[Coral-List] The effects of spilled oil on tropical marine systems

Glazer, Bob Bob.Glazer at MyFWC.com
Mon May 3 12:15:41 EDT 2010

Sorry for x-posts.

We, like everyone else along the coasts of the Gulf of Mexico, are sitting and hoping that the oil from Deepwater Horizon blowout doesn't reach our shores.  There have been several posts on the coral-list that have presented widely differing observations on the effects of oil on live corals.  Some have said there is no effect; others contradict that assertion.  However, I thought it wise to point out probably the most definitive study to date by Jeremy Jackson and colleagues who characterized the >8 million liter medium-weight crude oil spill (the current spill in the Gulf of Mexico has been reported to be light sweet crude but there is currently some discrepancy related to this) into the Panamanian coastline (Jackson et al. 1989. Ecological Effects of a Major Oil Spill on Panamanian Coastal Marine Communities. Science  pp 37-44). This is the spill that Gene alluded to; it resulted from a ruptured land-based storage tank.   Their assessment had the benefit of having baseline data acquired prior to the spill with which to compare the effects.

Without going too much into their results. I will briefly say that the oiling had a tremendous impact on red mangroves with whole coastal strips perishing.  Transplanted  mangroves did not take.  Thalassia testudinum beds died on oiled reef flats. Scleractinian corals in water depths <3m had from 45% - 96% loss of coral cover depending on the locations whereas unoiled reefs had essentially no loss in coral cover.  Although some effects were seen in deeper colonies, they report that the effects were not statistically significant.

That is just a brief overview of their findings.  There is a lot more to read in this article that can help us anticipate what we may encounter.  Many of you will remember the late Dr. Brian Keller's presentations at various fora on this event and it is at times like this that we miss his science most.

The complete Science article can be found at: http://cmbc.ucsd.edu/content/1/docs/jackson1989.pdf

Finally, in response to those who say there is no effect, the authors conclude that their study demonstrates that the assertion that there are no effects on subtidal corals is erroneous.  They acknowledge that dispersants may have played a role but also state that it is unlikely that dispersants alone were responsible for the mortality in corals and seagrasses.

Robert Glazer
Associate Research Scientist
Florida Fish and Wildlife Conservation Commission
Fish and Wildlife Research Institute
2796 Overseas Hwy., Ste. 119
Marathon, FL 33050
305-289-2330; 305-289-2334 (fax)
bob.glazer at myfwc.com<mailto:bob.glazer at myfwc.com>

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