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Pathways to the Abyss
[Reprinted from USGS Science Features: Top Story, May 27, 2015.]
A new video by the Bureau of Ocean Energy Management (BOEM) includes highlights of some of the contributions of U.S. Geological Survey (USGS) scientists during a five-year study of two deep mid-Atlantic canyons located about 150 kilometers (nearly 100 miles) offshore of Virginia and Maryland.
USGS researchers collaborated with academic and private organizations and institutions, BOEM, and the National Oceanic and Atmospheric Administration (NOAA) to conduct ecosystem-based science to support the responsible exploration and development of the nation’s resources. This interdisciplinary, collaborative effort represents one of the most comprehensive studies of deep-sea canyons.
Deep-sea canyon habitats are complex ecosystems encompassing a range of habitat types, including soft sediment, hard substrate, and chemosynthetic seeps. Deep-sea communities provide essential ecosystem services, including carbon cycling and food for animals higher in the food webs, and important habitat for marine species. However, little is known about species composition, food webs, and habitats in these canyons.
During the expeditions, the USGS conducted research examining canyon geology, oceanography, ecology, animal and microbial distribution, and genetics to help understand the community structure, food webs, and connectivity of deep-sea canyon ecosystems—from microbes to corals to fish.
USGS researchers played an integral role in planning the offshore expeditions and provided scientific support and expertise at sea. Amanda Demopoulos, research benthic ecologist at the Southeast Ecological Science Center, served as the USGS project chief, coordinating research with the project’s multiple principal investigators. She and Nancy Prouty, research oceanographer from the Pacific Coastal and Marine Science Center, led the deployment and use of deep-sea moorings; these provided continuous year-long records of the canyon environment and the flow of food resources to the seafloor. Jason Chaytor and Uri ten Brink of the Woods Hole Coastal and Marine Science Center, and Daniel Brothers from the Pacific Coastal and Marine Science Center, created detailed maps of the two canyons by processing and interpreting multibeam mapping data. These maps proved to be critical to expedition planning.
Demopoulos provided expertise on understanding the animals living within the canyon environments and associated linkages among these organisms. Prouty estimated the ages of deep-sea corals, using the skeletons to provide a history of oceanographic conditions in the region. Cheryl Morrison, research geneticist from Leetown Science Center, examined population and conservation genetics of deep-sea corals and crustaceans. Christina Kellogg, research microbiologist from the St. Petersburg Coastal and Marine Science Center, provided expertise in understanding the microbial ecology of deep-sea corals and canyon sediment.
Due to the challenging nature of working in these remote systems, the USGS researchers developed novel approaches and applied innovative technologies. For example, they used high-resolution multibeam mapping, instrumented moorings, and molecular, stable isotope, and trace element techniques to observe, sample, and conduct experiments within the deep sea. The use of these techniques is enhancing knowledge of critical deep-sea habitats across broad spatial scales (10s to 1,000s of kilometers) and depth ranges (350 to 2,200 meters).
Deep-sea corals found in the canyons are slow-growing and long-lived, with many living more than 100 years. They are extremely vulnerable to disturbance and slow to recover. Certain species of deep-sea corals exhibit differing patterns of connectivity, which has implications for the type of conservation strategy that may be applied to these vulnerable species. Examination of the coral-associated microbes suggests that microbes and corals may share similar biogeographic patterns.
Discrete animal communities were found inside the canyons that differed from those found on adjacent slopes, which indicates the canyons are serving as complex habitats supporting diverse communities. Canyons contain complex food webs thriving on food produced in surface waters. By developing long-term deep-sea observatories (moorings), the USGS investigators can better understand how the canyon environment may influence deep-sea canyon biodiversity and community function.
This pioneering research characterizing deep-sea communities across regions and habitats has allowed for the evaluation of ecosystem change by establishing critical baselines for deep-sea ecosystem health; these baselines help scientists measure changes caused by both natural and human disturbances. By addressing USGS’ vision of integrated science and assessment, this research supports ecosystem-based management by improving understanding of the ecology of significant, vulnerable, yet poorly understood biological communities.
The multiagency project was selected for the 2013 Department of the Interior Partners in Conservation Award (see “”) for its outstanding contributions to addressing and achieving conservation objectives via collaboration and partnering.
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