Microbial communities proliferate around Gulf of Mexico (GOM) gas hydrate mounds. Synergistic relationships exist between microbes and hydrates at the observable seafloor, and interactions may extend with changing emphasis to bottom of gas hydrate zone. To explore these interrelationships, NOAA, DOE, and MMS are sponsoring a microbial observatory in conjunction with a hydrate observatory on the seafloor near gas hydrate outcrops and multiple gas vents of the northern GOM at Mississippi Canyon 118. This paper discusses experiments to be conducted on the seafloor at MC-118 over a period of a few months before retrieval by submersible.
Microbes have been convincingly shown to proliferate near gas hydrate outcrops, oil seeps, and gas vents on the floor of the Gulf of Mexico (GOM), where microbial mats, so-called chemosynthetic communities, mussels, or tube worms are common occurrences (Roberts, 2004; Sassen et al., 2001). In the Cascadia Margin, bacterial populations and activity were found to increase by about an order of magnitude throughout gas hydrate zones wherever hydrates occurred, except in places of high H2S concentration (Cragg et al., 1996).
A hydrate-microbial relationship probably extends at least to the bottom of the gas hydrate zone (GHZ). In the GOM that bottom might be 200- 1000 m (Milkov and Sassen, 2002). Although most of the hydrate data in the GOM comes from the top 6 meters of sediments (Milkov and Sassen, 2000), prolific bacterial activities occur deep around hydrate occurrences in Blake Ridge and Cascadia Margin hydrate zones; additionally, deep bacterial activity around hydrates has been observed in the Nankai Trough (Reed et al., 2002).
Not only are there microbial-hydrate associations near the surface and deep in the hydrate zone, but the associations may extend beyond the bounds of the hydrate zone.
