Responses of the soft coral Xenia elongata following acute exposure to a chemical dispersant

TitleResponses of the soft coral Xenia elongata following acute exposure to a chemical dispersant
Publication TypeJournal Article
Year of Publication2015
AuthorsStudivan MS, Hatch WI, Mitchelmore CL
Date Published2015
Accession NumberMEDLINE:25713766
KeywordsDeepwater Horizon Oil Spill
AbstractLimited toxicology data are available regarding oil dispersant exposure to coral species. Corexit EC9500A (Corexit) is a commonly applied dispersant most well known for its use after the Deepwater Horizon spill in April, 2010. There is limited evidence that Corexit can cause a bleaching response in corals. The aims of the study were: (1) to determine the extent of bleaching after acute 24h and 72h exposures of sublethal concentrations (0-50ppm) of Corexit to the pulsing soft coral Xenia elongata and (2) to investigate a percent symbiont loss calculation using zooxanthellae density. The percent symbiont loss calculation was compared to a traditional metric of normalizing zooxanthellae density to soluble protein content. Percent symbiont loss was an effective measure of coral stress in acute Corexit exposures, while protein normalized zooxanthellae density was more variable. The bleaching data suggest a positive relationship between dispersant concentration and percent symbiont loss, culminating in excessive tissue necrosis and coral mortality within 72h in high concentration exposures (p<0.001). Percent beaching ranged from 25% in 5ppm exposures to 100% in 50ppm exposures. Corexit also caused a significant decrease in pulse activity (p<0.0001) and relative oxygen saturation (p<0.001), possibly indicating a reduction in photosynthetic efficiency. This study and other similar research indicate that dispersant exposure is highly damaging to marine organisms, including ecologically important coral species.