ACCESS NUMBER: 39187 

STUDY TITLE: Investigations of Chemosynthetic Communities on the Lower 

Continental Slope of the Gulf of Mexico 

REPORT TITLE: Investigations of Chemosynthetic Communities on the Lower 

Continental Slope of the Gulf of Mexico, Interim Report 

CONTRACT NUMBER: 1435-01-05-39187 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA: Central 

FISCAL YEARS OF PROJECT FUNDING: 2005; 2006; 2007; 2008, 2009 

COMPLETION DATE OF REPORT: June 2008 

COSTS: FY 2005 - $842,977; FY2006 - $798,028 

PROJECT MANAGER: James M. Brooks, Ph.D. 

AFFILIATION: TDI-Brooks International Inc. 

ADDRESS: 1902 Pinon Dr, College Station, TX 77845 

PRINCIPAL INVESTIGATOR(S)*

: Brooks, J. M.1, C. Fisher2, H. Roberts3, B. Bernard1, 

I. McDonald4, R. Carney3, S.Joye5, E.Cordes6, G. Wolff1, L. Gehring2 (

1 TDI-Brooks 

International Inc, 2

 The Pennsylvania State University, 3 Louisiana State University, 4

Texas A&M University – Corpus Christi, 5 The University of Georgia, 6 Harvard 

University) 

KEY WORDS: Gulf of Mexico, chemosynthetic communities, habitat, AUV, ROV, 

submersible, biology, photography, tubeworms, mussels, bacterial mats, education, 

population dynamics, food web, life histories, biodiversity and biogeography 

BACKGROUND: The largest oil reserves in the continental United States are found in 

the Gulf of Mexico. The Mineral Management Service (MMS) is responsible for 

overseeing the responsible extraction of these natural resources. By the early 1980s, 

energy companies had developed the technology to explore and extract oil and gas in 

waters up to 1,000 m deep and have continued to develop the technology to extract oil 

and gas from deeper water and now have the capability to drill oil wells in all water 

depths in the GOM Outer Continental Slope. 

During the mid to late 1980s, MMS contracted with the Geochemical and Environmental 

Research Group (GERG) at Texas A&M University (TAMU) to collect animals from 

areas of the deep sea floor associated with active oil and gas seeps. Bush Hill, a site 

that became one of the best studied seep sites in the world, was populated with giant 

tubeworms and mussels, which had only recently been discovered at deep-sea 

hydrothermal vents in the Pacific Ocean. Since that time similar (but different) cold-
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seep and hydrothermal-vent communities have been discovered in many different 

geological settings in the world’s oceans. 

Over the last 20 years these animals and communities have been studied at moderate 

depths in the Gulf of Mexico (GOM), along with the geology, geochemistry, and 

microbiology that allows them to flourish. The hydrocarbon seep communities in less 

than 1,000 m on the Upper Louisiana Slope of the Gulf of Mexico are the most 

intensively studied and most understood of any deep-sea cold-seep communities in the 

world. The basic biology of the dominant animals, their life histories, and the 

biodiversity and biogeography of the seep and coral communities on the Upper 

Louisiana Slope is now understood. The successional processes that lead to the 

eventual development of coral communities on carbonates created during periods of 

active hydrocarbon seepage is understood. Also discovered are new communities, 

such as the ice worms that inhabit methane ice and the mussels that ring the Brine Pool 

NR-1. 

Although several GOM hydrocarbon seep sites at depths greater than 1,000 m have 

been visited by scientists, only a single site has been the focus of more than a few 

exploratory dives. This site, at 2,200 m in Alaminos Canyon, has lush communities of 

tubeworms and mussels that are reminiscent of the shallower sites that are well known. 

However, the underlying geology and almost all of the species present are different. 

Preliminary studies indicate that the structure of the communities associated with the 

tubeworms and mussels is also quite different. The normal “background” fauna are 

different at this depth, and different patterns of interaction between these animals and 

the seep specific animals are expected. 

OBJECTIVES: The primary purpose of this research is to discover and characterize 

the sea floor communities that live in association with hydrocarbon seepage and on 

hard ground in the deep Gulf of Mexico. The sites studied are in areas energy 

companies will soon drill for oil and gas. Advances in understanding and knowledge of 

the ecology of this deep community and the types of communities that exist at depths 

between 1,000 and 2,200 m are the goals of this contract. 

DESCRIPTION: Preparation for this program began in the fall of 2005, when Harry 

Roberts began to study a variety of types of information that would help discover new 

hydrocarbon seep and hard-ground communities in the deep Gulf of Mexico. 

Information was gathered from thousands of cores collected by the TDI-Brooks 

International, Inc. group, satellite images of persistent oil slicks on the surface of the 

Gulf, and extensive collections of geophysical data and maps of the sea floor that were 

made available for this project by the Mineral Management Service. Fourteen sites 

were identified with a high potential to host lush chemosynthetic and/or deep-water 

coral communities. 

In March of 2006, the first cruise of this program, the Reconnaissance Cruise (RC), 

began on the RV GYRE. Thousands of pictures of the sea floor were taken at locations 

identified by Roberts and his team. These pictures provided the first look at the dive 

sites we were to dive on for the ALVIN mission. Some sites revealed little except a 
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muddy sea floor. At most of the sites there was strong evidence of seepage, and at 

least scattered occurrence of the types of animals expected at seep sites. In one case 

there were abundant soft corals, and at a few, there were large communities of seep 

animals. 

Based on the Reconnaissance Cruise Report, the images of the sea floor, previous 

knowledge of the geophysics and geochemistry of the sites, and a desire to explore 

over a wide depth and geographic range, the cruise and dives on the RV 

ATLANTIS/ALVIN for the Deep Chemosynthetic Community Characterization (DCCC) 

expedition were planned and completed in May 2006. 

SIGNIFICANT CONCLUSIONS:

Reconnaissance Cruise – 

• Trawls were completed at three sites, MC685, MC548 and AT209. Two box 

cores were collected at site WR265. 

• The number of survey photos captured with the bottom in view (BIV) was 10,922. 

• Site characterization and evaluation was completed on 24 sites. 

DCCC Cruise – 

• Multiple dives were made at four sites and the geology, geochemistry, 

microbiology and biology of the sites thoroughly characterized. 

• Longer-term studies were established at these sites to determine growth rates of 

some of the animals, monitor for visitation by mobile deep-sea fauna such as 

larger fishes and crabs, and follow the fine scale changes in seepage patterns 

and community composition (Figure 1). 

• A camera dedicated to taking down-looking pictures was used to construct 

mosaics of any new animal communities discovered. 

• Push cores were collected for geological, geochemical, and microbial analyses 

and for the study of some of the tiny animals that may live between the sand 

grains at the deep seep sites. 

• A chemical analyzer was used to characterize new habitats. 

• Collections for study of the larger animals that live at the sites was begun. 

• Communities with full mosaics were revisited and chemical analyzers used to 

characterize the chemistry in and around individual animals identified in the 

images. 

• Quantitative collections of other tubeworm communities, mussel beds, and clam 

beds were made using specialized collection tools built specifically for this task. 

• Ten nighttime trawls were completed. 

• Traps and cameras were used to capture and identify the visitors to the seep and 

coral communities being studied to aid in characterizing the more mobile fauna 

around the sites. 

• A rotary camera, left on the bottom for up to a year, is housed in a special glass 

tube and periodically “wakes up” to take 12 consecutive pictures as it rotates on 

a turntable. 
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• More than 14,000 down-camera and 400 macro images were recorded. 

• Acoustic Doppler Current Profilers (ADCP) were operated on station and with the 

ship underway to obtain an integrated picture of current direction and velocity in 

the upper 1,000 m of the water column. 

Autonomous Underwater Vehicle (AUV) 

Sites AT340, GC852, WR269, and AC601 were mapped in great detail using the C&C 

Technologies Autonomous Underwater Vehicle (AUV) in February 2007. The AUV is 

equipped with instrumentation for collecting high-resolution multibeam bathymetry, chirp 

sonar sub-bottom profiles, and side-scan sonar swaths. These data are well constrained 

with excellent navigation and the data sets are acquired as the AUV travels at a 

constant height, 40 m, above the seabed. The data sets were used during the 2007 

cruise. 

STUDY PRODUCTS: TDI-Brooks International Inc. 2008. Investigations of 

chemosynthetic communities on the lower continental slope of the Gulf of Mexico: 

Interim report for the U.S. Dept. of the Interior, Minerals Management Service Gulf of 

Mexico OCS Region, Metairie, LA. OCS Study MMS 2008-009. Contract No. 1435-01-

05-39187. 332 pp. 

Erik E. Cordes, Susan L. Carney, Stephane Hourdez, Robert S. Carney, James M. 

Brooks, Charles R. Fisher 2007. Deep-Sea Research I 54 (2007) 637–653. Cold seeps 

of the deep Gulf of Mexico: Community structure and biogeographic comparisons to 

Atlantic equatorial belt seep communities. 

TDI-Brooks International Inc. 2006. Investigations of Chemosynthetic Communities on 

the Lower Continental Slope of the Gulf of Mexico. Reconnaissance Cruise Report for 

the U.S. Department of the Interior, Minerals Management Service Gulf of Mexico OCS 

Region, Metairie, LA. Contract No. 1435-01-05-39187. 58 pp. 

TDI-Brooks International Inc. 2006. Investigations of Chemosynthetic Communities on 

the Lower Continental Slope of the Gulf of Mexico. Deep Chemosynthetic Community 

Characterization Cruise Report for the U.S. Department of the Interior, Minerals 

Management Service Gulf of Mexico OCS Region, Metairie, LA. Contract No. 1435-01-

05-39187. 225 pp. 

 
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*

 P.I.’s affiliation may be different from that listed for Project Managers. 

Chemosynthetic Sites visited 2006
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Chemosynthetic Sites visited 2007