Deepwater Horizon - 1 year on.

 It is now a year since the explosion of the Deepwater Horizon, which resulted in 205.8 million gallons of crude oil being released into the Gulf of Mexico. For 3 months, oil flowed into the Gulf from the gushing wellhead, making it the largest accidental marine oil spill in the history of the petroleum industry. The environmental consequences of the spill are still being felt today, and are likely to be for a long time yet.

 Over 8000 species live within the area of the oil spill, including more than 1,200 fish, 200 birds, 1,400 molluscs, 1,500 crustaceans, 4 sea turtles, and 29 marine mammals. Evidence is emerging that some of the cold-water corals in the Gulf may have been damaged by the oil spill, following a research cruise by a team of scientists led by Charles Fisher from Penn State University.

 Seven miles southwest of the spill at a depth of 1400 m, a community of deep sea corals (gorgonians and Madrepora) was discovered in November 2010, including many recently dead colonies and others that clearly are dying. Visible damage included bare skeleton where coral tissue had sloughed off and was often covered with what appeared to be decaying tissue. Some coral skeletons had no live tissue visible. Even the behaviour of the associated invertebrates, such as brittle stars, appeared impaired. None of the scientists, many of whom have worked in the Gulf for over a decade, had ever seen anything like this.

In November, the human occupied submersible Alvin made its first foray into post-spill Gulf waters, led by Chief Scientist Samantha Joye of the University of Georgia.Sediment and water columns samples were collected in the vicinity (2.5 miles and further out) of the Deepwater Horizon wellhead.

In December 2010, a team of NSF scientists revisited these deep-water corals using the submersible Alvin to carefully document the bottom and to collect samples of animals and sediment. The team also positioned a time-lapse camera, which operated until February, to create a record of how the corals repair or deteriorate in response to their recent damage.

 An area of particular concern in regards to cold-water corals was Viosca Knoll, a site approximately 20 miles from the Deepwater Horizon oil rig that hosts the largest known concentration of the cold-water coral, Lophelia pertusa, in the Gulf of Mexico. Scientists have observed no obvious physical impacts on these communities, with the corals behaving normally with no signs of distress. However, they may have suffered genetic mutations or lose their ability to reproduce, and thus these sites are being monitored for sub-lethal effects by USGS scientists. It is too early to draw conclusions about the environmental impact of this devastating oil spill.

 Further details of the spill and impacts can be found on Wikipedia, the BBC , NOAA and in a recent paper in Plos Biology. Image courtesy of the BBC