The relationship between the algal toxin microcystin and the chemical, physical and biological parameters in Lake Winnipeg

Abstract

Cyanobacterial algae blooms are of rising concern all over the world because of their increasing abundance and toxin release. Using an 18-year dataset (1999 to 2017), correlations between chemical, physical and biological parameters and the microcystin toxin in Lake Winnipeg were investigated. Multi-panel scatterplots with Pearson correlation coefficients found total boron in euphotic dataset and Anabaena biomass in the surface dataset had the strongest positive correlations. N variables such as total N, total Kjeldahl N, nitrate + nitrite and the N:P ratio may aid in controlling microcystin levels in Lake Winnipeg. Higher toxins correlated with higher N variables in the surface dataset (total N and total Kjaldahl N) and euphotic dataset (N:P ratio) and higher toxins and lower N variables correlated in the euphotic dataset (dissolved NO3 + NO2). Total suspended solids had a positive correlation with toxin levels in the surface dataset; Secchi disk depth and wind speed had negative correlations. Overall, I found that algal toxin concentrations in the epilimnion of Lake Winnipeg correlated best with several metrics of nitrogen availability, water clarity, Anabaena biomass and boron concentrations .