title: Eutrophication and Warming Boost Cyanobacterial Biomass and Microcystins.
abstract: Eutrophication and warming are key drivers of cyanobacterial blooms, but their combined effects on microcystin (MC) concentrations are less studied. We tested the hypothesis that warming promotes cyanobacterial abundance in a natural plankton community and that eutrophication enhances cyanobacterial biomass and MC concentrations. We incubated natural seston from a eutrophic pond under normal, high, and extreme temperatures (i.e., 20, 25, and 30 °C) with and without additional nutrients added (eutrophication) mimicking a pulse as could be expected from projected summer storms under climate change. Eutrophication increased algal- and cyanobacterial biomass by 26 and 8 times, respectively, and led to 24 times higher MC concentrations. This effect was augmented with higher temperatures leading to 45 times higher MC concentrations at 25 °C, with 11 times more cyanobacterial chlorophyll-aand 25 times more eukaryote algal chlorophyll-a. At 30 °C, MC concentrations were 42 times higher, with cyanobacterial chlorophyll-abeing 17 times and eukaryote algal chlorophyll-abeing 24 times higher. In contrast, warming alone did not yield more cyanobacteria or MCs, because the in situ community had already depleted the available nutrient pool. MC per potential MC producing cell declined at higher temperatures under nutrient enrichments, which was confirmed by a controlled experiment with two laboratory strains ofMicrocystis aeruginosa.Nevertheless, MC concentrations were much higher at the increased temperature and nutrient treatment than under warming alone due to strongly promoted biomass, lifting N-imitation and promotion of potential MC producers likeMicrocystis. This study exemplifies the vulnerability of eutrophic urban waters to predicted future summer climate change effects that might aggravate cyanobacterial nuisance.
authors.affiliation: Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands. miquel.lurling@wur.nl.|Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, 6700 AB, Wageningen, The Netherlands. miquel.lurling@wur.nl.
authors.forename: Miquel
authors.initials: M
authors.lastname: Lürling
authors.affiliation: Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands. jean.vanoosterhout@wur.nl.
authors.forename: Frank
authors.initials: F
authors.lastname: van Oosterhout
authors.affiliation: Aquatic Ecology & Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands. els.faassen@wur.nl.|Environmental Risk Assessment, Wageningen Environmental Research, Wageningen Resesarch, P.O. Box 47, 6700 AA Wageningen, The Netherlands. els.faassen@wur.nl.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Faassen
mesh_terms: D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000254:growth & development* / Q000378:metabolism*; D004784:Environmental Monitoring / Q000379:methods; D005068:Eutrophication; D052998:Microcystins / Q000009:adverse effects / Q000378:metabolism*; D061005:Ponds / Q000382:microbiology*; D013696:Temperature; D014871:Water Microbiology
chemical_list: D052998:Microcystins; D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: cell quota; climate change; cyanobacterial blooms; cyanotoxins; mitigation; seston