^aInstitute of Freshwater Ecology and Inland Fisheries, Department of Ecohydrology, Rudower Chaussee 6a, D-12489 Berlin, Germany,^bDepartment of Chemistry, Ben-Gurion University of the Negev, PO Box 653, Beer Sheva 84105, Israel, and ^cZentrum Mathematik, Technische Universität München, D-80290 München, Germany
Correspondence e-mail: yoel@bgumail.bgu.ac.il