By Mandy Joye, Professor, University of Georgia
Erik Cordes, Associate Professor, Temple University
Overview of extensive chemosynthetic mussel communities colonizing carbonate and sedimented mounds at a seep site south of Norfolk Canyon. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2013 ROV Shakedown and Field Trials in the U.S. Atlantic Canyons. Download larger version (jpg, 1.6 MB).
The DEEP SEARCH project is focused on better understanding the functional roles of three habitat types: submarine canyons, deep-sea corals, and cold seeps. Cold seeps create very interesting environments that provide resources and habitat for a wide variety of creatures. Bacteria and other microbes feed directly off of the gasses released (mostly methane and hydrogen sulfide), and animals like mussels and clams that have bacterial symbionts that use these chemicals also thrive at seep sites. These animals create larger and more complex habitats that can be used as homes by worms, crabs, fish, and all sorts of other creatures from the surrounding deep sea that are attracted to the food and structure at the seeps. When there is a lot of methane and sulfide, many of these animals have trouble dealing with the toxic environment and only a few can take advantage of the food there. But over time, the release of chemicals declines, and more of the deep-sea fauna can be found at the seeps.
White gas hydrate formed under a rock overhang. Bubbles being emitted from the seafloor are visible in the shadow below the rock. Laser scale denotes 10 centimeters. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2013 Northeast U.S. Canyons Expedition. Download larger version (jpg, 1.5 MB).
Recent work off of the U.S. east coast has uncovered nearly 600 gas plumes rising from the seafloor, yet less than one percent of these sites have been visually explored. In this region, cold seeps occur at the heads of canyons, ridges within canyons, and on the open continental slope. Cold seeps also occur south along the Blake Ridge, where there are massive gas hydrates. In these settings, gas bubbles emitted from the seafloor collect beneath the overhang, forming solid gas hydrate around the bubbles, which then combine to form a gas hydrate mass. All of these locations are under consideration for energy exploration in the coming years. It is our hope that we can find any sensitive communities that might be living in the area so that they can be appropriately managed.
Methane bubbles flow in small streams out of the sediment on an area of seafloor offshore Virginia, north of Washington Canyon. Quill worms, anemones, and patches of microbial mat can be seen in and along the periphery of the seepage area. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2013 ROV Shakedown and Field Trials in the U.S. Atlantic Canyons. Download larger version (jpg, 1.6 MB).
On this expedition, we will be collecting sediment and water samples to quantify geochemical signatures, including concentrations of methane and hydrogen sulfide, to assess microbial community composition and document rates and patterns of microbial activity. This integrated approach will allow us to evaluate how free-living microbial communities shape the geochemical signature of these environments. This work will contribute directly to two of the main themes of the DEEP SEARCH program: exploring and characterizing biological communities and describing oceanographic, geological, and geochemical conditions associated with habitat types. These data will also allow us to assess the sensitivity of microbial communities and their activity to disturbance. Finally, these data will contribute to the broader modeling effort being pursued by the project science team.
