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Description: TITLE: FUNCTIONAL POTENTIAL AS A DRIVER OF TAXON-SPECIFIC FITNESS IN CYANOBACTERIAL BLOOMS
Abstract:Cyanobacteria are a common component of phytoplankton of aquatic ecosystems. In freshwaters and some estuaries, dense accumulations, or blooms of cyanobacteria are a common phenomenon. Blooms may have a negative impact on recreational activities and they potentially impact human and ecosystem health by producing a variety of bioactive compounds, including some characterized as toxins (hepatotoxins, neurotoxins). Many bloom-formers are also capable of fixing atmospheric nitrogen (N2), providing them a niche when combined N is limiting in the environment. A field study conducted in the St. Johns River, Florida, showed that by using facultative diazotrophy, the toxin-producing, N2-fixing cyanobacterium Cylindrospermopsis raciborskii effectively competes in the phytoplankton community under both N limiting and N replete conditions. Studies from Klamath River and San Francisco Bay Delta, California, demonstrated microdiversity among the populations of Microcystis aeruginosa that is not evident in existing culture isolates, and gradual adaptation to the local conditions that may influence toxicity. Laboratory studies further suggested that light intensity plays a key role in the relative success of toxic and nontoxic strains of M. aeruginosa in blooms. These data demonstrate that a range of environmental and community-level interactions influence the composition and toxicity of cyanobacterial blooms.