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1990
Book Article
Titel
Alteration of organic substances during Eutrophication and effects of the modified organic substances on trophic interactions
Abstract
As far as investigated, eutrophication of water bodies changes the quality of organic substances with special respect to volatile odorous compounds and toxic substances. Among the volatile odorous compounds, dienals, alkenols, alkenones, alcohols, and ketones, which are produced mainly by chrysophytes, dominate in noneutrophic environments. Some of these substances are known to affect other microorganisms. Under eutrophicated conditions, when cyanobacteria gain dominance, geosmin, 2-methylisoberneol, and certain nor-carotenoids are the odorous compounds. Several strains of cyanobacteria are known to produce alkaloid or peptide toxins that negatively affect invertebrates, fish, and other vertebrates, whereas a direct effect on bacteria remains uncertain. By excreting siderochromes that selectively chelate ferric iron in laboratory cultures, cyanobacteria can outcompete eukaryotic algae under conditions of iron limitation. Field evidence, however, is lacking. The community effect of the eutrophication-mediated change in organic substances is a decreasing significance of large-bodied grazers which, however, possess the highest filtering efficiency and the widest spectrum of ingested particles. This community shift, in turn, seems to promote the cyanobacterial maintenance.
Language
English