1. Institute of Biochemical Technology and Microbiology 172/5, Technical University of Vienna, 1060 Vienna,1
2. Institute of Water Quality and Waste Management, Department of Chemistry and Microbiology, Technical University of Vienna, 1040 Vienna,2
3. Institute of Water Quality, Federal Agency for Water Management, 1220 Vienna,3
4. Yppenplatz 5/18, 1160 Vienna,4 and
5. Institute of Zoology, University of Vienna, 1090 Vienna,5Austria