Introduction and Project Overview

This report summarizes research funded by the U.S. Geological Survey (USGS) in collaboration with the University of North Carolina at Wilmington (UNCW) on the ecology of deep chemosynthetic communities in the Gulf of Mexico. The research was conducted at the request of the U.S. Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE; formerly Minerals Management Service) to complement a BOEMRE-funded project titled "Deepwater Program: Investigations of Chemosynthetic Communities on the Lower Continental Slope of the Gulf of Mexico." The overall research partnership, known as "Chemo III," was initiated to increase understanding of the distribution, structure, function, and vulnerabilities of these poorly known associations of animals and microbes for water depths greater than 1,000 meters (m) in the Gulf of Mexico. Chemosynthetic communities rely on carbon sources that are largely independent of sunlight and photosynthetic food webs. Despite recent research directed toward chemosynthetic and deep coral (for example, Lophelia pertusa) based ecosystems, these habitats are still poorly studied, especially at depths greater than 1,000 m. With the progression into deeper waters by fishing and energy industries, developing sufficient knowledge to manage these deep ecosystems is essential. Increased understanding of deep-sea communities will enable sound evaluations of potential impacts and appropriate mitigations.

Cruise reports and preliminary data for the BOEMRE-funded projects are included in reports prepared by TDI-Brooks International, Inc. (2006a, b; 2007), and a final report that complements this USGS report is near completion. Some USGS objectives were addressed with participation in the BOEMRE-supported cruises, while others were addressed through a USGS cruise (Ross, 2007). This research is part of a larger, long-term goal of the USGS deep-sea studies group to develop, integrate, and synthesize information on deep-sea corals (and hardgrounds) and chemosynthetic communities and to compare community composition, fauna/habitat linkages, genetic structures, and energetics across latitudes, habitat types, depth zones, and regions. A special issue of peer-reviewed papers that stemmed from this Chemo III project was recently published in the journal Deep-Sea Research – Part II (Roberts, 2010), and some of the data contained in this USGS report are also within the Deep-Sea Research publication.

Deep water (aphotic) coral, hardground, and chemosynthetic systems are important habitats for macrofauna, repositories of data on ocean climate and productivity, and hotspots of increased biodiversity. Fishes and crustaceans are megafauna of particular interest to decisionmakers, but their abundance, microhabitat affinities, and importance in structuring these biotic communities are poorly known. Understanding trophic (food web) linkages between the benthos and the overlying waters is fundamental ecological knowledge about how deep ecosystems function. Deciphering barriers to gene flow that may isolate populations has been problematic for marine species. Even so, some slope species exhibit unexpected population heterogeneity. Genetic techniques applied to organisms associated with coral, hardbottom, and chemosynthetic habitats from various locations provide insights into species biology, mechanisms regulating community structure (dispersal), and information about reproduction and recovery after various impacts. Microbes, specifically bacteria, are the foundation of deep-sea chemosynthetic communities and may provide vital functions to deep-sea corals. Viruses are the most numerous organisms in the ocean, and the majority appears to infect marine bacteria. As such, viruses control microbial diversity and carbon cycling. Little is known about viruses in the deep sea, and to understand cold seep dynamics, the viral ecology of this ecosystem (water and sediments) must be addressed. Sponges, important as deep-reef habitat for macrofauna, are recognized as "microbial apartment buildings," containing a wide variety of commensal and symbiotic bacteria and archaea. As with coral-associated microbes, assessing these microorganisms allows a better understanding of the biology of the macrofauna they inhabit, increases understanding of microbial biodiversity, and reveals species interdependencies.

The USGS Chemo III effort was composed of five interrelated study components, each with separate chapters in this report: Part I, midwater macrofauna (fishes and mobile invertebrates) taxonomy and ecology (abundances, habitat associations, behaviors); Part II, midwater and benthic trophic connectivity; Part III, crustacean taxonomy and ecology; Part IV, microbial ecology (composition, distributions); and Part V, genetics (including community genetics, phylogeography). While the above lists the five study parts as funded, actual chapter titles in this report are different (see Contents). This research in >1,000-m depths expanded and supplemented prior projects that focused on Lophelia pertusa communities (300-900 m) and provides comparisons with datasets from different areas/ecosystems (reviewed in Brooke and Schroeder, 2007; Ross and Nizinski, 2007). The four study areas and sampling completed in each area are illustrated in figure 1.1. Other chapters below may use different figures to document their sampling.

This USGS final report has been prepared, in part, to address time-dependent information needs as requested by the BOEMRE. Additional analyses, interpretation, and syntheses of the available data are expected to lead to future journal publications.

First posted March 2, 2012