The effects of a cyanobacterial crude extract on different aquatic organisms: Evidence for cyanobacterial toxin modulating factors

In an aquatic ecosystem, during cyanobacterial bloom lysis, a mixture of to xins and other cyanobacterial and bacterial components will be present in t he water, acting on aquatic organisms. Most of the research into toxic effe cts of cyanobacteria has involved the use of purified toxins. In this study , the "real-life" situation of a cyanobacterial lysis event was investigate d. For this purpose, intact cells from a natural cyanobacterial bloom from Lake Muggelsee, Berlin, were taken and the cells were broken by repeated fr eeze/thaw cycles. This crude extract was used to expose several aquatic org anisms ranging from microalgae (Scenedesmus armatus), macrophyte (Ceratophy llum demersum), invertebrate (Chaoborus crystallinus) up to fish eggs (Dani o rerio) to look at several physiological parameters such as detoxication e nzyme activity and, in the case of the microalgae and the macrophyte, also the effect on activity of photosynthesis. In all the tests, the cyanobacter ial crude extract caused stronger effects than the pure cyanobacterial toxi ns used in equivalent concentrations. (C) 2001 by John Wiley & Sons, Inc.