Reaching deep: BP oil spill had big impact on deep-sea coral

The Deepwater Horizon oil spill left some indelible images on most of our minds: the burning rig, the oiled birds and fish and turtles, the slicks stretching for what seemed like infinity across the ocean. But much of the oil that was released either never reached the Gulf of Mexico’s surface, or it came up for a breath and then sank back down into the depths. It was out of sight, but a new study adds to the reasons it shouldn’t have been out of mind: deep-water coral communities, important pieces of ocean ecosystems, were affected even at large distances from the wellhead itself.

Researchers from Penn State, the Woods Hole Oceanographic Institution, Louisiana State University, and others surveyed underwater sites in the Gulf of Mexico using several methods: first, they looked at seismic reflectivity assessments done by the oil and gas industry and submitted to the U.S. Bureau of Ocean Energy Management; promising sites could then be viewed using a camera tethered underneath a ship on the surface; and finally, an autonomous underwater vehicle named Sentry could actually dip down a few thousand feet and check out some of the sites in person.

In their paper in Proceedings of the National Academy of Sciences, the authors describe the discovery of five previously unknown coral communities in the Gulf; it is, after all, pretty hard to find small bits of life sitting on the sea floor a mile underwater. Soon after the spill in 2010, one such coral community was found to have been severely damaged; it was about 13 kilometers (8 deepwatercoral2miles) from the Macondo well, the site of the blowout. Among the newly discovered coral communities, at least two were also apparently damaged badly by oil, and one was almost twice as far away from and about 1400 feet deeper than the well itself. The image to the right shows some of the healthy and diseased bits of that particular site.

So the oil spill was bad, a thing we already knew; but this shows how important it is to find the full range of impacts of an environmental catastrophe like this. As the study authors write: “Although far removed from surface and coastal waters, and from the consciousness of most people, deep-sea environments play numerous roles in the health of the world’s oceans.” From shark spawning to nitrogen cycling, the deep oceans are a big deal even if they seem cold and remote.

This new study also showed that while the BP spill did a lot of damage, deep sea corals aren’t immune from more everyday human activity either. Two of the other four newly discovered deep-sea coral communities were also fouled, though not by oil: fishing line was the culprit, an obvious issue for a lot of species that might use the coral as habitat. It’s easy to note the oil on a beach, or a dolphin caught in line at the surface, but our reach extends far beyond what our eyes can see. – Dave Levitan | August 12 2014

Source: Fisher CR, Hsing PY, Kaiser CL, et al (2014). Footprint of Deepwater Horizon blowout impact to deep-water coral communities, Proceedings of the National Academy of Sciences, early edition. DOI: 10.1073/pnas.1403492111

Image: Wikimedia Commons, Kris Krug