CLIMATIC AND URBAN CONTROL OF THE TIMING AND MAGNITUDE OF MICROCYSTIN PEAKS IN HARDWATER EUTROPHIC LAKES
Human alteration of climate and nutrient cycles contribute to the global expansion of harmful algal and cyanobacterial blooms. In freshwater ecosystems, warmer water temperatures have led to earlier cyanobacterial blooms by increased growth rates and favoring buoyant taxa in thermally-stratified water columns, while nutrient pollution has enhanced biomass and its intrinsic toxicity. Elevated toxin content also depends on the presence of toxigenic strains, the chemical form of nitrogen (N), light regime, and cellular stoichiometry, but little is known of the hierarchy of mechanisms underlying extreme toxin production. Here we used 10-years of bi-weekly sampling for microcystin (MC) in seven productive hardwater lakes to quantify how environmental drivers influence the phenology and decadal trends in MC. Analysis of time series with generalized additive models (GAM) revealed that temporal patterns of MC content differed among lakes and both between and within years. MC content increased downstream of an urban source of N despite constant cyanobacterial biomass, whereas timing of peak MC levels shifted earlier in the summer in reference eutrophic lakes lacking urban pollution. Overall, MC peaks have become more intense and prolonged as a result of the dual effects of changing climate and nutrient pollution.
Hayes, N. M., University of Regina, Canada, Nicole.Hayes@uregina.edu
Haig, H. A., University of Regina, Canada, firstname.lastname@example.org
Simpson, G. L., University of Regina, Canada, Gavin.Simpson@uregina.ca
Leavitt, P. R., University of Regina, Canada, Peter.Leavitt@uregina.ca
Location: 323 B
Presentation is given by student: No