Oil spill dispersant could damage coral populations
By Sujata Gupta
03 August 2010, 17:45
Coral populations in the Gulf of Mexico could fall because of the Deepwater Horizon oil rig disaster – from contact not with oil but with the dispersant that’s supposed to get rid of it. Laboratory tests suggest that Corexit 9500A, the dispersant used by BP to tackle the largest offshore oil spill in US history, stops coral larvae latching onto the surfaces where they usually mature. The larvae, often the size of a pinhead, float in the sea before latching onto surfaces such as rocks on the sea floor, cliff faces or old oil rigs. It takes hundreds of years for a mature colony to develop. Researchers at Mote Marine Laboratory in Summerland Key, Florida, studied how larvae of shallow-water Mustard Hill corals (Porites astreoides) settled onto cement discs in three different combinations of liquids: seawater and oil, seawater and Corexit 9500A, and a combination of all three. Concentrations of oil and dispersant were comparable to those likely to be found around the Deepwater Horizon well head before it was capped. The team observed the larvae for 48 hours, which is around the time it takes for most coral larvae to settle. Preliminary and as yet unpublished results show larvae in the oil-water mix are able to latch onto the discs, whereas those in beakers containing the dispersant remained suspended in the water. …
