Toxicity assessment of oil components and an oil treating agent using the Photobacterium phosphoreum bioassay

The Microtox test, based on the bioluminescence inhibition of the marine bacterium Photobacterium phosphoreum was used to evaluate the toxicity of oil in seawater. First, the toxicity of the water soluble fraction (WSF) of a crude oil and its constituents such as aromatic and polyaromatic hydrocarbons was tested. The WSF toxicity was monitored while the evaporation and the photooxidation of oil components were in progress. In addition, the toxicity of various oil fractions formed in the marine environment after an oil spill, such as emulsified or degraded oil residues, surface film, dissolved components in the water column, and settling oil residues, were tested for their potential toxicity over a 2-month summer experiment conducted in five 3.5-m3 mesocosms. A new anti-adhesive oil-treating agent designed for the treatment of oil slicks at sea was also tested in mesocosms together with the treated crude oil. These preliminary results show that the Microtox test is very sensitive to oil compounds. Used in combination with mesocosms, it provides an efficient experimental tool to assess the toxicity of crude oil spilled at sea under natural conditions. 21 refs., 4 figs., 5 tabs