Anatoxin-a and neurotoxic cyanobacteria in German lakes and reservoirs

During a screening program conducted from 1995 to 1997 in Germany, 80 water bodies were analyzed, some regularly, some sporadically, for content of the neurotoxin anatoxin-a. Analysis for the majority of the samples was differentiated between anatoxin-a contained in the cells and that dissolved in the water. A total of 554 extracts (from 393 samples, many with analysis of seston as well as filtrate for differentiation of intra- and extracellular toxin content) were extracted with CH,CI, and derivatized with pentafluorobenzylbromide for GC-ECD analysis with a detection limit of 2.5 x 10(-4) mu g L-1. Only 22% of all analyzed samples contained anatoxin-a, and the highest concentration found was 13.1 mu g L-1 (the sum of the toxin in the cells and in the water). if anatoxin-a was detected, it was usually found in the seston fraction, but only in some of the corresponding filtrates (with one exception, where it was detected only in the filtrate). In these cases, concentrations were often even higher than in the seston. The earliest occurrence of anatoxin-a during the year was in May and the latest in November. Usually Anabaena and/or Aphanizomenon were present when anatoxin-a was found, (C) 1999 by John Wiley & Sons, Inc.