Toxic nostocales (cyanobacteria) in water bodies

5July 2010
Leibniz Institute for Freshwater Ecology and Inland Fisheries

Final symposium of interdisciplinary project NOSTOTOX, supported by the Federal Ministry of Education and Research, Veolia Wasser and Berliner Wasserbetriebe

Background: Over the past few years it has been observed that microcystin-producing cyanobacteria (Microcystis and Planktothrix) have decreased in German lakes, while species of the order Nostocales – native species as well as invasive species from tropical regions – have increased. As a consequence, minor microcystin concentrations have been observed while the toxin cylindrospermopsin that is produced by Nostocales, has been found to be widely distributed and to exceed the recommended drinking water guideline value of 1 μg L-1 in many cases. Recent data on the occurrence of further neurotoxins produced by cyanobacteria of the order Nostocales did not exist. Nostocales are superior competitors under conditions of high light intensity and nitrogen depletion because they can fix molecular nitrogen. The germination of their overwintering akinetes is regulated by temperature and the temporal starting point of the pelagic population development in spring determines the population size (the earlier the larger).
Working hypothesis: Combined effects of a declining trophic state and global warming benefit the development of Nostocales and cause a shift in species composition as well as in occurrences of certain toxins.
Aims: Mechanisms regulating Nostocales population dynamics and their toxin production as well as the decomposition of the toxins shall be studied along nutrient, light and temperature gradients.
Design models to simulate and predict the future abundance of Nostocales as well as the concentrations of their toxins that can be expected under conditions of continued declining trophic state and temperature increase.
Create a profound scientific basis on which management recommendations for inland waters as well as decision support systems required for the risk assessment of the drinking water supply can be developed.