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(59-01) Seasonal variation in effects of zinc- and copperpyrithione on aquatic microbial communities. Dahllöf, Ingela*,1, Maraldo, Kristine1, 1 NERI, Fredriksborgvej 399, Roskilde, Denmark ABSTRACT- Zinc- and copperpyrithione (ZPT and CPT) are two related anti-fouling compounds where ZPT was recently introduced on the Danish market. The effect of ZPT and CPT was investigated from March to mid August 2001 using aquatic microbial communities from Roskilde fjord, Denmark. The investigation included both algal and bacterial communities using 14C-incorporation, chlorophyll a and leucine-incorporation as endpoints. Size-fractionated (SF),14C-incorporaton and Chla were measured. ZPT experiments were performed eleven times (three for bacteria) and CPT experiments were performed seven times (three for bacteria). Changes in toxicity throughout the season were followed, as well as changes in nutrient levels, temperature, total and SF-chlorophyll and algal community structure. Changes in EC50 ZPT and CPT varied between 2 and 50 nM and 3 and 24 nM, respectively, for algal communities throughout the experimental period. EC50 for bacterial communities were at the three occasions between 5 and 8 nM. The changes in toxicity were partly due to changes in temperature, with higher EC50 values at higher temperatures. However, results from multivariate analysis, where toxicity changes are put in relation to abiotic factors and community structure, will be presented, in an attempt to further explain the observed differences in toxic response. Key words: zpt, cpt, microbial communities, mulitvariate analysis |
