While they may help clean up oil spills, chemicals known as dispersants may actually cause much more harm to the corals than the oil itself, according to research done by a team of marine scientists from Israel's National Institute of Oceanography in Haifa.
These special chemicals break up oil slicks on the surface into tiny droplets to help disperse the spills. Because coral reefs are often located along coastal areas where oil production and transportation centers are common, they are sometimes the victims of accidental spills and are thus subjected to these dispersants. To determine their effect on individual corals, the scientists exposed small branch clippings, otherwise known as "nubbins," of two species — Stylophora pistillata and Pocillopora damicornis, both found in the Red Sea — to solutions of 6 different dispersants for a period of 24 hours and monitored their health for the ensuing week.
In all cases, a large majority of the coral nubbins died after being exposed to the mixtures of dispersants and oil, with dispersants alone causing up to two-thirds of the observed deaths. Oil alone, on the other hand, did not result in any abnormal mortalities. Baruch Rinkevich, one of the lead authors on the study, believes the mixture is deadly because the droplets of oil get pulled deeper underwater and come into direct contact with the corals.
Does that mean we should get rid of all dispersants then? Not necessarily, according to Richard Aronson, a marine biologist at the Dauphin Island Sea Lab in Alabama, who argues that they still have some use, albeit under the right circumstances. Just don't dump them directly on coral reefs.
The authors believe their findings indicate that spill-recovery crews should try to physically contain oil spills that happen near coral or allow them to degrade naturally. As John Bruno, another marine biologist, plainly put it, however, it all comes down to whether the decision-makers choose to take these results into consideration: "Sooner or later, we are going to see a truly devastating spill hit a coral reef. Will the people that decide how to respond take the lessons of this timely study into account?"
Via ::ScienceNOW: For Coral, a Cure Worse Than the Disease (news website)
See also: ::Melting Coral Epidemic Sparked by Warming Oceans, ::Caribbean Corals Heading Towards Extinction?, ::Corals Engage in Fisticuffs with Global Warming
Images courtesy of laurence_grayson and YourLocalDave via flickr