Two types of communities exist on the deep sea floor of the gulf. Where hydrocarbons seep out of the sediment, clams and mussels live with symbiotic bacteria that tap sulfide or methane for energy. In the same areas, polychaete tubeworms grow up to several meters long and can live for centuries. Elsewhere, corals capture prey that floats by or detritus that sinks from above.
Expeditions have sampled sea-floor biota in the Gulf of Mexico for years with submersibles and ship-borne devices. In mid-May, a research vessel operated by the National Institute for Undersea Science and Technology (NIUST), a university consortium, began taking sediment and water samples from areas under and near the oil spill. Another group already had a passive sediment-sampling device in place nearby. When they retrieve the device, by October at the latest, they will know how much oil has settled onto the sea floor, either directly or entrained in seaweed.
Most sea-floor studies to date have been funded by NOAA and the Minerals Management Service. NOAA is supporting the NIUST mission, which detected oil below the surface. The crew returned to port late last week and will begin analyzing samples. Meanwhile, they are beginning to plan another trip for follow-up sampling.