Fachdokumente Online der Landesanstalt für Umwelt Baden-Württemberg

zur LUBW   zum Ministerium für Umwelt, Klima und Energiewirtschaft   zum Ministerium für Ländlichen Raum und Verbraucherschutz   zum Ministerium für Verkehr und Infrastruktur  


Assessment of causes, frequency and toxicological significance of toxic cyano-bacteria blooms in recreational waters. Development of measures to protect the general public.

Results of an investigation of distribution and frequency of cyanobacteria and cyano-toxins in freshwater lakes of Baden-Württemberg, South-West-Germany, are presented. Species known to produce toxins are Anabaena, Aphanizomenon, Microcystis, Planktothrix and Limnothrix.

In 1999 nutrients, dominant species, chlorophyll and toxins have been investigated. 155 water bodies, most of them with recreational use, were sampled, 76 of them frequently. A total of 397 samples were analysed, 325 for cyanobacteria. 55 % of the monitored lakes displayed a reasonable amount of cyanobacteria. Dominance occurred throughout the vegetation period with a maximum of occurrence between July and September. Dominance was observed even below guide levels for total phosphorus (40 µg/L) as proposed by UBA (German environmental agency). Microcystin concentrations in these lakes were up to 45 µg/L. The highest microcystin value was 566 µg/L. Therefore, there is a risk of development of toxic cyanobacterial bloom during the bathing season. The amount and variability of the toxin concentrations is not proportional to total phosphorus and chlorophyll-a. Therefore, the monitoring of lakes should include the toxin analysis for safety reasons. The toxin values measured have to be related to the chlorophyll-a content or, preferably, to the biovolume.


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