[Coral-List] Corexit oil dispersant and corals

[Robert H. Richmond]

In response to Ed Blume's and others' question on the effects of Corexit oil dispersant on corals, here is the summary from a Master's Thesis by a past graduate student of mine who performed some experiments on coral gametes and larvae:

MENDIOLA, W.J.C.  2004.  The effect of the oil dispersant, Corexit 9527, on reproduction of the spawning coral, Acropora surcuosa, and on larval settlement and metamorphosis of the brooding coral, Pocillopora damicornis. 40 pages. [Thesis Advisor:  R.H. Richmond].

Conclusions

The findings of this investigation clearly show that exposure to relatively realistic concentrations of Corexit 9527 may reduce fertilization in A. surculosa and reduce the larval settlement and metamorphosis of P. damicornis. One must keep in mind that these experiments were performed with dispersant only. During an actual oil spill, it is more likely that the larvae will be exposed to high amounts of dispersed oil rather than dispersant alone. As mentioned earlier, the effects of exposure to dispersed oil on many marine organisms is more damaging than oil or dispersant exposure alone. Epstein et al. (2000) found this to be true when testing six different oil dispersants (Inipol IP-90, Petrotech PTI-25, Bioreico R-93, Biosolve, and Emulgal C-100) on larvae of the coral, S. pistillata and Heteroxenia fuscescense. In an earlier study, Cook and Knap (1983) found that dispersed oil had a much more devastating effect on photosynthesis of the coral, D. strigosa than either the oil or dispersant alone (decreasing photosynthesis by 85% when exposed to 1 ppm of Corexit 9527 for 8 h). Negri and Heyward (2000) noted similar findings with respect to fertilization and metamorphosis of A. millepora larvae. 

The experiments in this study were used to determine the toxicity of Corexit 9527 alone on the corals, A. surculosa and P. damicornis. Further research is needed to determine the toxic effects of dispersed oil on these and other coral species through their life history stages. Armed with such data, environmental managers in this part of the world can better make informed decisions on whether to use this oil dispersant for oil spill clean up purposes. 



Please feel free to contact me for more details.



Bob



Robert H. Richmond, Ph.D.
Research Professor
Kewalo Marine Laboratory
University of Hawaii at Manoa
41 Ahui Street
Honolulu, Hawaii 96813
Phone: 808-539-7331
Fax: 808-599-4817
E-mail: richmond at hawaii.edu