Microcystis aeruginosa adversely impacts Daphnia spp.: Posing risks to food webs of the Great Lakes

Session: 41a. - Great Lakes Harmful Algal Blooms Research from Watershed Influence to Ecosystem Effects

Rene Shahmohamadloo, University of Guelph, rshahmoh@uoguelph.ca
David Poirier, Ontario Ministry of Environment and Climate Change, Dave.Poirier@ontario.ca
Xavier Ortiz Almirall, Ministry of Environment and Climate Change, Xavier.Ortiz@ontario.ca
Denina Simmons, University of Ontario Institute of Technology, denina.simmons@ontario.ca
Kathleen Stevack, University of Guelph, kstevack@uoguelph.ca
Satyendra Bhavsar, Ontario Ministry of Environment and Climate Change, s.bhavsar@utoronto.ca
Paul Sibley, University of Guelph, School of Environmental Sciences, psibley@uoguelph.ca

Abstract

Harmful algal blooms dominated by Microcystis are a troublesome nuisance to freshwater ecosystems used for drinking, irrigation, fishing, and recreational purposes. Many Microcystis blooms produce strains of the hepatotoxin microcystin that is capable of inflicting harm to zooplankton. Research on the effect of microcystins on zooplankton remains elusive; from one perspective, studies suggest Daphnia can be used to suppress phytoplankton, including cyanobacteria, and coexist in toxic blooms; however, studies have also indicated toxic effects on Daphnia that consume cell-bound microcystin. This dual perspective may be attributable to an evolutionary adaptation in Daphnia that ensures survival and reproduction in toxic cyanobacterial blooms. We examined reproduction and survival of laboratory-cultured Ceriodaphnia dubia and Daphnia magna in microcystin-producing Microcystis aeruginosa through a series of life-cycle bioassays. Test organisms were exposed to a concentration gradient ranging from 0.5 ?g/L to 100 ?g/L microcystin-LR which corresponds to values typically found in the Great Lakes during bloom season. Mortality was observed in C. dubia (LC₅₀ = 2 ?g/L) and D. magna (LC₅₀ = 37 ?g/L) exposed to microcystin-LR, and reproductive effects at concentrations as low as 2.5 ?g/L. This information will improve our understanding of the risks posed by microcystin-LR to food webs of the Great Lakes.

1. Keyword
Microcystis

2. Keyword
harmful algal blooms

3. Keyword
crustaceans