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September 2005

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

Scope and Objectives of This Project
Directed Missions of MMS
Background for This Project
Project Team
Scientific and Technical Context Write Up (PDF download)


TDI-Brooks has just been awarded a $3.16 million contract (#0105CT39187) with the Minerals Management Service (MMS) for a 4-year study of chemosynthetic communities on the lower continental slope of the Gulf of Mexico. As a bureau of the US Department of the Interior, the MMS has primary responsibility for the management of the mineral resources located on the nation's Outer Continental Shelf (OCS). The MMS administers the OCS competitive leasing program for oil and gas exploration, and oversees the safe and environmentally sound exploration and production of our nation's offshore natural gas, oil, and other mineral resources (

The award to TDI-Brooks includes a comprehensive study of existing 3-D seismic information for the purpose of locating the chemosynthetic communities, using a camera sled and other high-tech gear for the reconnaissance of identified areas, visiting known communities with the manned submersible ALVIN (, and documenting the communities with chemical sensors, microbiological examinations, and digital video using an autonomous underwater vehicle (AUV). This is an exciting, cutting-edge, multi-disciplinary scientific study for which TDI-Brooks is honored to be the prime contractor. In this capacity, TDI-Brooks will collaborate with a group of world-class and internationally-recognized scientists in the field of chemosynthetic communities.

Scope and Objectives of This Project

A. To characterize known, or newly discovered chemosynthetic communities at depths below 1,000-meters in the central and western Gulf of Mexico.

B. To characterize all other hard bottom biological communities encountered regardless of association with active hydrocarbon seep activity or living chemosynthetic community species in the central and western Gulf of Mexico.

C. To determine the comparative degree of sensitivity of anthropogenic impacts for both A and B above through a variety of approaches such as rarity, unique taxonomy/biodiversity, or other environmental risk assessment methodologies. This objective includes understanding how these deep communities are similar or different from their shallower water counterparts.

D. To further develop successful assessment methodologies for correlation of remote sensing information such as bathymetry, seabed acoustic reflectivity, subbottom structure, and other geophysical signatures obtained by non-visual techniques with the "potential" presence of non-soft bottom biological communities at depths below 1,000 meters. The objective is specifically targeted to result in some level of predictive capability that can be used by MMS to avoid impacts to lower slope sensitive biological communities.

E. To contribute to assessing and explaining diversity distribution and abundance of marine species at depths below 1,000 m in the central and western Gulf, as well as improving the understanding of the functional role of marine species in areas of active hydrocarbon seep activity or living chemosynthetic communities.

These objectives will be accomplished through a combination of both exploratory work and more focused studies including process-based work on known communities.

Directed Missions of MMS

Acting under acts of Congress, MMS serves as a prudent manager of the nation's seafloor mineral resources. That management role requires development of critical energy resources without unacceptable impact on other ocean users, the natural environment, and the human environment. The primary strategy that MMS employs to eliminate or minimize environmental impact is to identify sensitive habitat and then restrict or otherwise mitigate exploration, development, and production activity. Typically, reefs, other live bottoms, critical fish habitats, etc. are classed as sensitive on the basis of accumulated prior knowledge and directed MMS studies. The vast areas of seemingly homogenous soft bottoms are classed as insensitive. Even in the case of such insensitive areas, MMS and EPA regulations seek to limit the area and degree of impact.

Increased oil and gas activity beyond the shelf break and US recognition of the 200 m EEZ greatly increased MMS's environmental coverage. Faced with a very poorly studied and remote environment, MMS supported a series of deep surveys (Carney, 2001) along the Atlantic and Gulf of Mexico continental margins in the 1980's. These studies confirmed the existence of vast soft sediment habitats, but also recognized previously known live bottoms, and found unexpected chemosynthetic communities. Both deep live bottoms and chemosynthetic communities can be classed as sensitive habitats. It can be noted that the core participants in the propose work participated in these previous surveys in many ways.

The results of MMS's first study of upper slope chemosynthetic communities, Chemosynthetic Ecosystems Study (MMS Report 95-2001) began the trend continuing to this day of submersible-based investigation in a mixed exploration and detailed-study mode. A second study, Stability and Change in Gulf of Mexico Chemosynthetic Communities (MMS Report 2002-036) greatly increased knowledge of the ecology of these systems. The scientific value of these studies was increased by the initiative of the core members who successfully sought competitive funds from NOAA, DOE, and NSF.

The work proposed herein is designed to meet MMS' information needs concerning the location and functioning of seep communities deeper than the artificially imposed limit of 1000 m. Preliminary studies have shown that seep communities at the slope base are different from those on the upper slope in much the same way that the normal background fauna differ. Therefore, MMS can not simply extrapolate upper-slope data down the entire margin.

Background for This Project

Over the last half century, offshore exploration for hydrocarbons in the northern Gulf of Mexico has advanced from the bays and inner shelf to the continental slope-to-continental rise transition. Geophysical and geotechnical data collected in support of both exploration and production has largely been responsible for the foundation of our present understanding of slope geology. This database emphasizes the extremely complex geological framework of the northern Gulf's continental slope and the surprisingly important role that the expulsion of subsurface fluids and gases has on shaping surficial geology and biology of the modern seafloor.

Regional topography of the slope consists of basins, knolls, ridges, and mounds derived from the dynamic adjustments of salt to the introduction of large volumes of sediment over long time scales. Superimposed on this underlying topography is a smaller class of mounds, flows, and hard grounds that are the products of the transport of fluidized sediment, mineral-rich formation fluids, and hydrocarbons to the present sediment-water interface. The geologic response to the expulsion process is related both to the products being transported and the rate at which they arrive at the seafloor. Mud volcanoes and mudflows are typical of rapid flux settings where fluidized sediment is involved. Slow flux settings are mineral-prone. Authigenic carbonate mounds, hard grounds, crusts, and nodules are common to settings where hydrocarbons are involved. Barite in the form of small cones, chimneys, and crusts may also be found where expulsion of barium-rich water occurs. In settings between mud-prone rapid flux and mineral-prone slow flux environments, unique conditions occur to support and sustain densely populated communities of chemosynthetic communities. These areas correlate well with the occurrence of surficial exposures of gas hydrate.

Direct observation and sampling of these unusual geologic and biologic environments by the key personnel of our contract started in the mid-1980s using manned submersibles. To date, most submersible-supported research has been concentrated on the upper slope (<1,000 m). However, fluid and gas expulsion features, chemosynthetic communities, brine seeps, and slope instabilities occur over the slope's full depth range as imaged on geophysical data and confirmed by limited numbers of deep submersible dives and remotely operated vehicle (ROV) bottom imaging transects and samples.

Project Team

TDI-Brooks International Inc. (TDI-Brooks) has assembled a team that combines the most knowledgeable and experienced researchers specific to the requirements of this project in the Gulf of Mexico and includes scientists that are internationally recognized for their contributions to the global understanding of cold seep ecology, microbiology, physiology and geology. All of the key US members of the team are also very experienced with, and have led, large multidisciplinary projects and cruises. Dr. James Brooks will be the Project Manager and will take the lead in administration of this project and assist in the geochemical studies. Dr. Charles Fisher (Pennsylvania State University) will coordinate the biological studies, Dr. Harry Roberts (Louisiana State University) will coordinate the geological/geophysical studies, and Ms. Liz Goehring (Penn State and NSF Ridge 2000 office) will coordinate the education and outreach activities.

Dr. Charles Fisher will oversee the biological aspects of the study and the interface with geochemical measurements and studies. He will work closely with Dr. Roberts and other PIs to plan and conduct the submersible/ROV portions of the field work. His research group will take responsibility for in situ methane analyses, growth studies, quantitative collections, community composition and structure analyses, and trophic studies of the endemic and other closely associated seep and coral fauna. He will also be responsible for coordination with international collaborators. Dr. Erik Cordes will work with Fisher's team on studies of seep communities and take a leadership role on synthesis and publication of results for other hard bottom communities discovered. Dr. Stephane Schaeffer will oversee work in his laboratory, including molecular phylogenetic screening of foundation species and their symbionts (tubeworms, mussels and clams) and other potential new species (and symbioses) as needed. Dr. Robert Carney will lead the studies of interactions with background fauna and trophic exchange between seep/hard bottom communities and larger mobile fauna. Drs. Fisher, Carney, and Cordes will share responsibility for coordination with taxonomists and molecular phylogenists and proper curation of samples. Dr. Ian MacDonald will direct the use of digital imagery in all phases of the study, from the initial site survey and selection process to site descriptions and contributions to faunal inventory. Dr. Samantha Joye will be responsible for the microbial ecology and sulfide geochemistry studies.

In addition to this core team, we have assembled a team of collaborators that significantly expands our taxonomic expertise and brings in some of the top international seep research groups, at a very small additional cost to the project (transportation costs to cruises, minor supply costs, and shipping and curation costs for samples). Dr. Tim Shank (WHOI) has indicated his willingness to phylogentically characterize any potential new species of megafaunal crustaceans and to include at least the shrimp in his ongoing biogeographic analyses. Dr. Bob Vreijenhoek (MBARI) will do the same clams and their symbionts and other gastropods as needed. Limpets and snails will also be sent to Anders Waren (Swedish Museum of Natural History) and chitons to Julia Sigwart (University College Dublin) for morphological characterization. Dr. Stéphane Hourdez (Stacione Biologique de Roscoff, France) will take the lead on polychaete phylogenetic characterizations and descriptions of new species of polynoids and siboglinids (using both molecular and classical approaches). He will also assist with molecular characterization of foundation species during visits to PSU after the cruises (working in S. Schaeffer's laboratory at PSU). Dr. Stephane Cairns (Smithsonian) will oversee curation and identification of cnidarians, with assistance of Daphne Fautine (University of Kansas) and Dennis Opreska (Oak Ridge). Dr. Cheryl Morrison (USGS Leetown Science Center) has confirmed her willingness to include any samples of Lophelia pertusa collected in her ongoing studies of the phylogeography and population genetics of this foundation coral species, and also to collaborate with Dr. Cairns by contributing to the molecular systematics of other hard corals as needed. Dr. Sabine Stohr (Swedish Museum of Natural History) has agreed to examine all ophuiroids collected and is already working a brittle star that was one of the dominant species collected with mussels at some of the deeper sites in 2003. Dr. Monika Bright and her research team (Univ. Vienna) will sort and identify meiofauna collected with mussel and tubeworm communities and in sediment cores. Other faunal groups will be sent to appropriate experts as needed.

Additionally, two internationally recognized research groups from the Max Planck Institute of Marine Microbiology in Bremen will bring unique expertise and equipment to bear on the study. Nicole Dublier's group will use quantitative mRNA analyses to determine the relative activities of chemoautotrophic and methanotrophic symbiont populations in the dual symbiont-containing mussels. Antje Botieus' group will bring their in-situ seep-chemistry analysis system and expertise on the ALVIN and ROV cruises. Letters of commitment from all collaborators are available upon request.

TDI-Brooks' management and analytical team will provide critical support for the project. Dr. Bernie Bernard, TDI-Brooks Director and Laboratory Manager, will coordinate the isotope, hydrocarbon and ancillary measurements that are conducted in our laboratory. Dr. Thomas McDonald will be the principle hydrocarbon chemist for the project. Dr. Gary Wolff will act as the projects Data Manager as he has for numerous previous large multi-disciplinary MMS projects. Mr. Kathy Allen will be the projects technical editor. She along with Ms. Suzanne Cardwell will provide financial and project administrative support.

As described above, each of these PIs will have their own areas of responsibility with respect to analyses, equipment, manpower and deliverables. However, the activities of the groups will be integrated from planning and site selection through implementation and interpretation of the results. All biological studies will be interpreted in the context of the geochemical and geophysical characterization of the region and the specific sites. Nested within these base maps will be studies of fine scale geochemistry, mobile fauna densities, and microhabitat distribution of specific types of chemosynthetic or coral communities. Dr. Carney's work will provide the context on the background fauna expected at different depths necessary to interpret Dr. MacDonald's time lapse optical sampling of mobile fauna to the sites. Dr. Carney's trap and targeted collection samples will allow analysis of trophic interactions between this component of the deep sea fauna and the communities that are the focus of this project. Fisher's quantitative collection-based analyses of community structure and function will be interpreted in the context of these studies and Dr. MacDonald's photo surveys of each site. Dr. Carney's detailed studies of bivalve/gastropod interactions will be interpreted in the context of Dr. Fisher's quantitative studies and those of collaborating European investigators. The animal distribution and activity data will be interpreted in the context of sediment microbial activity and geochemical data collected by Dr. Joye's group and in situ water column data obtained by Dr. Boetius' group. Outreach activities will include input from all teams and will be coordinated by Liz Goehring, who is currently the Education and Outreach coordinator for the NSF Ridge 2000 Program. In addition to integrating this project into programs she has designed, she will work closely with the GoM area COSEE center in Southern Mississippi and the Ocean Exploration Program.

Scientific and Technical Context

Click below for a detailed technical discussion of the work in Adobe Acrobat Format.

Investigations of Chemosynthetic Communities on the Lower Continental Slope of the Gulf of Mexico PDF Download

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