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Purpose The main objective of the current study was to assess the impact of pleasure boat activities on harbour sediment quality in the Stockholm area. Sediment contamination is a growing ecological issue, and there is consequently a need to use sediment bioassays in combination with chemical analysis to determine the impact on the ecosystem. To generate sediment toxicity data relevant for the Baltic Sea, a secondary objective was to further develop and evaluate two well-established bioassays for saltwater, with the macroalga Ceramium tenuicorne and the crustacean Nitocra spinipes, to be useful also for toxicity testing of whole sediment. A major concern has been to minimize any manipulation of the sediments. A third objective was to assess whether a simple leaching procedure could be used to simulate sediment toxicity by comparing results from whole sediment and leachate tests. Materials and methods Surface sediments (0-2 cm) from five different types of pleasure boat harbours were collected. Chemical measurements of boat related compounds, i.e. tin organic substances (tributyltin (TBT), dibutyl tin, and monobutyl tin), polyaromatic hydrocarbons (PAHs), copper, zinc, lead, tin and irgarol were conducted. The sediments were tested for toxic effects using the established Microtox® test as well as the developed sediment tests with C. tenuicorne and N. spinipes. The endpoints are growth inhibition for the algal test and for the crustacean test mortality of larvae and rate of development expressed as the ratio between nauplia and copepodites. Two different procedures have been compared with both organisms, i.e. exposure to whole sediment and to leachate. The duration of both tests is around 1 week. Results and discussion All harbour locations were more or less heavily contaminated with remnants from use of antifouling paints. The sediment in a smaller marina (ca. 250 boats) contained the highest levels of TBT (max 1,400 µg/kg dry weight (dw)), whereas the centre of Stockholm City had the highest concentrations of all measured metals (max values Cu 252, Pb 830, Sn 25 and Zn 600 µg/kg dw) as well as high concentrations of total PAH (18 mg/kg dw). All three organisms were well suited to test the toxicity of contaminated sediments and were able to discriminate between more or less polluted sediments. The sediments in the smaller marina were most toxic along with sediments adjacent to slipways and sediments from the centre of Stockholm. No significant difference was found between the two different procedures for the algal tests. The whole sediment test was significantly more toxic to N. spinipes than the test using leachate. Conclusions Our results show that in spite of prohibition for many years to use tin organic substances and copper, boat activities still contribute with high concentrations of these toxic substances from anti-fouling paints in the surface sediment and that these have effects on organisms normally living in this environment. The present study has also demonstrated an expansion of two well-established t...

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