia sp.

3 

2 

5 

1 

46

5 

4 

3 

4 

1 

1 

1 

1 

1 

3 

1 

13

2 

9 

1 

6 

1 

1 

2 

1 

– 

– 

1 

– 

2 

– 

1 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

2 

– 

– 

– 

1 

– 

8 

5 

– 

– 

1 

– 

1 

– 

– 

– 

– 

1 

– 

– 

1 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

– 

2 

– 

– 

– 

– 

– 

– 

3 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

3 

2 

7 

1 

56

12

5 

3 

5 

1 

3 

1 

4 

1 

3 

2 

13

2 

10

1 

6 

1 

2 

4 

1 

 
230

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds 

n=141

Chaetognatha

Echinodermata

Paracarida

Stomatopoda

Chaetognatha

Holothuroidea

Ophiurida

Eucopiidae

Lophogastridae 

Molpadiidae

Myriotrochidae

Psychropotidae

Synallactidae

Synaptidae

Ophiodermatidae

Ophioleucidae

Euphausiidae sp. 

Nematoscelis megalops 

Nematoscelis sp. 

Stylocheiron abbreviatum 

Stylocheiron elongatum 

Thysanoessa spp. 

Thysanopoda tricuspida 

Eucopia cf. grimaldii

Eucopia sp. 

Gnathophausia zoea 

Neognathophausia ingens 

Stomatopoda sp.larva

Chaetognatha spp.(4)

Molpadia blakei 

Myriotrochus cf. rinkii 

Myriotrochus n. sp. 

Psychropotes depressa

Molpadiodemas involutus 

Paroriza sp. 

Zygothuria lactea 

Protankyra brychia 

Rynkatorpa felderi 

Bathypectinura heros 

Ophioleuce sp. 

5 

15

6 

1 

1 

9 

– 

2 

– 

2 

4 

11

38

7 

1 

1 

2 

7 

3 

1 

1 

1 

2 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

1 

– 

– 

– 

– 

– 

1 

– 

1 

– 

– 

– 

11

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

6 

15

6 

1 

1 

9 

1 

2 

1 

2 

4 

11

49

7 

1 

1 

2 

7 

3 

1 

1 

1 

2 

1 

 
231

Table 9.1. Overall diversity and abundance of invertebrates collected (all sampling methods combined) at three cold-seep sites (GC852, AC601, 

and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=64

AC601 

n=4

AT340 

n=40

VK826 

n=33

Total 

No. of 

Inds 

n=141

Ophiuridae Amphiophiura metabula 6 – – – 6 

Asteroidea Astropectinidae

cf. Ophiernus vallincola 

Dytaster insignis 

1 

1 

– 

– 

– 

– 

– 

– 

1 

1 

Plutonaster intermedius 1 – – – 1 

Goniasteridae Nymphaster arenatus 1 – – – 1 

Chordata/ Tunicata Pyrosomatida

Salpida

Pyrosomatidae

Salpidae

Pyrosoma atlanticum 

Iasis zonaria 

27

1 

1 

– 

3 

– 

2 

1 

33

2 

Salpa cf. maxima 

Salpa cf. fusiformis 

4 

2 

– 

– 

– 

– 

– 

– 

4 

2 

Salpa cylindrica 

Salpa sp. 

2 

3 

– 

– 

14

– 

– 

– 

16

3 

Salpidae sp. 1 – – – 1 

Total 622 11 185 94 912

 
232

0

20

40

60

80

100

120

Porifera

Ctenophora

CnidariaMolluscaAnnelida

Arthropoda/Crustacea

Chaetognatha

Chordata/Tunicata

Echinodermata

No. of Species

Surface

Midwater 

Bottom

Figure 9.2. Overall (all sampling sites combined) species richness of invertebrates for each major taxon collected by zone (surface, 

midwater, benthic) at three cold-seep sites (AC601, GC852, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, 

August 9-29, 2007.
233

Subphylum Crustacea (Phylum Arthropoda) was the dominant major taxon in both 

numbers of species and individuals, with a total of 85 species and 458 individuals represented in 

the samples (figs. 9.3, 9.4). Within the crustaceans, shrimps were the most speciose group with 

caridean and dendrobranchian shrimps constituting about half (41/85 species) of the total 

crustacean diversity. Carideans and dendrobranchians were equally diverse with 21 and 20 

species, respectively. Dendrobranchians were slightly more abundant than the carideans (135 

versus 126 individuals). Among the shrimps collected, Sergia hansjacobi represents a new 

record for the Gulf of Mexico fauna, having never been reported from this area before. 
234

Cnidaria, 27

Arthropoda/ 

Crustacea , 85

Ctenophora , 1

Mollusca , 43

Annelida, 1

Echinodermata, 

16

Chaetognatha, 4

Porifera , 4

Chordata/ 

Tunicata, 7

Figure 9.3. Overall (all sampling sites combined) species richness of all major invertebrate taxa collected at three cold-seep sites 

(AC601, GC852, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007.
235

0

50

100

150

200

250

300

350

400

450

500

Porifera

Cnidaria

Ctenophora

MolluscaAnnelida 

Arthropoda/Crustacea

Chaetognatha

Echinodermata

Chordata/Tunicata

No. of Species

No. of Inds

Figure 9.4. Overall (all sampling sites combined) species richness and abundance of major invertebrate taxa collected at three coldseep sites (AC601, GC852, and AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. 
236

Mollusca was the second most diverse phylum collected, and samples of these organisms 

consisted of 43 species and 181 individuals. Cephalopoda was the most diverse class of 

molluscs (15 families, 31 species). Gastropods and bivalves were also represented in the 

samples, including two individuals of Bathymodiolus brooksii, the mussel commonly found at 

deeper (1,000-3,300 m) chemosynthetic sites.

For the other groups of invertebrates, cnidarians (27 species, 108 individuals) were well 

represented in the samples with 25 species of jellies (Cubozoa, Scyphozoa, and Hydrozoa), two 

species of hydroids, and two species of anthozoans. All major taxa within the Echinodermata, 

except for crinoids, were represented in the relatively small collections of this group (16 species, 

37 individuals). Samples consisted of nine species of sea cucumbers, four species of brittle stars, 

and three species of sea stars. Salps and pyrosomes (Urochordata), sponges (Porifera), 

chaetognaths (Chaetognatha), and polychaetes (Annelida) made up the remainder of the major 

taxa collected in these samples.

Among the invertebrates collected, the shrimp Gennadas valens (Dendrobranchiata: 

Benthesicymidae) was the most abundant species with 56 specimens collected, representing 6

percent of total individuals captured. The pyrosome P. atlanticum (n = 33) and chaetognaths (n

= 49) were also relatively abundant in the samples. Sixty-seven of the species (36 percent)

collected during this study were represented by single individuals, while another 30 species (16

percent) were each represented by only two individuals.

Comparing the distribution of species among study sites revealed that most species 

(129/188) were collected at only one of the four sites sampled. Forty-two species and 16 species 

were collected at two and three of the four sites, respectively. Only one species, Pyrosoma 

atlanticum, was collected at all study sites.
237

9.3.1 Species composition and relative abundance among study sites

Species diversity and relative abundance of invertebrates was highest at GC852 (table 

9.1, fig. 9.5). Collections from the 64 stations sampled at this site yielded 622 individuals, 

consisting of at least 148 species and representing all phyla collected except Ctenophora and all 

class/orders identified in the study with exception of the Cubozoa. Crustaceans were the most 

speciose taxa with 73 species represented in collections. Crustaceans were also the numerical 

dominants of the GC852 megafaunal assemblage, where they constituted 55 percent of the total 

individuals collected at this site. Sixty-three percent of the crustacean catch taken here consisted 

of shrimps. Molluscs, echinoderms, and cnidarians contributed 34, 16, and 15 species, 

respectively, to the overall diversity at this site. 

239

Although numbers of species and individuals were much less at AT340, species richness 

estimates were comparable proportionately (ratio of number of species to number of individuals) 

to that of GC852. Collections from the 40 stations sampled at AT340 yielded 185 individuals, 

consisting of at least 55 species, representing 6 of the 9 phyla collected in this study. No 

ctenophores, annelids, or echinoderms were collected in these samples. Crustaceans were the 

most speciose group with 22 species, followed by molluscs with 18 species and cnidarians with 9 

species. Crustaceans were also the numerically dominant group at this site, constituting 41 

percent of the total individuals collected. Amphipods, the most abundant crustacean taxon 

collected at this site, made up 47 percent of the crustacean catch. 

Species richness (proportion of number of species to number of individuals) was much 

higher at VK826 than at the other sites. Collections from the 33 stations sampled here yielded 94 

individuals, representing at least 38 species and 6 of the 9 phyla collected in this study. No 

annelids, chaetognaths, or echinoderms were collected in these samples. Crustaceans were the 

most speciose with 13 species, followed by molluscs with 11 species and cnidarians with 9 

species. Again, crustaceans were the numerically dominant group among invertebrates sampled, 

and they accounted for 38 percent of the total individuals collected at this site. Cnidarians 

contributed 31 percent of the individuals and molluscs 20 percent to the total specimens caught 

at this site. 

9.3.2 Species composition and relative abundance among zones

Invertebrates were collected in 14 of 58 stations where surface gear was deployed. No 

invertebrates were collected in the six surface tows made at AC601. Overall, 113 individuals 

representing 6 phyla, at least 18 families, and 26 species were collected in surface tows (table 

9.2). Phylum Cnidaria was the most speciose group with eight species, followed by crustaceans 
240

with seven species (fig. 9.6). Crustacea was the numerically dominant taxon, with 44 individuals 

(39 percent); amphipods made up 64 percent of the crustacean catch. Surface sampling was most 

productive at AT340, where 78 percent of the total number of individuals and 85 percent of the 

total species were collected. 
241

Table 9.2. Invertebrate species and number of individuals collected at the 

Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. 

[n, number of stations where invertebrate specimens were collected; –, no value]

surface over two cold-seep sites (GC852 and AT340) and one 

Phylum Class or Order Family Species GC852 

n= 2

AT340 

n= 8

VK826 

n=4

No. of Inds 

n=14

Porifera

Cnidaria

Mollusca

Arthropoda/ Crustacea

Chaetognatha

Chordata/ Tunicata

Demospongiae

Cubozoa

Hydrozoa

Scyphozoa

Cephalopoda

Gastropoda/ 

Heterobranchia

Amphipoda

Copepoda

Decapoda/Brachyura

Decapoda/Caridea

Euphausiacea

Chaetognatha

Salpida

Alatinidae

Tamoyidae

Aequoridae

Aglaopheniidae

Pelagiidae

Ulmaridae

Octopodidae

Tremoctopoteuthidae

Cavoliniidae

Platyscelidae

Pronoidae

Megacalanidae

Calappidae

Portunidae

Oplophoridae

Euphausiidae

Chaetognatha

Salpidae

Demospongiae sp. larvae (3)

Alatina sp.

Tamoya haplonema 

Hydrozoa sp.

Aequorea macrodactyla 

Aglaophenia sp.

Scyphozoa sp.

Pelagia noctiluca 

Aurelia aurita 

Macrotritopus defilippi 

Tremoctopus violaceus 

Cavolinia tridentata 

Diacavolinia cf. elegans 

Platyscelidae sp.

Parapronoe sp.2

Bathycalanus princeps 

Calappa cf. tortugae

megalopa

Portunus sayi 

Oplophorus gracilirostris 

Thysanopoda tricuspida 

Chaetognatha spp. (3)

Salpa cylindrica 

1

–

–

–

–

–

–

–

–

–

–

–

5

–

–

–

–

–

–

–

–

–

6

1

–

1

6

1

–

3

–

1

5

4

9

28

1

1

–

1

1

1

5

14

4

–

1

–

–

–

1

–

1

–

–

–

–

–

–

–

1

10

–

–

–

–

11

1

1

1

6

1

1

3

1

1

5

4

14

28

1

1

1

11

1

1

5

14

Total 6 89 18 113
242

Chordata/ 

Tunicata, 1

tognatha, 3

/ 

Chae

Arthropoda

Crustacea, 7

Mollusca, 4

Cnidaria, 8

Porifera, 3

Figure 9.6. Species richness of all major invertebrate taxa collected using surface gear over three cold-seep sites (AC601, GC852, and 

AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. 
243

Benthic invertebrates were collected by a variety of gear. Four otter trawl samples were 

collected at GC852; otherwise, epibenthic mega-invertebrates were taken from box core samples 

(see Chapter 3 for composition of macro-invertebrate fauna collected with box cores) or from 

midwater Tucker trawls that hit the bottom. Overall, 160 epibenthic mega-invertebrates were 

collected at 11 stations. These represented 6 phyla and at least 35 families and 57 species (table 

9.3). Crustacea was the most speciose taxon with 31 species, followed by echinoderms with 16 

species (fig. 9.7). Crustaceans were also the numerically dominant taxon, constituting over half 

(58 percent) of the total individuals collected with benthic gear. Among the crustaceans, 

caridean shrimps were the most abundant group, making up 35 percent of the crustaceans 

sampled. Benthic sampling was most productive at GC852, where 91 percent of the total 

individuals and 86 percent of the total species were collected. 
244

Table 9.3. Invertebrate species and number of individuals collected on the bottom at two cold-seep 

pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. 

[n, number of stations where invertebrate specimens were collected; – , no value]

sites (GC852 and AT340) and one Lophelia 

Phylum Class or Order Family Species GC852 

n=5

AT340 

n=1

VK826 

n=5

No. of Inds 

n=11

Porifera 

Cnidaria 

Mollusca

Arthropoda/Crustacea

Demospongiae

Pennatulacea

Anthozoa

Bivalvia

Cephalopoda

Gastropoda

Amphipoda

Decapoda/Anomura

Decapoda/Astacidea 

Decapoda/Brachyura

Decapoda/Caridea

Umbellulidae

cf. Hormathiidae

Mytilidae

Bolitaenidae

Lycoteuthidae

Octopodidae

Cavoliniidae

Turridae

Phronimidae

Chirostylidae

Galatheidae

Parapaguridae

Nephropidae

Majidae

Glyphocrangonidae

Nematocarcinidae

Demospongiae sp.

Umbellula sp.

cf. Hormathiidae

Bathymodiolus brooksii 

Japetella diaphana 

Selenoteuthis scintillans

Macrotritopus defilippi 

cf. Cavolinia tridentata 

Leucosyrinx verrilli 

Phronima sedentaria 

Eumunida picta

Munida microphthalma 

Munida sanctipauli 

Munidopsis cf. bermudezi molt

Munidopsis n.sp.

Munidopsis penescabra

Munidopsis similis 

Parapagurus sp.

Nephropsis aculeata

Nephropsis agassizii 

Majidae sp.

Glyphocrangon aculeata

Glyphocrangon longirostris 

Glyphocrangon cf. nobilis

Nematocarcinus ensifer

2

13

–

2

1

1

–

7

1

1

–

4

–

1

–

–

1

8

–

1

4

3

1

1

1

–

–

1

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

1

–

–

–

3

–

3

–

1

2

–

–

2

–

–

–

–

–

–

2

13

1

2

1

1

1

7

1

1

3

4

3

1

1

2

1

8

2

1

4

3

1

1

1
245

Table 9.3. Invertebrate species and number of individuals collected on the bottom at two cold-seep sites (GC852 

pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

and AT340) and one Lophelia 

Phylum Class or Order Family Species GC852 

n=5

AT340 

n=1

VK826 

n=5

No. of Inds 

n=11

Chaetognatha 

Echinodermata

Decapoda/ 

Dendrobranchiata

Decapoda/Palinura

Stomatopoda

Chaetognatha 

Asteroidea

Holothuroidea

Oplophoridae

Pandalidae

Aristeidae

Benthesicymidae

Sergestidae

Polychelidae

Astropectinidae

Goniasteridae

Molpadiidae

Myriotrochidae

Psychropotidae

Synallactidae

Nematocarcinus rotundus

Acanthephyra eximia

Acanthephyra purpurea 

Heterocarpus oryx 

Plesionika acanthonotus 

Stylopandalus richardi 

Hemipenaeus carpenteri 

Hepomadus tener 

Benthesicymus bartletti 

Gennadas valens 

Sergia mollis 

Sergia splendens 

Sergia wolffi 

Polycheles sculptus 

Stomatopoda sp. larva

Chaetognatha sp.

Dytaster insignis 

Plutonaster intermedius 

Nymphaster arenatus

Molpadia blakei 

Myriotrochus cf. rinkii 

Myriotrochus n. sp. 

Psychropotes depressa

Molpadiodemas involutus 

Paroriza sp. 

14

4 

1 

6 

– 

1 

3 

2 

9 

4 

1 

1 

1 

6 

2 

1 

1 

1 

1 

7 

1 

1 

2 

7 

3 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

14

4 

1 

6 

1 

1 

3 

2 

9 

4 

1 

1 

1 

6 

2 

1 

1 

1 

1 

7 

1 

1 

2 

7 

3 
246

Table 9.3. Invertebrate species and number of individuals collected on the bottom at two cold-seep sites (GC852 and AT340) and one Lophelia 

pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007.—Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n=5

AT340 

n=1

VK826 

n=5

No. of Inds 

n=11

Zygothuria lactea 1 – – 1 

Synaptidae Protankyra brychia 1 – – 1 

Rynkatorpa felderi 1 – – 1 

Ophiurida Ophiodermatidae Bathypectinura heros 2 – – 2 

Ophioleucidae Ophioleuce sp. 1 – – 1 

Ophiuridae Amphiophiura metabula 6 – – 6 

cf. Ophiernus vallincola 1 – – 1 

Total 146 1 13 160
247

Mollusca, 6

Arhropoda/ 

Crustacea, 31

Chaetognatha , 1

Echinodermata, 16

Porifera , 1 Cnidaria , 2

Figure 9.7. Species richness of major invertebrate taxa collected using bottom gear at two cold-seep sites (GC852 and AT340) and one 

Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. 
248

Of the 159 midwater stations sampled, invertebrates were collected at 116 stations. 

Overall, 659 individuals representing 7 phyla, at least 62 families, and 132 species were taken in 

these samples (table 9.4). Crustaceans were again both the most taxonomically diverse and 

numerically dominant group, with 64 species and 332 individuals (fig. 9.8). Dendrobranchian 

shrimps were the most speciose and abundant group within the Crustacea, comprising 17 species 

and 123 individuals. Caridean shrimps were represented by 15 species and 92 individuals. 

Molluscs ranked second in both abundance (154 individuals) and diversity (38 species). 

Cephalopods were the dominant taxon within the molluscs, with 29 species and 100 individuals. 

No sponges or echinoderms were collected in the midwater samples. Midwater sampling was 

most productive at GC852, where 57 of 116 tows were conducted. Seventy-four percent of the 

total individuals and 83 percent of the total species were collected at this site.
249

Table 9.4. Invertebrate species and number of individuals collected in midwater 

at one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. 

[n, number of stations where invertebrate specimens were collected; – , no value] 

over three cold-seep sites (GC852, AC601, and AT340) and 

Phylum Class or Order Family Species GC852 

n= 57

AC601 

n= 4

AT340 

n= 31

VK826 

n=24

No. of Inds 

n=116

Ctenophora

Cnidaria

Mollusca

Cydippida

Cubozoa

Hydrozoa

Scyphozoa

Cephalopoda

Pleurobrachiidae

Alatinidae

Aequoreidae

Eirenidae

Geryoniidae

Halicreatidae

Hippopodiidae

Pandeidae

Rhopalonematidae

Atollidae

Nausithoidae

Pelagiidae

Periphyllidae

Ulmaridae

Bolitaenidae

Chtenopterygidae

Pleurobrachiidae sp.

Alatina sp.

Aequorea sp.

Zygocanna vagans 

Tima sp.

Geryonia probascidalis 

Halicreas minimum

Hippopodius hippopus 

Vogtia cf. serrata 

Vogtia spinosa 

Campaniclava clionis 

(on Clio recurva)

Colobonema sericeum 

Atolla sp.

Atolla vanhoeffeni

Atolla wyvelli

Nausithoe cf. aurea 

Nausithoe punctata 

Nausithoe sp.

Pelagia noctiluca

Periphylla periphylla 

Aurelia aurita 

Bolitaena pygmaea

Japetella diaphana

Chtenopteryx sepioloides 

–

–

–

4

1

–

1

5

1

1

4

1

3

4

5

1

–

2

–

11

–

–

7

1

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

–

2

–

–

–

–

–

–

–

2

–

2

–

–

–

–

–

–

2

1

1

2

–

3

1

–

4

–

1

–

–

–

–

2

–

–

–

–

1

–

17

–

–

–

–

–

3

1

2

8

1

1

1

5

1

1

8

1

5

4

5

1

1

2

17

13

1

1

9

1
250

Table 9.4. Invertebrate species and number of individuals collected in midwater over three cold-seep sites (GC852, AC601, and AT340) and 

at one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. ––Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n= 57

AC601 

n= 4

AT340 

n= 31

VK826 

n=24

No. of Inds 

n=116

Cranchiidae

Enoploteuthidae

Histioteuthidae

Lycoteuthidae

Neoteuthidae

Octopodidae

Octopoteuthidae

Ommastrephidae

Onychoteuthidae

Pyroteuthidae

Sepiolidae

Tremoctopodidae

Bathothauma lyromma 

Cranchia scabra

Helicocranchia pfefferi

Liguriella podophthalma

Sandalops melancholius 

Abralia redfieldi

Abraliopsis atlantica 

Abraliopsis sp. 

Ancistrocheirus lesueurii 

Enoploteuthis anapsi 

Enoploteuthis sp. 

Selenoteuthis scintillans

Histioteuthidae sp. 

Stigmatateuthis arcturi 

Lycoteuthis springeri 

Neoteuthis thielei 

Macrotritopus defilippi 

Octopoteuthis cf.

megaptera 

Ommastrephes bartramii

Onykia carriboea 

cf. Pterygioteuthis giardi 

Pyroteuthidae sp.

Pyroteuthis magaritifera 

Heteroteuthis dispar 

Tremoctopus violaceus 

– 

1 

2 

1 

– 

1 

1 

1 

3 

1 

– 

1 

– 

17

1 

1 

1 

1 

– 

1 

7 

– 

– 

3 

– 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

1 

2 

2 

– 

– 

– 

– 

2 

1 

– 

– 

– 

– 

– 

– 

1 

12

1 

2 

– 

3 

– 

– 

– 

– 

– 

1 

– 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

1 

1 

– 

7 

– 

1 

1 

– 

1 

1 

2 

1 

1 

4 

3 

1 

3 

1 

1 

3 

1 

18

1 

1 

1 

2 

1 

2 

26

1 

4 

4 

3 
251

Table 9.4. Invertebrate species and number of individuals collected in midwater over three cold-seep sites (GC852, AC601, and AT340) and 

at one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n= 57

AC601 

n= 4

AT340 

n= 31

VK826 

n=24

No. of Inds 

n=116

Annelida

Arthropoda/ 

Crustacea

Gastropoda/ 

Polycheata

Amphipoda

Heterobranchia

Vampyroteuthidae

Atlantidae

Carinariidae

Cavoliniidae

Peraclididae

Pterotracheidae

Alciopidae

Lanceolidae

Oxycephalidae

Phronimidae

Phrosinidae

Platyscelidae

Pronoidae

Vampyroteuthis 

infernalis

cf. Atlanta sp.

Carinaria lamarcki 

Cavolinia tridentata

Cavolinia uncinata 

Clio recurva 

Cliopsis cf. krohnii 

Diacria cf. rampali

cf. Peracle sp.

Pterotrachea cf. 

coronata 

Alciopidae sp.

Lanceola sp.

Rhabdosoma whitei 

Streetsia challengeri 

Phronima sedentaria 

Anchylomera blossevillei 

Phrosina semilunata 

Platyscelus sp.

Platysceloidea sp.

Parapronoe sp.

Pronoidae sp.

2 

4 

1 

1

1 

6 

3 

5 

7 

12

1 

2 

2 

9 

8 

2 

2 

1 

3 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

1 

4

– 

2 

– 

– 

– 

2 

– 

– 

– 

– 

6 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

2 

1 

– 

– 

2 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

– 

2 

4 

2 

5

1 

10

4 

5 

7 

16

1 

2 

2 

1 

15

8 

2 

2 

1 

3 

1 
252

Table 9.4. Invertebrate species and number of individuals collected in midwater over three cold-seep sites (GC852, AC601, and AT340) and 

at one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n= 57

AC601 

n= 4

AT340 

n= 31

VK826 

n=24

No. of Inds 

n=116

Copepoda

Decapoda/Brachyura

Decapoda/Caridea

Decapoda/Dendrobranchiata

Vibiliidae

Megacalanidae

Calappidae

Portunidae

Nematocarcinidae

Oplophoridae

Palaemonidae

Pandalidae

Pasiphaeidae

Benthesicymidae

Vibilia sp.

Bathycalanus princeps 

Brachyura sp.

Calappa cf. tortugae 

megalopa

Portunus sp. 

Nematocarcinus 

rotundus

Nematocarcinus ensifer 

Acanthephyra cf. 

brevirostris 

Acanthephyra 

curtirostris 

Acanthephyra pelagica

Acanthephyra purpurea 

Janicella spinicauda 

Meningodora vesca 

Notostomus elegans 

Oplophorus 

gracilirostris

Systellaspis debilis 

Systellaspis sp. 

Leander tenuicornis 

Stylopandalus richardi 

Pasiphaea merriami 

Gennadas valens

Gennadas elegans 

Gennadas sp. 

2 

6 

– 

– 

– 

6 

2 

2 

2 

1 

14

2

2 

3 

2 

8 

4 

1 

17

7 

42

5 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

2 

1 

– 

– 

– 

1 

– 

1 

– 

– 

– 

1 

– 

1 

1 

– 

– 

3 

7 

– 

– 

– 

– 

8 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

3 

– 

– 

– 

– 

3 

– 

– 

– 

2 

6 

1 

1 

1 

6 

2 

2 

3 

1 

15

3

2 

3 

8 

15

4 

1 

17

10

52

7 

1 
253

Table 9.4. Invertebrate species and number of individuals collected in midwater over three cold-seep sites (GC852, AC601, and AT340) and 

at one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007). —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n= 57

AC601 

n= 4

AT340 

n= 31

VK826 

n=24

No. of Inds 

n=116

 Decapoda/Palinura

 

Euphausiacea

Penaeidae

Sergestidae

Solenoceridae

Polychelidae

Scyllaridae

Euphausiidae

Funchalia villosa 

Deoergestes curvatus

Deoergestes henseni 

Parasergestes armatus 

Sergestes atlanticus 

Sergestidae sp. 

Sergia grandis

Sergia hansjacobi 

Sergia regalis

Sergia robusta

Sergia splendens

Sergia talismani 

Sergia wolffi 

Pleoticus robustus 

Polycheles sculptus larva

Scyllaridae sp. larva

cf. Thysanopoda sp. 

Euphausia sp.

Euphausiidae sp.

Nematoscelis megalops 

Nematoscelis sp. 

Stylocheiron 

abbreviatum 

Stylocheiron elongatum 

Thysanoessa sp. 

Thysanopoda sp. 

5 

4 

3 

4 

1 

1 

1 

1 

3 

1 

12

2 

8 

1 

1 

1 

– 

1

5 

15

6 

1 

1 

9 

2 

– 

1 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

1 

– 

– 

– 

– 

– 

– 

– 

1 

5 

– 

– 

1 

– 

1 

– 

– 

– 

1 

– 

– 

1 

– 

– 

1 

– 

– 

1 

– 

– 

– 

– 

– 

– 

2 

– 

– 

– 

– 

– 

– 

3 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

– 

12

5 

3 

5 

1 

3 

1 

4 

3 

2 

12

2 

9 

1 

1 

2 

1 

1

6 

15

6 

1 

1 

9 

3 
254

Table 9.4. Invertebrate species and number of individuals collected in midwater over three cold-seep sites (GC852, AC601, and AT340) and 

at one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007. —Continued 

[n, number of stations where invertebrate specimens were collected; – , no value] 

Phylum Class or Order Family Species GC852 

n= 57

AC601 

n= 4

AT340 

n= 31

VK826 

n=24

No. of Inds 

n=116

Paracarida Cystisomatidae

Eucopiidae

Cystisoma cf. latipes 

Eucopia cf. grimaldii

3 

2 

– 

– 

– 

– 

– 

– 

3 

2 

Lophogastridae

Eucopia sp. 

Gnathophausia zoea 

Neognathophausia 

ingens 

2 

4 

– 

– 

– 

1 

– 

– 

– 

– 

– 

1 

2 

4 

Stomatopoda Stomatopoda sp. larva 11 – – – 11

Chaetognatha

Chordata/ 

Tunicata

Chaetognatha

Pyrosomatida

Salpida

Pyrosomatidae

Salpidae

Chaetognatha sp. 

Pyrosoma atlanticum 

Iasis zonaria 

37

27

1 

– 

1 

– 

6 

3 

– 

– 

2 

1 

43

33

2 

Salpa cf. fusiformis 

Salpa cf. maxima 

2 

4 

– 

– 

– 

– 

– 

– 

2 

4 

Salpa cylindrica 

Salpa sp. 

2 

3 

– 

– 

– 

– 

– 

– 

2 

3 

Salpidae sp. 1 – – – 1 

Total 486 11 99 63 659
255

Arthropoda/ 

Crustacea, 64

Annelida, 1

Mollusca, 38

Cnidaria, 20

Ctenophora, 1

Chordata/ 

Tunicata, 7

Chaetognatha, 1

Figure 9.8. Species richness of major invertebrate taxa collected using midwater gear over three cold-seep sites (AC601, GC852, and 

AT340) and one Lophelia pertusa site (VK826) in the Gulf of Mexico, August 9-29, 2007.
256

9.4 Discussion

Throughout the Gulf of Mexico, over 90 cold-seep sites have been discovered; of these 

sites, at least 84 support seep-associated megafaunal communities (Fisher and others, 2007). 

Seep sites are described as oases because biomass and diversity of organisms associated with the 

seep are much greater than that of the surrounding deep-sea habitats (Carney, 1994). The 

characteristic chemoautotrophic invertebrates that inhabit seep sites, mostly epifaunal mussels 

and tubeworms, derive their nutrition from symbiotic relationships with sulfide- or methaneoxidizing bacteria (MacAvoy and others, 2002). The level of trophic interaction between the 

resident seep chemosynthetic organisms and those species found outside the direct influence of 

the cold seep has been the topic of recent investigations (MacAvoy and others, 2008a; b). Nonresident organisms that may benefit either directly or indirectly from the chemo-based food web 

at the seep site are considered to be background species more typical of the Gulf deep-sea 

community. Although the mobile benthic fauna occurring at several seep sites has been studied 

(MacAvoy and others, 2008b), it has not been determined whether the production from the seeps 

translates to assemblages occurring in the water column near the seeps. This study represents the 

first attempt to investigate the composition of the midwater invertebrate assemblage occurring 

over chemosynthetic environments in the Gulf of Mexico and to assess whether these 

assemblages are influenced by the enhanced productivity of nearby seep sites. 

To address the question of whether the midwater invertebrate faunal assemblage benefits 

directly or indirectly from chemosynthetic based production, we must first know the faunal 

composition, relative abundances, and relative distributions of invertebrate species collected over 

the cold-seep sites. If production from cold seeps has an influence on the midwater invertebrate 

assemblage, one would expect an increase in species richness over seep sites, or an increase in 
257

relative abundances of invertebrates over seep sites, and (or) the presence of unique species over 

seep sites (that is, species endemic to these areas). Based on data presented here, the midwater 

invertebrate assemblage collected over several seep sites does not appear to be influenced by the 

chemosynthetic production from these cold seeps. For example, shrimp, the most speciose taxon 

collected, are not unusually diverse when compared to results from other studies conducted at 

nonseep sites in the eastern Gulf region (Hopkins and others, 1989; 1994). Our study over the 

seep sites and other previous studies from the eastern Gulf indicate that the species collected 

represent a subset of the total diversity of species reported in the eastern Gulf of Mexico 

(Hopkins and others, 1989). Additionally, most species collected in this study are also reported 

from other nonseep habitats. For example, most decapod species collected over the seeps also 

appear in tallies of the bathypelagic decapod assemblage of the eastern Gulf of Mexico (Burghart 

and others, 2007) and are included among decapods found on continental slope and abyssal plain 

habitats in the Gulf (Wicksten and Packard, 2005). Based on previously published geographic 

distributions, the majority of species represented in our samples have widespread distributions. 

All but one species (Sergia hansjacobi) are listed in the most current checklist of Gulf of Mexico 

decapods (Felder and others, 2009). Thus, the species composition of the midwater assemblage 

collected in this study is representative of species previously reported at these depths from this 

region of the Gulf of Mexico. 

Populations of species we collected are not likely enhanced by the chemosynthetic 

environment at the seeps, since the relative abundance of the midwater invertebrate faunal 

assemblage over these seep sites was not dramatically increased compared to that of nonseep 

sites. If increased productivity at the cold-seep environments was influencing the overlying 

water column, then high densities of organisms would be expected. Instead, the majority of 
258

species were represented by only one or two individuals. Multiple individuals may not have been 

collected in a single sample due to temporal or spatial distributions of the organisms or possibly 

through gear avoidance. However, it is unlikely that observed patterns in abundances could be 

an artifact of sampling, as other mesopelagic collections made in the eastern Gulf of Mexico also 

yielded relatively low numbers of caridean shrimps (Hopkins and others, 1989) and cephalopods 

(Passarella and Hopkins, 1991). Low abundances of midwater invertebrates are characteristic of 

oligotrophic tropical-subtropical gyres (Hopkins and others, 1989; Passerella and Hopkins, 

1991). Results presented here were consistent with those reported in these other studies where 

sampling, both in number of tows and extent of coverage, was more intensive. Possibly, similar 

oligotrophic conditions are present in the north-central Gulf region, as was suggested for the 

eastern Gulf. Further sampling, particularly of productivity parameters, is needed to confirm or 

refute this hypothesis. 

No unique species were collected over the cold-seep sites. This is not an unexpected 

result since many benthic species collected in association with cold-seep habitats are not 

endemic to these habitats. Rather, species taken at cold-seep sites are either considered to be 

opportunistic species found in the vicinity of the seeps but not restricted to these habitats (that is, 

vagrants; Martin and Haney, 2005) or are species not usually found associated with seeps but are 

incidentally captured from habitats adjacent to seep sites (Carney, 1994). 

Although no significant increases in species richness were observed for invertebrate 

samples taken in the water column over seep sites, species richness was relatively high for some 

taxa, suggesting that a large proportion of the background species was collected. This finding is 

significant, given that these data were collected with only a modest amount of sampling effort 

confined to a small region within the larger Gulf of Mexico ecosystem. Additionally, 
259

preliminary examination of the data illustrated that the species accumulation curve for all 

midwater invertebrate taxa collected in this study had reached an asymptote. This suggests that 

our sampling, although limited on both spatial and temporal scales, adequately represented the 

midwater invertebrate faunal assemblage from this region of the Gulf of Mexico. Our findings 

are comparable with previous studies, which covered a greater area and included more sampling 

effort (for example, Hopkins and others, 1989). Fifteen species of caridean shrimps were 

captured in 116 trawls in the present study compared to the findings of Hopkins and others 

(1989), where 22 species were captured in 338 trawls. Of the species collected, nine were 

common to both studies. Species richness and abundances reported here may be characteristic of 

the midwater faunal assemblage reported throughout the entire Gulf. Many species collected in 

the present study are reported in annotated lists discussed by other researchers. Several species 

in common between the present study and others are wide-ranging species distributed throughout 

the entire Gulf of Mexico (Felder and others, 2009). 

Our sampling regime produced collections of limited spatial and temporal coverage, and 

the species reported here are only a subset of a larger, more speciose assemblage. Catch 

composition may be dependent on the time of year the samples are collected, depth of capture, 

time of capture, and (or) the type of gear used. If midwater organisms in this region have patchy 

spatial distributions, our sampling locations and times when samples were taken would not 

adequately target the full spectrum of organisms constituting the total faunal assemblage. Our 

collections share some similarities to those described by other researchers at similar location and 

depths, but more extensive sampling will be needed to determine the overall diversity, 

abundance, and distribution of the midwater invertebrate faunal assemblage occurring in this 

region across seasons, discrete depths, and time of day. 
260

Sampling throughout the water column provides a more complete picture of the faunal 

assemblages occurring over and near to chemosynthetic communities. However, conclusions 

from this study remain speculative. Given the sampling regime for this investigation, several 

data gaps prohibit more definitive conclusions. For example, the midwater sampling conducted 

over chemosynthetic sites did not necessarily sample the portion of the water column that is 

directly influenced by chemosynthetic processes. Therefore, further study is needed to address 

the transfer of energy from chemosynthetic sources through the midwater food chain. Vertically

migrating organisms are a likely conduit. Isotope analysis could indicate utilization of chemobased carbon by some midwater species. Samples were taken for some midwater invertebrate 

species, and these data are in the process of being analyzed (A.W.J. Demopoulos, unpub. data, 

2011). But more precise and directed stratified sampling in conjunction with simultaneous 

collection of physical data from each site is needed to better assess the relationship between 

chemosynthetic and the overlying pelagic communities. Results from this study provide baseline 

and background information for the sites sampled. This analysis sets the stage for future work 

and to a better understanding of a potential link between chemosynthetic and pelagic systems. 

9.5 Acknowledgements

We thank the captain and crew of the R/V Cape Hatteras. The science crew from the 

USGS Chemo III cruise is acknowledged for help with sample collecting, processing, and data 

requests. C. Ahearn, L. Cole, A. Collins, C. Mah, D. Pawson, E. Strong, D. Tippett, and M. 

Vecchione helped with species identifications. Figure 1 was used with permission by S.W. Ross. 

T. Munroe read earlier drafts and provided helpful suggestions. 
261

10. ANALYSIS OF FUNGAL DIVERSITY IN SEDIMENT FROM A METHANE 

SEEP, GULF OF MEXICO

By Andrew D. Thaler 

Duke University Marine Lab, Beaufort, NC

10.1 Introduction and Rationale

The extent of fungal diversity in marine ecosystems is poorly characterized, especially in 

the deep sea. A conservative estimate of global fungal biodiversity places the minimum total 

number of species at approximately 1.5 million (Hawksworth, 1991). This estimate was 

determined by calculating the number of fungal species that occur in close association with 

plants and does not account for fungi that occur in ecosystems whose primary production is not 

photosynthetically derived. Fungi in deep-sea chemosynthetic ecosystems may represent a 

reservoir of previously undiscovered biodiversity. 

Marine-occurring fungi are found in mangroves, driftwood, shallow sediments, algae, 

coral (Hyde and others, 1998), and in deep-sea sediments (Damare and others, 2006). Fungi 

facilitate the decomposition of wood as well as lignin, chitin, and keratin (Reisert and Fuller, 

1962; Kohlmeyer, 1972) and form marine lichens through symbiotic relationships with algae 

(Grube and Blaha, 2005). Until recently, only five species of fungi were reported from the deep 

sea (Kohlmeyer and Kohlmeyer, 1979; Hawksworth, 2001). Fungi have been found at 

hydrothermal vent (Gadanho and Sampaio, 2005) and methane seep ecosystems (Takishita and 

others, 2006; 2007). Pathogenic black yeasts were discovered infecting Bathymodiolus mussels 
262

at a Fiji Basin hydrothermal vent field (Van Dover and others, 2007). With few exceptions the 

ecologic contribution of these fungi to deep-sea chemosynthetic ecosystems remains unknown. 

The deep sea represents Earth’s largest ecosystem. It is characterized by a pattern of high 

biodiversity and relatively low biomass, which reverses in areas of chemosynthetic activity – 

such as hydrothermal vents, whale falls, and methane seeps – where large aggregations of 

specially adapted organisms occur (Van Dover, 2000). Methane seeps are formed when 

hydrocarbons are released from gas hydrate reservoirs, providing an energy source for 

chemosynthetic communities (Van Dover and others, 2003). Many species of marine-occurring 

fungi can actively degrade hydrocarbons, and some common marine fungi thrive in hydrocarbonrich environments (Ahearn and Meyers, 1976). Cryptococcus curvatus, a basidiomycete yeast, is 

the dominant eukaryotic microbe at methane seeps in Kurishima Knoll (Sea of Japan) (Takishita 

and others, 2006). 

The Chemo III cruise provided an ideal opportunity to investigate fungal biodiversity at a 

seep site in the Gulf of Mexico and compare samples against the findings in Kurishima Knoll. In 

addition to examining the total biodiversity, chemical features of the seeps could also be 

measured, allowing for a finer scale assessment of fungi distribution at this methane seep 

ecosystem. 

10.2 Methods

10.2.1 Recovery

A single box core (Ocean Institute Mark III [50x50 cm]) was collected from Alaminos 

Canyon lease block 601 during the Chemo III research cruise onboard the R/V Cape Hatteras. 

Twenty-two sub-cores were taken from that box core using sterile 40-mL serological pipettes (tip 
263

removed; 1-cm diameter, 33-cm length). Sub-cores were sealed with parafilm and frozen (-5  ̊C 

topped with dry ice) for storage and transport. Reduction-oxidation potential sediment gradient 

was recorded by Amanda W.J. Demopoulos, USGS. 

10.2.2 Extraction and Amplification

Sub-cores were sectioned in 1-cm increments by sediment depth (to 10 cm), and 

environmental DNA was extracted using a MoBio PowerSoil soil extraction kit. The first 900 

base pairs of the large-subunit rDNA (LSU), an information-rich region that contains three 

divergent domains and is a standard barcode for the Fungal Tree of Life project, were amplified 

using primers (LR0R and LR5) that show an affinity for fungi. The resulting PCR product was 

cloned using Invitrogen TopoTA topo cloning kit and sequenced in the forward direction. 

Figure 10.1. Primers used for amplification of fungal LSU and ITS (internal transcribed spacer) regions.

10.2.3 Analysis

Recovered sequences were compared against the National Center for Biotechnology 

Information (NCBI) database and aligned using ClustalW (Thompson and others, 1994). The 

program PAUP (phylogenetic analyis using parsimony) was used to generate maximum 

parsimony, maximum likelihood, and neighbor joining trees that were assembled and compared 

for consistency. 

Primer Region Direction Sequence

LROR LSU Forward ACCCGCTGAACTTAAGC 

LR3 LSU Reverse CCGTGTTTCAAGACGGG 

LR5 LSU Reverse TCCTGAGGGAAACTTCG 

LR7 LSU Reverse TACTACCACCAAGATCT 

ITS1 ITS Forward TCCGTAGGTGAACCTGCGG 

ITS4 ITS Reverse TCCTCCGCTTATTGATATGC 
264

10.3 Results

Thirty-nine fungal sequences were recovered from the Alaminos Canyon methane seep (table 

10.1). While many sequences aligned with known terrestrial fungal phylotypes, 25 belonged to an 

unknown Ascomycete clade with no known terrestrial members. These samples closely corrrelated with 

the reduction/oxidation boundary in the sediment (fig. 10.2). Phylotype accumulation curves indicate 

that total fungal diversity has not yet been completely sampled (fig. 10.3). 

Table 10.1. Total sequences recovered, fungal sequences recovered, and sequences recovered from 

unidentified ascomycete clade by 2-cm sediment depth intervals from the Alaminos Canyon methane 

seep (2,300 m). 

[S ediment becomes reduced at ~4 cm depth] 

Total sequences Depth (cm) recoveredTotal fungal sequences 

recovered

Sequences recovered from 

unidentified ascomycete clade

0 – 2 27 11 4 

2 – 4 27

4 – 6 7 

23

5 

18

3 
265

Figure 10.2. Redox profile for the Alaminos Canyon methane seep boxcore, mV, millivolts; cm, 

centimeters. Courtesy of A.W.J. Demopoulos, USGS. Shaded area is the region dominated by an 

unidentified ascomycete clade. 
266

Figure 10.3. Eukaryotic phylotypes recovered from Alaminos Canyon methane seep, 0–2 cm and 2–4 

cm. Greater depths are not shown due to few sequences recovered below the redox zone. 

10.4 Discussion

The unidentified Alaminos Canyon ascomycete clade could represent a previously 

undescribed group of fungi that may be endemic to the deep sea. Previous studies by Takishita 

and others (2006) noted that the diversity of microbial organisms decreases steeply below the 

sediment surface and becomes dominated by a single fungal species, a trend similar to what we 

observe at Alaminos Canyon. Takashita and others did not connect sediment depth to the 

geochemical properties of the methane seep environment. 

The Alaminos Canyon ascomycete clade is located immediately above the boundary 

where the redox potential transitions from oxidized to reduced. The Alaminos Canyon 

ascomycete clade is present in low numbers both above and below this region. The site 

specificity of this group indicates that it is not the product of contamination from terrestrial 
267

spores and it may have an ecologic role in the seep environment. Cloning from PCR-amplified 

fragments of environmental samples does provide a good survey of diversity, but it cannot be 

used to estimate biomass. Since no recovered sequence was 100 percent identical to any other, 

we can assume that each sequence recovered represents an individual and thus that the 

occurrence of the Alaminos Canyon ascomycete clade increased 450 percent from the top 2 cm 

of sediment to 2 – 4 cm depth. 

Other fungal species recovered were closely allied to terrestrial species. These could be 

opportunistic fungi that have taken hold in the deep sea, or spore-derived contaminants that, 

while present, do not contribute to the ecosystem. 

10.5 Acknowledgments

Partial funding for this project was provided by NSF Grant DEB-0732984, Duke 

University, and the Marine Conservation Molecular Facility at the Duke University Marine Lab. 

Ship time was funded by the U.S. Geological Survey Chemo III Cruise. The author would like 

to thank Steve W. Ross of UNC Wilmington for graciously providing the opportunity to 

participate in this cruise, Amanda W.J. Demopoulos (USGS) for providing the redox profile for 

the Alaminos Canyon methane seep, and the crew of the R/V Cape Hatteras for their hard work 

and patience. The author would also like to thank Jason Jackson and Gregory Bonito for their 

guidance and expertise in working with fungal genetics and for their encouragement and 

willingness to help. 
268

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