1. Department F.-A. Forel for Environmental and Aquatic Sciences, University of Geneva, Boulevard Carl-Vogt 66, CH-1205 Geneva, Switzerland
2. Institute of Analytical Chemistry of the Czech Academy of Sciences, Veveří 97, 602 00 Brno, Czech Republic
3. Service de l’écologie de l’Eau, Geneva, Switzerland
4. Museo Nacional de Ciencias Naturales, CSIC, Serrano 115 dpdo, E-28006 Madrid, Spain