1. Department of Environmental Chemistry and Ecotoxicology, University of Gdañsk, 18 Sobieskiego Street, PL 80-952 Gdañsk, Poland, Environmental Measurement Group, National Institute of Advanced Industrial Science and Technology, Onogawa 16-1, Tsukuba, Ibaraki 305-8569, Japan, and Department of Ecology and Evolution, Johan Wolfgang Goethe - University Frankfurt, 70 Siesmayerstrasse, D-60054 Frankfurt, Germany