OCS Study 

MMS 2003-063 

 

Coastal Marine Institute 

Historical Reconstruction 

of the Contaminant Loading and 

Biological Responses in the 

Central Gulf of Mexico Shelf Sediments 

Cooperative Agreement

Coastal Marine Institute 

Louisiana State University 

U.S. Department of the Interior

Minerals Management Service 

Gulf of Mexico OCS Region 
U.S. Department of the Interior Cooperative Agreement 

Minerals Management Service Coastal Marine Institute 

Gulf of Mexico OCS Region Louisiana State University 

OCS Study 

 MMS 2003-063 

 

Coastal Marine Institute 

Historical Reconstruction 

of the Contaminant Loading and 

Biological Responses in the 

Central Gulf of Mexico Shelf Sediments 

Editors 

R. Eugene Turner 

Edward B. Overton 

Nancy N. Rabalais 

Barun K. Sen Gupta 

October 2003 

Prepared under MMS Contract 

14-35-0001-30660-19930 

by 

Coastal Marine Institute 

Louisiana State University 

Baton Rouge, Louisiana 70803 

Published by 
iii 

DISCLAIMER 

This report was prepared under contract between the Minerals Management Service (MMS) and 

Louisiana State University, Coastal Ecology Institute. This report has been reviewed by the 

MMS and approved for publication. Approval does not signify that the contents necessarily 

reflect the views and policies of the Service, nor does mention of trade names or commercial 

products constitute endorsement or recommendation for use. It is, however, exempt from review 

and compliance with MMS editorial standards. 

REPORT AVAILABILITY 

Extra copies of the report may be obtained from the Public Information Office (Mail Stop 5034) 

at the following address: 

 U.S. Department of the Interior 

 Minerals Management Service 

 Gulf of Mexico OCS Region 

 Attention: Public Information Office (MS 5034) 

 1201 Elmwood Park Boulevard 

 New Orleans, Louisiana 70123-2394 

 Telephone Number: (504) 736-2519 or 

 1-800-200-GULF 

CITATION 

Suggested citation: 

Turner, R.E., E.B. Overton, N.N. Rabalais, and B.K. Sen Gupta (eds.). 2003. Historical 

reconstruction of the contaminant loading and biological responses in the Central Gulf of 

Mexico shelf sediments. U.S. Dept. of the Interior, Minerals Management Service, Gulf 

of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2003-063. 140 pp. 

ACKNOWLEDGMENTS 

The authors acknowledge and thank the many people who participated in the collection, analysis 

and discussions resulting in this conclusion, especially, Q. Dortch, B. Fry, D. Justic’, J.M. Lee, 

T.A. Oswald, and E.M. Swenson, and the crew of the R/V Pelican. 

ABOUT THE COVER 

Artist, Mary Lee Eggart, depicts Louisiana foraminifers on a golden-mean spiral. 
v 

ABSTRACT 

We documented changes in chemical contaminants and biological components of dated 

sediments collected from the central Gulf of Mexico continental shelf to evaluate the relative 

sources and concentrations. These include trace metals, selected organic compounds, 

phytoplankton pigments, diatom remnants and foraminifera. 

The distribution of the selected organic compounds suggests a chronic contaminant loading from 

the river itself, from oil and gas exploration in the Gulf of Mexico, perhaps from natural seeps in 

the area, and the chronological usage of chlorinated agricultural pesticides. The total 

organochlorine pesticide and total poly aromatic hydrocarbon (PAH) concentrations begin 

increasing above background levels after World War II. The organochlorine pesticide 

concentrations peaked from the 1940’s through the 1970’s in most of the cores, but not all, and 

some were not dominated by any one pesticide. The petrogenic (petroleum in origin) PAHs were 

assessed by quantitating the total hopanes. The hopanes were present in almost all of the cores 

and began increasing after WWII. The prominent PAH analytes in most of the cores were 

pyrene, fluoranthene, and phenanthrene, which are associated with pyrogenic sources. 

The fluctuations in the accumulation of Barium (Ba), but not Vanadium (V), are coincidental 

with the presumed use of barite on this shelf. The fluctuations in V concentration in the 

sediments are coincidental with the national consumption of V. Copper (Cu), Cadmium (Cd), 

and Zinc (Zn) concentrations in sediments fluctuate coincidentally with V, not Ba, thus 

indicating that the dominant source of these trace metals in offshore sediments are derived from 

riverine sources, and are not primarily from in situ industrial processes releasing them on the 

shelf. This is not to suggest that local site-specific contamination is not a significant 

management or health concern. 

There is a general increase in chlorophyll a, pheopigments, zeaxanthin, fucoxanthin and most 

carotenoids over time, with the change gradual from 1955 to 1970, followed by a fairly steady 

increase to 1997. These patterns are consistent with the increased accumulation of diatom 

remnants in sediments. The increasing pigments and greater concentrations in areas where 

hypoxia is more likely to occur indicate an increase in eutrophication or a worsening of hypoxia 

or both. 

The temporal trend in forminifera is one of diversity reduction and increasing dominance. No 

definite relationship could be established between the contaminant concentration in sediments 

and the composition of foraminiferal assemblage. The only match between a contaminant high 

and a diversity low was at the 1970-1975 level in one core; the significance of this match is 

unclear. Deformed Foraminifera, one indicator of extreme chemical pollution, are not present in 

either of the cores. On the other hand, the diversity and relative-abundance changes of 

foraminiferal species fit the model of progressively worsening seasonal hypoxia in the area. 

These analyses indicate that both OCS development and riverine sources exert strong influences 

on the sediment constituents offshore, and that these influences may be independent of one 

another. 
vii 

 

TABLE OF CONTENTS 

ABSTRACT..................................................................................................................................v 

LIST OF FIGURES .....................................................................................................................ix 

LIST OF TABLES.................................................................................................................... xiii 

CHAPTER 1. INTRODUCTION .............................................................................................1.1 

CHAPTER 2. ORGANICS ANALYSES.................................................................................2.1 

 Abstract..........................................................................................................................2.1 

 Introduction....................................................................................................................2.2 

 Methodology..................................................................................................................2.3 

 Preparation and Extraction.................................................................................2.3 

 Instrument Configuration and Calibration.........................................................2.4 

 Quantitative Analysis.........................................................................................2.5 

 Quality Assurance (QA)/Quality Control (QC).................................................2.5 

 Instrumental QA/QC..........................................................................................2.6 

 Results ............................................................................................................................2.6 

 Organochlorine Pesticides (OC) and Polychlorinated Biphenyls (PCB’s)........2.7 

 Polycyclic Aromatic Hydrocarbons (PAH’s) ..................................................2.10 

 Individual Core Results....................................................................................2.15 

 Discussion....................................................................................................................2.16 

 Organochlorine (OC) Pesticides ......................................................................2.18 

 Polycyclic Aromatic Hydrocarbons (PAH’s) ..................................................2.18 

 Recommendations........................................................................................................2.19 

CHAPTER 3. TRACE METAL, C, N AND BIOLOGICALLY-BOUND SILICATE 

 IN DATED SEDIMENTS FROM THE LOUISIANA CONTINENTAL 

 SHELF ...........................................................................................................3.1 

 Abstract..........................................................................................................................3.1 

 Introduction....................................................................................................................3.2 

 Methods..........................................................................................................................3.3 

 Sediment Dating.................................................................................................3.3 

 Diatom Remains.................................................................................................3.4 

 Total Organic Carbon ........................................................................................3.4 

 Trace Metals.......................................................................................................3.4 

 Grain Size...........................................................................................................3.4 

 Mineral Production and Use ..............................................................................3.5 

 Results and Discussion ..................................................................................................3.5 

 Sediment Accretion Rates..................................................................................3.5 

 General Sediment Quality Near and Far from the Mississippi River Delta ......3.6 

 Trace Metals.......................................................................................................3.6 
viii 

TABLE OF CONTENTS 

(continued) 

 Diatom Remains and Organic Content ............................................................3.10 

 Summary......................................................................................................................3.11 

CHAPTER 4. ECOSYSTEM HISTORY REVEALED THROUGH PRESERVED 

PHYTOPLANKTON PIGMENTS.................................................................4.1 

 Abstract..........................................................................................................................4.1 

 Introduction....................................................................................................................4.1 

 Study Area .....................................................................................................................4.2 

 Methods..........................................................................................................................4.4 

 Sediment Grain Size Analysis ...........................................................................4.4 

 Chloropigments by High Performance Liquid Chromatography (HPLC).........4.4 

 Results and Discussion ..................................................................................................4.5 

 Sediment Grain Size ..........................................................................................4.5 

 Phytoplankton Pigments ....................................................................................4.6 

 Summary......................................................................................................................4.16 

CHAPTER 5. HISTORICAL RECONSTRUCTION OF THE CONTAMINANT LOADING 

AND BIOLOGICAL RESPONSES IN THE CENTRAL GULF OF MEXICO 

SHELF SEDIMENTS: FORAMINIFERA.....................................................5.1 

 Abstract..........................................................................................................................5.1 

 Introduction....................................................................................................................5.1 

 Materials and Methods...................................................................................................5.2 

 Results and Discussion ..................................................................................................5.3 

 Species Diversity ...............................................................................................5.3 

 Species Distribution...........................................................................................5.4 

 Community Change .........................................................................................5.13 

 Additional Data................................................................................................5.18 

 Significant Stratigraphic Trends and Interpretations .......................................5.22 

 Summary and Conclusions ..........................................................................................5.23 

CHAPTER 6. LITERATURE CITED......................................................................................6.1 

CHAPTER 7. APPENDICES ...................................................................................................7.1 

Appendix A. Total Organochlorine Pesticide Histograms............................................7.3 

Appendix B. Organochlorine Pesticide Concentrations for Sediment Cores ...............7.9 

Appendix C. Total Organochlorine Pesticide Histograms by Decade........................7.15 

Appendix D. Total PAH Histograms ..........................................................................7.19 

Appendix E. PAH Concentrations for Sediment Cores..............................................7.25 

Appendix F. Total PAH Histograms by Decade ........................................................7.33 

Appendix G. Total PAH vs. Estimated Total Hopane Concentrations 

 by Core and Date..................................................................................7.41 
ix 

LIST OF FIGURES 

Figure 1.1. The production of oil and gas in southern Louisiana in 1941, 1964 

 and 1981 .................................................................................................................1.1 

Figure 1.2. The oil and produced water production for leases in the Gulf of 

 Mexico OCS. The mean water depth of new oil leases in the Gulf 

 of Mexico, by year. The percentage of oil spilled of the total 

 production in the Gulf of Mexico, by year.............................................................1.2 

Figure 2.1. Location of the core samples analyzed for organic contaminants...........................2.3 

Figure 2.2. Total organochlorine (OC) pesticide and breakdown product 

 distributions in the core samples collected from the Mississippi Delta Bight 

 prior to 1950 and after 1950.....................................................................................2.9 

Figure 2.3. Total OC pesticide concentrations prior to the 1950’s, after the 1950’s 

 and the overall totals in OCS cores collected from the Mississippi Delta Bight.....2.9 

Figure 2.4. Total PAH concentrations prior to 1950, after 1950 and overall totals 

 from core samples collected in the Mississippi Delta Bight..................................2.12 

Figure 2.5. Estimated total hopane concentrations prior to the 1950’s, after the 1950’s and the 

 overall total from core samples collected from the Mississippi Delta Bight.........2.13 

Figure 2.6. Total PAH (petrogenic PAH’s) distributions in the core samples collected 

 from the Mississippi Delta Bight prior to 1950 and after 1950 ............................2.14 

Figure 2.7. Estimated total hopanes (petrogenic PAH’s) distributions in the core samples 

 collected from the Mississippi Delta Bight prior to 1950 and after 1950 .............2.14 

Figure 3.1. Sampling locations where sediment cores were collected .....................................3.3 

Figure 3.2. The vertical distribution of 210Pb in six cores collected for this study ....................3.5 

Figure 3.3. Sedimentation rates (cm yr-1) west of the Mississippi River delta..........................3.6 

Figure 3.4. The relationship between sediment density and organic content 

 and aluminum and sand..........................................................................................3.6 
x 

LIST OF FIGURES 

(continued) 

Figure 3.5. The relationship between the concentration (μg g-1) of vanadium and 

 barium in six sediment cores ..................................................................................3.7 

Figure 3.6. The normalized concentration of barium (μg Ba / g Al) in six dated 

 sediment cores from various depth zones on the Louisiana shelf ..........................3.8 

Figure 3.7. The normalized concentration of vanadium (μg V / g Al) in six 

 dated sediment cores from various depth zones on the Louisiana shelf.................3.9 

Figure 3.8. The relationship between the percent carbon and nitrogen in dated 

 sediments from six cores (dry weight basis) ........................................................3.11 

Figure 3.9. The concentration of percent biogenic silica (Bsi) and % carbon vs. 

 dated horizon for sediments from the continental shelf west of the 

 Mississippi River delta in 10 to 100 m water depth.............................................3.12 

Figure 3.10. Core locations in the MDB where increasing concentrations of %BSi 

 or %C were observed in the last three decades ....................................................3.13 

Figure 4.1. Frequency distribution of hypoxic bottom-water during mid-summer 

 for years 1985-2001 with core stations superimposed ...........................................4.2 

Figure 4.2. Vertical distribution of % sand, % silt and % clay for cores as indicated..............4.5 

Figure 4.3. Vertical distribution of chlorophyll a and chlorophyll a/pheopigment ratio 

(Chla/Pheo) for cores E30-1, E50-1, E60-2, F35-2 and D50G ..............................4.7 

Figure 4.4. Vertical distribution of zeaxanthin and zeaxanthis/ß-carotene ratio for 

 cores E30-1, E50-1, E60-2, F35-2 and D50G ........................................................4.8 

Figure 4.5. Vertical distribution of fucoxanthin and diadinoxanthin for cores 

 E30-1, E50-1, E60-2, F35-2 and D50G..................................................................4.9 

Figure 4.6. Vertical distribution of alloxanthin and diatoxanthin for cores E30-1, 

 E50-1, E60-2, F35-2 and D50G ...........................................................................4.10 

Figure 4.7. Vertical distribution of chloropigments in core D50G; chla 

 (chlorophyll a), total phaeo (total phaeopigments), Fuco (fucoxanthin), Ddx 

(diadinoxanthin), allo (alloxanthin), Diato (diatoxanthin), Lutein, 

 zea (zeaxanthin), Cantha (canthaxanthin), B-caro (ß-carotene)...........................4.11 
xi 

LIST OF FIGURES 

(continued) 

Figure 4.8. Vertical distribution of chloropigments in core I3; chla (chlorophyll a), 

 total pheo (total phaeopigments), Fuco (fucoxanthin), Ddx (diadinoxanthin), 

 Diato (diatoxanthin), Lutein, zea (zeaxanthin), B-caro (ß-carotene) ...................4.12 

Figure 4.9. Trend of average Secchi disk depth on the Louisiana shelf west of 

 the Mississippi River delta ...................................................................................4.15 

Figure 5.1. Core locations.........................................................................................................5.2 

Figure 5.2. Distribution of species richness through time. A, core E60; B, core F35 ..............5.4 

Figure 5.3. Distribution of Shannon-Wiener diversity index through time. A, core 

 E60; B, core F35.....................................................................................................5.6 

Figure 5.4. Distribution of dominant species through time. A, core E60; B, core F35 ............5.7 

Figure 5.5. Distribution of Ammonia–Elphidium Index in Core F35 .......................................5.8 

Figure 5.6. Distribution of relative abundances of Bulimina marginata, Cancris 

sagra, Fursenkoina pontoni, Saccammina diflugiformis, and Uvigerina 

hispido-costata in core E60....................................................................................5.8

Figure 5.7. Distribution of relative abundances of Bulimina marginata and Bolivina 

 lowmani in core F35 ...............................................................................................5.9

Figure 5.8. Distribution of relative abundances of Quinqueloculina. Core E60; 

 core E35................................................................................................................5.10 

Figure 5.9. Distribution of relative abundances of agglutinated and 

 porcelaneous species groups, core E60 ................................................................5.11 

Figure 5.10. Distribution of relative abundances of agglutinated and 

 porcelaneous species groups, core F35 ................................................................5.12 

Figure 5.11. Cluster analysis of E60 foraminiferal data; dendrogram for 12 cases................5.13 

Figure 5.12. Cluster analysis of F35 foraminiferal data; dendrogram for 33 cases................5.14 

Figure 5.13. Eigenvalues scree plot for E60 foraminiferal data .............................................5.15 

Figure 5.14. Factor loadings, Factor 1/Factor2 core E60 .......................................................5.16 
xii 

LIST OF FIGURES 

(continued) 

Figure 5.15. Factor loadings, Factor 1/Factor3 (A) and Factor 2/Factor 3 (B), 

 core E60 .......................................................................................................................5.17 

Figure 5.16. Plots of factor scores against time, core E60. A, Factor 1. B, Factor 2.............5.17 

Figure 5.17. Distribution of relative abundance of Quinqueloculina; core G27 ....................5.19 

Figure 5.18. Cluster analysis of BL10 core data, dendrogram for 51 cases ...........................5.20 
xiii 

LIST OF TABLES 

Table 2.1. Physical and chemical information from samples from the Mississippi 

 Delta Bight.........................................................................................................2.7 

 

Table 2.2. Target OC pesticides and breakdown products, PCB’s in the core samples .....2.8 

Table 2.3. Target PAH’s in the originally proposed GC/MS-SIM method......................2.10 

Table 2.4. Target PAH’s and oil biomarkers in GC/MS-SIM oil fingerprinting method .2.11 

Table 3.1. Results from a simple linear regression analysis of the relationship 

 between Cd, Cu, and Zn (Y) versus both vanadium and barium (x) in 

 dated sediments from six core samples from the Louisiana shelf ..................3.10 

Table 4.1. The taxonomic origin of pigments from Louisiana shelf sediment 

 cores and their relative concentrations in algal groups......................................4.3 

Table 4.2. Likelihood of exposure to hypoxia for each station based on mid-summer 

 cruise data and more frequent observations off Terrebonne Bay ......................4.4 

Table 4.3. Results of linear regressions among sediment pigments, sediment 

 biogenic silica and Mississippi River annual nitrate load................................4.13 

Table 5.1. Eigenvalues for E60 foraminiferal data...........................................................5.15 

Table 5.2. Factor loadings for 12 foraminiferal taxa in core E60.....................................5.16 

Table 5.3. Factor scores for 12 samples in core E60 ........................................................5.18 

Table 5.4. Eigenvalues for BL10 foraminiferal data ........................................................5.21 

Table 5.5. Factor loadings for 18 foraminiferal species from core BL10.........................5.21 
CHAPTER 1 

INTRODUCTION 

Oil and gas recovery from the northern Gulf of Mexico started in earnest after WWII, beginning 

in shallow water. Offshore production on the Outer Continental Shelf (OCS) at the turn of the 

last century was primarily off the Louisiana coast, and amounted to more than 600 million 

barrels of oil annually (1 bbl. = 42 gal.) and new leases were located in an average 100 m water 

depth (Figures 1.1 and 1.2, top). This non-renewable resource recovery was accompanied by a 

volume of produced water slightly larger than the oil recovered (Figure 1.2, middle). The 

percentage of oil spilled has declined since the peak in the mid-1970s, to the point where it is 

now about 0.005 % of the produced volume (Figure 1.2, bottom). Not all of this spilled oil is 

recovered where it is spilled. The produced water, the oil spilled and chemicals used in the 

mineral recovery phase have received some attention because of potential ecosystem impacts on 

this biologically-rich environment. 

Figure 1.1. The production of oil and gas in southern Louisiana in 1941, 1964 and 1981 (from 

the Louisiana Geological Survey). 
 

1.2 

Figure 1.2. Top: The oil and produced water production for leases in the Gulf of Mexico OCS. 

Middle: The mean water depth of new oil leases in the Gulf of Mexico, by year. 

Bottom: The percentage of oil spilled of the total production in the Gulf of Mexico, 

by year. Data are from the U.S. Minerals Management Service (2003) and the U.S. 

Coast Guard (2003). 
 

1.3 

A pervasive, continuing, and confounding feature of the OCS Program and continental shelf 

investigations involves evaluation of the relative influences of these oil and gas recovery efforts 

against a background of regional forcing functions, such as riverine sources, climate, and 

estuarine exchanges that vary 'naturally' and have also changed over decades from landscapescale influences (Bender et al. 1979). In other words, is the in situ release of contaminants as 

significant as the changes occurring from landuse changes in the Mississippi River watershed, 

and can they be detected against a background that includes a substantial natural variability. 

These influences complicate estimations of the more localized releases of oil and gas drilling and 

production operations. Whether containinant releases are significant in terms of background or 

'natural' amounts is an issue complicated by transport and degradation processes. A National 

Academy of Sciences report on MMS offshore studies, the Rowe and Turner (1989) 

recommendations, and Bender et al. (1979) contain similar conclusions: (1) basic information on 

the ecosystem is missing, (2) a broad analysis is informative, and more interdisciplinary studies, 

especially of long-term nature, are required, (3) the benthos is a repository of long-term trends, 

and (4) the role of the Mississippi River must be teased out of the more localized impacts by oil 

and gas recovery efforts. 

In this context, we attempted to document changes in chemical contaminants of the central Gulf 

of Mexico continental shelf sediments, the biogeochemical signature of ecosystem changes 

found within them, and the biological response by the foraminiferal community. We place these 

changes within the framework of the regional influence of the Mississippi River, oil and gas 

recovery efforts, and the natural variability of the ecosystem. The approach was to analyze 

constituents in dated sediment cores. The work required: (1) careful collection of sediment cores 

from the continental shelf, (2) dating these cores in meaningfully long increments, (3) 

determination of sediment N, P and organic C, and trace metals and organic compounds, 

including petroleum biomarkers within core segments, and (4) quantitative estimation of benthic 

foraminiferal species abundances. 

The questions we addressed included: 

•What are the historical changes in contaminant storage of the Outer Continental Shelf 

(OCS) ecosystem? 

•Are the anticipated biomarkers of petroleum sources localized or regional; are they 

temporally isolated in the sediment core? 

•To what depth contour and distance downstream of the Mississippi River plume do these 

influences, if any, extend? 

•Are these changes reflected in the assemblages of benthic foraminifera and other 

ecosystem indicators? 

The report is divided into four (4) chapters addressing aspects of these questions on this shelf. 

Our primary analyses is of the constituents in dated sediments before mineral recovery activity 

began up to the mid-1990s. Chapter 2 (Organic Analyses; Overton, Miles, and Ashton) 

examines three main categories of pollutants or bio-indicators: total polycyclic aromatic 

hydrocarbons, or PAHs, (indicative of pyrogenic PAHs), total hopanes (indicative of petrogenic 

PAHs) and total organochlorine pesticides. Chapter 3 (Trace Metal, C, N and Biologicallybound Silicate in Dated Sediments from the Louisiana Continental Shelf; Turner, Milan, 
 

1.4 

Rabalais) documents the regional changes in trace metals and in biological materials (carbon, 

nitrogen, biogenic silica) in time and space. Chapter 4 (Ecosystem History Revealed through 

Preserved Phytoplankton Pigments; Rabalais, Atilla and Normandeau) and Chapter 5 (Historical 

Reconstruction of the Contaminant Loading and Biological Responses in the Central Gulf of 

Mexico Shelf Sediments: Foraminifera; Sen Gupta and Platon) examines two different aspects 

of the planktonic record. 
CHAPTER 2 

 ORGANICS ANALYSES 

Edward B. Overton, M. Scott Miles, and Buffy M. Ashton 

Department of Environmental Studies, Louisiana State University 

ABSTRACT 

The distribution of selected organic compounds within ten dated cores taken from the 

Mississippi Delta Bight off coastal Louisiana suggests a chronic contaminant loading from 

several sources including the river itself, oil and gas exploration in the central Gulf of Mexico 

(GOM) shelf area, natural seeps, and the historical usage of chlorinated agricultural pesticides. 

Data interpretations were broken down into three main categories: total organochlorine (OC) 

pesticides; total polycyclic aromatic hydrocarbons, or PAH’s, (indicative of pyrogenic PAH’s); 

and estimated total hopanes (indicative of petrogenic hydrocarbons). The sediments were also 

analyzed for polychlorinated biphenyls (PCB’s); however, PCB’s were not detected at part per 

billion levels. Therefore, data analyses focused on the OC pesticides, the PAH’s and the 

petrogenic hydrocarbons. The total OC pesticide and PAH concentrations begin increasing 

above background levels after World War II. The estimated total hopanes, which are considered 

to be petroleum biomarkers, were present in almost all of the cores; however, the concentrations 

show a gradual increase after the 1950’s, especially in the vicinity of transect “E”. 

Gas Chromatography/Electron Capture Detection (GC/ECD) was used to obtain the OC pesticide 

data. Gas Chromatography/Mass Spectrometry (GC/MS) was used to obtain both the pyrogenic 

PAH and petrogenic hydrocarbon data. The initial GC/MS method was based on a combination 

of Technical Memorandum NMFS F/NWC-92 and the U.S. EPA analytical methods for 

detecting target PAH analytes. This methodology was appropriate for isolating PAH compounds 

of pyrogenic origin; however, it was inadequate for isolating compounds indicative of petrogenic 

sources. Therefore, a more detailed GC/MS methodology, which includes certain parent PAH 

compounds, their alkyl homologs, and the hopanes and steranes, was employed to confirm the 

presence of petrogenic contamination and help in the determination of the contamination 

sources. 

The purpose of analyzing the sediment cores for OC pesticides, PAH’s and hopanes was to 

document the contamination changes of the central GOM, Outer Continental Shelf (OCS) 

sediments and try to place the changes within the framework of the regional influence of the 

Mississippi river and/or oil and gas exploration activities. Based on the distribution of these 

organic analytes, the Mississippi River is a regional source of the OC pesticides and the 

pyrogenic PAH’s. On the other hand, the hopanes detected in the sediment cores represent a 

local influence of natural geologic hydrocarbon seeps, or oil and gas exploration in the GOM. 

Atmospheric input of the targeted contaminants appears to be minimal to none. 
 

2.2 

INTRODUCTION

Organic contaminants are introduced into the sediment column by four main transport processes: 

• Aeolian transport of fossil fuels and wood combustion products followed by deposition 

on the sea surface and subsequent sedimentation; 

• Riverine transport of combined point and non-point sources of input; 

• Direct introduction of waste materials via anthropogenic activities such as pipeline and 

oil spills or barge disposal; and, 

• Resuspension of materials reaching coastal marine sediment via bullet one and two 

followed by deposition in settling areas (Boehm and Farrington 1984). 

The contaminants of concern, once associated with the suspended solids in the water column, are 

eventually deposited attached to these sediments (Santschi et al. 2001). Hence, in theory, 

sediment cores can provide valuable information regarding the history of persistent 

contamination and the changes in chemical contamination throughout the course of time. The 

purpose of analyzing the sediment cores for organochlorine (OC) pesticides, PAH’s and other 

petroleum related hydrocarbons was to document these changes in central Gulf of Mexico Outer 

Continental Shelf sediments and try to place the changes within the framework of the relative 

influences of oil and gas recovery efforts compared to the regional influence of the Mississippi 

River, and to some extent, atmospheric influences. 

The agricultural use of OC pesticides began in 1945 with broad scale applications of DDT 

(dichlorodiphenyltrichloroethane) (Reich et al. 1986). DDT was the most widely used pesticide 

in this first generation pesticide class because it was the most effective and had the longest 

lasting efficacy. Additionally, it was very common to mix DDT with other pesticides such as 

lindane (hexachlorocyclohexane) to treat a wide range of insect pests. Other organochlorine 

pesticides were mixtures of several OC pesticides. For example, chlordane, or technical 

chlordane, was 60-75% chlordane (in the cis and trans isomeric forms) and 25-40% related 

compounds such as trans-nonachlor and heptachlor. The target OC pesticides in this study (with 

the exception of lindane which is still used in head lice treatments) are no longer registered for 

use in the United States and were phased out in the 1970’s and 1980’s. However, due to their 

persistence in the environment they are still detectable in several environmental matrices. 

Oil and gas production in the Gulf of Mexico began in 1947 and peaked in 1971. Production 

then declined through the late 1970’s until the 1980’s, during which production peaked again in 

1984. In the late 1980’s, the price of oil collapsed as a result of sharp increases in crude oil 

prices associated with declines in output and increases in inflation in many industrialized 

countries. Initially, Gulf of Mexico production began in the shallower depths (<330 m) of the 

OCS and it wasn’t until the 1990’s that production platforms began to move into deeper waters. 

The Gulf of Mexico is rich in subsurface gas and oil fields and has been one of the mainstays of 

the United States oil industry. This has been attributed to rapid sediment deposition, active salt 

deformation and sea floor seeps which contribute to the vertical migration of oil and gas (Sassen 

et al. 2001). The target PAH’s and petrogenic hydrocarbons in this study are compounds 

common in oil; however, they can also be common in other types of hydrocarbon waste (i.e. 

industrial waste or creosote contamination). Compounds universal in crude oils and petroleum 

products that are commonly used for the exclusive identification of these types of products in the 
 

2.3 

environment are called oil biomarkers. These compounds include the alkyl homologs of certain 

PAH parent compounds and the triterpane and steranes. Oil biomarkers are important oil 

constituents because they are generally more resistant to environmental weathering than most of 

the other oil compounds. Additionally, oil biomarker distribution can be unique for each type of 

oil and each different geographic source of petroleum, which results in each oil having a unique 

oil fingerprint. 

METHODOLOGY 

We analyzed sediments for the distribution of selected organic compounds within ten dated cores 

taken from the central GOM-OCS Bight area west of the Southwest Pass of the Mississippi River 

off coastal Louisiana (Figure 2.1). One of the cores sampled, I3, does not appear in the figure. 

Figure 2.1. Location of the core samples analyzed for organic contaminants. 

Preparation and Extraction

The sediment samples, when received by LSU-DES, were free of extraneous materials such as 

pebbles, weeds, etc. The samples were weighed to 10 g, if possible. If 10 g were not available, 

the whole sample was weighed. The samples were then extracted with dichloromethane (DCM) 

and spiked with surrogate standards at a final extract concentration of 200 μg ml-1. The samples 
 

2.4 

were then placed in an ultrasonic bath for 15 minutes. The DCM was filtered through a funnel 

containing anhydrous sodium sulfate into a round bottom flask. This extraction procedure was 

repeated two more times for each core section/depth. The combined decantates were 

concentrated to 2.0-mL using a combination of rotary evaporation and Kuderna-Danish 

concentrator tubes. 

Alumina/silica gel chromatographic columns were prepared for the clean-up of the concentrated 

extracts. Silica gel was activated at 170oC for 12 hours and partially deactivated with 3% (v/w) 

distilled water. Five grams of silica gel was slurry packed in dichloromethane over 10 g of 

alumina, previously activated at 400oC for 4 h and partially deactivated with 1% distilled water 

(v/w). The final extracts, in hexane, were concentrated using Kuderna-Danish tubes heated in a 

water bath at 60oC to a final volume of 1.0-mL. 

After initial full scan GC/MS analysis of representative samples of the individual core sections 

showed non-detection of the OC pesticides, PCB’s and PAH’s, 5-6 section extracts within each 

core were combined to lower analyte detection limits. Representative samples of the combined 

sections, after concentration to 2.0-mL, were then run on the GC/MS in selected ion monitoring 

mode (SIM). Analyte detection was still low, so the combined extracts were then concentrated 

to a final volume of either 1.0-mL for cores E30, E50, E60, and F35, or 0.1-mL for the remaining 

cores. 

Instrument Configuration and Calibration

GC/ECD 

Because analyte detection limits were low for the OC pesticides and PCB’s on the GC/MS, the 

samples were prepared for analysis on a HP5890 GC with an electron capture detector (ECD). 

The GC was operated in temperature program mode with the initial column temperature of 

120oC, held for 3 minutes, then increased to 200oC at a rate of 15oC/minute and held at this 

temperature for 8 minutes. The temperature was then increased to 270oC at a rate of 3oC/minute 

and held at this final temperature for 1.00 minute. The injector temperature was set at 250oC and 

only high-temperature, low thermal bleed septa were used. The ECD was maintained at 290oC. 

Several of the samples that contained OC pesticides concentrations >2 ug g-1 were run on a 

HP6890 GC-ECD/NPD in the Formulations Laboratory in the Louisiana State University 

Agricultural Chemistry Department for secondary column confirmation. The oven temperature 

program parameters were the same as described above. The injector was set at 265oC and the 

ECD was maintained at 350oC. The injection was split at a ratio of 2:1. The column was a HP608 (30 m x 0.53 mm ID x 0.5 μm film). As mentioned previously, PCB’s were not detected at 

ppb levels, and therefore, only the OC pesticide data from the GC/EDC was quantitated and 

evaluated. 

GC/MS 

A HP5890 GC/5971 MSD operated in selected ion monitoring mode (SIM) was configured with 

a DB-5 high resolution capillary column (30 meter x 0.25 mm ID x 0.25 micron film, J&W 

Scientific). The GC flow rates were adjusted to provide the optimal separation. For the PAH’s, 

the GC was operated in temperature program mode with the initial column temperature of 60oC 
 

2.5 

held for 3 minutes, then increased to 320oC at a rate of 10oC/minute and held at the upper 

temperature for 5 minutes. The injector temperature was set at 250oC and only high-temperature, 

low thermal bleed septa were used. The interface to the MS was maintained at 280oC. The 

GC/MS parameters were the same for the OC pesticides and PCBs; however, the ion groups 

were changed to reflect the analytes of interest. The method for GC/MS full scanning analysis 

on representative samples from each core was also the same, except the MS was operated in full 

scan mode and not in SIM mode. 

Quantitative Analysis

OC Pesticides 

The concentrations of the target OC pesticides were determined by an external standard method. 

Using EPA SWP Method 8081B as a guideline, a single point calibration using a calibration 

standard near the mid-point of the expected range of the OC pesticides was performed. 

Verification of the calibration was performed at least once each 12-hour shift by injecting a 

calibration verification standard prior to conducting any sample analyses. The concentration of 

each OC pesticide compound was calculated to two (2) significant figures. 

PAH’s 

The concentrations of the target PAH’s were determined by an internal standard method and 

response factors calculated from a 3-point calibration curve using commercially available 

standards for the analytes of interest. The concentration of each PAH compound was calculated 

to two (2) significant figures. Background levels of analytes and percent recoveries (60-120%) 

for each surrogate standard were monitored throughout the analyses. The internal standards were 

2-fluorobiphenyl and terphenyl-d14, and the surrogate standards were naphthalene-d8, 

acenaphthene-d10, phenanthrene-d10, chrysene-d12, and perylene-d12. 

Quality Assurance/Quality Control

General QA/QC 

Reagent grade or pesticide grade chemicals/solvents were used in all the extractions and 

analyses. The standard solutions and sample extracts were stored in polytetrafluoroethylene 

(PTFE)-sealed vials, in a refrigerator at a temperature of 4oC. All glassware and labware was 

washed in hot, soapy water; rinsed with tap water and distilled water; rinsed with methanol and 

then dichloromethane; and placed in an oven set at 130oC overnight prior to any sample 

preparation and extraction. 

Analytical QA/QC 

An extraction blank was prepared with each set of extracted samples to insure that there was no 

contamination from the solvents, glassware, or laboratory equipment used during the 

concentration procedures. 

All method blanks, duplicates, and sediment samples were spiked with surrogate standards prior 

to extraction. The surrogate recoveries were acceptable if they fell within the range of 60-120% 

(EPA acceptance criteria). 
 

2.6 

Instrumental QA/QC

GC/ECD 

A daily calibration standard was the first injection of each sequence on the GC/ECD, which was 

then followed by a hexane blank. The calibration was verified at least once each 12-hour shift. 

If the results from these injections verified proper instrument performance, the analysis of 

samples continued; however, if the daily standard indicated instrumental problems, then no 

further analytical work was performed until the instrument was restored to good operating 

condition. 

The identities of all analytes were established using correlation of their retention times in the 

samples to the daily retention time window. Retention time windows were established to allow 

for minor shifts in absolute retention times as a result of sample loadings and normal 

chromatographic variability. For quantification of analytes of interest, daily calculation of 

calibration factors for each analyte at one calibration level was used to check the percent relative 

standard deviation, or %RSD (a measure of precision). The %RSD of the calibration factors for 

each analyte had to be within acceptable QC limits on a daily basis (i.e., %RSD must be <15% 

each day to be considered acceptable). 

 

GC/MS

The MS was tuned to PFTBA (perfluorotributylamine, the most commonly used tuning 

compound required for automatic tuning of the instrument) prior to each set of analyses. If the 

tune was significantly different from prior tune parameter values, the instrument was checked for 

malfunctions (e.g., air leaks, worn septum, dirty liner, etc.) and returned to normal operating 

conditions. Appropriate internal standards were added just before GC/MS analysis to verify that 

the injection was made correctly. 

The identities of all analytes were established using correlation of their retention times and mass 

spectral data. For quantification of analytes of interest, three concentration levels for each 

analyte were used for the initial calibration curve. The linearity and %RSD was calculated for 

each analyte and found to be within the acceptable limits. The same GC operating conditions 

were used for the initial calibration curve and for the sample extracts. 

A daily calibration standard (at one concentration level) was the first injection after the tune, 

followed by a blank. If the results from these injections verified proper instrument performance, 

the analysis of samples continued; however, if the daily standard indicated instrumental 

problems, then no further analytical work was performed until the instrument was restored to 

good operating condition. 

RESULTS 

Table 2.1 is a summary table for the cores analyzed and displays the pertinent physical and 

chemical information for each core analyzed. 
 

2.7 

Table 2.1 

Physical and chemical information from samples from the Mississippi Delta Bight. 

PHYSICAL CHEMICAL 

Core Core Dates Sedimentation

Rate 

Total 

PAH’s 

(Pyrogenic 

PAH’s) 

Estimated 

Total Hopanes 

(Petrogenic 

Hydrocarbons) 

Total OC 

Pesticides 

C10 1974-1989 1.00 cm yr -1 230 ng g-1 81 ng g-1 0.00 ng g-1

D50G 1777-1997 1.24 cm yr -1 2400 ng g-1 1100 ng g-1 0.81 ng g-1

D80 1974-1997 0.46 cm yr -1 5300 ng g-1 1100 ng g-1 2200 ng g-1

E30 1960-1997 1.10 cm yr -1 110 ng g-1 3100 ng g-1 3400 ng g-1

E50 1938-1997 1.00 cm yr -1 380 ng g-1 4100 ng g-1 13000 ng g-1

E60 1931-1997 0.74 cm yr -1 120 ng g-1 4400 ng g-1 99 ng g-1

F35 1945-1997 0.84 cm yr -1 180 ng g-1 2200 ng g-1 140 ng g-1

G40 1806-1989 0.12 cm yr -1 900 ng g-1 140 ng g-1 44 ng g-1

G50 1896-1916 0.15 cm yr -1 330 ng g-1 52 ng g-1 3500 ng g-1

I3 1934-1999 0.46 cm yr -1 790 ng g-1 170 ng g-1 700 ng g-1

Organochlorine Pesticides (OC) and Polychlorinated Biphenyls (PCB’s)

The concentrations of OC pesticides and PCB’s in the samples were below the GC/MS detection 

limit, even in the SIM mode. Even though it was not originally described in the scope of work, 

the extracts were re-analyzed using a GC with electron capture detector (ECD). This method, 

GC/ECD, is 10 to 100 times more sensitive for OC pesticides than the GC/MS-SIM analytical 

procedure and is generally preferred for these types of chlorinated compounds. The drawback to 

GC/ECD is that the identification of the target OC pesticides and PCB’s is by retention time and 

the chromatographic behavior of many of the targeted OC pesticides can result in co-elution. 

Compound identification determined from the retention times of a single-column analysis are 

generally confirmed on a second column (LSU-DES analysis confirmation was obtained from 

analyses performed at the LSU-Agricultural Chemistry Formulations Laboratory). The target 

OC pesticides and PCB’s are listed in Table 2.2. The OC pesticides in the list include both 

parent pesticides and their common breakdown products. Several of the OC pesticides were 

detected using GC/ECD; however, PCB’s were not present at ppb levels. 
 

2.8 

Table 2.2 

Target OC pesticides and breakdown products, and PCB’s in the core samples. 

Target OC Pesticides Target PCB’s 

Aldrin Heptachlor Epoxide Dichlorobiphenyl Nonachlorobiphenyl 

cis-Chlordane Hexachlorobenzene Trichlorobiphenyls Decachlorobiphenyl 

2,4’-DDD, 4,4’-DDD Lindane (γ-BHC) Tetrachlorobiphenyl 

2,4’-DDE, 4,4’-DDE Mirex Pentachlorobiphenyl 

2,4’-DDT, 4,4’-DDT trans-Nonachlor Hexachlorobiphenyl 

Dieldrin Endrin Heptachlorobiphenyl 

Heptachlor Octachlorobiphenyl 

The OC pesticide concentrations peaked from the 1940’s through the 1970’s in most of the cores. 

Some cores, C10 for example, had no OC pesticides present. Cores along the “D” transect 

(D50G and D80) were not dominated by any one pesticide. The cores along transect “E” (E30, 

E50, and E60) were dominated by cis-chlordane, one of the isomers present in technical 

chlordane (primarily used for termite control). There was only one core analyzed from transect 

“F” and it was also dominated by cis-chlordane. The two cores along transect “G” (G40 and 

G50) had different dominating OC pesticides throughout the core profile. The last core, I3 (not 

shown in Figure 2.1), was dominated by dieldrin, a pesticide primarily used in insecticidal 

laquers for wood preservation (Rose 1963) and as a soil insecticide (Thomson 1979). 

The estimated date ranges of the sediment cores correspond to, and the highest concentrations of 

the OC pesticides are consistent with, the time periods in which most of these compounds were 

still approved for use. Core E30 has the highest concentrations of OC pesticides after these 

compounds were no longer approved for usage. Histograms of the total OC pesticide 

distribution and the tabular OC pesticide data for each core and composited sections are given in 

Appendices A and B respectively. Figure 2.2 is a 3-D plot with the x and y axes oriented to the 

coast of Louisiana by core transect and shelf depth. Figure 2.3 is a histogram that displays the 

same data set in a 2-D format. These graphical representations clearly display the difference in 

distribution of the total OC pesticides prior to the 1950’s and after the 1950’s in the OCS study 

area. OC pesticide concentrations broken down by decade, beginning with the 1940’s through 

the 1990’s, are in Appendix C. 
 

2.9 

Figure 2.2. Total organochlorine (OC) pesticide and breakdown product distributions in the 

core samples collected from the Mississippi Delta Bight prior to 1950 (left) and 

after 1950 (right).

 Figure 2.3. Total OC pesticide concentrations prior to the 1950’s (front), after the 1950’s 

(middle) and the overall totals (back) in OCS cores collected from the Mississippi 

Delta Bight. 

Due to the levee system of the Mississippi River in Louisiana, no pesticides used for agricultural 

purposes in Louisiana enter the Mississippi River. Therefore, the pesticides detected in the 

sediment cores are most likely from the upper Mississippi River basin. This area of the 

Before 

1950 

After 

1950 

Total OC Pesticides and Breakdown Products 

 by Core Transect and OCS Depth (m) 
 

2.10 

Mississippi River basin is the largest and most intensively farmed region in the nation (Goolsby 

and Pereira 1995). There were five sections of core samples that contained significantly elevated 

levels of the OC pesticides. These samples seemed to contain pesticides with three distribution 

patterns. Pattern “A” in the 1976-1978 section of D80 contained a total of 2100 ng g -1 total 

pesticides comprised mostly of nonachlor (an ingredient in technical chlordane), chlordane, 

dieldrin, endrin and the DDT’s. Pattern “B”, in the 1993-1997 section of core E30, contained a 

total of 2100 ng g -1 total pesticides comprised of lindane, heptachlor, aldrin, chlordane and 

dieldrin. Pattern “C” in sections of cores from transect E50 (1959-1964 and 1948-1953) and 

G50 (1956-1989) contained the full list of target OC pesticides with concentrations of 7000, 

4800 and 3500 ng g-1 respectively. 

It is not likely that Mississippi River is the source of these elevated levels of OC pesticides 

because the high octanol/water partition coefficients (Kow) of these compounds limits the 

movement of the pesticides once deposited. The Kow of many PAH’s are within a similar range 

as the OC pesticides; therefore, if sediment deposition patterns were a factor the same spikes in 

the PAH concentrations would be apparent, which they are not. The OC pesticides are very 

persistent in the environment and would not easily degrade in an anaerobic sediment matrix. 

Hence, these OC pesticides were most likely directly deposited in these areas as opposed to 

originating from the river and moving west across the shelf with the dilution plume. On the 

other hand, the date ranges that correspond with the elevated levels of OC pesticides in these 

core sections indicate that they are not related to oil and gas recovery efforts. 

Polycyclic Aromatic Hydrocarbons (PAH’s)

The concentrations of PAH’s in the sediment cores analyzed by LSU-DES range from 5.5 ng g-1

to 1200 ng g-1. A total of 24 compounds, shown in Table 2.3, were targeted in the originally 

proposed GC/MS-SIM methodology (NOAA Technical Memorandum NMFS F/NWC-92 and 

EPA SWP-846). Several of these PAH’s were detected; mainly fluoranthene and pyrene. 

Despite the fact that the target PAH’s in Table 2.3 are common oil constituents, they may also 

indicate other sources of pollution. Therefore, the original methodology was not able to 

distinguish contamination related to oil and gas recovery efforts from other pollution sources. 

Table 2.3 

 Target PAH’s in the originally proposed GC/MS-SIM method. 

Naphthalene Fluoranthene 

2-Methyl Naphthalene Pyrene 

1-Methyl Naphthalene Benzo (a) Anthracene 

2,3,5-Trimethyl Naphthalene Chrysene 

2,6-Dimethyl Naphthalene Benzo (b) Fluoranthene 

Acenaphthylene Benzo (k) Fluoranthene 

Acenaphthene Benzo (e) Pyrene 

Biphenyl Benzo (a) Pyrene 

Fluorene Perylene 

Phenanthrene Indeno (1,2,3-cd) Pyrene 

Anthracene Dibenzo (a,h) Anthracene 

1-Methyl Phenanthrene Benzo (g,h,i) Perylene 
 

2.11 

 For further investigation, all of the sample extracts were re-analyzed with a GC/MS-SIM oil 

fingerprinting method (modified U.S. EPA SWP-846 method 8270) developed by Louisiana 

State University-Department of Environmental Studies/Response and Chemical Assessment 

Team (LSU-DES/RCAT). This oil fingerprinting method includes several of the original target 

PAH’s in Table 2.3; however it has been expanded to include dibenzothiophene (DBT; a sulfur 

related PAH), PAH alkyl homologs and other oil biomarker compounds such as the hopanes and 

steranes (Table 2.4). It was evident that after data from these additional analyses were examined, 

that much more information regarding the nature of the PAH and petrogenic contamination was 

gained using the oil fingerprinting method compared to the originally proposed analytical 

method. The oil fingerprinting method provided valuable information regarding the presence of 

petrogenic hydrocarbons that would have been overlooked by the originally proposed method. 

Accordingly, PAH data interpretations were broken down into two categories: total PAH’s, 

indicative of pyrogenic PAH’s, obtained from the original GC/MS method; and estimated total 

hopanes, indicative of petroleum related hydrocarbons, obtained from the GC/MS oil 

fingerprinting method. In an effort to obtain additional petrogenic source data, other oil 

biomarker compounds (i.e., the total C-3 DBT’s versus the total C-3 Phenanthrenes; a sulfur to 

non-sulfur ratio) obtained from the fingerprinting method were examined; however, the 

estimated total hopanes provided the best petrogenic data trends. 

Table 2.4 

Target PAH’s and oil biomarkers in GC/MS-SIM oil fingerprinting method. 

Acenaphthylene C-3 Dibenzothiophenes C-2 Naphthobenzothiophenes 

Acenaphthene Dibenzo(a,h)Anthracene C-3 Naphthobenzothiophenes 

Anthracene Fluoranthene Normal Alkanes (nC10-nC35) 

Benzo(a)Anthracene Fluorene Perylene 

Benzo(a)Pyrene C-1 Fluorenes Phenanthrene 

Benzo(b)Fluoranthene C-2 Fluorenes C-1 Phenanthrenes 

Benzo(e)Pyrene C-3 Fluorenes C-2 Phenanthrenes 

Benzo(g,h,i) Perylene Hopanes C-3 Phenanthrenes 

Benzo(k)Fluoranthene Indeno(1,2,3-cd)Pyrene C-4 Phenanthrenes 

Chrysene Naphthalene Pyrene 

C-1 Chrysenes C-1 Naphthalenes C-1 Pyrenes 

C-2 Chrysenes C-2 Naphthalenes C-2 Pyrenes 

C-3 Chrysenes C-3 Naphthalenes C-3 Pyrenes 

Dibenzothiophene C-4 Naphthalenes C-4 Pyrenes 

C-1 Dibenzothiophenes Naphthobenzothiophene Steranes 

C-2 Dibenzothiophenes C-1 Naphthobenzothiophenes 

The pyrogenic PAH data trend shows a gradual increase in these contaminants over the course of 

time, and suggests a chronic contaminant loading from the Mississippi River. Total PAH 

concentrations begin increasing above background levels after the World War II era (See Figure 

2.4). Histograms of the total PAH distribution, the tabular PAH data for each core and 
 

2.12 

composited sections, and the PAH distributions by decade are given in Appendices D, E and F 

respectively. 

On the other hand, the distribution of the petrogenic PAH’s (estimated total hopane 

concentrations) indicate contamination from oil and gas exploration in the Gulf of Mexico, and 

perhaps from natural geologic hydrocarbon seeps in the area. The hopanes, assessed by 

quantitating the total hopanes, were present in almost all of the cores; however, the hopane 

concentrations began increasing after the WWII era (Figure 2.5), especially in the vicinity of 

transect E. 

All hydrocarbon levels are used to indicate relative loading of the respective samples since no 

data are available to correlate hydrocarbon loading with initial source input levels. This being 

said, the postulation is that pyrogenic loading is predominately associated with riverine inputs, 

while petrogenic loading is associated with production and exploration activities or possibly 

natural geologic hydrocarbon seeps in the vicinity of transect E in the study area. 

 

Figure 2.4. Total PAH concentrations prior to 1950 (front), after 1950 (middle) and overall 

totals (back) from core samples collected from the Mississippi Delta Bight. 
 

2.13 

 Figure 2.5. Estimated total hopane concentrations prior to the 1950’s (front), after the 1950’s 

(middle) and the overall total (back) from core samples collected from the 

Mississippi Delta Bight. 

Figures 2.6 and 2.7 are 3-D plots with the x and y axes oriented to the coast of Louisiana by core 

transect and OCS depth (as displayed in Figure 2.1). Figure 2.6 displays the total PAH 

distribution in the study area of the OCS prior to the 1950’s and after the 1950’s. On the other 

hand, Figure 2.7 displays the estimated total hopanes in the same manner. Appendix G contains 

trend data that compares the total PAH’s (pyrogenic in nature) to the estimated total hopane 

concentrations (petrogenic in nature) for each core by core depth. An inverse relationship exists 

between the pyrogenic PAH’s and the petrogenic hydrocarbons; generally, when the total 

pyrogenic PAH’s were high, the petrogenic hopanes were low. This correlation is supported by 

the fact that the greatest amount of sediment deposition is occurring near the mouth of the 

Mississippi River (see Figure 3.3 in the next chapter). 

Theoretically, heavier suspended particles are going to settle out in the shelf area closest to the 

mouth of the river and, as a result the concentrations of contaminants adsorbed on the sediments 

from the river are going to be higher near the source of the sediment plume and will decrease as 

the sediment plume moves west. The highest concentrations of pyrogenic PAH’s occur in 

transect D, which is within an area of higher sediment deposition off the mouth of the 

Mississippi River. The concentrations of pyrogenic PAH’s begin to decrease in transects west of 

transect D, until they increase once again in transects G and I3. This increase is probably due to 

estuarine run-off in the area that contains pyrogenic PAH’s from marsh-burning practices. The 

lowest pyrogenic PAH concentrations are in transects E and F; however, these transects have the 

highest estimated total hopanes concentrations. For that reason, it is believed that oil and gas 

recovery and/or natural geologic hydrocarbon seeps are concentrated in this vicinity and are local 

sources of petrogenic contamination. 
 

2.14 

 Figure 2.6. Total PAH (pyrogenic PAH’s) distributions in the core samples collected from the 

Mississippi Delta Bight prior to 1950 (left) and after 1950 (right). 

Figure 2.7. Estimated total hopanes (petrogenic PAH’s) distributions in the core samples 

collected from the Mississippi Delta Bight prior to 1950 (left) and after 1950 

(right). 

Before 

1950 

After 

1950 

Total PAH’s by Transect and OCS Depth (m)

Before 

1950 

After 

1950 

Estimated Total Hopanes by Transect and OCS Depth (m) 
 

2.15 

Individual Core Results

Core C10 

No OC pesticides were detected in this core. The most dominant PAH’s in core C10 were 

pyrene, fluoranthene, phenanthrene, and 1-methyl phenanthrene. The highest concentration of 

PAH’s (130 ng g-1) was in sections 24-34 (ca. 1978-1974). 

Core D50G 

The only OC pesticide detected in this core was DDT (0.81 ng g-1) in sections 63-75 (ca. 1947-

1937). The most dominant PAH’s in core D50G were pyrene, fluoranthene, phenanthrene, 

anthracene and benzo(k)fluoranthene. The highest concentration of PAH’s (490 ng g-1) was in 

sections 38-48 (ca. 1967-1959). 

Core D80 

There were several OC pesticides and their associated breakdown products detected throughout 

the core depth including: heptachlor, aldrin, cis-chlordane, endrin, DDD, trans-nonachlor, 

dieldrin, DDT and DDE. The highest concentrations of OC pesticides (2100 ng g-1) were in 

sections 37-42 (ca. 1978-1976). Pyrene, fluoranthene, phenanthrene, and fluorene were the most 

dominant PAH’s within core D80. Sections 25-30 (ca. 1984-1981) had the highest concentration 

of PAH’s (1200 ng g-1). The OC pesticides were first detected in sections 19-24 (ca. 1986-1984) 

and were present throughout the rest of the core depth. 

Core E30 

OC pesticides were detected in all sections of core E30 and include: cis-chlordane, 

hexachlorobenzene, aldrin, heptachlor, heptachlor epoxide, trans-nonachlor, dieldrin, and 

lindane. The highest concentrations of the OC pesticides (2100 ng g-1) were in sections 1-5 (ca. 

1997-1993). The most dominant PAH’s in core E30 were chrysene, benzo(a)anthracene, 

benzo(k)fluoranthene, benzo(e)pyrene, benzo(g,h,i)perylene, fluoranthene, pyrene, 

benzo(b)fluoranthene, and perylene. The highest concentration of PAH’s, 26 ng g-1, was in 

sections 11-15, dating from 1987-1982. 

Core E50 

The OC pesticides were first detected in sections 6-10 (ca. 1992-1987) and were present 

throughout the rest of the core depth. All of the target OC pesticides were detected in this core. 

Sections 31-35 had the highest concentration of OC pesticides, 7000 ng g-1, of all the cores. The 

date range for these sections is 1964-1959. The most dominant PAH’s in core E50 were 

benzo(g,h,i)perylene, chrysene, fluoranthene, benzo(a)anthracene, perylene, pyrene, 

benzo(b)fluoranthene, benzo(e)pyrene, indenopyrene, dibenzo(a,h)anthracene, and 

benzo(a)pyrene. Sections 21-25, dating from 1975-1970, contained the highest concentrations of 

PAH’s (140 ng g-1). 

Core E60

OC pesticides detected in sections 1-15 (ca. 1997-1977) and sections 21-35 (ca. 1975-1948) 

included cis-chlordane, heptachlor epoxide, DDT, aldrin, trans-nonachlor, endrin, DDD, and 

heptachlor. Sections 31-35 contained the highest concentrations of OC pesticides (31 ng g-1) and 

dated from 1954-1948. Chrysene, fluoranthene, pyrene, perylene, benzo(a)anthracene, and 
 

2.16 

phenanthrene were the most dominant PAH’s in core E60. Sections 46-47 (ca. 1933-1931) had 

the highest concentration of PAH’s (28 ng g-1). 

Core F35

Core F35 had OC pesticides present throughout the depth of the core. The most dominant 

pesticide was cis-chlordane, followed by DDD, endrin, trans-nonachlor, and heptachlor epoxide. 

The sections with the highest OC pesticide concentrations (33 ng g-1) were 16-20 (ca. 1976-

1971). The most dominant PAH’s in core F35 were benzo(a)anthracene, chrysene, 

benzo(g,h,i)perylene, benzo(a)pyrene, perylene, indeno(1,2,3-cd)pyrene, fluoranthene, pyrene, 

dibenzo(a,h)anthracene, and benzo(e)pyrene. The highest PAH concentrations, a total of 67 ng 

g

-1, were in sections 26-30 dating from 1963-1957. 

Core G40 

The most dominant OC pesticides in Core G40 were DDD, hexachlorobenzene, dieldrin, transnonachlor, DDT, cis-chlordane, lindane, endrin and aldrin. OC pesticides were detected 

throughout the depth of the core, but sections 1-6 contained the highest concentrations, 44 ng g-1. 

Core G40 was dominated by the PAH’s perylene, fluoranthene, pyrene, 1-methyl phenanthrene, 

and phenanthrene. The highest concentration of PAH’s (510 ng g-1) was in sections 1-6 (ca. 

1989-1939). 

Core G50 

OC pesticides were present in sections 1-5 of Core G50 and included: heptachlor epoxide, DDT, 

endrin, aldrin, DDD, trans-nonachlor, cis-chlordane, dieldrin, lindane, DDE, and heptachlor. 

The concentration of OC pesticides in these sections was 3500 ng g-1. The dominant PAH’s in 

core G50 were pyrene, phenanthrene, fluoranthene, and perylene. The highest concentration of 

PAH’s (140 ng g-1) was in sections 1-5 (ca. 1989-1956). 

Core I3 

The most dominant OC pesticide in core I3 was dieldrin, followed by heptachlor epoxide and 

heptachlor. Other pesticides detected include: hexachlorobenzene, aldrin, DDT, endrin, DDD, 

and lindane. The OC pesticides were present throughout the depth of the core. Sections 13-17 

(ca. 1969-1959) had OC pesticide concentrations of 460 ng g-1. Core I3 was dominated by the 

following PAH’s: pyrene, phenanthrene, 1-methyl phenanthrene, and fluoranthene. Sections 13-

17 (ca. 1969-1959) had the highest concentrations of PAH’s—230 ng g-1. 

DISCUSSION 

The Mississippi river drains the largest and most intensely farmed region in the United States. 

Concerns over the adverse effects from anthropogenic activities (e.g., expanding populations; 

industries; agricultural practices) on the water quality of the Mississippi River began to emerge 

after World War II (Goolsby and Pereira 1995), and by the 1960’s a decline in the water quality 

along with many other adverse side effects of urbanization were evident. The results from these 

anthropogenic activities are distributed in the sediments deposited on the OCS by the Mississippi 

River. PAH’s and OC pesticides normally adsorb onto suspended particles in the water column 
 

2.17 

and are transported and deposited as sediments. Therefore, OCS sediment cores can, 

theoretically, be used to retrace the history of chemical contamination over a period of time. 

Trends apparent in the data show that the levels of OC pesticide contamination were consistent 

with the beginning and peak application of these first generation pesticides, and that the PAH 

contamination, both pyrogenic and petrogenic, gradually increase as time progresses beginning 

around the time of oil exploration (around 1950). Atmospheric input of the targeted 

contaminants appears to be minimal to none due to the fact that some of the contaminants were 

not distributed equally throughout the study region. The Mississippi River is the principle source 

of the OC pesticides and the pyrogenic PAH’s. Due to the levees in Louisiana, state agricultural 

run-off does not generally enter this river system; therefore, the OC pesticides detected in the 

sediment cores were due to a regional influence. 

There were two anomalies present in the total OC pesticide concentrations in core E50, sections 

31-35 (ca.1964-1959) and 41-45 (ca.1953-1948), and core G50, sections 1-5 (ca.1989-1956). 

The total pesticide concentrations in the aforementioned sections were almost an order of 

magnitude higher than the other core’s total pesticide concentrations. All target OC pesticides 

were detected in these sections of E50 and G50. It is not likely the Mississippi River is the 

source of these elevated levels of OC pesticides because the Kow of these compounds limits the 

movement of the pesticides once deposited. If sediment deposition patterns were a factor, the 

same spikes in the total PAH concentrations would be apparent because the Kow of many PAH’s 

are within a similar range as the OC pesticides. Hence, these OC pesticides were most likely 

directly deposited in these areas as opposed to originating from the river and moving west across 

the shelf with the sediment dilution plume. The OC pesticides are very persistent in the 

environment and would not easily degrade in an anaerobic sediment matrix. Therefore, all of the 

target OC pesticides and breakdown products would be distributed in the neighboring core 

transects with similar shelf depth. It is possible that factors such as annual usage, spring flux, the 

phase out of OC pesticides in the late 1970’s and 1980’s, flood events, limited-biodegradation, 

gravity-driven sediment transport and post-depositional mixing from storm surges contributed to 

the variations in the OC pesticides from core to core within the study area. On the other hand, 

the date ranges that correspond with the elevated levels of OC pesticides in these core sections 

indicate that they are not related to oil and gas recovery efforts. 

The pyrogenic PAH’s have an inverse relationship with the petrogenic hydrocarbons; generally, 

when the total PAH’s were high, the hopanes (representing the petrogenic-related hydrocarbons) 

were low or below the total PAH’s. Since the heavier suspended particles are going to settle out 

in the shelf area closest to the mouth of the river, the concentrations of contaminants adsorbed on 

the sediments from the river are going to be higher near the source of the sediment plume and 

will decrease as the sediment plume moves west. The highest concentrations of pyrogenic 

PAH’s occur in transect D, which is within an area of higher sediment deposition off the mouth 

of the Mississippi River. The concentrations of pyrogenic PAH’s begin to decrease in transects 

west of transect D, until they increase once again in transects G and I3 (probably related to 

marsh-burning practices and estuarine run-off). Transects E and F have the lowest pyrogenic 

PAH concentrations; however, the highest estimated total hopanes concentrations. For that 

reason, it is believed that the hopanes represent a local influence of natural geologic hydrocarbon 

seeps or oil and gas exploration. 
 

2.18 

Organochlorine (OC) Pesticides

The target OC pesticides in this study are no longer registered for agricultural use in the United 

States and their presence in the sediment cores is indicative of their environmental persistence. 

Examination of the estimated Koc (octanol/water partition coefficient) values for theses 

compounds indicate that they are generally immobile or slightly mobile in soils/sediment. 

Previous studies of sediments from the Mississippi River and Gulf of Mexico have indicated that 

concentrations of individual OC pesticides can vary from 0.49 ng g-1 to as high as 900 ng g-1

(Laska et al. 1976; Murray et al. 1981). The concentrations of total OC pesticides in the 

sediment cores analyzed by LSU-Department of Environmental Studies range from 0.61 ng g-1 to 

7000 ng g-1. Outside of the fact that cores E50 and G50 had high concentrations of the OC 

pesticides, the rest of the pesticide concentrations in the cores were consistent with other 

historical reconstruction of contaminant loading studies (Barber and Writer 1998; Carr et al. 

1996; Santschi et al. 2001). The OC pesticides and associated breakdown products commonly 

found throughout all of the cores were heptachlor epoxide, cis-chlordane, endrin, 4-4’-DDD, and 

4,4’-DDT. 

The majority of pesticides used in the Mississippi River basin, both presently and historically, 

are applied in the upper part of the basin, mainly in Illinois, Iowa, Indiana, eastern Nebraska, and 

southern Minnesota (Goolsby and Pereira 1995). The major crops in these states are corn and 

soybean. The OC pesticides used for these crops prior to their phase out in the late 1970’s and 

the 1980’s might have included: DDT; dieldrin; lindane; endrin; aldrin; and heptachlor (Rose 

1963). Again, it is important to note that the levee system in the state of Louisiana prevents 

agricultural runoff from entering the Mississippi River. Therefore, any of the OC pesticides 

present in the OCS are from agricultural runoff in the Midwest and possibly the Atchafalaya. 

Some of the OC pesticides of local interest that may have been used prior to their ban in the U.S. 

included: lindane (cotton); DDT (cotton; soybeans; sugar cane; mosquitoes); aldrin (cotton; 

sugar cane; beetles that eat strawberry seeds); endrin (cotton); heptachlor (mosquitoes; cotton; 

sugar cane) (Rose 1963). The OC pesticide list was very similar on a regional and local level, 

probably due to the fact that this “first generation” of pesticides worked extremely well on a very 

broad range of pests and were very persistent. 

Polycyclic Aromatic Hydrocarbons (PAH’s)

The results of the PAH analyses performed by LSU-DES appear to be consistent with research 

from other historical reconstructions of contaminant loading (Barber and Writer 1998; Boehm 

and Farrington 1984; Carr et al. 1996; Overton et al. 1986; Santschi et al. 2001). The 

concentrations of PAH’s in the sediment cores analyzed by LSU-DES range from 5.5 ng g-1 to 

1200 ng g-1. The dominance of fluoranthene and pyrene in the total PAH concentration, and also 

the presence of the benzofluoranthenes and benzopyrenes indicates an assemblage of 

combustion-PAH-dominated sediments. The PAH compounds on the original target compound 

list were ineffective at distinguishing petrogenic from pyrogenic hydrocarbon contamination 

since the list did not include typical oil biomarkers, such as dibenzothiophene (DBT), the alkyl 

homologs of the parent PAH’s, and the hopanes and steranes. Alkyl homologs of the PAH 

compounds, as well as the pentacyclic hopane and sterane type compounds, are known to be 

associated with petroleum sources, and quantifying the “total” hopanes proved to be very 

valuable in distinguishing regional influences from local influences. 
 

2.19 

RECOMMENDATIONS 

Many of the important PAH’s (DBT, the alkyl homologues, hopanes and steranes) were 

excluded in the proposed Technical Memorandum NMFS F/NWC-92 and EPA SWP-846 

GC/MS-SIM method used in this research. These compounds are very important oil biomarkers 

because they provide valuable oil fingerprint information and remain detectable and relatively 

unchanged in oil residues after natural environmental weathering processes (Ashton et al. 2000; 

Philip and Oung 1988). Analyzing for these biomarkers in the sediment samples allows OCS 

activities to be discriminated from non-OCS activities; mainly due to the fact that the biomarkers 

can be quantitated, background levels of petrogenic activity can be determined and variations 

from background can be distinguished. Much more information could be gained, as far as OCS 

versus non-OCS activities are concerned, if future sediment cores were analyzed for the target 

compounds listed in Table 2.2. These target analytes are part of an oil fingerprinting GC/MSSIM method developed by LSU-DES/RCAT to determine whether spilled oil can be matched to 

a suspected source oil. This fingerprinting method is a modified version of U.S. EPA SW-846 

Method 8270. 

The proposed methodology for detecting the OC pesticides by GC/MS would have been prudent 

if the concentrations of the pesticides were greater than 10 μg g-1 (parts per million). 

Unfortunately, most of the pesticide concentrations were below this level. Therefore, any future 

OC pesticide analysis should be done by GC/ECD (U.S. EPA SW-846 Method 8081B). 

Furthermore, normalization of the OC pesticide concentrations in the sediments to the TOC may 

provide additional information regarding the distribution patterns in the OCS. 

Future studies should also consider taking larger core samples and have more sampling points. 

A few additional cores in transect F, especially in the 50m area of the shelf, would have provided 

more information relating to the contaminant distribution pattern along the shelf and the relation 

of the distribution between transects E and G. Larger core samples would provide larger 

sediment samples to be divided for the various analyses that were performed in this project. A 

larger sample size would also allow for a lower detection limit of the trace organic compounds 

targeted. 
CHAPTER 3 

TRACE METAL, C, N AND BIOLOGICALLY-BOUND SILICATE 

IN DATED SEDIMENTS FROM THE LOUISIANA CONTINENTAL SHELF

R. Eugene Turner and C.S. Milan

Coastal Ecology Institute, and Department of Oceanography and Coastal Sciences 

Louisiana State University 

and 

N.N. Rabalais 

Louisiana Universities Marine Consortium 

ABSTRACT 

The development of the OCS for oil and gas recovery started in the 1950s and peaked in the 

1990s, while moving further offshore and into deeper waters. We examined the sedimentary 

record offshore for indicators of industrial by-products of OCS development and of national 

industrial products, primarily using Vanadium (V) and Barium (Ba) concentrations normalized 

for Aluminum (Al). Barium is primarily used in drilling muds in Barite, whereas V is an 

important strengthening component of metal alloys, including steel. The fluctuations in the 

accumulation of Ba, but not V, are coincidental with the presumed use of Barite. The fluctuations 

in V concentration in the sediments are coincidental with the national consumption of V. Copper 

(Cu), Cadmium (Cd), and Zinc (Zn) concentrations in sediments fluctuate coincidentally with V, 

not Ba, thus indicating that the dominant source of these trace metals in offshore sediments are 

derived from riverine sources, and are not primarily from in situ industrial processes releasing 

them on the shelf. This is not to suggest that local site-specific contamination is not a significant 

management or health concern. 

The hypoxic zone that consistently covers much of this continental shelf in summer is attributed 

to N loading from the Mississippi River. Increased nitrogen loading from river to shelf stimulates 

diatom production whose subsequent loading to the bottom layer and metabolism results in 

oxygen being depleted faster than it is replaced. In the last two decades there has been an 

increased accumulation of organic matter in sediments near the mouth of the Mississippi River. 

This coupling between river water, surface water and bottom water has recently expanded 

westward towards the Texas coast, west of the Atchafalaya River delta. The accumulation of 

Biologically-bound silica (BSi) and carbon in dated sediments is not coincidental with variations 

in either V or Ba consumption rates. 

These analyses indicate that both OCS development and riverine sources exert strong influences 

on the sediment constituents offshore, and that these influences may be independent of one 

another. 
 

3.2 

INTRODUCTION 

Both small and large oil spills are a ubiquitous consequence of oil and gas recovery and 

transportation in the coastal zone (National Research Council 2003). But there are also other 

contaminants released that are of concern, whose accumulation in sediments is used to 

reconstruct the historical pollutant loading rates, at least in a relative way (Bricker 1993; 

Ravichandran et al. 1995; Cochran et al. 1998; Santschi 2001). The temporal and spatial 

significance of potential contamination from Outer Continental Shelf (OCS) activities in the 

northern Gulf of Mexico remains a vexing problem for management. The in situ release of 

contaminants may or may not be as significant as the changes occurring from landuse changes in 

the Mississippi River watershed, and be undetectable against a background that includes a 

substantial natural variability. Landuse changes in the Mississippi River watershed resulted in 

coastal eutrophication and contributed to a larger, more severe and longer lasting hypoxic water 

mass in the bottom layer of the same region (Turner and Rabalais 1994a). These changes may be 

more significant to the shelf ecosystem than those resulting from contaminant releases related to 

OCS development. However, without knowledge of these larger scale influences, we may be 

subject to overly simplistic arguments, and remain profoundly uncertain about management 

impacts, hence remedial strategies. In this context, we attempted to document the changes in 

trace metals and organics produced in situ within the central Gulf of Mexico continental shelf. 

We were interested in how the historical accumulations of trace metals, especially V and Ba, 

varied in relationship to the production and consumption of these metals. Vanadium is alloyed 

with other metals to strengthen them, particularly in the manufacture of steel. This steel is used 

to build the skeleton of oil and gas platforms (http://www.mii.org/Minerals/photovan.html, 

Mineral Information Institute). Barite (BaSO4) is an important additive for oil-well drilling mud, 

which is a "weighting agent" that is crushed and mixed with water and other materials and 

pumped into the drill hole. Its weight counteracts the force of the oil and gas when it is released 

from the ground, which allows the rig operators to prevent explosive releases of the oil and gas 

during recovery. Over 75% of barite consumption in the U.S. is for this drilling application 

(http://www.mii.org/Minerals/photovan.html, Mineral Information Institute). If the source of V 

or B in the sediments were influenced by either local or riverine sources, then variations in the 

sediment record might be observed to fluctuate with variations in either national consumption 

patterns (V or Ba) or in shelf-wide application of drilling mud (Ba) or oil and gas well structural 

development (V). Interpretations of changes in Zn, Cu, or Cd (and other pollutants) depend on 

knowledge of these source-accumulation relationships. Lastly, we attempted to document the 

sedimentary accumulation of diatoms (measured as the residual silica in the buried frustules, also 

known as the biologically-bound silica, or BSi) and organic matter produced in situ within the 

region where sediments for the trace metal analyses were collected, if not the same sample. This 

effort was meant to help frame the controlling impact of the Mississippi River on the biological 

productivity in the oil and gas recovery operations. 
 

3.3 

METHODS 

Sediments were collected using aged steel tubing with sharpened ends that were carefully pushed 

into a box core with a twisting motion to reduce compactions, which was always less than 10%. 

Sample locations (Figure 3.1) are from the region of locally high sedimentary carbon, sediment 

phytoplankton pigments from in situ phytoplankton production (marine origin), and BSi (about 

1% TOC, 28.1 μg g dry weight-1, and 0.6% BSi, respectively). These sediments were directly 

downstream and beneath the Mississippi River’s dilution plume, and their constituents reflect the 

in situ primary production and subsequent transport of organics from surface to bottom waters 

very near the river delta (Turner and Rabalais 1994a). One sample was taken further west 

beyond where the Atchafalaya river debouches onto the shelf (about 91.5 o W). Six cores are 

described herein that were collected in 1997, or later. Additional samples were from a suite of 

archived cores collected in April 1989. 

Figure 3.1. Sampling locations where sediment cores were collected. All but one (I3) are from 

the western side of the Mississippi River delta. The letters correspond to sampling 

transects. 

Sediment Dating

Sediment cores were analyzed for residual chemical and biological remnants. Sediment dating 

involved 210Pb isotope counts in a non-destructive manner using a Princeton Gamma-Tech 60 
 

3.4 

mm diameter intrinsic germanium "N" type coaxial detector (40% efficiency) interfaced to an 

EG&G Ortec 92X spectrum master integrated gamma-spectroscopy system. This unit provides 

detector power, signal acquisition and amplification of 4096 channels and is equipped with an 

automatic sample changer for 40 samples. Calculations of accretion rates are based upon the 

decay constant of 210Pb and the decay and non-decay-corrected activities of 210Pb with depth 

(Nittrouer et al. 1979). Estimates beyond the 200 yBP limit of the method using the approaches 

applied here assume linear accumulation rates, which may not always be the case. 

Cores were cut into 0.5 to 2 cm sections, depending on need. Samples were set aside (weighed 

and measured to determine proportional representation of a whole sample) for non-destructive 

analyses (e.g., foraminifera). 

Diatom Remains

Diatoms accumulate silica in their frustrules which remain after death. Biologically-bound silica 

(BSi) was estimated using the methods described by DeMasters (1981). Aliquots of dried 

sediments were digested at 85o C in 50 ml polypropylene centrifuge tubes, using a 2% solution 

of NaCO3, and subsampled at 1, 2, 3 and 5 hours. The intercept of a linear regression analysis of 

silicate concentrations vs. time was used to estimate the concentration of BSi. This method 

assumes that BSi digests within 1 hour, but that non-biologically bound silica continues to 

dissolve at a slower rate over the next several hours. The method is an indirect means to obtain 

relative measures of diatom density in sediments and has been successfully applied in the region 

by Turner et al. (1994a) and Parsons et al. (2002). 

Total Organic Carbon 

Sediment samples for total organic carbon (TOC) were ground and the carbonate material 

removed by using hydrochloric acid. Subsamples for analysis were weighed on a Cahn microbalance and analyzed with a Control Equipment Elemental Analyzer, Model 240 XA with a 

multi-sampler injector. Duplicate samples for the maximum and minimum TOC readings for 

each run were performed for quality control. Some samples were combusted in a Carlo Erba 

elemental analyzer coupled to a Thermoquest Delta Plus isotope ratio mass spectrometer 

functioning as a continuous flow system (Barrie and Prosser 1996) to determine C, N and S 

quantities. 

Trace Metals 

Samples for trace metal analyses were digested in nitric acid, hydrogen peroxide and 

hydrochloric acid (EPA Method 3050B) prior to analysis by inductively coupled plasma atomic 

emission spectrometry (ICP-AES). Simple linear regression analyses were made using the 

concentration of V and Ba versus Cd, Cu and Zn. The Adjusted Coefficient of Determination 

(Adj. R2) was accepted only if p < 0.01. Metals were normalized to Al to compensate for 

variations in clay content, which is a standard analytical approach (e.g., Ravichandran et al. 

1985; Santschi et al. 2001). 

Grain Size 

Grain size distributions down to 0.3 μm. were determined using a Coulter Multisizer with 256 

channelizer capability and using 280 μm, 140 μm and 50 μm aperture tube sizes. Samples were 

sieved through 20-μm Nitex before analysis with the 50-μm aperture tube. Coulter Accucomp 
 

3.5 

software was used to overlay distributions from each tube, and sand, silt and clay fractions were 

identified using the final combined distribution. Coarser samples were sieved to isolate larger 

sand particles unsuitable for Coulter Multisizer analysis. Where appropriate, these sand 

measurements were combined with the Coulter Multisizer data, assuming a constant particle 

density for the sand fraction, to produce a total grain size distribution. 

Mineral Production and Use

Data on annual U.S. industrial production and apparent consumption (a combination of data on 

production, exports, imports and net change in stockpiles) for V and barite is from Kelly et al. 

(2001). These data were plotted by year since 1900 and compared to the estimated concentration 

of the various constituents for sediments dated as described above. 

RESULTS AND DISCUSSION 

Sediment Accretion Rates

Sediment accretion rates for six cores were determined using the vertical distribution of 210Pb 

(Figure 3.2). The accretion rates ranged between 0.41 (I3, western shelf) and 1.24 cm yr-1. The 

accretion rate for 34 sediment cores collected in the region shown in Figure 3.1 was 0.99 ±1.22 

cm yr

-1 (mean ± 1 Std. Dev.). The highest sedimentation rates are along transects B and C 

(Figure 3.1), and the rates decline in a westward direction (Figure 3.3). 

Figure 3.2. The vertical distribution of 210Pb in six cores collected for this study. Other 

sediments were also used from dated cores described by Turner and Rabalais 

(1994a). A simple linear regression of the Ln Excess Sed210 vs. depth (cm) is shown 

(exclusive of the surface mixed layer), with the estimated sediment accumulation 

rate (cm yr-1). 

 
 

3.6 

Figure 3.3. Sedimentation rates (cm yr-1) west of the Mississippi River delta (unpublished data 

of the Principal Investigators, and substantiated by several others, including Eadie et 

al. 1994; Nelson et al. 1994; Blackwelder et al. 1996). 

General Sediment Quality Near and Far from the Mississippi River Delta

The sediments within the Mississippi Delta Bight (MDB), where all but one of the sediment 

cores reported here came from, had a different organic, density, silt and clay content than did 

core I3, which came from the western shelf (Figure 3.4). Compared to the western shelf (core 

I3) the MDB sediments tended to have more organic content, a lower density, a higher 

concentration of Al, and more sand. 

Figure 3.4. The relationship between sediment density and organic content (left panel) and 

aluminum and sand (right panel). The samples from core I3 (western Louisiana 

shelf) are indicated in each panel. All the other samples are from the Mississippi 

Delta Bight. 

Trace Metals

There was no statistically-significant relationship between the concentration of V and Ba in any 

set of sediments from an individual core, or, from the aggregated set of data from all six cores 

(Figure 3.5). This is an important observation used in a subsequent discussion concerned with 
 

3.7 

the historical accumulation of V and Ba as they are related to fluctuations in source materials 

from the Mississippi River watershed and from oil and gas recovery in situ. If V and Ba were 

from only one of these two sources (atmospheric transport for these metals is presumed to be 

insignificant, but it may be quite important for other metals, e.g., Pb (Trefrey et al. 1985), and if 

the source amounts were proportional over the last 100 years, and otherwise behave the same 

during deposition and post-burial, then there would be a significant relationship between V and 

Ba concentration. This direct relationship was not observed, which does not prove that different 

sources were important. 

Figure 3.5. The relationship between the concentration (μg g-1) of vanadium and barium in six 

sediment cores. No correlation is found between the two variables when analyzed 

by individual core or when aggregated together. 

The accumulation of Ba in sediments rises and falls with the national production and 

consumption rate of Barite (Figure 3.6). Variations in barite use are coincidental with the rise of 

oil and gas recovery efforts on this shelf. Barite is primarily used as an additive to assist in the 

safe recovery of the mineral product. Higher concentrations of Ba in sediments and Ba 

consumption begins in the late 1940s, there is a peak in the early 1980s, and then a decline 

thereafter. Cores E50 and E60 had a rise about a decade apart, which may reflect the expansion 

of drilling activities into deeper waters (Figure 1.2). The cores from the MDB collected in the 

shallowest water (E30 and F35) were not deep enough to retrieve samples from before the 1970s. 

Some details of the annual peaks and troughs in production/consumption are not well-preserved 

in the sedimentary record, presumably due to mixing, but also, perhaps, to issues related to the 

field application of drilling muds, and post-application downstream transport to the west. The 

lag between the rise and fall in production and the subsequent variations in core I3 is about two 

to three years, which could be due to bioturbation in the surface layer. An additional 

complication is that sediment dating may not be either precise enough or sedimentation rates 

sufficiently consistent from year-to-year (e.g., from hurricane influences) to capture a signal 

varying among a few years. 
 

3.8 

The accumulation of V in sediments rises and falls with its national production and consumption 

rate (Figure 3.7). There are six valleys and peaks in the national V production rate which appear 

to be present in the sedimentary record, though not dramatically so in all cases. A lag of a few 

years and about a decade between industrial production and accumulation in sediments is 

suggested for the region near, and far, from the Mississippi River, respectively. 

Figure 3.6. The normalized concentration of barium (μg Ba / g Al) in six dated sediment cores 

from various depth zones on the Louisiana shelf. The industrial production and 

consumption of barium in the United States is shown in the top panel. Possible 

coincidental peaks in the industrial production and the appearance of vanadium in 

sediments are indicated with the lightly shaded arrows. A lag of < 2 years and about 

a decade between industrial production and accumulation in sediments is suggested 

for the region near (E30, F35, D50, and D60), and far (I3), from the Mississippi 

River, respectively. 
 

3.9 

Figure 3.7. The normalized concentration of vanadium (μg V / g Al) in six dated sediment cores 

from various depth zones on the Louisiana shelf. The industrial production of 

vanadium in the United States is shown in the top panel. Possible coincidental peaks 

in the industrial production and the appearance of vanadium in sediments are 

indicated with the lightly shaded arrows. A lag of a few years and about a decade 

between industrial production and accumulation in sediments is suggested for the 

region near (E30, F35, D50, and D60), and far (I3), from the Mississippi River, 

respectively. 
 

3.10 

The concentration of Cu, Cd and Zn were strongly and positively correlated (Adj. R2 > 0.5), with 

the concentration of V in all the cores (Table 3.1). The relationship between the concentration of 

Cu, Cd and Zn were also positively correlated with Ba concentration, but weakly so (Adj. R2

 < 

0.15). This suggests that the factors controlling the accumulation of these three elements is more 

similar to the suite of factors affecting V than to Ba concentrations on this shelf. 

Table 3.1 

Results from a simple linear regression analysis of the relationship between Cd, Cu, and Zn (Y) 

versus both vanadium and barium (x) in dated sediments from six core samples from the 

Louisiana shelf. The Adjusted R2 value is shown if the relationship is both positive (a direct 

relationship) statistically-significant at p < 0.05. N.S. = not significant. The total sample 

number is between 63 and 145 sample pairs. The more significant correlation between Cu, Cd 

and Zn for either V and Ba is highlighted in bold. 

 V Ba

Cu 0.80 0.14 

Cd 0.74 0.09 

Zn 0.54 0.08 

The temporal variations in the accumulation of Ba appears to vary concurrently with the 

production and use of barite on this shelf, implying, but not proving, a cause-and-effect 

relationship. Some calculations may help determine if sufficient barite is released to account for 

the observed concentration in the sediments. We assumed that the average impacted area is a 

generous 100,000 km2, that barite is 48% Ba, and that the use on the shelf is 75% of the 

consumption rate for 1990 to 2000 (1,732,636 mt). The average density of all sediment samples 

(n = 174) is 0.63 g cm-3, and the average sedimentation rate for 34 cores is 0.99 cm yr-1. The 

average Ba concentration was 192 μg g-1 (dry wt), of which 150 μg Ba g-1 was assumed to be 

recent accumulation that is above a ‘background’ historical concentration (pre-1900s). A 

sedimentary ‘capture rate’ of 15 % of the barite used would explain a 150 μg g-1 change in Ba 

concentration above this background amount. Similar sedimentary capture efficiencies could be 

estimated for other constituents of drilling mud, if the proportional amounts (relative to Ba) were 

known. However, the proportional amounts are not well-known, partly because of variations 

among operators and product evolution, and also because of proprietary protections. 

Diatom Remains and Organic Content

The carbon and nitrogen content of sediment in all six cores is strongly related (Figure 3.8), and 

there is no obvious distinction in the C/ N ratio among cores, despite the differing sand, carbon 

and clay content (Figure 3.4). 

The amount of BSi and carbon in sediments among cores varies considerably across the shelf 

(Figure 3.9). Some locations had a rise in either or both BSi and carbon in recent decades, 
 

3.11 

whereas others did not. The location of the sampling sites with increases in BSi or %C is in the 

center of the sample grid, which is also where the most frequent occurrence of summer hypoxia 

occurs (Figure 4.1). The areas without increases are outside the area that most frequently 

experiences hypoxic water formation in the summer. This result is consistent with the 

conclusion that the organic matter which is consumed in the bottom waters to create low oxygen 

conditions is also accumulating in the sediments. The concentration of BSi increased steeply in 

the last decade for core I3 (west of the Atchafalaya River), which is later than occurred in all 

analyses of cores collected in the MRB (Figure 3.9). The implication is that the size of the 

hypoxic zone is expanding in a westerly direction, as predicted by the application of a StreeterPhelps model of nitrogen loading and hypoxic zone size (Scavia et al. 2003). 

The amount of carbon stored in the sediments from 1970 to 1990 was estimated using the 

average sedimentation rate mentioned earlier (0.99 cm y-1), the average carbon content in 

sediments dated >1980, and the dry density. The average accumulation rate is 64 g C m-2

 y

-1. 

Figure 3.8. The relationship between the percent carbon and nitrogen in dated sediments from 

six cores (dry weight basis). 

SUMMARY 

The development of the OCS for oil and gas recovery started in the 1950s and peaked in the 

1990s, while moving further offshore into deeper waters. The sedimentary record offshore shows 

fluctuations in the accumulation of Ba that are coincidental with the presumed use of Barite, a 

primary industrial application in OCS development. The fluctuations in V concentration in the 

sediments are not coincidental with Ba, but they are coincidental with the national consumption 

of V. Cu, Cd, and Zn concentrations in sediments fluctuate coincidentally with V, not Ba, thus 

indicating that the dominant source of these trace metals in offshore sediments are derived from 

riverine sources, and are not primarily from in situ industrial processes releasing them on the 

shelf. This is not to suggest that local site-specific contamination is not a significant 

management or health concern. 
 

3.12 

Figure 3.9. The concentration of percent biogenic silica (BSi) and % carbon vs. dated horizon 

for sediments from the continental shelf west of the Mississippi River delta in 10 to 

100 m water depth. The data are for a 3 year running average. The letter is the 

transect shown in Figure 3.1. The number with the letter is the water depth, except 

for core I3 (16.2 m). Stations F35 and D50 have data from multiple cores (from 

different sampling dates). 
 

3.13 

Figure 3.10. Core locations in the MDB where increasing concentrations of %BSi or %C were 

observed in the last three decades (data in Figure 3.9). 

The hypoxic zone that covers much of the shelf in summer is attributed to loading of nitrogen 

from the Mississippi River (Rabalais et al. 2002b). Higher nitrogen loading from river to shelf 

increases surface production of diatoms whose organic loading to the bottom layer and 

subsequent metabolism results in oxygen being depleted faster than it is replaced. This coupling 

between river water, surface water and bottom water, therefore, extends from the MRB and 

westward off the Texas coast. Thus the influence of the river is demonstrably significant to the 

whole shelf, and not the region within a few tens of kms of the river’s mouth. 
CHAPTER 4 

ECOSYSTEM HISTORY REVEALED THROUGH PRESERVED 

PHYTOPLANKTON PIGMENTS 

Nancy N. Rabalais, Nazan Atilla, Claire Normandeau 

Louisiana Universities Marine Consortium 

ABSTRACT 

Pigments determined by high performance liquid chromatography (HPLC) provide useful 

information concerning water column and epibenthic plant and microbial communities in both 

extant communities and accumulated sediments in lakes, estuaries and the ocean. Chlorophyll a

provides an estimate of overall biomass, and carotenoid pigments provide taxonomic biomarkers 

characteristic of phytoplankton. HPLC pigments have proven useful in identifying the 

components of microphytobenthic communities and documenting the change of phytoplankton 

communities in freshwater and marine environments. We examined the pigments preserved in 

sediment cores to document the changes in phytoplankton community composition, 

phytoplankton abundance, and conditions of hypoxia over time. Carbon accumulated in 

sediments of the Louisiana continental shelf in water depths of 20 to 60 m are primarily marine 

phytoplankton sourced and represent the history of phytoplankton communities in the overlying 

water. There is a general increase in chlorophyll a, pheopigments, zeaxanthin, fucoxanthin and 

most carotenoids over time, with the change gradual from 1955 to 1970, followed by a fairly 

steady increase to 1997, the time the cores were collected. The highest chloropigment 

concentrations were in cores E30, E50 and F35, which were located in areas more likely to be 

exposed to seasonal hypoxia. The increasing pigments and greater concentrations in areas where 

hypoxia is more likely to occur indicate an increase in eutrophication or a worsening of hypoxia 

or both. 

INTRODUCTION 

Pigments determined by high performance liquid chromatography (HPLC) provide useful 

information concerning water column and epibenthic plant and microbial communities in both 

extant communities and accumulated sediments in lakes, estuaries and the ocean. Chlorophyll a

provides an estimate of overall biomass, and carotenoid pigments provide taxonomic biomarkers 

characteristic of phytoplankton (Table 4.1; summarized in Jeffrey et al. 1997). HPLC pigments 

have proven useful in identifying the components of microphytobenthic communities (e.g., 

Cariou-Le Riaux-Gobin et al. 1987; Cariou-Le Gall and Blanchard 1995; Buffan-Dubau and 

Carman 2000a) and documenting the change of phytoplankton communities over time in 

freshwater and marine environments (e.g., Züllig 1981; Hodgson et al. 1997, 1998; Bianchi et al. 

2000, 2002). In the case of reconstructing historic changes in phytoplankton, knowing the 

presence or absence of particular taxa in dated sediment cores or their change in abundance 

(biomass) can help identify the influence of natural variability or human-induced changes in 

water quality. 
 

4.2

STUDY AREA 

The distribution of the sediment cores in relation to the frequency of present-day bottom-water 

hypoxia (dissolved oxygen less than 2 mg l-1, for the period 1985-2001) is shown in Figure 4.1. 

This frequency distribution represents hypoxia at the time of the mid-summer cruise, but not 

severity or seasonal progression for the remainder of the year. Based on the distribution for midsummer hypoxia and knowledge of the depths at which hypoxia is likely to occur at other times 

of the year, the likelihood of hypoxia at each of the stations can be predicted (Table 4.2). 

Figure 4.1. Frequency distribution of hypoxic bottom-water during mid-summer for years 1985-

2001 (modified from Rabalais et al. 2002a ) with core stations superimposed. 
 

4.3

Table 4.1 

The taxonomic origin of pigments from Louisiana shelf sediment cores and their relative 

concentrations in algal groups as identified by Jeffrey and Mantoura (1997). 

 

 Algal Division/Class 

Pigment 

abbreviation Cyanophyta1

Rhodophyta Cryptophyta Chlorophyceae Prasinophyceae Euglenophyta Eustigmatophyta Bacillariophyta Dinophyta2

Prymnesiophyceae Chrysophyceae 

Chlorophylls 

Chlorophyll a chla + + + + + + + + + + + 

Pheophytin a pheoa Chlorophyll degradation products 

Pheophytin b pheob Chlorophyll degradation products 

Pheophytin alike phea-l Chlorophyll degradation products 

 

Carotenes 

ß-carotene bcaro - - - - - ° ° ° ° 

 

Xanthophylls 

Alloxanthin allo + + + 

Canthaxanthin canth 1 

Diadinoxanthin ddx + + + + + 

Diatoxanthin diato ° ° ° ° ° 

Fucoxanthin fuco + 2 + + 

Lutein lutein + - 

Peridinin peri + 

Violaxanthin viola + + + 

Zeaxanthin zea + + - ° 

 

1 Many freshwater filamentous cyanophytes have a wide range of carotenoids, not found in the 

picoplanktonic cyanobacteria (e.g., echinenone, canthaxanthin, see Nichols (1973) as reported 

in Jeffrey and Mantoura (1997)). 

2 Several dinoflagellates have no trace of peridinin but have pigments characteristic of their 

endosymbionts (Jeffrey and Mantoura 1997). 

+ = major pigment 

- = minor pigment 

o = trace pigment 
 

4.4

METHODS 

Sediment Grain Size Analysis

Sediment grain size analysis was determined on sediments from which the organic matter was 

removed either by combustion of dried, ground sediments or by treatment of wet sediment with 

3.5% H2O2). For some samples, the coarse fraction was dry sieved and the fine fraction was 

determined with a Coulter Multisizer with 256 channelizer capability. For other samples, the 

sediments were dispersed in sodium hexametaphosphate (2.55 g l-1 H2O) overnight, then wet 

sieved through a 63 m sieve to collect the sand fraction. The mud fraction was divided into %silt 

and %clay by timed gravimetric extraction of dispersed sediments (Folk 1974). 

Chloropigments by High Performance Liquid Chromatography (HPLC)

Plant pigments were extracted and analyzed by high performance liquid chromatography 

(HPLC) according to the methods of Wright et al. (1991). Pigments were extracted with a 

combination of sonication and 100% acetone. The filtered extract (0.2 m) was injected into a 

Waters HPLC equipped with a 600 Controller and 600 Pump, 996 Photodiode Array Detector, 

and 474 Fluorescence Detector. The use of three columns (Waters Nova-Pak C18 3.9 x 150 mm, 

a Rainin Microsorb C18, and a Vydac Reverse-Phase C18) maximized peak separation. 

Table 4.2 

Likelihood of exposure to hypoxia for each station based on mid-summer cruise data 

and more frequent observations off Terrebonne Bay (Rabalais et al. 2002b). 

 Relative Hypoxia Exposure

Station High High-Med Medium Low

 I3 X 

 E30 X 

 F35 X 

 E50 X 

 D50 X 

 E60 X 

Pigment identification was determined by comparing retention times and visible absorption 

spectra of pigments with pure standards. Chlorophyll a and b and ß–carotene were purchased 

from Sigma Chemical Co. Peridinin, fucoxanthin, zeaxanthin, violaxanthin, alloxanthin, 

diadinoxanthin, echinenone, canthaxanthin, lutein, and neoxanthin were purchased from The 

International Agency for C14 Determination, VKI Water Quality Institute, Denmark. Standards 

of chlorophyll a and b were converted to pheophytin a and b by acidification and standards of 

pheophorbides a and b and chlorophyllide a were obtained by the method detailed in BuffanDubau and Carman (2000b). Pigment concentrations were expressed as g g dry sediment-1. 
 

4.5

RESULTS AND DISCUSSION 

Sediment Grain Size

Sediments from all cores from the MDB (D50, E30, E50, E60, and F35) were primarily silts, 

averaging 80% silt with variable clay and sand proportions (Figure 4.2). Sediments in the core 

from the southwestern Louisiana shelf (I3) were primarily sands, averaging > 90%, with a finer 

fraction at the surface and a clayey layer in the lower section (pre-1950s). 

% % 

Figure 4.2. Vertical distribution of % sand, % silt and % clay for cores as indicated. 
 

4.6

% % 

Figure 4.2. Vertical distribution of % sand, % silt and % clay for cores as indicated (continued). 

Phytoplankton Pigments 

Source of Pigments 

Sources of organic carbon accumulated in Louisiana shelf sediments can potentially come from 

the water column, microphytobenthos, and terrestrial, marsh or submersed plants. The stable 

carbon isotope measurements of cores from the MDB, however, indicate that the overwhelming 

source of the carbon in accumulated sediments is marine phytoplankton and not allochthonous 

carbon in the source of terrestrial carbon from the drainage system of the Mississippi River or 

from export of marsh plant detritus from the coastal wetlands (Turner and Rabalais 1994a). 

Stable carbon isotope ratios for the core from the southwest Louisiana shelf indicate the same 

marine phytoplankton source (B. Fry, unpublished data). Thus, changes in the chloropigments in 

the sediments represent changes in the phytoplankton community in the overlying water column. 

Time Sequences of Pigments 

There is a general increase in chlorophyll a, pheopigments, zeaxanthin, fucoxanthin and most 

carotenoids over time, with the change gradual from 1955 to 1970, followed by a fairly steady 

increase (Figures 4.3-4.8). The concentrations are greater in E30, E50, and F35 than in E60 and 

D50, comparable to their relative listing for likelihood of hypoxia exposure as High-Medium and 
 

4.7

Medium compared to Low (Table 4.2). The only distinguishing rise or fall in carotenoid 

concentrations occurred in E30 at 1988. Carotenoids were dramatically lower in1988 than 

before or after. The 1988 date corresponds with a period of severe drought in the Mississippi 

River basin, 100-yr low river discharge, and low nutrient loads. 

Figure 4.3. Vertical distribution of chlorophyll a and chlorophyll a/pheopigment ration 

(Chla/Pheo) for cores E30-1, E50-1, E60-2, F35-2 and D50G. 

The longer D50G core taken with a gravity corer contains sediments dated to 1785 (Figure 4.7). 

Most carotenoids and chlorophyll a concentrations did not increase in the core until the 1970-

period. Zeaxanthin (cyanobacteria) and ß-carotene concentrations showed a rise in more recent 

sediments beginning in the 1940s. There were also indications of historical cyanobacterial 

abundance in the 1785 to 1820 period and a rise then decrease for the 1860 to 1940 period with 

the peak concentrations occurring in the 1885 to 1935 period. 

The degradation products of chlorophylls are pheopigments. As chlorophyll degradation 

proceeds, the ratio of chlorophyll a/pheopigments will decrease. Chlorophyll a degrades more 

slowly in hypoxic/anoxic conditions than in oxic conditions (Sun et al. 1991, 1993). Thus, a 

high chlorophyll a/pheopigment ratio may indicate high deposition rates of chlorophyll a or 

hypoxic/anoxic conditions of the overlying water. The chlorophyll a/pheopigment ratio 

increased with newer sediments in an up-core direction, but varied by core (Figure 4.3). The 

ratio generally increased gradually from mid-1950s for core E60, since 1960 for core E50, and 

since 1965 for core E30. Core F35 was not deep enough to sample sediments prior to 1962, but 
 

4.8

the ratio was high at that point. These results indicate an increase in eutrophication, hypoxia, or 

both post-1950 with a dramatic rise post-1970. 

Figure 4.4. Vertical distribution of zeaxanthin and zeaxanthis/ß-carotene ratio for cores E30-1, 

E50-1, E60-2, F35-2 and D50G. 

Specificity of Pigments 

Of the chlorophylls, only chlorophyll a was detected in the sediments. Chlorophyll b is unlikely 

to be present because it is unstable in sediments. The presence of pheophorbide b indicated that 

chlorophyll b was at one time present in the water column. The highest overall concentration of 

pheopigments, however, was due to those derived from chlorophyll a. 

Lutein, along with chlorophyll b, signifies the presence of detrital material from chlorophytes 

and vascular plants, but does not decay as rapidly as chlorophyll b (Bianchi et al. 1991). Lutein 

was present in relatively low and fairly uniform concentrations throughout the vertical depth of 

the cores in the MDB (example for D50 in Figure 4.7) and minimal in core I3 (Figure 4.8). The 

low concentrations of lutein would, therefore, represent a minimal contribution of terrestrialsourced or freshwater phytoplankton to the accumulated carbon on the shelf. For those cores that 

pre-date 1950, there was an increase in the amount of lutein in the sediments beginning in the 

1960-1970 period. Because lutein is fairly stable in anoxic sediments (Abele-Oeschger 1991), 

the increase in its concentration post 1960-1970 could signify increasing anoxic conditions in the 

sediments. 
 

4.9

 

Figure 4.5. Vertical distribution of fucoxanthin and diadinoxanthin for cores E30-1, E50-1, 

E60-2, F35-2 and D50G. 

The lack of the biomarker for prymnesiophytes and low values for the dinoflagellate biomarker, 

peridinin, indicated that the fucoxanthin present in the sediments originated from diatoms. The 

only station with trace amounts of peridinin that would indicate historic dinoflagellate blooms 

was I3. This station is closest to areas along the southwestern Louisiana coast and upper Texas 

coast (Figure 4.1) that experience periodic Karenia brevis or Gymonodinium sanguineum blooms 

(Harper and Guillen 1989; Dortch et al. 1999; Q. Dortch, unpubl. data). Other pigments that 

represented high biomass of phytoplankton were zeaxanthin (cyanobacteria) and ß-carotene 

(ubiquitous among several algae). Lower concentrations (and their representative phytoplankton 

taxa) were represented by diatoxanthin (trace in diatoms, dinoflagellates, prymnesiophytes, and 

raphidophytes), alloxanthin (cryptophytes), diadinoxanthin (primarily diatoms, dinoflagellates, 

prymnesiophytes, and raphidophytes), and canthaxanthin (some cyanobacteria) (Table 4.1). 

Because of differential degradation of chloropigments (Leavitt 1993), the proportion of one 

pigment to another cannot be used as a proxy for relative biomass of phytoplankton taxa over 

time. The differences in rate of change among the carotenoids are evident in the few correlations 

between individual pigments (Table 4.3). The time course of any individual pigment, however, 

can be an indicator of change in the productivity of a taxa. 
 

4.10

Figure 4.6. Vertical distribution of alloxanthin and diatoxanthin for cores E30-1, E50-1, E60-2, 

F35-2 and D50G. 

Mississippi Delta Bight 

Chlorophyll a decreased at a faster rate with depth than many of the carotenoid pigments (e.g., 

fucoxanthin, zeaxanthin, and ß-carotene) consistent with the fact that the chlorophylls are more 

labile than the carotenoids (Hodgson et al. 1997). Overall, carotenoids increased through time 

(more production) but some at a faster rate (differences in degradation or productivity of specific 

taxa or both). 

Fucoxanthin (diatoms) was present in all cores (Figure 4.5) in the post-1970 period with the 

exception of core D50G in which concentrations were minimal in all but the upper two slices 

(Figure 4.6). Fucoxanthin is known to degrade more quickly than chlorophyll a (Klein and 

Riaux-Gobin 1991; Cariou-LeGall and Blanchard 1995), and its absence prior to the 1950s may 

be due to its degradation rather than a lack of diatom production. However, both fucoxanthin 

and chlorophyll a declined at similar rates indicating an increase in production of diatoms since 

the 1970s. Under anoxic conditions in lakes (Züllig 1981; Hodgson et al. 1997 1998), 

fucoxanthin was preserved. Therefore, it is not unreasonable to also hypothesize that a reason 

for the increase in fucoxanthin since the 1970s would be increasing overlying water anoxia and 

that its relative change over time indicated periods of eutrophication and anoxia (Züllig 1981). 
 

4.11

Zeaxanthin (cyanobacteria) was present at trace levels through the depth of all cores with no 

peaks prior to the early 1950s, a gradual rise from 1950 to 1970, and a greater rate of increase 

since 1970 (Figure 4.4). There was also an indication of high concentrations during the early 

1990s consistent with the flood of the Mississippi River in 1993. The increase of the relatively 

stable pigment zeaxanthin (Züllig 1981; Bianchi et al. 2000) would indicate an increase in 

cyanobacterial populations in more recent times. The lack of historic peaks, similar to those seen 

in paleostratigraphy from the Baltic (Bianchi et al. 2000), would indicate that cyanobacteria were 

not a major biomass component of the phytoplankton community of the shelf prior to the 1950s. 

This is confirmed by the zeaxanthin/ ß-carotene ratios (Bianchi et al. 2000), which show no 

trends over long periods, mostly between 1 and 1.5, and no exceptionally high peaks that would 

indicate cyanobacterial biomass (Figure 4.4). 

Figure 4.7. Vertical distribution of chloropigments in core D50G; chla (chlorophyll a), total 

phaeo (total phaeopigments), Fuco (fucoxanthin), Ddx (diadinoxanthin), allo 

(alloxanthin), Diato (diatoxanthin), Lutein, zea (zeaxanthin), Cantha (canthaxanthin), 

B-caro (ß-carotene). 
 

4.12

Figure 4.8. Vertical distribution of chloropigments in core I3; chla (chlorophyll a), total pheo 

(total phaeopigments), Fuco (fucoxanthin), Ddx (diadinoxanthin), Diato 

(diatoxanthin), Lutein, zea (zeaxanthin), B-caro (ß-carotene). 

Alloxanthin concentrations begin to rise after 1950 in all cores from the MDB. Peaks in the 

sediment record from the early 1950s to present indicate aperiodic cryptophyte blooms (Figure 

4.6). Diatoxanthin (a trace carotenoid in several algal groups) followed a similar pattern to 

alloxanthin (Figure 4.6). Diadinoxanthin (indicative of several algal groups) concentrations 

increased slowly since 1970 then more rapidly after 1985 (Figure 4.5). 

Southwestern Louisiana Shelf 

The sedimentary nature and chloropigments of core I3 from the southwestern shelf were 

sufficiently different from those of the MDB cores to segregate those results from the other cores 

(Figure 4.8). The sediments of the I3 core were primarily sands as opposed to silts for all others 

(Figure 4.2), and the pigment concentrations were the lowest of all the cores. Zeaxanthin was 

the dominant carotenoid as in the other cores, but ß-carotene was not a major component as it 

was with cores from the Mississippi Delta Bight (MDB). This means that the zeaxanthin/ ßcarotene ratio was much higher in the I3 core than the cores from the bight, a ratio of 10 to 40 

versus 1-1.5, respectively, and that significant cyanobacterial blooms have occurred in this area 

since 1970. The chlorophyll a/pheopigment ratio increased steadily from the 1970s indicating 

increasing euthrophication or worsening hypoxic conditions or both. The trace levels of lutein 

indicate that terrestrially-derived plant materials are not a significant source of carbon 

accumulating in the sediments of core I3. 
 

4.13

Table 4.3 

Results of linear regressions among sediment pigments, sediment biogenic silica and Mississippi 

River annual nitrate load (from 1969 to 1997). Underlined values are for R > 0.90, 

 significant at p < 0.05. 

 CORE D50G 1 2 3 4 5 6 7 8 

1 Diadinoxanthin 1 

2 Diatoxanthin 0.85 1 

3 Fucoxanthin 0.76 0.41 1 

4 Alloxanthin 0.91 0.95 0.59 1 

5 Zeaxanthin 0.89 0.96 0.51 0.96 1 

6 Chlorophyll a 0.96 0.85 0.82 0.92 0.9 1 

7 BSi 0.35 0.46 0.12 0.42 0.44 0.43 1 

8 Nitrate 0.51 0.68 0.23 0.55 0.67 0.47 0.5 1 

 

 CORE F35 1 2 3 4 5 6 7 8 

1 Diadinoxanthin 1 

2 Diatoxanthin 0.52 1 

3 Fucoxanthin 0.93 0.46 1 

4 Alloxanthin 0.76 0.59 0.69 1 

5 Zeaxanthin 0.64 0.81 0.58 0.88 1 

6 Chlorophyll a 0.9 0.69 0.88 0.84 0.82 1 

7 BSi 0.57 0.7 0.55 0.46 0.57 0.52 1 

8 Nitrate 0.33 0.11 0.34 0.46 0.3 0.29 0.08 1 

 

 CORE E60 1 2 3 4 5 6 7 8 

1 Diadinoxanthin 1 

2 Diatoxanthin 0.44 1 

3 Fucoxanthin 0.59 0.49 1 

4 Alloxanthin 0.64 0.92 0.72 1 

5 Zeaxanthin 0.6 0.92 0.34 0.85 1 

6 Chlorophyll a 0.78 0.82 0.8 0.94 0.8 1 

7 BSi 0.31 0.02 0.18 0.14 0.11 0.21 1 

8 Nitrate 0.36 0.62 0.26 0.69 0.62 0.55 0.12 1 

 
 

4.14

Table 4.3 

Results of linear regressions among sediment pigments, sediment biogenic silica and Mississippi 

River annual nitrate load (from 1969 to 1997). Underlined values are for R > 0.90, 

significant at p < 0.05. (continued) 

 CORE E50 1 2 3 4 5 6 7 8 

1 Diadinoxanthin 1 

2 Diatoxanthin 0.73 1 

3 Fucoxanthin 0.95 0.61 1 

4 Alloxanthin 0.84 0.95 0.7 1 

5 Zeaxanthin 0.73 0.94 0.59 0.96 1 

6 Chlorophyll a 0.93 0.86 0.87 0.93 0.88 1 

7 BSi 0.01 0.03 0.13 0.08 0.13 0.03 1 

8 Nitrate 0.46 0.52 0.44 0.57 0.46 0.55 0.24 1 

 

 CORE E30 1 2 3 4 5 6 7 8 

1 Diadinoxanthin 1 

2 Diatoxanthin 0.87 1 

3 Fucoxanthin 0.94 0.77 1 

4 Alloxanthin 0.88 0.98 0.78 1 

5 Zeaxanthin 0.87 0.94 0.80 0.97 1 

6 Chlorophyll a 0.95 0.88 0.93 0.90 0.93 1 

7 BSi 0.86 0.63 0.94 0.63 0.66 0.84 1 

8 Nitrate 0.42 0.56 0.32 0.47 0.41 0.36 0.27 1 

Relationships with Other Indicators of Productivity 

The increase in concentration of chlorophyll a and fucoxanthin should be consistent with an 

increase in BSi as an indicator of diatom production as seen in prior results from the MDB 

(Turner and Rabalais 1994a) and Charlotte Harbor sediments (Turner et al. 2001). Most BSi 

profiles for sediments, however, were fairly uniform and did not show a positive relationship 

with chloropigments (R values well below 0.5). The exception was station E30, the station most 

likely to be in the epicenter of biogenic silica accumulation and surface sediment chlorophyll a

concentrations (Turner and Rabalais 1994a). BSi and fucoxanthin were positively related (R = 

0.94, p < 0.05). The relationships of BSi to chlorophyll a and other carotenoids for core E30 

were also positive, but not significant. 

Surface water productivity in the MDB has increased since the 1950s as indicated by several 

water column and sediment indicators. These include increase in diatom-based production 

(Turner and Rabalais 1994a, b), accumulation of marine-origin carbon (Eadie et al. 1994), and 

decrease in Secchi disk depth (Figure 4.9; Rabalais et al. 2002c). The decrease in water clarity is 

not due to an increase in suspended sediment concentration, because the suspended sediment 

concentration of the Mississippi River has been reduced by 50% since 1950 when the largest 

natural sources of sediments in the drainage basin were cut off from the Mississippi River main 

stem by the construction of large reservoirs on the Missouri and Arkansas Rivers (Meade 1995). 
 

4.15

Mississippi River nitrate load is closely correlated with indicators of productivity in the 

overlying water column (Justic’ et al. 1993, 1996) and hypoxia in bottom waters (Scavia et al. 

2003), and should therefore be correlated with similar indicators in the sediment cores. None of 

the correlations, however, were significant (Table 4.3). This is likely the result of a much shorter 

time frame for the Mississippi River nitrate load data (back to 1969) when nitrate had already 

increased over historic values, versus the sediment core data that date back to at least 1930 for 

stations D50, E50 and E60 but only to the early 1960s for stations E30 and F35 (where hypoxia 

is more likely to occur). This is also the reason the R-values for correlations with the longer time 

sequence for D50, E50 and E60 were higher than the values for E30 and F35 where hypoxia is 

more likely to occur. 

Figure 4.9. Trend of average Secchi disk depth on the Louisiana shelf west of the Mississippi 

River delta. The data are restricted to stations with surface water salinity between 20 

and 25 psu and depths between 10 and 100 m. The slope of the regression line is 

significant at the 8% level of significance. The error bars are ±1 s.e. (From Rabalais 

et al. 2002c). 

Relationships with Indicators of Hypoxia 

The results of foraminiferan cluster analyses for core E60 indicate trends similar to a proposed 

evolution of seasonal hypoxia (Blackwelder et al. 1966) with a significant change in 

foraminiferal composition in the middle of the 20th century. The increases in chloropigments for 

core E60 also began in the 1955-1960 period. There were no clear clusters of foraminiferans in 

the F35 core, because the time sequence was not long enough. However, the chlorophyll a

concentrations in that core, beginning in early 1960, indicated already elevated levels suggestive 

of increased production or worsening hypoxia or both. The increasing trend in relative 

abundances of the foraminiferan, Buliminella morgani, in cores F35 and E60 as a consequence of 

progressive hypoxia are paralleled by increases in chloropigments. 

Bacterial chloropigments from a sediment core collected in a chronic area of hypoxia in 27 m 

water depth 50 km west of the MDB study area (Chen et al. 2001) confirmed a worsening of 

hypoxia since the early 1960s consistent with results of several other workers (Nelsen et al. 
 

4.16

1994; Rabalais et al. 1986; Sen Gupta et al. 1996). The concentrations of chloropigments in 

sediment cores from the MDB, which date back only to 1963 but are likely to experience 

Medium-High hypoxia (E 30, F 35; Table 4.2), are elevated, consistent with the findings of Chen 

et al. (2001) and the several foraminiferan studies. 

SUMMARY 

The carbon accumulated in sediments of the Louisiana continental shelf in water depths of 20 to 

60 m are primarily from marine phytoplankton and contains the history of phytoplankton 

communities in the overlying water. There is a general increase in chlorophyll a, pheopigments, 

zeaxanthin, fucoxanthin and most carotenoids over time, with the change gradual from 1955 to 

1970, followed by a fairly steady increase to 1997, the time the cores were collected. The 

highest chloropigment concentrations were in cores E30, E50 and F35, which were located in 

areas more likely to be exposed to seasonal hypoxia. The increasing pigments and greater 

concentrations in areas where hypoxia is more likely to occur indicate an increase in 

eutrophication, or a worsening of hypoxia, or both. 
 

CHAPTER 5 

HISTORICAL RECONSTRUCTION OF THE CONTAMINANT LOADING AND 

BIOLOGICAL RESPONSES IN THE CENTRAL GULF OF MEXICO SHELF 

SEDIMENTS: FORAMINIFERA 

Barun K. Sen Gupta 

Department of Geology and Geophysics, Louisiana State University

and 

Emil Platon 

Energy and Geoscience Institute, University of Utah 

ABSTRACT 

Two cores, F35 and E60, were processed for the investigation of benthic Foraminifera; seventy 

four species were identified. Foraminiferal data reported by previous workers from two other 

Louisiana shelf cores were also examined for comparison. Core F35 covers the time span of 

1943-1997, E60 1915-1997. In both cores the temporal trend is one of diversity reduction and 

dominance increase. Cluster analysis of foraminiferal relative abundance data from E60 shows 

significant assemblage changes in between the 1915-1936, 1938-1978 and 1979-1997 time 

intervals. No definite relationship could be established between the contaminant concentration 

in sediments and the composition of foraminiferal assemblage. The only match between a 

contaminant high (PAH 37 ng g-1, OC pesticides 35 ng g-1) and a diversity low was at the 1970-

1975 level in core F35; the significance of this match is unclear. Deformed Foraminifera, one 

indicator of extreme chemical pollution, are not present in either of the cores. On the other hand, 

the diversity and relative-abundance changes of foraminiferal species fit the model of 

progressively worsening seasonal hypoxia in the area. 

 

INTRODUCTION 

Nearshore benthic Foraminifera are sensitive indicator organisms of marine environments and 

environmental stresses. Their meiofaunal size and substantial population densities facilitate 

quantitative studies of these species. In addition, the calcitic shells of many Foraminifera are 

much better preserved in the sedimentary record than the aragonitic shells of invertebrates such 

as molluscs. Some species of Foraminifera are tolerant of many environmental stresses, 

including oxygen depletion and various forms of toxicity, and may be present in substrates that 

are devoid of other shelled organisms. Dominance shifts in benthic foraminiferal assemblages 

have been recorded in many nearshore areas affected by industrial or municipal pollution, and a 

reduction in diversity has been noticed in extreme cases. In this context, we investigated the 

distribution of benthic Foraminifera in two Gulf of Mexico box cores in order to (a) assess the 

possible effects of hydrocarbon contamination on these shelled protozoans (because of toxicity 

or oxygen depletion) and (b) interpret environmental changes in historical time that affected 

foraminiferal microhabitats. Comparisons were made with published data from two other cores 

taken from the same area. 
 

5.2

MATERIALS AND METHODS 

The locations of the cores used for the present study (as well as those of two other cores from 

which comparable data were available) are shown in Figure 5.1. Box cores were collected in 

April 1997 from 35 and 60 m water depths (stations F35 and E60). After retrieval, each box core 

was examined for disturbance, and was recognized as undisturbed if the overlying water was 

clear and invertebrate tracks were visible at the sediment surface. Subsamples from each box 

core were obtained with 7-cm diameter plastic tubes and sliced at 1-cm intervals. 

Approximately half of these 1-cm slices became the primary samples for this study. Selected 

samples were washed over a 63 μm sieve and dried. The resulting residuum was split with a 

microsplitter to provide an aliquot of approximately 300 shells of benthic Foraminifera. All of 

these specimens were picked and identified at the species level. 

Figure 5.1. Core locations. Cores F35 and E60 were taken in spring 1997 (primary material for 

this study); BL10, core 10 of Blackwelder et al. (1996); G27, core studied by Sen 

Gupta et al. (1996) and Rabalais et al. (1996). Water depths: F35, 35 m; E60, 60 m; 

BL10, 29 m; G27, 27 m. 

Parameters such as distribution of taxa (species and/or higher level), species diversity (see 

below), and univariate and multivariate responses were examined. The chosen sampling 

intervals for the foraminiferal study were linked to the time spans represented by the cores and 

the sampling intervals for petroleum biomarkers. In the core-top samples, living Foraminifera 

was recognized by the Rose Bengal stain. 
 

5.3

Species diversity was assessed by two measures computed from the foraminiferal counts: (1) 

species richness (S), i.e., the number of species present in the sample or aliquot, and (2) Shannon 

Wiener Index given by the equation H(S) = -pilnpi, where pi is the proportion of the ith species. 

Simple linear regression (SLR) and multivariate analyses (Cluster Analysis, Principal 

Components Analysis) of foraminiferal data were performed in order to find additional clues to 

historical changes in the composition of the benthic foraminiferal community. Absolute ages of 

samples were estimated on the basis of accumulation rates calculated by 210Pb dating (R. E. 

Turner, personal communication). The characteristics of sediments in Louisiana Bight that make 

210Pb analysis a reliable technique for determining accumulation rates include (1) high deposition 

rates (> 1 mm/yr); (2) shallow mixed surface zone (< 15 cm); (3) high proportions of silt and 

clay (> 40%), and (4) negligible effect of bioturbation. Thus, in the 210Pb profiles, an extended 

radioactive decay region between the surface mixed layer and the lower region of background 

activities allow the determination of sediment accumulation rates (R. E. Turner, personal 

communication). 

RESULTS AND DISCUSSION 

Species Diversity

Seventy four species of benthic Foraminifera were identified, 42 from F35 and 55 from E60; 23 

species were present in both cores. Plots of species richness are in Figure 5.2. Three intervals 

can be distinguished in the species-richness curve for core E60. During the first interval, 1915-

1936, a relatively high number (27-29) of benthic foraminiferal species populated the habitat. 

Species richness decreased steadily from 27 in 1936 to 12 in 1970 and then remained nearly 

constant at values that averaged 10.6 for the rest of the investigated time interval (1976-1997). 

The decreasing trend of the number of benthic foraminiferal species at E60 was tested with 

simple linear regression (SLR). This procedure, performed at 95 % confidence, explained 92% 

of the data variability (correlation coefficient, r = 0.92) and showed that the species richness 

increased with the core depth with a β (slope) value of 0.47. At the 35-m station (core F35), 

species richness decreased from 23 to 7 between 1943 and 1948 and remained at a relatively low 

level during the subsequent period (1948-1997), with a mean of 8. The SLR for F35 (species 

richness against depth) could explain only 30% of the data variability. Thus, the decreasing 

trend in species richness in F35 (with the exception of the highest value recorded for the oldest 

sample) is not as evident as in E60. 

Trends of Shannon-Wiener index (Figure 5.3) are similar to those of species richness. In E60, 

this diversity index decreased steadily from 2.29 in 1915 to 0.81 in 1997, whereas in F35 the 

value changed from 1.74 in 1943 to 1.31 in 1948. Most subsequent values remained between 1.3 

and 1.5, but a pronounced minimum value of 0.38 was attained around 1973. This drop in the 

Shannon-Wiener Index is due to a significant reduction in the number of minor components of 

the foraminiferal assemblage. Regression analysis of E60 data shows (with 95% confidence) 

that diversity index increased downcore. The SLR’s “best fit” explained 92% of the response 

variable. No significant pattern of diversity change can be deciphered from the SLR analysis 

performed on the F35 data. 
 

5.4

Species Distribution

Dominant Species 

Stratigraphic distributions of the three dominant species, Buliminella morgani, Nonionella

basiloba, and Epistominella vitrea, are shown in Figure 5.4. The sum of proportions of these 

species in E60 ranges between 0.62 and 0.94, with a mean of 0.86. An increasing trend of this 

sum is evident especially between 1915 and 1945. A significant increase in the relative 

abundance of Buliminella morgani between 1988 and 1997 is also noticeable. In F35, the sum of 

the relative abundances of Buliminella morgani, Epistominella vitrea, and Nonionella basiloba

shows an increasing trend between 1943 and 1955. Two pronounced drops occurred in 1970 and 

1976. During the second half of the century, these three hyaline species comprise, on average, as 

much as 91% of the foraminiferal assemblages in both of the cores. 

Figure 5.2. Distribution of species richness through time. A, core E60; B, core F35. 
 

5.5

Ammonia and Elphidium 

The Ammonia-Elphidium foraminiferal index (or A-E index, given by NA/(NA + NE)X100) is 

regarded as an indicator of oxygen stress (Sen Gupta et al. 1996). Its value stays above 60% in 

most F35 samples, and above 80% in the youngest part (1979-1997) of this core (Figure 5.5). 

Because of the low numbers of both Ammonia (<12 per sample) and Elphidium (<6 per sample, 

with one exception), however, the fluctuations of the A-E index are difficult to interpret; neither 

of the two taxa are present in 7 samples, thus resulting in a zero value of the index. The A-E 

index reaches a maximum value (100) in several samples towards the top of the core due to the 

lack of Elphidium specimens. In E60, only two specimens of Ammonia were found; there was no 

Elphidium. 

Minor Species 

Some species of benthic Foraminifera in E60 have low relative abundances, but they occur in a 

significant number of samples. The plot in Figure 5.6 shows the relative abundance distributions 

of Bulimina marginata, Cancris sagra, Fursenkoina pontoni, Saccammina difflugiformis, and 

Uvigerina hispido-costata. It is evident that the relative abundances of all these species 

decreased especially between 1915 and 1945. Relative abundances of Bolivina lowmani and 

Bulimina marginata from F35 are plotted in Figure 5.7. These proportions are highly variable 

through time. 
 

5.6

Figure 5.3. Distribution of Shannon-Wiener diversity index through time. A, core E60; B, core 

F35. 

 
 

5.7

Figure 5.4. Distribution of dominant species through time. A, core E60; B, core F35. 

Legend: N. basil. B. morg. E. vitr. All three
 

5.8

Figure 5.5. Distribution of Ammonia–Elphidium Index in Core F35. The maximum value of 100 

is for samples where no Elphidium was found; the zero value is for samples in which 

both Ammonia and Elphidium were absent. 

Figure 5.6. Distribution of relative abundances of Bulimina marginata, Cancris sagra, 

Fursenkoina pontoni, Saccammina diflugiformis, and Uvigerina hispido-costata in 

core E60.
 

5.9

Figure 5.7. Distribution of relative abundances of Bulimina marginata and Bolivina lowmani in 

core F35.

Quinqueloculina 

For the time periods represented by the two cores, Quinqueloculina is a minor taxon with 

persistent stratigraphic trends (Figure 5.8). At station E60, it was present in very low numbers 

before 1943, but absent later. At the shallower F35 station, Quinqueloculina is sporadically 

present, reaching a proportion of about 0.03 in 1943 and proportions between 0.003 and 0.01 in 

the post 1975 period; it was absent in the 1948-1975 time interval. 

 

Agglutinated and Porcelaneous Groups 

Foraminiferal orders with agglutinated shells (Astrorhizida, Lituolida, Textulariida) and 

porcelaneous shells (Miliolida, which includes the genus Quinqueloculina) suffered a decline, or 

even disappeared, in water depths between 35 and 60 m during the past century on this shelf. At 

E60, the proportion of the agglutinated group dropped from 0.08 in 1915 to 0.006 in 1943, 

whereas that of the porcelaneous group declined from 0.06 to 0.003 during the same time span 

(Figure 5.9). During the subsequent period, up to 1997, both groups were extremely rare or 

absent at this site. The historical record of benthic Foraminifera at F35 m is shorter than the one 

at E60, but reduced proportions of agglutinated and porcelaneous taxa are still apparent (Figure 

5.10). Here the proportion of agglutinated taxa was 0.06 in 1943, but zero during the 1990s, 

whereas that of porcelaneous taxa was about 0.04 in 1943 and, with one exception, also zero for 

the 1990s. 
 

5.10

Figure 5.8. Distribution of relative abundances of Quinqueloculina. Top, core E60; bottom, 

core E35. 

 
 

5.11

Figure 5.9. Distribution of relative abundances of agglutinated (top) and porcelaneous (bottom) 

species groups, core E60. 
 

5.12

Figure 5.10. Distribution of relative abundances of agglutinated (top) and porcelaneous (bottom) 

species groups, core F35. 
 

5.13

Community Change

A Cluster Analysis (CA) procedure was applied to foraminiferal data from E60 and F35. In 

addition, Principal Components Analysis (PCA) was used in the analysis of the E60 data. Three 

main clusters are present (Figure 5.11). They correspond to the intervals 1915-1936, 1938-1978 

and 1979-1997, and thus agree well with the distribution trend of the species richness. Major 

changes in the benthic foraminiferal assemblage at this location took place within the 1936-1938 

and 1978-1979 intervals. 

Figure 5.11. Cluster analysis of E60 foraminiferal data; dendrogram for 12 cases. Linkage 

procedure, Ward’s Method; correlation coefficient, Euclidean distance. 

The cluster diagram for F35 core data (Figure 5.12) shows no meaningful major clusters of the 

samples. It is noticeable that temporally successive samples representing the 1970-1975 time 

interval belong to an isolated cluster whose distance from the other clusters is relatively large. 

This is due to a very low representation of minor components in the 4 samples of the 1970-1975 

cluster. The core-bottom (1943) sample whose high species richness makes it different from the 

rest of the F35 samples has an anomalous placement within the dendrogram. The numerical 

similarity between this sample and others in the same cluster (1959, 1960, 1977) is caused by the 

absence of certain species rather than by a very similar species content. Overall, the lack of any 

meaningful clustering of the foraminiferal data of F35 is partly due to the short time interval 

covered by the analyzed samples. However, as shown by species richness, a shift in the benthic 

foraminiferal content could have taken place prior to 1948. A longer stratigraphic record is 

needed in order to better determine when such a shift occurred. 
 

5.14

Figure 5.12. Cluster analysis of F35 foraminiferal data; dendrogram for 33 cases. Linkage 

procedure, Ward’s Method; correlation coefficient, Euclidean distance. The arrow 

points to the core-bottom sample whose species richness differentiates it from the 

rest of the samples. 

The scree plot of eigenvalues for the E60 data (Figure 5.13) reveals two significant factors that 

account for 64.7% of the total variance. However, given the relatively high proportion of 

variance (14.8%) explained by a third factor, that too was considered. As seen in Table 5.1, 

factor 1 accounts for almost half (46.7%) of the total variance and its “major parameters” (Table 

5.2) are Nonionella basiloba, Uvigerina hispido costata, Fursenkoina pontoni, Cancris sagra, 

the agglutinated group, Pyrgo, and other porcelaneous taxa including Quinqueloculina and 

Triloculina (Q/T – ina). Factor 2 accounts for 18% of total variance. Significant loadings onto 

factor 2 are those of Buliminella morgani and Epistominella vitrea. Within factor 3, Bulimina

marginata, Bolivina lowmani, and other species of Bolivina (B. spp), show significant loadings 

(Table 5.2). Thus, most of the variability in the data set is due to changes in the stratigraphic 

distribution of the agglutinated and porcelaneous taxa, and a few hyaline taxa. It is noticeable 

that in E60, Buliminella morgani, perhaps the most opportunistic species in the area of seasonal 

hypoxia of northwestern Gulf of Mexico (Blackwelder et al. 1996; Platon and Sen Gupta 2001), 

has a significant loading onto factor 2 which accounts for 18% of the total variance. Plots of 

loadings onto factor 1, 2, and 3 (Figures 5.14 and 5.15) reveal similar behavior of the data on 

Fursenkoina pontoni, Cancris sagra, Uvigerina hispido-costata, the agglutinated species group, 

the Quinqueloculina-Triloculina group, and Pyrgo. The data on Nonionella basiloba behave the 

opposite way. 
 

5.15

Figure 5.13. Eigenvalues scree plot for E60 foraminiferal data. Arrow marks a significant 

change in slope of curve and indicates the presence of two significant factors. 

Table 5.1 

Eigenvalues for E60 foraminiferal data. Extraction: principal components. 

Factor Eigenval Variance Eigenval % 

1 5.6070398 46.725332 5.6070398 46.725 

2 2.1608055 18.006713 7.7678454 64.732 

3 1.7773271 14.811059 9.5451724 79.543 
 

5.16

Table 5.2 

Factor loadings for 12 foraminiferal taxa in core E60. 

Rotation: normalized Varimax; extraction: principal components. 

Taxa Factor 

1 

Factor 

2 

Factor 

3 

N. basiloba -0.71051 0.3475779 0.0676453 

E. vitrea 0.1329909 0.7868568 -0.250877 

B. morgani -0.066129 -0.947769 -0.102249 

U. hispido costata 0.7395553 0.1880553 0.5665451 

F. pontoni 0.7402202 0.2667797 -0.219597 

B. marginata 0.0028491 0.4325385 0.7023258 

C. sagra 0.9486338 -0.040595 0.0333846 

B. lowmani -0.026707 0.2134872 -0.770596 

B. spp. 0.3590785 -0.281262 0.7904396 

Agglutinated 0.8520473 0.2180553 0.3812768 

Pyrgo 0.7512396 0.1741379 0.5153114 

Q/T - ina 0.8778652 0.0941215 0.3418745 

Expl.Var 4.7123098 2.1449108 2.6879519 

Prp.Totl 0.3926925 0.1787426 0.223996 

Figure 5.14. Factor loadings, Factor 1/Factor 2 core E60. 
 

5.17

Figure 5.15. Factor loadings, Factor 1/Factor3 (A) and Factor 2/Factor 3 (B), core E60. 

Figure 5.16 depicts the temporal distribution of factor 1 and factor 2 scores (data in Table 5.3). 

A change from positive to negative values of factor 1 scores took place after 1938. This trend is 

related to the reduced abundances or even disappearance of taxa with positive scores in younger 

sediments (Table 5.2). The factor 2 scores vary less in time. A very negative value of the score 

calculated for the core-top sample is due to the high abundance of Buliminella morgani

associated with reduced proportions of Epistominella vitrea and Nonionella basiloba. 

Figure 5.16. Plots of factor scores against time, core E60. A, Factor 1. B, Factor 2. 
 

5.18

Table 5.3 

Factor scores for 12 samples in core E60. 

 

Obs. Factor 

1 

Factor 

2 

Factor 

3 

1 -0.048191 -3.023071 -0.121067 

2 -0.368304 0.8202798 -1.051938 

3 -0.520913 0.6882466 -0.465986 

4 -0.85864 -0.016316 0.2509972 

5 -0.12036 -0.152501 -1.422886 

6 -0.670037 0.141852 -0.56499 

7 -0.840622 -0.160083 1.1244943 

8 -0.68357 0.1101386 0.4775404 

9 -0.211689 0.7416906 0.9235517 

10 1.6443484 0.3358802 -1.535607 

11 0.2702164 0.5065064 1.2350393 

12 2.4077612 0.0073767 1.1508508 

Additional Data

Published data (Blackwelder et al. 1996; Rabalais et al. 1996, Sen Gupta et al. 1996) from two 

cores from shallower sites in the study area (Figure 5.1; BL10 and G27, water depths 29 m and 

27 m, respectively) were also examined and analyzed for comparison with data from F35 and 

E60. Figure 5.17 depicts the temporal distribution of the relative abundance of Quinqueloculina

in G27. Its historical decline and its disappearance in the1890s suggests a progressively 

worsened environmental condition for this genus. Trends similar to those observed in the E60 

and G27 data have been noticed by Blackwelder et al. (1996) in BL10. They report a decreasing 

trend for both the pocelaneous and agglutinated groups. 
 

5.19

Figure 5.17. Distribution of relative abundance of Quinqueloculina; core G27. 

The raw foraminiferal data of Blackwelder et al. (1996) were subjected to multivariate analyses 

(CA and PCA). The results of this CA are depicted in Figure 5.18. Two major clusters, placed 

at a relatively large linkage distance one from another, suggest a major change in the 

foraminiferal assemblage taking place in late 1940s or early 1950s. 
 

5.20

Figure 5.18. Cluster analysis of BL10 core data, dendrogram for 51 cases. Linkage procedure, 

Ward’s Method; correlation coefficient, Euclidean distance. 

Successive runs of PCA against foraminiferal data from BL10 core revealed the existence of four 

factors that explain 68.32% of the total variance, the first two factors accounting for 50.26% of 

the variance (Table 5.4). Important high loadings of considered variables (foraminiferal species) 

on factor 1 are those of Buliminella morgani, Nonionella opima, Quinqueloculina tanagos, 

Bigenerina irrelgularis, Textularia mayori, and Quinqueloculina horrida (Table 5.5). Among 

loadings on factor 2, those of Buliminella morgani, Epistominella vitrea, Ammonia 

parkinsoniana, A. pauciloculata, Nonionella atlantica, and Pyrgo nasutus show significant (> 

0.6) values. Noticeable loads in the next two sets of loadings include those of Epistominella 

vitrea, Hanzawaia concentrica (factor 3), and Ammonia parkinsoniana typica (factor 4). 

[Taxonomic note: “Ammonia pauciloculata” of Blackwelder et al. (1996) may have been 
 

5.21

included within A. parkinsoniana in this study, because the distinction is subtle and 

controversial.] 

Table 5.4 

Eigenvalues for BL10 foraminiferal data (raw data from Blackwelder et al. 

1996). Extraction: principal components. 

Factor Eigenval % total 

Variance 

Cumululative

.Eigenval 

Cumululative 

% 

1 6.975127 38.75071 6.975127 38.75071 

2 2.071704 11.50947 9.046831 50.26017 

3 1.659239 9.217992 10.70607 59.47817 

4 1.591264 8.840354 12.29733 68.31852 

Table 5.5 

 Factor loadings for 18 foraminiferal species from core BL10 (raw data from Blackwelder 

et al. 1996). Rotation: normalized Varimax; extraction: principal components. 

Species Factor 

1 

Factor 

2 

Factor 

3 

Factor 

4 

B. morgani -0.64443 -0.67949 -0.04239 -0.09684 

E. vitrea 0.008331 -0.69939 -0.60564 0.023484 

E. gunteri 0.218805 0.47532 0.55822 0.041476 

B. lowmani -0.14123 0.337416 -0.58652 0.040451 

A. parkinsoniana 0.220137 0.820384 -0.18493 0.132664 

N. opima -0.85387 0.161868 0.02265 0.179732 

A. pauciloculata 0.281875 0.696989 0.051267 0.031923 

N. atlantica -0.05035 0.761433 0.122944 -0.0019 

H. concentrica 0.239366 0.15558 0.762594 0.039075 

A. parkinsoniana typica -0.13212 -0.22732 0.392379 -0.6875 

Q. tanagos 0.803254 0.232209 0.123191 -0.00185 

P. nasutus 0.523701 0.67358 0.1062 -0.11404 

Q. bicarinata 0.398886 0.527317 0.05401 -0.31529 

Q. poeyanum 0.138989 0.331983 -0.03012 -0.66056 

B. irregularis 0.729607 0.156321 0.258504 0.194536 

T. mayori 0.714906 0.423283 0.329993 0.099306 

D. compressa 0.199352 0.164346 0.378003 0.652702 

Q. horrida 0.658773 0.355881 0.294589 0.267591 

Expl.Var 4.032517 4.384495 2.247846 1.632476 

Prp.Totl 0.224029 0.243583 0.12488 0.090693 
 

5.22

Significant Stratigraphic Trends and Interpretations

Relationship with Contaminant Loading 

Data on chemical contaminants are available for both F35 and E60 (Overton et al., this report). 

In F35, PAH peaks are at 26-30 cm (years 1956-1962) and 16-20 cm (1970-1975); an 

organochlorine (OC) pesticide peak is also present at 16-20 cm, but not at 26-30 cm. In E60, 

both the PAH and OC pesticide high values (not necessarily peaks) are in the oldest sample (46-

47 cm, 1915-1917). We compared the stratigraphic locations of these contaminant peaks or high 

values with low and high values of foraminiferal parameters in the same cores (but different 

subcores). 

In F35, the foraminiferal diversity trends (species richness and Shannon-Wiener function) do 

show a dip in the 16-20 cm section, within a relatively steady (but noisy) post-1945 pattern. The 

relative abundances of two dominant species (Bolivina lowmani and Bulimina marginata) also 

show this dip, but in addition, they show comparable dips at levels where neither PAH nor OC 

pesticides show any conspicuous shift. The A-E index shows a dip at 17-18 cm, but, as 

explained earlier, this index shows erratic shifts in F35 because of very low absolute abundances 

of these two taxa. The agglutinated group shows a peak in relative abundance (after the initial 

decline) at 20 cm, but this is a computing artifact, due to the fact that the much larger calcareous 

group was reduced at this level (reflected in the overall diversity drop). The porcelaneous group 

is absent in the large 16-35 cm interval. 

In E60, various foraminiferal parameters show a decline from the oldest sample, but we cannot 

ascertain when the decline began, and the values (of diversity, several dominant species, and 

agglutinated and porcelaneous groups) are much lower at younger levels. So the PAH and OC 

pesticide high values in this sample do not imply a link with foraminiferal parameters. In any 

case, even the highest values of PAH in E60 (~30 ng g-1) is rather low when compared to the 

values in F35. In contrast, the maximum OC pesticide value in E60 is higher than any in F35. 

Judging by the highest values of PAH in three other cores (500-1200 ng g-1 in D50G, D80, G40), 

however, even the highest values of PAH in both F35 (70 ng g-1) and E60 (30 ng g-1) are modest. 

(The PAH measure for the 16-20 cm segment, where some foraminiferal parameters show a 

decline, is only 37 ng g-1.) The same inference can be made regarding the highest values of OC 

pesticides in F35 (35 ng g-1) and E60 (80 ng g-1) when comparisons are made with the highest 

values in cores in D80, E30, and G50 (2000-3500 ng g-1). 

 

Thus, the distributions of chemical and foraminiferal data from F35 and E60 suggest either a 

minor effect (in F35, 1970-1975 levels) or (more likely) no traceable effect of chemical 

contaminants on the historical change in foraminiferal assemblages. We did not find any 

deformed shells of benthic Foraminifera in our samples, as has been reported for coastal 

environments with severe chemical (especially metal) pollution (Yanko et al. 1999). 

Relationship with Seasonal Hypoxia 

Change of foraminiferal species diversity as a consequence of spatial or temporal environmental 

change is frequently reported in the literature (e.g., Bandy et al. 1964a; 1964b; Sen Gupta and 

Kilbourne 1974; Alve 1990 1995; Nelsen et al. 1994; Jannink et al. 1998). Both species richness 
 

5.23

and Shannon-Wiener Index decreased from older to younger samples in F35 and E60. This 

suggests a possible connection with worsening seasonal hypoxia in the study area, as has been 

previously reported for the Ammonia-Elphidium (A-E) Index (Sen Gupta et al. 1996). This A-E 

Index becomes rather erratic or meaningless in deeper (>30 m) shelf waters, because the paucity 

or absence of these two taxa in these water depths. Thus, the trend of the A-E Index in F35 

cannot be confidently interpreted as a clear proxy signal of progressive seasonal hypoxia, 

although persistently high values (80-100%) are confined to the youngest time interval (1981-

1997). 

Several other foraminifers commonly reported from this area seemingly tolerate oxygen 

deficiency, and prefer organic rich sediments in other marine areas. These taxa include Bulimina 

marginata (Bandy et al. 1964b), Uvigerina peregrina (Miller and Lohman 1982; Lutze 1980; 

Van der Zwaan et al. 1986), Bolivina lowmani (Bizon and Bizon 1984), Fursenkoina (Seiglie 

1968, 1971), Nonionella (Seiglie 1968; Sen Gupta and Machain-Castillo 1993; Bernhard and Sen 

Gupta 1999), Cancris (Seiglie 1968; Jonkers 1984; Van der Zwaan and Jorissen 1991), 

Epistominella (Verhallen 1997), and Buliminella (Bandy et al. 1964a, b 1965). In a previous 

study (Platon and Sen Gupta 2001), we showed that Buliminella morgani dominates living 

assemblages of benthic Foraminifera from the sediment-water interface down to a substrate 

depth of 5-10 cm, possibly in severely dysoxic, or even anoxic, microhabitats. Given this 

adaptation, it is expected that the biostratigraphical record would reveal an increasing trend in 

relative abundances of Buliminella morgani as a consequence of progressive hypoxia, which is 

indeed the case. 

Laboratory experiments on foraminiferal subsurface activity under oxygen-stress conditions 

suggest that the miliolid Quinqueloculina prefers oxic environments and has the ability of 

moving away from the anoxic sediment layers (Moodley et al. 1998). In both F35 and E60, 

Quinqueloculina is absent or virtually absent after 1945, which may indicate the attainment of a 

critical threshold of hypoxia, in intensity or duration. 

Results of cluster analysis of the E60 data bring further insight into foraminiferal responses to 

progressive seasonal oxygen depletion on the Louisiana shelf. Three stratigraphically-separated 

assemblages (for 1915-1936, 1938-1978 and 1979-1997 time intervals, marked by reduction of 

species diversity and increase in species dominance, can be recognized in core E60. This pattern 

agrees with the three-stage foraminiferal assemblage evolution under seasonal hypoxia suggested 

by Blackwelder et al. (1996) for the BL10 core. Furthermore, cluster analysis of published data 

from BL 10 (Blackwelder et al. 1996) reveals a significant change in foraminiferal composition 

in the middle of the 20th century. 

SUMMARY AND CONCLUSIONS 

Various aspects of the numerical data on foraminiferal distribution in cores F35 and E60—

diversity, relative abundances of key species, and sample groupings identified by cluster and 

factor analysis–– indicate progressive changes from the oldest to the youngest stratigraphic level. 

For E60, which covers a longer time span (1915-1997) than F35 (1943-1997), the diversity 

measures (species richness and Shannon-Wiener index) and the cluster pattern indicate 
 

5.24

significant changes in the foraminiferal assemblage in between the 1915-1936, 1938-1978, and 

1979-1997 time intervals, but not within them. These changes are imprinted on a background of 

overall diversity reduction and dominance increase. 

No unequivocal relationship could be detected between contaminant concentration in sediments 

and composition of the foraminiferal assemblage. The only match between a contaminant high 

and a diversity low was at the 1970-1975 segment in core F35, and that may indicate a 

connection, but we note that the values of both PAH (37 ng g-1) and OC pesticides (35 ng g-1) are 

more than an order of magnitude lower than those recorded in some other cores from the study 

area. Deformed Foraminifera, one indicator of extreme chemical pollution, are not present in 

either of the cores. 

The overall decline in foraminiferal species diversity and increase in species dominance during 

the time intervals represented in cores F35 and E60 agree with the results of previous 

foraminiferal studies of paleohypoxia in the study area. The extreme decline of porcelaneous 

taxa, especially of Quinqueloculina, in the younger parts of the cores also conforms to the results 

of these earlier studies. The same is true of the increase in the relative abundance of Buliminella 

morgani in F35. The stratigraphic signal of the Ammonia-Elphidium index (indicator of 

nearshore oxygen stress on the Louisiana shelf and elsewhere) is noisy in F35, putatively 

because of the paucity of these two taxa at the water depth of this site (35 m). 
CHAPTER 6 

LITERATURE CITED 

Abele-Oeschger, D. 1991. Potential of some carotenoids in two recent sediments of Kiel Bight as 

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CHAPTER 7 

APPENDICES 
APPENDIX A 

Total Organochlorine Pesticide Histograms 
7.5 

Tota l OC Pe sticide Distribution for Core D50G

0.0

0.5

1.0

1.5

2.0

2-12

14-2426-3638-4850-6163-7579-95

99-119

123-144148-168172-194200-224228-248254-274

Conc (ng/g)

De pth (cm )

Tota l OC Pe sticide Distribution for Core D80

0

500

1000

1500

2000

2500

3000

3500

1-6

7-12

13-18

19-24

25-30

31-36

37-42

43-47

Conc (ng/g)

De pth (cm )

Tota l OC Pe sticide Distribution for Core C10*

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1-12

24-34

Conc (ng/g)

De pth (cm ) 1986-1984 1984-1981

1981-1979

1978-1976

1975-1974

1947-1937
7.6 

Tota l OC Pe sticide Distribution for Core E30

0

500

1000

1500

2000

2500

3000

3500

1-5

6-10

11-1516-2021-2526-3031-35

Conc (ng/g)

Tota l OC Pe sticide Distribution for Core E50

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

1-5

6-10

11-15

16-20

21-25

26-30

31-35

36-40

41-45

46-5051-54

Conc (ng/g)

De pth (cm )

Tota l OC Pe sticide Distribution for Core E60

0

10

20

30

40

50

60

1-5

6-10

11-1516-2021-2526-3031-3536-4041-4546-47

Conc (ng/g)

De pth (cm )

1997-1991

De pth (cm )

1997-1993

1992-1988

1987-1982

1981-1977

1976-1972

1971-1966

1965-1960

1992-19871986-1982

1980-1976

1975-19701969-1965

1964-1959

1958-1954

1953-1948

1947-1942

1941-1938

1990-1984

1983-1977

1968-1963

1961-1956

1954-1948
7.7 

Tota l OC Pe sticide Distribution for Core G40

0

20

40

60

80

100

1-6

7-12

13-17

18-22

Conc (ng/g)

De pth (cm )

Tota l OC Pe sticide Distribution for Core G50

0

1000

2000

3000

4000

5000

6000

7000

1-5

6-10

11-14

Conc (ng/g)

De pth (cm )

Tota l OC Pe sticide Distribution for Core F35

0

10

20

30

40

50

60

1-5

6-10

11-1516-2021-2526-3031-3536-39

Conc (ng/g)

De pth (cm )

1999-1992

1990-1985

1983-1978

1976-1971

1970-1964

1963-19571956-1950

1949-1945

1949-1922

1989-1939

1989-1956
7.8 

Tota l OC Pe sticide Distribution for Core SW I3

0

200

400

600

800

1-6

7-12

13-1718-2223-27

Conc (ng/g)

De pth (cm )

1999-1986

1984-1971

1969-1959

1944-1934

1999-1986
APPENDIX B 

 Organochlorine Pesticide Concentrations for Sediment Cores 
7.11 

Sample Name 4A 4C 2A 2B 2C 2D 2E

Core C10 C10 D50G D50G D50G D50G D50G

Depth 1-12 24-34 2-12 14-24 26-36 38-48 50-61

Date Range 1989-1984 1978-1974 1996-1988 1987-1979 1977-1969 1967-1959 1958-1949

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd nd nd nd

Lindane (g-BHC) nd nd nd nd nd nd nd

Heptachlor nd nd nd nd nd nd nd

Aldrin nd nd nd nd nd nd nd

Heptachlor Epoxide nd nd nd nd nd nd nd

trans-Nonachlor nd nd nd nd nd nd nd

cis-Chlordane nd nd nd nd nd nd nd

4, 4' DDE nd nd nd nd nd nd nd

Dieldrin nd nd nd nd nd nd nd

Endrin nd nd nd nd nd nd nd

4, 4' DDD nd nd nd nd nd nd nd

4,4' DDT nd nd nd nd nd nd nd

TOTAL OCPs (ng/g) 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Sample Name 2F 2G 2H 1A 1B 1C 1D

Core D50G D50G D50G D50G D50G D50G D50G

Depth 63-75 79-95 99-119 123-144 148-168 172-194 200-224

Date Range 1947-1937 1934-1921 1918-1902 1899-1882 1879-1862 1859-1842 1837-1817

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd nd nd nd

Lindane (g-BHC) nd nd nd nd nd nd nd

Heptachlor nd nd nd nd nd nd nd

Aldrin nd nd nd nd nd nd nd

Heptachlor Epoxide nd nd nd nd nd nd nd

trans-Nonachlor nd nd nd nd nd nd nd

cis-Chlordane nd nd nd nd nd nd nd

4, 4' DDE nd nd nd nd nd nd nd

Dieldrin nd nd nd nd nd nd nd

Endrin nd nd nd nd nd nd nd

4, 4' DDD nd nd nd nd nd nd nd

4,4' DDT 0.81 nd nd nd nd nd nd

TOTAL OCPs (ng/g) 0.81 0.00 0.00 0.00 0.00 0.00 0.00

Sample Name 3A 3B 4D 4E 4F 4G 4H

Core D50G D50G D80 D80 D80 D80 D80

Depth 228-248 254-274 1-6 7-12 13-18 19-24 25-30

Date Range 1814-1798 1793-1777 1995-1992 1992-1990 1989-1987 1986-1984 1984-1981

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd nd nd nd

Lindane (g-BHC) nd nd nd nd nd nd nd

Heptachlor nd nd nd nd nd 35 nd

Aldrin nd nd nd nd nd 20 12

Heptachlor Epoxide nd nd nd nd nd nd nd

trans-Nonachlor nd nd nd nd nd nd nd

cis-Chlordane nd nd nd nd nd nd 5.8

4, 4' DDE nd nd nd nd nd nd nd

Dieldrin nd nd nd nd nd nd 4.4

Endrin nd nd nd nd nd nd nd

4, 4' DDD nd nd nd nd nd 12 nd

4,4' DDT nd nd nd nd nd nd 1.2

TOTAL OCPs (ng/g) 0.00 0.00 0.00 0.00 0.00 67 24
7.12 

Sample Name 4I 4J 4K 2N1235-16 2N1235-12 2N1235-18 2N1235-36

Core D80 D80 D80 E30 E30 E30 E30

Depth 31-36 37-42 43-47 1-5 6-10 11-15 16-20

Date Range 1981-1979 1978-1976 1975-1974 1997-1993 1992-1988 1987-1982 1981-1977

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd 290 140 nd

Lindane (g-BHC) nd nd nd 230 nd nd nd

Heptachlor nd nd nd 450 nd nd nd

Aldrin nd nd nd 480 77 nd nd

Heptachlor Epoxide nd 32 nd nd nd 62 nd

trans-Nonachlor 2.0 370 nd nd 90 nd nd

cis-Chlordane 25 320 9.0 680 100 69 79

4, 4' DDE nd 140 nd nd nd nd nd

Dieldrin nd 310 nd 250 nd nd nd

Endrin 1.2 390 nd nd nd nd nd

4, 4' DDD 2.0 310 10 nd nd nd nd

4,4' DDT nd 190 nd nd nd nd nd

TOTAL OCPs (ng/g) 30 2100 19 2100 560 270 79

Sample Name 2N1235-35 2N1235-08 2N1235-15 2N1235-01 2N1235-05 2N1235-22 2N1235-23

Core E30 E30 E30 E50 E50 E50 E50

Depth 21-25 26-30 31-35 1-5 6-10 11-15 16-20

Date Range 1976-1972 1971-1966 1965-1960 1997-1993 1992-1987 1986-1982 1980-1976

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd nd nd nd

Lindane (g-BHC) nd nd nd nd nd nd nd

Heptachlor nd nd nd nd nd nd 7.0

Aldrin nd nd nd nd nd 71 nd

Heptachlor Epoxide nd nd nd nd nd nd 22

trans-Nonachlor nd nd nd nd nd nd 1.3

cis-Chlordane 220 100 86 nd 38 nd 26

4, 4' DDE nd nd nd nd nd nd 3.3

Dieldrin nd nd nd nd nd nd nd

Endrin nd nd nd nd nd nd nd

4, 4' DDD nd nd nd nd nd 20 nd

4,4' DDT nd nd nd nd nd nd nd

TOTAL OCPs (ng/g) 220 100 86 0.00 38 91 60

Sample Name 2N1235-27 2N1235-02 2N1235-04 2N1235-06 2N1235-17 2N1235-28 2N1235-03

Core E50 E50 E50 E50 E50 E50 E50

Depth 21-25 26-30 31-35 36-40 41-45 46-50 51-54

Date Range 1975-1970 1969-1965 1964-1959 1958-1954 1953-1948 1947-1942 1941-1938

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene 55 nd 550 3.1 420 nd nd

Lindane (g-BHC) 230 nd 540 39 460 3.5 nd

Heptachlor 2.1 3.5 520 26 370 nd nd

Aldrin 2.4 17 640 9.9 530 nd nd

Heptachlor Epoxide nd 51 690 nd 600 nd nd

trans-Nonachlor 7.1 nd 740 nd 620 12 nd

cis-Chlordane 30 94 640 16 510 37 nd

4, 4' DDE nd nd 120 2.1 56 nd 2.1

Dieldrin 3.8 6.5 610 1.9 540 nd nd

Endrin 9.1 13 780 6.8 660 nd nd

4, 4' DDD 2.9 25 830 nd 67 nd 59

4,4' DDT nd nd 310 nd nd nd nd

TOTAL OCPs (ng/g) 240 210 7000 110 4800 53 61
7.13 

Sample Name 2N1235-26 2N1235-31 2N1235-24 2N1235-29 2N1235-10 2N1235-33 2N1235-32

Core E60 E60 E60 E60 E60 E60 E60

Depth 1-5 6-10 11-15 16-20 21-25 26-30 31-35

Date Range 1997-1991 1990-1984 1983-1977 1976-1970 1968-1963 1961-1956 1954-1948

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd nd nd nd

Lindane (g-BHC) nd nd nd nd nd nd nd

Heptachlor nd 0.67 nd nd nd nd 1.2

Aldrin nd nd nd nd 1.2 0.48 4.3

Heptachlor Epoxide 1.8 nd 1.6 nd 0.85 nd 1.6

trans-Nonachlor nd 4.0 9.9 nd 4.0 nd 14

cis-Chlordane nd 19 13 nd nd nd nd

4, 4' DDE nd nd nd nd nd nd nd

Dieldrin nd nd nd nd nd nd nd

Endrin 1.4 2.1 nd nd 2.6 nd nd

4, 4' DDD nd 1.2 nd nd nd nd 9.5

4,4' DDT nd nd nd nd 4.1 nd nd

TOTAL OCPs (ng/g) 3.2 27 24 0.0 13 0.48 31

Sample Name 2N1235-34 2N1235-30 2N1235-07 2N1235-13 2N1235-20 2N1235-25 2N1235-09

Core E60 E60 E60 F35 F35 F35 F35

Depth 36-40 41-45 46-47 1-5 6-10 11-15 16-20

Date Range 1947-1941 1940-1934 1933-1931 1999-1992 1990-1985 1983-1978 1976-1971

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd nd nd nd

Lindane (g-BHC) nd nd nd nd nd nd nd

Heptachlor nd nd nd nd nd nd nd

Aldrin nd nd nd nd nd nd nd

Heptachlor Epoxide nd nd nd nd 1.3 nd 1.2

trans-Nonachlor nd nd nd nd 9.1 nd 2.9

cis-Chlordane nd nd nd 14 14 16 29

4, 4' DDE nd nd nd nd nd nd nd

Dieldrin nd nd nd nd nd nd nd

Endrin nd nd nd 2.3 1.1 1.1 nd

4, 4' DDD nd nd nd nd nd nd nd

4,4' DDT nd nd nd nd nd nd nd

TOTAL OCPs (ng/g) 0.0 0.0 0.0 16 25 17 33

Sample Name 2N1235-21 2N1235-19 2N1235-11 2N1235-14 3H 3I 3J

Core F35 F35 F35 F35 G40 G40 G40

Depth 21-25 26-30 31-35 36-39 1-6 7-12 13-17

Date Range 1970-1964 1963-1957 1956-1950 1949-1945 1989-1939 1939-1889 1889-1847

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd 39 nd nd

Lindane (g-BHC) nd nd nd nd nd nd nd

Heptachlor nd nd nd nd nd nd nd

Aldrin nd nd nd nd nd nd nd

Heptachlor Epoxide 1.7 nd 0.19 0.67 nd nd nd

trans-Nonachlor 2.8 nd nd 0.12 nd nd nd

cis-Chlordane 12 7.3 6.2 6.7 nd nd nd

4, 4' DDE nd nd nd nd nd nd nd

Dieldrin nd nd nd nd nd nd nd

Endrin nd nd 0.31 nd nd nd nd

4, 4' DDD 3.3 1.3 2.5 1.5 5.2 nd nd

4,4' DDT nd nd nd nd nd nd nd

TOTAL OCPs (ng/g) 20 8.6 9.2 9.0 44 0.00 0.00
7.14 

Sample Name 3K 4L 4M 4N 3C 3D 3E

Core G40 G50 G50 G50 SWI3 SWI3 SWI3

Depth 18-22 1-5 6-10 11-14 1-6 7-12 13-17

Date Range 1847-1805 1989-1956 1956-1922 1922-1892 1999-1986 1984-1971 1969-1959

Compounds Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Hexachlorobenzene nd nd nd nd nd nd nd

Lindane (g-BHC) nd 190 nd nd nd nd nd

Heptachlor nd 16 nd nd nd nd 37

Aldrin nd 22 nd nd 0.76 nd nd

Heptachlor Epoxide nd nd 0.71 nd 2.7 nd 61

trans-Nonachlor nd 590 nd nd nd nd nd

cis-Chlordane nd 540 nd nd nd nd nd

4, 4' DDE nd 170 nd nd nd nd nd

Dieldrin nd 380 nd nd nd 100 360

Endrin nd 650 0.77 nd nd 7.3 nd

4, 4' DDD nd 510 1.1 nd nd 1.9 nd

4,4' DDT nd 469 1.6 nd nd 20 1.3

TOTAL OCPs (ng/g) 0.00 3500 4.2 0.00 3.5 130 460

Sample Name 3F 3G

Core SWI3 SWI3

Depth 18-22 23-27

Date Range 1956-1946 1944-1934

Compounds Conc (ng/g) Conc (ng/g)

Hexachlorobenzene 4.0 nd

Lindane (g-BHC) nd 38

Heptachlor 1.8 nd

Aldrin nd nd

Heptachlor Epoxide nd nd

trans-Nonachlor nd nd

cis-Chlordane nd nd

4, 4' DDE nd nd

Dieldrin 58 nd

Endrin 2.0 nd

4, 4' DDD 2.9 1.2

4,4' DDT 1.4 nd

TOTAL OCPs (ng/g) 70 39
APPENDIX C

Total Organochlorine Pesticide Histograms by Decade
7.17 

TOTAL OC PES TICIDES , 1990's

0

1000

2000

3000

4000

5000

6000

7000

8000

C10 D50G D80 E30 E50 E60 F35 G40 G50 SW I3

Core

Conc (ng/g)

TOTAL OC PESTICIDES, 1980's

0

1000

2000

3000

4000

5000

6000

7000

8000

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL OC PESTICIDES, 1970's 

0

1000

2000

3000

4000

5000

6000

7000

8000

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
7.18 

TOTAL OC PESTICIDES, 1960's 

0

1000

2000

3000

4000

5000

6000

7000

8000

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL OC PESTICIDES, 1950's 

0

1000

2000

3000

4000

5000

6000

7000

8000

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL OC PESTICIDES, 1940's

0

1000

2000

3000

4000

5000

6000

7000

8000

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
APPENDIX D

Total PAH Histograms
7.21 

Total PAH Distribution for Core C10*

0

20

40

60

80

100

120

140

160

180

200

1-12

24-34

Depth (cm )

Conc (ng/g)

1989-1984

1978-1974

Total PAH Distribution for Core D50G

0

100

200

300

400

500

600

700

800

2-12

14-2426-3638-4850-6163-7579-95

99-119

123-144148-168

172-194

200-224228-248254-274

De pth (cm )

Conc (ng/g)

1997-1988

1987-1979

1977-1969

1958-1949

1967-1959

1947-1937

1934-1921

1918-1902

1899-1882

1879-1862

1859-1842

1837-1817

1814-1798

1793-1777

Total PAH Distribution for Core D80

0

200

400

600

800

1000

1200

1400

1600

1800

1-6

7-12

13-1819-2425-3031-3637-4243-47

De pth (cm )

Conc (ng/g)

1997-1992

1992-1990

1989-1987

1986-1984

1984-1981

1981-1979

1978-1976

1975-1974

*Missing sections 13-23 
7.22 

Total PAH Distribution for Core E30 

0

5

10

15

20

25

30

35

40

45

50

1-5

6-10

11-15

16-2021-2526-3031-35

Depth (cm )

Conc (ng/g)

1997-1993

1992-1988

1987-1982

1981-1977

1976-1972

1971-1966

1965-1960

Total PAH Distribution for Core E50

0

20

40

60

80

100

120

140

160

180

200

220

1-5

6-10

11-15

16-20

21-25

26-30

31-3536-4041-4546-5051-54

De pth (cm )

Conc (ng/g)

1997-1993

1992-1987

1986-1982

1980-1976

1975-1970

1969-1965

1964-1959

1958-1954

1953-1948

1947-1942

1941-1938

Total PAH Distribution for Core E60

0

5

10

15

20

25

30

35

40

45

50

1-5

6-10

11-15

16-20

21-2526-30

31-35

36-4041-45

46-47

De pth (cm )

Conc (ng/g)

1997-1991

1990-1984

1983-1977

1976-1970

1968-1963

1961-1956

1954-1948

1947-1941

1940-1934

1933-1931
7.23 

Total PAH Distribution for Core F35

0

10

20

30

40

50

60

70

80

90

100

110

1-5

6-10

11-1516-2021-2526-3031-3536-39

Depth (cm )

Conc (ng/g)

1997-1992

1990-1985

1983-1978

1976-1971

1970-1964

1963-1957

1956-19501949-1945

Total PAH Distribution for Core G40

0

100

200

300

400

500

600

700

800

1-6

7-12

13-17

18-22

De pth (cm )

Conc (ng/g)

1989-1939

1931-1889

1881-1847

1839-1806

Total PAH Distribution for Core G50

0

20

40

60

80

100

120

140

160

180

200

220

1-5

6-10

11-14

De pth (cm )

Conc (ng/g)

1989-1956

1949-1922

1916-1896
7.24 

Total PAH Distribution for Core SW I3

0

50

100

150

200

250

300

350

400

1-6

7-12

13-1718-22

23-27

De pth (cm )

Conc (ng/g)

1999-19861984-1971

1969-1959

1956-1946

1944-1934
APPENDIX E

PAH Concentrations for Sediment Cores
7.27 

Sample Name 4A 4C 2A 2B 2C 2D 2E

Core C10 C10 D-50G D-50G D-50G D-50G D-50G

Depth (cm) 1-12 24-34 2-12 14-24 26-36 38-48 50-61

Date Range 1989-1984 1978-1974 1997-1988 1987-1979 1977-1969 1967-1959 1958-1949

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.89 1.0 1.6 3.1 1.3 11 1.8

1-Methyl Naphthalene 0.15 0.17 0.48 0.88 0.17 2.3 0.54

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 1.4 0.31 1.7 2.1 0.27 9.0 0.54

Acenaphthylene 2.5 6.3 5.1 5.2 3.1 18 7.2

Acenaphthene 3.2 1.9 3.2 2.6 0.87 12 4.2

Biphenyl nd nd nd nd nd nd nd

Fluorene 0.74 1.3 1.9 1.6 0.62 8.8 4.2

Phenanthrene 15 21 22 15 5.9 94 46

Anthracene 1.1 0.56 4.0 2.7 1.5 20 8.5

1-Methyl Phenanthrene 9.5 4.9 nd nd nd nd nd

Fluoranthene 23 42 26 23 8.0 120 45

Pyrene 23 38 30 30 15 150 50

Benzo (a) Anthracene 2.7 2.5 4.5 7.0 0.79 5.5 2.0

Chrysene 2.4 1.7 5.1 6.5 0.83 6.1 2.0

Benzo (b) Fluoranthene 1.7 1.7 6.2 11 1.3 6.6 3.1

Benzo (k) Fluoranthene 3.1 2.5 7.5 16 1.4 8.7 4.0

Benzo (e) Pyrene 2.1 1.8 6.1 11 1.3 6.2 3.2

Benzo (a) Pyrene 1.4 0.81 4.5 8.9 1.0 3.5 2.3

Perylene 6.4 4.3 10 13 1.1 6.0 3.6

Indeno (1,2,3 - cd) Pyrene 0.72 0.52 2.1 5.8 0.42 2.0 1.7

Dibenzo (a,h) anthracene 0.39 0.28 1.0 3.2 0.21 1.1 1.0

Benzo (g,h,i) perylene 1.1 1.0 3.1 12 1.0 3.4 2.9

TOTAL PAHs (ng/g) 100 130 150 180 46 490 190

*Co-eluting with internal standard

Sample Name 2F 2G 2H 1A 1B 1C 1D 

Core D-50G D-50G D-50G D-50G D-50G D-50G D-50G

Depth (cm) 63-75 79-95 99-119 123-144 148-168 172-194 200-224

Date Range 1947-1937 1934-1921 1918-1902 1899-1882 1879-1862 1859-1842 1837-1817

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 1.2 1.1 1.2 0.35 0.21 0.40 1.8

1-Methyl Naphthalene 0.40 0.26 0.33 0.31 0.21 0.07 0.45

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.53 0.24 0.28 0.88 0.35 0.21 1.3

Acenaphthylene 6.0 4.4 4.6 7.8 8.1 1.7 4.7

Acenaphthene 4.3 1.7 2.1 5.1 2.8 1.7 2.0

Biphenyl nd nd nd nd nd nd nd

Fluorene 2.2 2.0 1.2 3.4 2.8 1.2 1.8

Phenanthrene 34 25 18 52 43 15 23

Anthracene 6.8 4.9 3.8 2.3 5.8 2.1 3.3

1-Methyl Phenanthrene nd nd nd nd nd nd nd

Fluoranthene 47 34 23 61 47 17 31

Pyrene 44 34 26 53 56 22 31

Benzo (a) Anthracene 2.6 1.7 1.9 2.9 3.3 1.9 4.4

Chrysene 2.8 1.7 2.0 3.0 2.6 2.0 5.3

Benzo (b) Fluoranthene 2.9 1.6 1.8 2.5 2.9 2.0 5.5

Benzo (k) Fluoranthene 3.6 2.3 2.8 3.5 3.8 2.4 7.8

Benzo (e) Pyrene 2.8 1.7 2.0 2.8 3.0 2.1 6.0

Benzo (a) Pyrene 2.3 1.2 1.6 1.7 2.3 1.8 4.4

Perylene 4.4 3.1 3.9 3.5 6.2 4.9 8.3

Indeno (1,2,3 - cd) Pyrene 1.0 0.56 0.59 1.2 1.5 1.0 2.6

Dibenzo (a,h) anthracene 0.56 0.29 0.38 0.75 0.86 0.63 1.5

Benzo (g,h,i) perylene 1.5 0.77 1.1 1.5 1.8 1.3 4.3

TOTAL PAHs (ng/g) 170 120 99 210 190 81 150

*Co-eluting with internal standard
7.28 

Sample Name 3A 3B 4D 4E 4F 4G 4H

Core D-50G D-50G D80 D80 D80 D80 D80

Depth (cm) 228-248 254-274 1-6 7-12 13-18 19-23 25-30

Date Range 1814-1798 1793-1777 1997-1992 1992-1990 1989-1987 1986-1984 1984-1981

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.76 1.9 1.5 1.6 1.0 6.7 10

1-Methyl Naphthalene 0.34 0.72 0.17 0.21 0.20 1.8 1.5

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.27 1.0 3.4 3.5 3.1 2.3 2.2

Acenaphthylene 2.0 3.0 8.7 9.8 14 22 44

Acenaphthene 3.3 4.2 8.8 8.2 8.2 8.1 10

Biphenyl nd nd nd nd nd nd nd

Fluorene 1.2 2.8 30 30 38 4.0 6.4

Phenanthrene 21 73 54 45 57 120 200

Anthracene 2.5 5.4 3.8 4.2 5.6 9.5 21

1-Methyl Phenanthrene nd nd 48 14 14 92 43

Fluoranthene 22 65 87 77 140 200 450

Pyrene 37 94 88 77 120 220 410

Benzo (a) Anthracene 1.7 1.5 4.8 4.6 3.9 3.7 2.4

Chrysene 0.82 0.49 4.6 4.8 5.0 4.4 3.2

Benzo (b) Fluoranthene 1.0 0.68 3.6 5.5 5.3 5.1 3.0

Benzo (k) Fluoranthene 1.5 1.0 3.8 3.5 4.0 5.8 3.5

Benzo (e) Pyrene 1.0 0.71 3.2 5.0 5.2 5.5 2.6

Benzo (a) Pyrene 0.82 0.55 1.8 2.6 2.4 2.5 1.3

Perylene 3.7 3.3 6.4 8.7 6.4 6.4 3.3

Indeno (1,2,3 - cd) Pyrene 0.38 0.29 1.0 1.9 1.8 1.7 1.0

Dibenzo (a,h) anthracene 0.25 0.14 0.55 1.0 0.84 0.95 0.60

Benzo (g,h,i) perylene 0.59 0.37 1.7 3.0 3.1 3.3 1.6

TOTAL PAHs (ng/g) 100 260 360 310 440 730 1200

*Co-eluting with internal standard

Sample Name 4I 4J 4K 2N1235-16 2N1235-12 2N1235-18 2N1235-36

Core D80 D80 D80 E30 E30 E30 E30

Depth (cm) 31-36 37-42 43-47 1-5 6-10 11-15 16-20

Date Range 1981-1979 1978-1976 1975-1974 1997-1993 1992-1988 1987-1982 1981-1977

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 12 12 13 0.13 0.24 0.16 0.05

1-Methyl Naphthalene 1.3 1.6 1.6 0.07 0.12 0.14 0.04

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 2.3 2.3 1.4 0.10 0.06 0.14 0.02

Acenaphthylene 41 17 16 0.06 0.05 0.12 0.02

Acenaphthene 3.8 3.7 3.6 0.12 0.29 0.20 0.06

Biphenyl nd nd nd nd nd nd nd

Fluorene 5.0 4.1 2.6 0.13 0.17 0.25 0.03

Phenanthrene 160 64 170 0.76 1.3 1.1 0.22

Anthracene 15 11 4.7 0.03 0.05 0.02 0.01

1-Methyl Phenanthrene 17 13 10 0.67 0.69 0.75 0.06

Fluoranthene 340 83 310 1.4 1.9 2.2 0.56

Pyrene 330 110 380 1.3 2.0 2.4 0.57

Benzo (a) Anthracene 2.2 2.3 2.0 1.5 2.1 2.5 0.78

Chrysene 2.8 2.1 2.2 1.8 2.1 2.6 0.93

Benzo (b) Fluoranthene 2.7 3.2 2.8 1.4 1.3 1.6 0.40

Benzo (k) Fluoranthene 3.7 3.4 3.4 1.5 1.6 2.0 0.35

Benzo (e) Pyrene 2.8 2.6 2.6 1.5 0.93 1.9 0.48

Benzo (a) Pyrene 1.6 1.3 1.3 0.68 0.78 1.6 0.29

Perylene 3.5 3.3 2.2 1.2 1.4 3.3 0.63

Indeno (1,2,3 - cd) Pyrene 1.3 1.4 0.92 0.63 0.80 0.93 0.45

Dibenzo (a,h) anthracene 0.66 0.53 0.46 nd 0.06 0.31 0.14

Benzo (g,h,i) perylene 2.0 1.9 1.8 1.5 0.88 2.0 0.46

TOTAL PAHs (ng/g) 950 340 930 16 19 26 6.5

*Co-eluting with internal standard
7.29 

Sample Name 2N1235-35 2N1235-08 2N1235-15 2N1235-01 2N1235-05 2N1235-22 2N1235-23

Core E30 E30 E30 E50 E50 E50 E50

Depth (cm) 21-25 26-30 31-35 1-5 6-10 11-15 16-20

Date Range 1976-1972 1971-1966 1965-1960 1997-1993 1992-1987 1986-1982 1980-1976

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.09 0.18 0.25 0.43 0.16 0.06 0.12

1-Methyl Naphthalene 0.05 0.16 0.17 0.19 0.11 0.06 0.07

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.02 0.09 0.09 0.17 0.08 0.07 0.06

Acenaphthylene 0.03 0.06 0.19 0.01 0.08 0.05 0.14

Acenaphthene 0.08 0.20 0.36 0.28 0.31 0.19 0.32

Biphenyl nd nd nd nd nd nd nd

Fluorene 0.02 0.17 0.22 0.30 0.33 0.07 0.11

Phenanthrene 0.15 0.76 1.7 2.4 1.6 0.52 0.71

Anthracene 0.02 0.03 0.04 0.15 0.09 0.01 0.02

1-Methyl Phenanthrene 0.25 0.44 1.2 1.1 1.1 0.26 0.56

Fluoranthene 0.84 0.82 2.1 2.6 2.7 0.66 1.5

Pyrene 0.75 1.0 3.4 2.3 2.6 0.58 1.5

Benzo (a) Anthracene 0.70 1.6 2.4 3.4 2.3 0.86 1.6

Chrysene 1.4 1.2 2.4 2.7 2.1 0.89 2.4

Benzo (b) Fluoranthene 0.35 0.72 1.8 2.5 1.4 0.49 1.1

Benzo (k) Fluoranthene 0.59 0.86 1.8 3.0 2.0 0.60 1.4

Benzo (e) Pyrene 0.72 0.65 1.1 2.8 1.6 0.50 1.2

Benzo (a) Pyrene 0.43 0.71 1.3 3.3 1.4 0.35 1.2

Perylene 0.72 1.5 1.9 3.6 2.2 0.71 1.7

Indeno (1,2,3 - cd) Pyrene 0.43 0.31 0.85 6.7 1.5 0.56 1.3

Dibenzo (a,h) anthracene nd 0.12 nd 5.5 0.56 0.65 0.51

Benzo (g,h,i) perylene 0.93 0.71 1.9 11 1.6 0.93 1.1

TOTAL PAHs (ng/g) 8.5 12 25 54 26 9.1 19

*Co-eluting with internal standard

Sample Name 2N1235-27 2N1235-02 2N1235-04 2N1235-06 2N1235-17 2N1235-28 2N1235-03

Core E50 E50 E50 E50 E50 E50 E50

Depth (cm) 21-25 26-30 31-35 36-40 41-45 46-50 51-54

Date Range 1975-1970 1969-1965 1964-1959 1958-1954 1953-1948 1947-1942 1941-1938

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.13 0.13 0.11 0.14 0.14 0.04 0.17

1-Methyl Naphthalene 0.08 0.09 0.09 0.25 0.10 0.03 0.12

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.08 0.06 0.07 0.06 0.08 0.04 0.08

Acenaphthylene 0.06 0.20 0.10 0.06 0.12 0.04 nd

Acenaphthene 0.27 0.31 0.30 0.12 0.11 0.07 0.22

Biphenyl nd nd nd nd nd nd nd

Fluorene 0.70 0.33 0.09 0.26 0.18 0.04 0.11

Phenanthrene 3.6 2.2 1.0 0.99 1.2 0.19 0.79

Anthracene 0.32 0.10 0.06 0.03 0.02 0.01 0.04

1-Methyl Phenanthrene 4.5 1.7 0.87 0.86 0.55 0.29 0.83

Fluoranthene 20 2.6 1.3 1.5 1.2 1.3 0.95

Pyrene 14 2.9 1.7 2.1 1.4 1.2 0.85

Benzo (a) Anthracene 12 2.7 1.5 2.3 1.4 0.87 1.0

Chrysene 15 2.8 1.9 1.6 1.9 1.8 1.2

Benzo (b) Fluoranthene 11 2.8 1.0 2.1 0.90 1.2 0.58

Benzo (k) Fluoranthene 13 3.1 1.2 1.3 1.0 0.94 0.78

Benzo (e) Pyrene 11 3.0 1.0 1.4 0.67 1.9 0.51

Benzo (a) Pyrene 11 3.2 1.0 1.6 0.56 1.2 0.67

Perylene 5.1 3.6 1.6 1.8 1.3 2.1 0.72

Indeno (1,2,3 - cd) Pyrene 7.0 3.2 0.83 1.2 0.47 1.5 0.61

Dibenzo (a,h) anthracene 2.6 2.0 0.50 0.64 0.07 0.66 0.50

Benzo (g,h,i) perylene 12 6.8 1.8 2.1 0.67 1.9 1.4

TOTAL PAHs (ng/g) 140 44 18 23 14 17 12

*Co-eluting with internal standard
7.30 

Sample Name 2N1235-26 2N1235-31 2N1235-24 2N1235-29 2N1235-10 2N1235-33 2N1235-32

Core E60 E60 E60 E60 E60 E60 E60

Depth (cm) 1-5 6-10 11-15 16-20 21-25 26-30 31-35

Date Range 1997-1991 1990-1984 1983-1977 1976-1970 1968-1963 1961-1956 1954-1948

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.10 0.14 0.12 0.10 0.17 0.08 0.11

1-Methyl Naphthalene 0.05 0.04 0.11 0.05 0.09 0.05 0.09

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.05 0.04 0.04 0.03 0.09 0.04 0.05

Acenaphthylene 0.06 0.02 0.04 0.04 0.05 0.07 0.04

Acenaphthene 0.14 0.06 0.23 0.07 0.18 0.12 0.14

Biphenyl nd nd nd nd nd nd nd

Fluorene 0.08 0.05 0.11 0.05 0.19 0.04 0.03

Phenanthrene 0.36 0.29 0.71 0.38 0.51 0.21 0.35

Anthracene 0.02 0.01 0.02 0.02 0.04 0.01 0.02

1-Methyl Phenanthrene 0.23 0.19 0.47 0.22 0.46 0.13 0.16

Fluoranthene 1.3 1.8 2.2 1.8 1.0 1.0 1.1

Pyrene 1.0 1.7 2.0 1.7 1.1 1.2 1.5

Benzo (a) Anthracene 0.66 1.0 1.4 1.6 1.4 0.78 0.74

Chrysene 1.4 1.3 1.9 1.4 1.7 1.1 1.4

Benzo (b) Fluoranthene 0.40 0.75 1.0 0.69 0.66 0.50 0.51

Benzo (k) Fluoranthene 0.54 0.86 1.2 0.92 0.77 0.57 0.69

Benzo (e) Pyrene 0.76 0.68 1.1 0.80 0.80 0.62 0.72

Benzo (a) Pyrene 0.49 0.46 1.0 0.43 0.62 0.41 0.59

Perylene 0.72 0.57 1.1 0.73 0.94 0.69 0.63

Indeno (1,2,3 - cd) Pyrene 0.55 0.47 0.86 0.93 0.39 0.47 0.42

Dibenzo (a,h) anthracene 0.16 0.05 0.53 nd 0.33 0.06 0.09

Benzo (g,h,i) perylene 0.60 0.65 1.4 1.4 0.39 0.66 0.83

TOTAL PAHs (ng/g) 9.6 11 18 13 12 8.8 10

*Co-eluting with internal standard

Sample Name 2N1235-34 2N1235-30 2N1235-07 2N1235-13 2N1235-20 2N1235-25 2N1235-09

Core E60 E60 E60 F35 F35 F35 F35

Depth (cm) 36-40 41-45 46-47 1-5 6-10 11-15 16-20

Date Range 1947-1941 1940-1934 1933-1931 1997-1992 1990-1985 1983-1978 1976-1971

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.08 0.06 0.59 0.26 0.11 0.05 0.17

1-Methyl Naphthalene 0.05 0.03 0.39 0.10 0.17 0.03 0.13

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.03 0.04 0.26 0.06 0.07 0.07 0.06

Acenaphthylene 0.04 0.03 0.18 0.09 0.08 0.03 0.07

Acenaphthene 0.15 0.11 1.0 0.44 0.20 0.19 0.18

Biphenyl nd nd nd nd nd nd nd

Fluorene 0.03 0.05 0.58 0.30 0.14 0.05 0.25

Phenanthrene 0.20 0.29 2.4 1.0 0.50 0.33 0.95

Anthracene 0.01 0.02 0.07 0.04 0.01 0.02 0.05

1-Methyl Phenanthrene 0.07 0.19 1.7 0.91 0.34 0.19 0.84

Fluoranthene 0.44 0.49 1.9 1.8 0.88 0.64 1.3

Pyrene 0.50 0.61 2.1 1.8 0.87 0.72 1.7

Benzo (a) Anthracene 0.79 0.81 2.9 2.8 1.4 0.82 2.4

Chrysene 0.81 0.77 3.8 1.5 1.4 0.79 2.0

Benzo (b) Fluoranthene 0.28 0.26 1.5 1.2 1.0 0.29 2.5

Benzo (k) Fluoranthene 0.31 0.35 1.5 1.5 0.93 0.50 2.4

Benzo (e) Pyrene 0.28 0.36 1.6 1.3 1.1 0.33 3.8

Benzo (a) Pyrene 0.25 0.23 1.2 1.1 1.2 0.24 5.2

Perylene 0.40 1.0 1.7 2.6 1.6 0.27 4.4

Indeno (1,2,3 - cd) Pyrene 0.38 0.25 1.2 0.72 3.1 0.40 1.4

Dibenzo (a,h) anthracene 0.05 0.09 nd 0.08 2.5 0.46 1.7

Benzo (g,h,i) perylene 0.39 0.08 1.5 1.3 5.4 0.58 3.8

TOTAL PAHs (ng/g) 5.5 6.1 28 21 23 7.0 35

*Co-eluting with internal standard
7.31 

Sample Name 2N1235-21 2N1235-19 2N1235-11 2N1235-14 3H 3I 3J

Core F35 F35 F35 F35 G40 G40 G40

Depth (cm) 21-25 26-30 31-35 36-39 1-6 7-12 13-17

Date Range 1970-1964 1963-1957 1956-1950 1949-1945 1989-1939 1931-1889 1881-1847

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.08 0.14 0.23 0.16 2.2 0.92 0.85

1-Methyl Naphthalene 0.07 0.08 0.08 0.09 0.93 0.15 0.28

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.07 0.09 0.08 0.08 1.2 0.44 0.28

Acenaphthylene 0.07 0.08 0.04 0.05 17 6.0 1.5

Acenaphthene 0.24 0.38 0.54 0.20 13 8.0 1.1

Biphenyl nd nd nd nd nd nd nd

Fluorene 0.09 0.08 0.14 0.16 3.2 2.1 0.69

Phenanthrene 0.57 0.41 0.51 0.61 109 43 7.1

Anthracene 0.04 0.02 0.03 0.02 2.5 1.3 0.85

1-Methyl Phenanthrene 0.44 0.29 0.15 0.56 35 18 15

Fluoranthene 0.91 0.51 0.43 0.57 139 72 8.3

Pyrene 1.3 0.65 0.44 0.67 166 70 10

Benzo (a) Anthracene 1.3 1.8 0.86 0.92 2.5 1.7 0.88

Chrysene 1.4 1.6 1.1 1.2 1.9 1.0 0.72

Benzo (b) Fluoranthene 1.0 1.6 0.16 0.26 1.3 1.2 0.64

Benzo (k) Fluoranthene 1.2 1.7 0.26 0.53 1.5 0.91 0.91

Benzo (e) Pyrene 1.0 2.4 0.20 0.47 1.2 0.92 0.67

Benzo (a) Pyrene 0.75 1.5 0.22 0.24 0.68 0.49 0.34

Perylene 2.2 2.0 0.70 0.43 9.5 7.4 29

Indeno (1,2,3 - cd) Pyrene 0.69 15 0.22 0.18 0.39 0.29 0.26

Dibenzo (a,h) anthracene 0.90 13 nd 0.07 0.18 0.16 0.19

Benzo (g,h,i) perylene 1.7 24 0.36 0.26 0.63 0.50 0.53

TOTAL PAHs (ng/g) 16 67 6.7 7.7 510 240 80

*Co-eluting with internal standard

Sample Name 3K 4L 4M 4N 3C 3D 3E

Core G40 G50 G50 G50 SWI3 SWI3 SWI3

Depth (cm) 18-22 1-5 6-10 11-14 1-6 7-12 13-17

Date Range 1839-1806 1989-1956 1949-1922 1916-1896 1999-1986 1984-1971 1969-1959

Name Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g) Conc (ng/g)

Naphthalene nd nd nd nd nd nd nd

2-Methyl Naphthalene 0.60 7.3 6.9 5.4 3.3 2.6 1.9

1-Methyl Naphthalene 0.22 1.6 1.5 1.3 0.91 0.73 0.74

2,3,5-Trimethyl Naphthalene* -- -- -- -- -- -- --

2,6-Dimethyl Naphthalene 0.37 0.77 0.60 0.54 1.3 1.3 1.6

Acenaphthylene 0.49 2.0 2.1 2.1 3.6 4.4 5.9

Acenaphthene 0.67 3.7 3.8 3.8 7.8 14 10

Biphenyl nd nd nd nd nd nd nd

Fluorene 0.80 2.6 2.4 2.4 5.0 5.1 5.6

Phenanthrene 8.3 32 21 18 25 28 48

Anthracene 0.60 3.2 2.6 2.0 2.3 2.4 2.9

1-Methyl Phenanthrene 13 0.00 0.00 0.00 29 32 35

Fluoranthene 7.6 35 20 15 28 36 50

Pyrene 10 44 25 19 48 40 51

Benzo (a) Anthracene 0.47 0.47 0.37 0.23 2.3 1.9 2.8

Chrysene 0.68 0.60 0.50 0.36 1.3 0.31 0.71

Benzo (b) Fluoranthene 0.51 0.42 0.33 0.21 2.6 0.64 1.2

Benzo (k) Fluoranthene 0.36 0.50 0.42 0.29 3.2 0.43 1.4

Benzo (e) Pyrene 0.32 0.33 0.36 0.30 2.2 0.46 0.74

Benzo (a) Pyrene 0.08 0.28 0.20 0.17 2.3 0.42 0.92

Perylene 28 8.0 9.2 16 2.3 2.4 3.9

Indeno (1,2,3 - cd) Pyrene 0.13 0.13 0.17 0.07 1.1 0.17 0.43

Dibenzo (a,h) anthracene 0.06 0.08 0.00 0.07 0.62 0.09 0.26

Benzo (g,h,i) perylene 0.20 0.25 0.25 0.19 1.3 0.25 0.60

TOTAL PAHs (ng/g) 73 140 98 87 170 170 230

*Co-eluting with internal standard
7.32 

Sample Name 3F 3G

Core SW I3 SW I3

Depth (cm) 18-22 23-27

Date Range 1956-1946 1944-1934

Name Conc (ng/g) Conc (ng/g)

Naphthalene nd nd

2-Methyl Naphthalene 1.7 1.9

1-Methyl Naphthalene 0.86 0.79

2,3,5-Trim ethyl Naphthalene* -- --

2,6-Dim ethyl Naphthalene 1.1 1.6

Acenaphthylene 2.6 1.0

Acenaphthene 3.1 8.0

Biphenyl nd nd

Fluorene 2.5 2.8

Phenanthrene 31 25

Anthracene 1.8 1.5

1-Methyl Phenanthrene 30 14

Fluoranthene 26 12

Pyrene 25 11

Benzo (a) Anthracene 1.9 0.81

Chrysene 1.3 0.72

Benzo (b) Fluoranthene 0.76 0.41

Benzo (k) Fluoranthene 0.92 0.35

Benzo (e) Pyrene 0.42 0.20

Benzo (a) Pyrene 0.44 0.23

Perylene 3.5 2.3

Indeno (1,2,3 - cd) Pyrene 0.25 0.14

Dibenzo (a,h) anthracene 0.22 0.08

Benzo (g,h,i) perylene 0.40 0.25

TOTAL PAHs (ng/g) 130 85

*Co-eluting with internal standard
APPENDIX F

Total PAH Histograms by Decade
7.35 

TOTAL PAH's, 1990's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc. (ng/g)

TOTAL PAH's, 1980's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1970's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
7.36 

TOTAL PAH's, 1960's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1950's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1940's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
7.37 

TOTAL PAH's, 1930's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1920's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1900's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
7.38 

TOTAL PAH's, 1890's 

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1870's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1860's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
7.39 

TOTAL PAH's, 1850's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1820's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)

TOTAL PAH's, 1800's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
7.40 

TOTAL PAH's, 1780's

0

500

1000

1500

2000

2500

3000

3500

C10 D50G D80 E30 E50 E60 F35 G40 G50 SWI3

Core

Conc (ng/g)
APPENDIX G

Total PAH vs. Estimated Total Hopane Concentrations by Core and Date
7.43 

CORE C10

0

20

40

60

80

100

120

140

1989-

1984

1978-

1974

Conc (ng/g)

TOTAL PAHs EST. HOPANES

CORE D50G

0

50

100

150

200

250

300

350

400

450

500

1997-19881987-19791977-19691967-19591958-19491947-19371934-19211918-19021899-18821879-18621859-18421837-18171814-17981793-1777

Conc (ng/g)

TOTAL PAHs EST. HOPANES

CORE D80 

0

200

400

600

800

1000

1200

1400

1997-

1992

1992-

1990

1989-

1987

1986-

1984

1984-

1981

1981-

1979

1978-

1976

1975-

1974

Conc (ng/g)

TOTAL PAHs EST. HOPANES
7.44 

CORE E30

0

50

100

150

200

250

300

350

400

450

500

550

600

1997-

1993

1992-

1988

1987-

1982

1981-

1977

1976-

1972

1971-

1966

1965-

1960

Conc (ng/g)

TOTAL PAHs EST. HOPANES

CORE E50

0

100

200

300

400

500

600

700

800

900

1997-

1993

1992-

1987

1986-

1982

1980-

1976

1975-

1970

1969-

1965

1964-

1959

1958-

1954

1953-

1948

1947-

1942

1941-

1938

Conc (ng/g)

TOTAL PAHs EST. HOPANES

CORE E60

0

200

400

600

800

1000

1200

1997-

1991

1990-

1984

1983-

1977

1976-

1970

1968-

1963

1961-

1956

1954-

1948

1947-

1941

1940-

1934

1933-

1931

Conc (ng/g)

TOTAL PAHs EST. HOPANES
7.45 

CORE F35

0

100

200

300

400

500

600

1997-

1992

1990-

1985

1983-

1978

1976-

1971

1970-

1964

1963-

1957

1956-

1950

1949-

1945

Conc (ng/g)

TOTAL PAHs EST. HOPANES

CORE G40

0

100

200

300

400

500

600

1989-

1939

1931-

1889

1881-

1847

1839-

1806

Conc (ng/g)

TOTAL PAHs EST. HOPANES

CORE SWI3

0

50

100

150

200

250

1999-

1986

1984-

1971

1969-

1959

1956-

1946

1944-

1934

Conc (ng/g)

TOTAL PAHs EST. HOPANES

*Analysis not performed on CORE G50 due to only two data points 
The Department of the Interior Mission

As the Nation's principal conservation agency, the Department of the Interior has responsibility 

for most of our nationally owned public lands and natural resources. This includes fostering 

sound use of our land and water resources; protecting our fish, wildlife, and biological diversity; 

preserving the environmental and cultural values of our national parks and historical places; 

and providing for the enjoyment of life through outdoor recreation. The Department assesses 

our energy and mineral resources and works to ensure that their development is in the best 

interests of all our people by encouraging stewardship and citizen participation in their care. 

The Department also has a major responsibility for American Indian reservation communities 

and for people who live in island territories under U.S. administration. 

The Minerals Management Service Mission 

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS) 

primary responsibilities are to manage the mineral resources located on the Nation's Outer 

Continental Shelf (OCS), collect revenue from the Federal OCS and onshore Federal and Indian 

lands, and distribute those revenues. 

Moreover, in working to meet its responsibilities, the Offshore Minerals Management Program 

administers the OCS competitive leasing program and oversees the safe and environmentally 

sound exploration and production of our Nation's offshore natural gas, oil and other mineral 

resources. The MMS Minerals Revenue Management meets its responsibilities by ensuring the 

efficient, timely and accurate collection and disbursement of revenue from mineral leasing and 

production due to Indian tribes and allottees, States and the U.S. Treasury. 

The MMS strives to fulfill its responsibilities through the general guiding principles of: (1) being 

responsive to the public's concerns and interests by maintaining a dialogue with all potentially 

affected parties and (2) carrying out its programs with an emphasis on working to enhance the 

quality of life for all Americans by lending MMS assistance and expertise to economic 

development and environmental protection.