Cold seeps are locations where reduced, hydrocarbon-rich fluids escape the seafloor. They are often associated with high levels of methane and hydrogen sulfide, which are used by chemoautotrophic Bacteria and Archaea as sources of energy. Cold seeps, as a result, harbor dense biological communities with species that often do not occur in other environments. Well-studied methane seeps occur all along the Pacific Coast of North America, and we have a great deal of evidence suggesting that seeps are a common feature along the coast of San Diego County. For example, seep-associated animals have been collected in the past off San Onofre and the US/Mexico border, sound profiles have revealed features indicative of gas seepage such as seafloor pockmarks (large pits) and bubble plumes, and tar balls have washed up on local beaches.
The multibeam and sub-bottom profiler emit sound waves that bounce off density gradients in the ocean and below the seafloor. After receiving the echoes, these instruments will provide us data that show us the topography of the ocean bottom, bubble plumes that may be rising through the water, or sediment disruptions that may be occurring deep below the seafloor. We will process and interpret these data to select ROV target sites where we believe fluids are actively seeping from the seafloor.
Thr Scripps ROV, complete with video camera and manipulator claw, will perform the initial exploration of any newly-discovered seeps. We will attempt to collect samples of rocks, sediment, or animals that will help us determine how the animals and geology of these seeps compare to others in southern California and elsewhere on the Pacific Coast.
Photo: This carbonate rock was collected from Hydrate Ridge, a methane seep off the coast of Oregon in September 2010. Visible are provannid snails, pyropeltid limpets, and tube-building ampharetid polychaetes worms. This entire community is part of a food web that depends on chemosynthetic archaea and bacteria, such as the filamentous sulfide-oxidizing bacteria in this picture. Photo credit: Ben Grupe.
Costa Rica Methane Seep
Photo: This methane seep off the coast of Costa Rica is characterized by carbonate substrate, which is precipitated by chemosynthetic microbes. These rocks provide a surface to which habitat-forming species such as tubeworms (Lamellibrachia sp.) and mussels (Bathymodiolus sp.) can attach. Image courtesy of the Woods Hole Oceanographic Institute.
Photo: Onboard R/V Melville, we will use various tools to search for cold seeps on the seafloor. By sending out sound waves and listening for the echoes, a sub-bottom profiler will create pictures such as this one, which shows plumes of gas rising from the ocean floor in Chile. Photo credit: Ben Grupe.
Discovered in San Diego... Over 100 Years Ago!
Photo: In 1903, a vessel called the Albatross was exploring the deep-sea off the coast of San Diego. When they were 15 miles off Point Loma, in Mexican waters, they trawled up a new species of snails that was described as Provanna lomana. As it turns out, that was only the first discovery of a large family of snails that lives nowhere except cold seeps and hydrothermal vents. If we do discover seeps off the coast of San Diego, it’s likely that Provanna lomana will have beaten us there. Photo credit: Greg Rouse.
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