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(433) Modes of action of whole sediment and elutriate on embryogenesis in oysters, Crassostrea gigas. Geffard, Olivier1, His, Edouard1, Seaman, Matthias2, Budzinski, Hélène3, Garrigues, Philippe3, 1 2 3 ABSTRACT- The toxicity of contaminated sediments is usually evaluated using either of two sediment treatments: whole sediment and sediment elutriates. We investigated the mechanisms by which these two act upon embryos and larvae of oysters, Crassostrea gigas. First we evaluated the degree of contamination and the toxicity of 10 different marine sediments. Three of these sediments were subsequently selected to study the modes of action of the two sediment treatments. The first sediment was contaminated by heavy metals, the second by polyaromatic hydrocarbons (PAH), and the third was contaminated by both. The strongest biological effects were caused by whole sediment, mostly during the phase preceding the formation of the embryos (i.e., during the first six hours of exposure to the sediment particles). The effects were closely correlated to the degree of contamination. The whole sediments therefore accurately reflect the potential toxicity of sediments present in the natural environnement. The toxicity of the elutriates was not correlated to the degree of contamination, but it was correlated to the levels of dissolved organic carbon, which is known to play an important role in the bioavailability of micropolluants. The elutriates therefore reflect micropollutant toxicity resulting from sediment resuspension during dredging operations and from the dumping at sea of contaminated sediments. Key words: Sediment toxicity, Bioassays, Whole sediment and elutriate, Oyster embryos and larvae |
