PYRENE TOXICITY TO AQUATIC PELAGIC AND BENTHIC ORGANISMS IN SINGLE-SPECIES AND MICROCOSM TESTS

The fate and effects of pyrene, an ubiquist PAH, were studied in single-species tests and laboratory microcosm assays using two lacustrine sediments of contrasted organic carbon content (TOC : 1.3 and 20.9%). Sediment-associated pyrene content declined rapidly in the 28-day microcosm assays, likely due to a decrease of pyrene extractibility. From exposure to dissolved pyrene, the first acute effects were observed at < 10 μ g/L for microalgae, around 10 μ g/L for microcrustacean invertebrates, whereas pyrene was not acutely toxic to duckweeds. In microcosms (tested nominal concentration : 50 g/g wet sediment), response of pelagic and benthic organisms could be mainly explained by exposure to water phases, either overlaying water (daphnids) or pore water (amphipods). Chironomids were not sensitive to pyrene. The lower toxicity observed in microcosms with the organic rich sediment could be explained by differences in pyrene partition due to the amount of organic carbon, as predicted by the EqP theory.