ASSESSING IMPACTS ON BALTIC COASTAL ECOSYSTEMS WITH MESOCOSM AND FISHBIOMARKER TESTS - A COMPARISON OF NEW AND OLD WOOD PULP BLEACHING TECHNOLOGIES

This study has taken an advanced ecotoxicological approach to assess t he effects on the aquatic environment of pulp bleaching effluents (rep resenting different types of bleaching technology) using land-based mo del ecosystems which mimic the sublittoral zone of the Baltic Sea. Exp osure was carried out at realistic, low concentrations over a time per iod of 4.5 months. The effluent from the conventional or oldest bleach ing technology was most toxic to invertebrates, causing secondary effe cts on algal production. However, when assessing the overall effects o n algae, invertebrates, fish growth and fish physiology caused by the effluents from newer bleaching technologies, no correlation was observ ed between concentration of adsorbable organic halogen (AOX) and level of effect. Nor was there any correlation between the levels of conjug ated chlorophenolics or resin acids in the bile of rainbow trout and p hysiological effects in the fish. This lack of relationship between co ncentration of chlorinated organic substances and biological responses makes it necessary to search for alternative bioactive compounds. Pos sible candidates might be plant sterols originating from the pulped wo od.