Dissolved humic substances – ecological driving forces from the individual to the ecosystem level ? *

*Institute of Biology, Freshwater Ecology, Arboretum, Humboldt University at Berlin, Berlin, Germany †Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany ‡Faculty of Biology, Moscow State University, Moscow, Russia §Institute of Botany, Zˇ aliu ̨ ju ̨ Ezˇeru ̨ , Vilnius, Lithuania –Central Asian Hydrometerological Institute NIGMI, Tashkent, Uzbekistan **Institute of Biology, Irkutsk State University, Irkutsk, Russia ††Baikalian Research Centre, Irkutsk, Russia ‡‡Environment and Engineering Department, College of Resource and Environment, Huazhong Agricultural University, Wuhan, China §§Departamento de Ecologica, Universidade Federal do Rio de Janeiro, Ilha do Funda ̃o, Rio de Janeiro, RJ, Brazil ––Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, U.S.A. ***Environment Canada, National Water Research Institute, Burlington, ON, L7R 4A6 Canada