1. Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FIN-40351 Jyväskylä, Finland (E-mail: esa.salminen@jyu.fi, jukka.rintala@jyu.fi)
2. Water Problems Institute, Russian Academy of Sciences, Gubkina str. 3, 117735 Moscow, Russia (E-mail: vavilin@iwapr.msk.su)