Toxicities of Diesel Oil, Dispersant and Dispersed Oil to Tetraselmis chuii and Chaetocheros calcitrans.

Oil spillage accidents can cause severe short-term effects to marine organisms and may lead to devastating long-term impact to marine environments. This study determined the influence of water accommodated fractions (WAFs) of diesel oil, chemically enhanced WAFs (CEWAFs) of diesel oil and oil dispersant (IPAC-OCD) to the toxicity of green algae, Tetraselmis chuii, and marine diatom, Chaetocheros calcitrans. Both the phytoplankton species were exposed to different concentrations of WAFs, CEWAFs and dispersant (0%, 5%, 10%, 20%, 40%, 80%). All of the toxicants significantly reduced the growth of phytoplankton, however, the level of response varied by solution and species. The dispersant has the highest impact among all the chemicals studied. The dispersant is very highly toxic to C. calcitrans, but still practically non-toxic to T. chuii. Even though, WAFs have higher impact to T. chuii than C. calcitrans, the chemicals are practically non-toxic to both phytoplankton species and, moreover, in short-term exposure, low concentration of WAFs may stimulate the growth of C. calcitrans. However, the mixture of diesel oil WAFs and dispersant cause synergistic toxicity to C. calcitrans that increases the WAFs toxicity. This finding implies that the dispersant application to mitigate the oil spills may negatively impact the marine phytoplankton. [ABSTRACT FROM AUTHOR]