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STUDY TITLE: Stability and Change in Gulf of Mexico Chemosynthetic Communities 

REPORT TITLE: Stability and Change in Gulf of Mexico Chemosynthetic Communities, 

Volume I: Executive Summary and Volume II: Final Report 

CONTRACT NUMBER: 14-35-0001-30813 

SPONSORING OCS REGION: Gulf of Mexico OCS Region 

APPLICABLE PLANNING AREA: Central Gulf of Mexico 

FISCAL YEARS OF PROJECT FUNDING: 1997-2002 

COMPLETION DATE OF REPORT: August 2002

COSTS: FY 1997: $664,500 FY 1998: $668,900 FY 1999: $564,000 FY 2000-2002: 

640,700 

CUMULATIVE PROJECT COST: $2,538,100 

PROJECT MANAGER: Ian R. MacDonald 

AFFILIATION: Texas A&M University 

ADDRESS: Geochemical and Environmental Research Group, 727 Graham Rd., 

College Station, TX 77845 

PRINCIPAL INVESTIGATORS: Robert Carney, Charles F. Fisher, Norman Guinasso, 

Samantha Joye, Mahlon C. Kennicutt II, Ian R. MacDonald, Paul A. Montagna, John W. 

Morse, Douglas C. Nelson, Eric Powell, William Sager, Roger Sassen, Stephen 

Schaeffer, and Gary Wolf 

KEYWORDS: Chemosynthetic fauna, seep, continental slope, geochemistry, 

biogeochemistry, molecular ecology, age and growth, Lamellibrachia, Bathymodiolus, 

Beggiatoa, parasitology, marine GIS

BACKGROUND: The program was fundamentally concerned with the effect that 

development of offshore energy reserves might have upon dense assemblages of deepsea organisms, particularly chemosynthetic tubeworms, mussels, and clams, as well as 

fish and crustaceans, which live in association with them. Hydrocarbons from 

commercial oil and gas reserves escape into the sea bottom at natural seeps found 

commonly across the Gulf of Mexico’s northern continental slope. Chemosynthetic 

animals utilize chemical energy from hydrocarbons to maintain colonies that have 

unusually high biomass compared with the sea bottom elsewhere. Chemosynthetic 

communities at hydrocarbon seeps were discovered in 1984 and have been previously 
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investigated in studies funded by MMS. However, more knowledge was needed about 

the life history and ecology of chemosynthetic communities in the Gulf of Mexico. 

OBJECTIVES: The objectives of this project were as follows: Review biotic and abiotic 

features of existing conceptual models of chemosynthetic communities which explain 

observed patterns of distribution and abundance, in order to develop an effective, 

refined plan for continued research. Further evaluate the physical-chemical factors (e.g., 

depth, temperature, water chemistry, sediment types, and dissolved gasses) which 

influence, limit, enhance, or control the distribution, abundance, and growth of 

chemosynthetic communities. Further investigate the sources (e.g., deep versus 

shallow or petrogenic versus biogenic) of any necessary dissolved gasses and the 

likelihood that petroleum production may ultimately deprive the animals of an energy 

source. Further determine if chemosynthetic communities are robust or fragile, and 

whether they are essentially permanent or ephemeral; characterize age, growth rate, 

turnover rates, reproduction and recruitment, and patterns of senescence and death in 

the dominant chemosynthetic animals; further examine recovery rates of communities 

damaged by physical disturbance. Further determine the reliability of methods for 

detecting chemosynthetic communities using remote acoustic and/or geophysical 

devices, imaging instrumentation, hydrocarbon measurements, and/or other available 

technologies. 

DESCRIPTION: A highly integrated program of sample collection and site description 

was conducted during two cruises with the submersible Johnson Sea Link. All 

collections and stations were carefully documented with video and still photography and 

an exhaustive and carefully controlled list of collection, stations, and observations was 

made to ensure accurate sample identification and tracking. Principal sampling methods 

included sediment collection, water and gas collection, animal collections and 

manipulations, and photographic documentation. Additional sampling was conducted 

from other surface ships and from the Navy submarine NR-1. Analysis and reporting on 

samples was carried out in laboratories at Texas A&M University and five other 

institutions. 

SIGNIFICANT CONCLUSIONS: At four representative study areas, tube worms 

(Lamellibrachia c.f. barhami) and mussels (Bathymodiolus childressi) and bacteria 

(Beggiatoa) were found to derive their food supply from the organic enrichment at the 

sea bottom caused by the oil and gas. Seawater sulfate in sediment pore fluids is 

chemically reduced to hydrogen sulfide at exceptionally high rates. The chemosynthetic 

organisms in turn support an abundant food chain of associated fish, crustaceans, and 

other invertebrates. Water circulation provides the mechanism by which larvae can be 

transported across the slope. Genetic fingerprinting of the fauna confirmed that gene 

pool of the chemosynthetic species is well mixed. Distinctive geological and 

geophysical signatures indicate active oil and gas seepage and presence of shallow 

deposits of gas hydrates. Tubeworm longevity appears to exceed 200 years for the 

larger specimens. Mussels, also comparatively long-lived, showed differing levels of 

health among the study sites, partly because of parasitic infestations. Distribution of 

sessile animals at the seeps is highly patchy, probably due to multiple settlement events 
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of transient vents. Communities require many generations to develop their present 

form. Chemosynthetic communities in the northern Gulf of Mexico appear to be locally 

fragile, but regionally robust. 

STUDY RESULTS: Samples were collected and analyzed from four chemosynthetic 

communities located at water depths from 550 to 620 m in the central Gulf of Mexico. 

Side scan sonar images and other geophysical products were examined to determine 

the characteristic signature of chemosynthetic communities. Individual tube worms and 

mussels were marked and released to determine age and growth characteristics. 

Stable isotopes were used to examine trophic interactions between chemosynthetic 

animals and heterotrophic fauna. Geochemical characteristics and processes of 

inorganic and organic components of the surface sediments were detailed. Parasites of 

mussels were identified. Molecular techniques were used to examine the degree of 

isolation among separate chemosynthetic communities. 

STUDY PRODUCTS: MacDonald, I.R., ed. 2002. Stability and Change in Gulf of 

Mexico Chemosynthetic Communities. Volume I: Executive Summary and Volume II: 

Technical Report. Prepared by the Geochemical and Environmental Research Group, 

Texas A&M University. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of 

Mexico OCS Region, New Orleans, LA. OCS Study MMS 2002-035 and 036 483 pp. 

The following peer-reviewed publications (published or in press) were written by 

principal investigators and their students or collaborators based on collections and 

analyses performed under the auspices of this program: 

Bergquist, D. C., F. M. Williams, and C. R. Fisher. 2000. Longevity record for deep-sea 

invertebrate. Nature 403: 499-500. 

Callender W. R. and Powell, E. N. 1999. Why did ancient chemosynthetic seep 

and vent assemblages occur in shallower water than they do today? Intl. Jnl. of Earth 

Sci. 88 (3): 377-391. 

Callender R, Powell E.N. 2000. Long-term history of chemoautotrophic clamdominated faunas of petroleum seeps in the northwestern Gulf of Mexico. FACIES. 43: 

177-204. 

Fisher, C. R., I. R. MacDonald, R. Sassen, C. M. Young, S. Macko, S. Hourdez, R. 

Carney, S. Joy, and E. McMullin. 2000. Methane ice worms: Hesiocaeca methanicola

colonizing fossil fuel reserves. Naturwissenschaften 87 (4): 184-187. 

Freytag, J.K., Girguis, P.R., Bergquist, D.C., Andras, J.P., Childress, J.J., Fisher, C.R. 

2001. A paradox resolved: Sulfide acquisition by roots of seep tubeworms sustains net 

chemoautotrophy. PNAS. 98(23): 13408-13413. 
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Gardiner, S.L., McMullin, E., Fisher, C.R. 2001. Seepiophila jonesi, a new genus and 

species of vestimentiferan tube worm (Annelida : Pogonophora) from hydrocarbon seep 

communities in the Gulf of Mexico. Proc. of the Biol. Soc. of Wash. 114(3): 694-707. 

Hourdez, S., L. A. Frederick, A. Schernecke, and C. R. Fisher. 2001. Functional 

respiratory anatomy of a deep sea orbiniid polychaete from the Brine Pool NR-1 in the 

Gulf of Mexico. Invertebrate Biology. 120(1): 29-40. 

Julian, D., F. Gaill, E. Wood, A. J. Arp, and C. R. Fisher. 1999. Roots as a site of 

hydrogen sulfide uptake in the hydrocarbon seep vestimentiferan Lamellibrachia sp. J. 

Exp. Biol. 202; 2245-2257. 

Lanoil BD, Sassen R, La Duc MT, Sweet ST, Nealson KH. 2001. Bacteria and Archaea 

physically associated with Gulf of Mexico gas hydrates. Applied and Env. Microbiol. 67 

(11): 5143-5153. 

Macavoy, S.E., Carney, R.S., Fisher, C.R., and Macko, S.A. 2002. Use of 

chemosynthetic biomass by large, mobile, benthic predators in the Gulf of Mexico. Mar. 

Ecol. Prog. Ser. 225: 65-78. 

MacDonald, I.R. 1998. Habitat formation at Gulf of Mexico hydrocarbon seeps. Cahiers 

de Biologie Marine. 39 (3-4): 337-340. 

MacDonald, I. R., D. Buthman, W. W. Sager, M. B. Peccini, and N. L. Guinasso Jr. 

2000. Pulsed flow of hydrocarbons from a mud volcano. Geology. 28(10): 907-910. 

McMullin, E., D. C. Bergquist, and C. R. Fisher. 2000. X-metazoans: Real animals in 

extreme environments. Space Biol. Bull. 13: 1-12. 

Nelson, K. and C. R. Fisher. 2000. Absence of cospeciation in deep-sea 

vestimentiferan tubeworms and their bacterial endosymbionts. Symbiosis. 28(1): 1-15. 

Powell, E.N., R.D. Barber, M.C. Kennicutt, and S.E. Ford. 1999. Influence of parasitism 

in controlling the health, reproduction and PAH body burden of petroleum seep 

mussels. Deep Sea Research. 46. 2053-2078. 

Pruski, A. M., A. Fiala-Médioni, C. R. Fisher, and J. C. Colomines. 2000. Free amino 

compound composition of symbiotic invertebrates from the Gulf of Mexico hydrocarbon 

seeps. Mar. Biol . 136: 411-420. 

Sager, W. W., C. S. Lee, I. R. Macdonald, and W. W. Schroeder. 1999. High-frequency 

near-bottom acoustic reflection signatures of hydrocarbon seeps on the northern Gulf of 

Mexico continental slope. Geo Marine Letters. 18 (4). 267-276. 

Sager, W. W., I. R. MacDonald, W. R. Bryant, R. L. Carlson, and D. B. Prior, TAMU2 

digital side-scan sonar survey of Louisiana Slope areas containing active oil seeps and 
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halokinetic sediment modification, paper 8595, Proceedings of the 1998 Offshore 

Technology Conference, Houston, 4-7 May 1998, 57-69, 1998. 

Sager, W. W., M. C. Kennicutt II and Gas Hydrate Science Team, Proposal to the 

Ocean Drilling Program for Drilling Gas Hydrate in the Gulf of Mexico, paper 12111, 

Proceedings of the 2000 Offshore Technology Conference, Houston, 1-4 May 2000. 

Sassen R, Sweet ST, Milkov AV, DeFreitas DA, Kennicutt MC. 2001. Thermogenic 

vent gas and gas hydrate in the Gulf of Mexico slope: Is gas hydrate decomposition 

significant? Geology. 29(2): 107-110. 

Scott, K. M., M. Bright, and C. R. Fisher. 1998. The burden of independence: Inorganic 

carbon utilization strategies of the sulfur chemoautotrophic hydrothermal vent isolate 

Thiomicrospira crunogena and the symbionts of hydrothermal vent and cold seep 

vestimentiferans. Cah. Biol. Mar. 39: 379-382. 

Smith, E. B., K. M. Scott, E. R. Nix, C. Korte, and C. R. Fisher. 2000. Growth and 

condition of seep mussels at a Gulf of Mexico Brine Pool. Ecology 81:2392-2403. 

Urcuyo, I.A., Massoth, G.J., MacDonald, I. R., Fisher, C.R. 1998. In situ growth of the 

vestimentiferan Ridgeia piscesae living in highly diffuse flow environments in the main 

Endeavour Segment of the Juan de Fuca Ridge. Cahiers De Biologie Marine 39(3-

4):267-270.