Toxicity of third generation dispersants and dispersed Egyptian crude oil on Red Sea coral larvae

Harmful effects of five third-generation oil dispersants (Inipol IP-90, Petrotech PTI-25, Bioreico R-93, Biosolve and Emulgal C-100) on planula larvae of the Red Sea stony coral Stylophora pistillata and the soft coral Heteroxenia fuscescense were evaluated in short-term (2-96 h) bioassays. Larvae were exposed to Egyptian oil water soluble fractions (WSFs), dispersed oil water accommodated fractions (WAFs) and dispersants dissolved in seawater, in different concentrations. Mortality, settlement rates and the appearance of morphological and behavioural deformations were measured. While oil WSF treatments resulted in reductions in planulae settlement only, treatments by all dispersants tested revealed a further decrease in settlement rates and additional high toxicity. Dispersed oil exposures resulted in a dramatic increase in toxicity to both coral larvae species. Furthermore, dispersants and WAFs treatments caused larval morphology deformations, loss of normal swimming behaviour and rapid tissue degeneration. Out of the five tested dispersion agents, the chemical Petrotech PTI-25 displayed the least toxicity to coral larvae. We suggest avoidance of the use of chemical dispersion in cases of oil spills near or within coral reef habitats. (C) 2000 Elsevier Science Ltd.