Over the past 20 years of work in the deep Gulf of Mexico we have assembled a large database on over 40 sites with chemosynthetic communities and 14 natural sites with extensive cold-water coral development. As a result of the ongoing oil leak at the Deep Water Horizon rig, some of these sites are very likely to be exposed to high concentrations of hydrocarbons and dispersant. Visitation, imaging, and sampling in the very near future at a subset of these sites will provide timely information on any acute impacts on benthic fauna, as well as provide ground-truthing of data suggesting that the oil/dispersant mixture is spreading along density gradients at depth. We propose to revisit sites where we have ongoing studies, including pre-exposure tissue and live coral samples, and well-marked and navigated mosaics of coral and coral/tubeworm communities. A site in MMS lease block VK 826 and another in MC 751 are identified as high-priority sites with extant mosaics, excellent pre-existing macrofauna sample sets, and are currently monitored with time series sediment traps. A third high-priority site is in MMS lease Block MC 294, within 7 miles of the leak site. This site harbors a typical seep community of mussels and tubeworms. Numerous others could be visited if ongoing plume modeling and ground-truthing work suggests other important areas or depths in the Gulf of Mexico for study. At each site visited, we will conduct high resolution imaging of the hard ground megafaunal communities for comparisons to similar imagery collected last year and make a series of macrofauna collections for a suite of analyses. These analyses will include analysis of hydrocarbon load (tissue PAHs), Comet assays to assess DNA damage, analysis of phospholipids fatty acid biomarkers from bacteria in coral mucous, and also experiments with living Lophelia pertusa for growth studies under laboratory conditions. Broader Impacts For the first time in US history, we are dealing with a massive leakage and spread of oil and trial dispersants (potentially much more toxic to life than the oil itself), which have been directly injected at over 1500m into the deep sea. The scale of this disaster dwarfs any previous oil spills and how plumes of these substances will travel in the deep sea and what their effects on the benthos will be is still almost completely unknown. As a result, there is a critical need to assess the impact on deep-sea megafauna communities and communicate those results as soon as possible.
In October 2010, approximately six months after the Deepwater Horizon oil spill, deep-water coral communities at 4300 feet and 11km from the site of the Macondo well were found covered in a brown flocculent material and with signs of tissue damage (Image 1). In December 2010, the autonomous underwater vehicle Sentry was deployed, to map and photograph the ocean floor and six dives were taken with the deep submergence vehicle Alvin to obtain a better look at the damaged corals (Image 2). During six dives in Alvin, sediments and samples of the corals and brown flocculent material from the corals were collected for analysis . The primary aim of this NSF funded research was to determine the composition of the brown flocculent material covering the corals and the source of any petroleum hydrocarbons present. Because oil can naturally seep from cracks in the sea floor of the Gulf, pinpointing the source of petroleum hydrocarbons in Gulf samples can be challenging. This is especially difficult because oil is comprised of a complex mixture of different chemical compounds. However, there are often slight differences in oils that can be used to trace their origin. To identify the oil found in the coral communities comprehensive two-dimensional gas chromatography was used to separate oil compounds by molecular weight providing a "fingerprint" of the oil. This petroleum analysis coupled to the analysis of 69 images from 43 individual corals at the site yielded strong evidence that the coral communities were impacted by oil from the Macondo well spill. These findings are significant because biological communities in the deep Gulf of Mexico are separated from human activity at the surface by approximately 4,000 feet of water and are therefore not expected to be impacted by a typical oil spill. This finding underscores the unprecedented nature of the Deepwater Horizon oil spill in terms of its magnitude, release in deep water, and impact to deep-water ecosystems. These findings have been published in the Proceedings of the National Academy of Sciences.
