title: The dual role of nitrogen supply in controlling the growth and toxicity of cyanobacterial blooms.
abstract: Historically, phosphorus (P) has been considered the primary limiting nutrient for phytoplankton assemblages in freshwater ecosystems. This review, supported by new findings from Lake Erie, highlights recent molecular, laboratory, and field evidence that the growth and toxicity of some non-diazotrophic blooms of cyanobacteria can be controlled by nitrogen (N). Cyanobacteria such as Microcystis possess physiological adaptations that allow them to dominate low-P surface waters, and in temperate lakes, cyanobacterial densities can be controlled by N availability. Beyond total cyanobacterial biomass, N loading has been shown to selectively promote the abundance of Microcystis and Planktothrix strains capable of synthesizing microcystins over strains that do not possess this ability. Among strains of cyanobacteria capable of synthesizing the N-rich microcystins, cellular toxin quotas have been found to depend upon exogenous N supplies. Herein, multi-year observations from western Lake Erie are presented demonstrating that microcystin concentrations peak in parallel with inorganic N, but not orthophosphate, concentrations and are significantly lower (p<0.01) during years of reduced inorganic nitrogen loading and concentrations. Collectively, this information underscores the importance of N as well as P in controlling toxic cyanobacteria blooms. Furthermore, it supports the premise that management actions to reduce P in the absence of concurrent restrictions on N loading may not effectively control the growth and/or toxicity of non-diazotrophic toxic cyanobacteria such as the cosmopolitan, toxin-producing genus, Microcystis.
authors.affiliation: School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Hwy, New York 11968, USA. Electronic address: christopher.gobler@stonybrook.edu.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Gobler
authors.affiliation: Center for Applied Aquatic Ecology, North Carolina State University, Raleigh, NC 27606, USA.
authors.forename: JoAnn M
authors.initials: JM
authors.lastname: Burkholder
authors.affiliation: NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48108, USA.
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Davis
authors.affiliation: School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Hwy, New York 11968, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Harke
authors.affiliation: Cooperative Institute for Limnology and Ecosystems Research, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Johengen
authors.affiliation: NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48108, USA.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Stow
authors.affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Post Office Box 50, Wageningen 6700 AB, The Netherlands.
authors.forename: Dedmer B
authors.initials: DB
authors.lastname: Van de Waal
mesh_terms: D000458:Cyanobacteria / Q000378:metabolism / Q000502:physiology*; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology; D052998:Microcystins / Q000378:metabolism / Q000633:toxicity; D009584:Nitrogen / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism
chemical_list: D052998:Microcystins; D010758:Phosphorus; D009584:Nitrogen
keywords: Cyanobacteria; Diazotrophy; Microcystis; Nitrogen; Nutrients; Phosphorus