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3C - Fate and effects of TBT (WEP/167) Effects of tributyltin and nutrients on coastal North Sea plankton communities in enclosures. Jak, Robbert1, 1 TNO-MEP, Dept. for Ecological Risk Studies, Den Helder, The Netherlands ABSTRACT- Marine copepods have shown to be relatively sensitive to the antifoulant tributyltin (TBT). To assess ecotoxicity levels and its consequences on plankton community functioning, a number of enclosure studies were performed. In a dose-regression designed experiment, with six duplicated concentrations in enclosures of 1.2 m3, effect levels were assessed for the dominant copepod Temora longicornis. Effect levels varied with exposure time, since exposure concentrations showed a first order decrease. Considering actual effective concentrations, an EC10 for population development was estimated as low as 2.4 ng/L. The impairment of copepod development resulted in an increase of gross primary production, as was manifested by enhanced pH levels. In two additional experiments the interaction between TBT (EC50 level) and nutrient additions were studied: a regression design (range of nutrient addition levels * 2 TBT levels), and a factorial design (2 nutrient * 2 TBT levels). The latter experiments showed that the biomass of the copepod community increased with nutrient supply, and that this increase was hampered by TBT. Also phytoplankton levels were enhanced by nutrient supply, TBT did not contribute to enhanced phytoplankton levels as a consequence of reduced grazing. Measured concentrations of TBT in the coastal environment have shown to be in the range of EC50 values for copepod development. Moreover, highest concentrations of TBT are found in the summer period when copepod production is most significant. The impact of TBT on plankton communities will be presented and discussed with regard to ecological implications at environmental relevant levels. Key words: zooplankton communities, TBT, enclosures |
