title: How rising CO2and global warming may stimulate harmful cyanobacterial blooms.
abstract: Climate change is likely to stimulate the development of harmful cyanobacterial blooms in eutrophic waters, with negative consequences for water quality of many lakes, reservoirs and brackish ecosystems across the globe. In addition to effects of temperature and eutrophication, recent research has shed new light on the possible implications of rising atmospheric CO2concentrations. Depletion of dissolved CO2by dense cyanobacterial blooms creates a concentration gradient across the air-water interface. A steeper gradient at elevated atmospheric CO2concentrations will lead to a greater influx of CO2, which can be intercepted by surface-dwelling blooms, thus intensifying cyanobacterial blooms in eutrophic waters. Bloom-forming cyanobacteria display an unexpected diversity in CO2responses, because different strains combine their uptake systems for CO2and bicarbonate in different ways. The genetic composition of cyanobacterial blooms may therefore shift. In particular, strains with high-flux carbon uptake systems may benefit from the anticipated rise in inorganic carbon availability. Increasing temperatures also stimulate cyanobacterial growth. Many bloom-forming cyanobacteria and also green algae have temperature optima above 25°C, often exceeding the temperature optima of diatoms and dinoflagellates. Analysis of published data suggests that the temperature dependence of the growth rate of cyanobacteria exceeds that of green algae. Indirect effects of elevated temperature, like an earlier onset and longer duration of thermal stratification, may also shift the competitive balance in favor of buoyant cyanobacteria while eukaryotic algae are impaired by higher sedimentation losses. Furthermore, cyanobacteria differ from eukaryotic algae in that they can fix dinitrogen, and new insights show that the nitrogen-fixation activity of heterocystous cyanobacteria can be strongly stimulated at elevated temperatures. Models and lake studies indicate that the response of cyanobacterial growth to rising CO2concentrations and elevated temperatures can be suppressed by nutrient limitation. The greatest response of cyanobacterial blooms to climate change is therefore expected to occur in eutrophic and hypertrophic lakes.
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands. Electronic address: P.M.Visser@uva.nl.
authors.forename: Petra M
authors.initials: PM
authors.lastname: Visser
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands.
authors.forename: Jolanda M H
authors.initials: JMH
authors.lastname: Verspagen
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Sandrini
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands; Department of Marine Microbiology, Royal Netherlands Institute for Sea Research (NIOZ), P.O. Box 140, 4400 AC Yerseke, The Netherlands.
authors.forename: Lucas J
authors.initials: LJ
authors.lastname: Stal
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands.
authors.forename: Hans C P
authors.initials: HCP
authors.lastname: Matthijs
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: Institute of Marine Sciences, University of North Carolina at Chapel Hill, 3431 Arendell Street, Morehead City, NC 28557, USA.
authors.forename: Hans W
authors.initials: HW
authors.lastname: Paerl
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94248, 1090 GE Amsterdam, The Netherlands.
authors.forename: Jef
authors.initials: J
authors.lastname: Huisman
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D000458:Cyanobacteria / Q000502:physiology*; D005068:Eutrophication; D057232:Global Warming; D060106:Lakes
chemical_list: D002245:Carbon Dioxide
keywords: Climate change; Cyanobacteria; Harmful algal blooms; Lakes; Rising CO(2); Temperature