title: The ecological stoichiometry of toxins produced by harmful cyanobacteria: an experimental test of the carbon-nutrient balance hypothesis.
abstract: The elemental composition of primary producers reflects the availability of light, carbon and nutrients in their environment. According to the carbon-nutrient balance hypothesis, this has implications for the production of secondary metabolites. To test this hypothesis, we investigated a family of toxins, known as microcystins, produced by harmful cyanobacteria. The strain Microcystis aeruginosa HUB 5-2-4, which produces several microcystin variants of different N:C stoichiometry, was cultured in chemostats supplied with various combinations of nitrate and CO(2). Excess supply of both nitrogen and carbon yielded high cellular N:C ratios accompanied by high cellular contents of total microcystin and the nitrogen-rich variant microcystin-RR. Comparable patterns were found in Microcystis-dominated lakes, where the relative microcystin-RR content increased with the seston N:C ratio. In total, our results are largely consistent with the carbon-nutrient balance hypothesis, and warn that a combination of rising CO(2) and nitrogen enrichment will affect the microcystin composition of harmful cyanobacteria.
authors.affiliation: Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam, The Netherlands.
authors.forename: Dedmer B
authors.initials: DB
authors.lastname: Van de Waal
authors.forename: Jolanda M H
authors.initials: JM
authors.lastname: Verspagen
authors.forename: Miquel
authors.initials: M
authors.lastname: Lürling
authors.forename: Ellen
authors.initials: E
authors.lastname: Van Donk
authors.forename: Petra M
authors.initials: PM
authors.lastname: Visser
authors.forename: Jef
authors.initials: J
authors.lastname: Huisman
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D005618:Fresh Water / Q000032:analysis; D052998:Microcystins / Q000096:biosynthesis*; D046931:Microcystis / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D014871:Water Microbiology
chemical_list: D052998:Microcystins; D002245:Carbon Dioxide; D009584:Nitrogen