ABSTRACT
A great number of pulp mills border the coast of the northern Baltic, particularly along the Gulf of Bothnia. Surveys of the benthic macrofauna, which have regularly been carried out in the receiving waters during the last 20 years, have generally failed to detect changes more than 2–3 km from the pulp mill. In contrast we found effects on the meiofauna community several kilometers beyond the area earlier reported as affected when macrofauna density and biomass were used. Density and biomass of nematodes were low at all stations except one when compared with the reference station and a strong negative correlation (p < 0.01) occurred between nematodes and sediment concentrations of EOCl. The most abundant Baltic ostracod (Paracyprideis fennica) appeared particularly sensitive. Its density and biomass were generally reduced when compared with the reference and also showed a strong negative correlation with EOCl (p < <0.001). Kinorhynchs were reduced in density and biomass at all stations except the southernmost but showed no clear correlation with the concentration of EOCl, suggesting other factors were responsible for the reduction. Density of harpacticoids on the innermost station was higher than other sites in the area and there was no correlation between density and EOCl. The pulp mill changed the bleaching process (from chlorine to elemental chlorine free) between 1987 and 1991. This resulted in substantially decreased discharges of COD and chlorinated substances. Meiobenthic responses at the inner station indicated a recovery of most taxa and species except the most sensitive ostracod species, Paracyprideis fennica, which was still absent close to the mill.
