CONCENTRATIONS, BIOMAGNIFICATION AND SPATIAL VARIATION OF ORGANOCHLORINE COMPOUNDS IN A PELAGIC FOOD-WEB IN THE NORTHERN PART OF THE BALTICSEA

Zooplankton, mysis (Mysis sp.) and herring (Clupea harengus) were coll ected at two pelagic locations in the northern part of the Baltic Sea, one in Bothnian Bay (BB) and the other in the Bothnian Sea (BS), in o rder to investigate concentrations, composition profiles, biomagnifica tion features and spatial differences of organochlorine contaminants. Compounds included in this study are hexachlorocyclohexanes (HCHs), DD Ts, hexachlorobenzene (HCBz), chlordanes (CHLs), dieldrin, mirex and p olychlorinated biphenyls (PCBs). All groups of compound were detected in every sample investigated, with the exception of mirex that was det ected only in the herring samples. The concentrations of organochlorin e compounds in all samples ranged, e.g. from 250 to 1500 ng/g lipid fo r PCBs and from 6 to 1500 ng/g lipid for CHLs. The biomagnification fa ctor (BMF) is calculated as the concentration of the compounds in the organism divided by the concentration in food normalised to lipids. In the zooplankton-mysis-herring food web, large variations in BMFs betw een the different compound groups were observed. The highest BMFs were obtained for the CHLs followed by the DDTs and the lowest for the HCH s. Nonachlorinated CHLs had the highest BMFs within the group of CHLs and for the DDTs p,p'-DDT had a higher biomagnification potential than its metabolites p,p'-DDE and p,p'-DDD. Finally, concentration and bio magnification differences between the two stations were observed. The herring in the southernmost station (BS) displayed approximately two- to sixfold higher biomagnification than the herring from the north (BB ). (C) 1998 Elsevier Science B.V. All rights reserved.