Chlorinated dibenzo-p-dioxins and dibenzofurans patterns in the baltic herring and sprat

Contents of persistent organic pollutants in the sea organisms have been studied in Estonia since the early seventies. In our earlier work the profile of polychlorinated biphenyls in grey seals from the Baltic, Eastern and Northern-Eastern England, and the St. Lawrence Estuary (Canada), were examined by Principal Component Analysis (PCA). The patterns differ between juveniles and adult animals, but the gender of adults and geography do not appear to play a role . The objective of this paper is to examine the patterns of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the Baltic herring (Clupea harengus) and sprat (Sprattus sprattus). In the end of September – beginning of October, 2002, fish samples were taken for testing the dioxin level were collected from four areas of Estonian coastal sea. The analysis of fish samples was done at the Institute of Ecological Chemistry of the National Research Centre for Environment and Health in Neuhenberg (Germany). The concentrations were centered by subtracting means, and scaled by dividing by standard deviations. For an examination of the CDDF ‘ profiles’ , the concentrations were adjusted to a sum of 100 (%) before centering and scaling (Table 4). The data were analyzed by Principal Component Analysis (PCA). In the 1980s-90s the feeding of pelagic fishes, changed due to altered hydrological conditions. The feeding intensity of herring decreased and its food spectrum shifted towards the energetically less valuable zooplankton. As a result, the mean body weight of herring and sprat decreased significantly. Increase in the percentage rate of empty stomachs of Baltic herring and sprat in the beginning of 1990s may turn out to be one of the reasons for the decrease of persistent organic pollutants concentration in Baltic fish and seals.