The Lake Erie Harmful Algal Blooms Grab: High-resolution mapping of toxic and bioactive metabolites (cyanotoxins/cyanopeptides) in cyanobacterial harmful algal blooms within the western basin

Abstract

Cyanobacterial bioactive metabolites (cyanotoxins/cyanopeptides) inhibit enzymes such as proteases, carboxypeptidases, and phosphatases that disrupt metabolic processes relevant to human and ecosystem health. From surface water samples collected in 2017 (n = 44), 2018 (n = 100), and 2019 (n = 171), we report concentrations of more than 20 biologically active cyanobacterial compounds in the western basin of Lake Erie, one of the five Laurentian Great Lakes with multinational jurisdiction. Toxic microcystins LA and LR as well as anabaenopeptin B and F were most frequently detected at >90%. Microcystins RR and YR and anabaenopeptin A were detected at relatively high frequency at >80% in 2019. There was strong correlation among arginine-containing microcystin variants (RR, YR, HtyR, LR, HilR, WR, D-Asp3-LR, Spearman's Rho >0.80) but not with arginine-lacking LY, LW, LF. Anabaenopeptin F, with the arginine sidechain, also correlated with these same arginine-containing microcystin variants (Spearman's Rho >0.70). In 2019, only 4% of lake water samples exceeded the recreational water guideline for total microcystins (10 µg l^-1) set by Health Canada with the maximum concentration ∼26 µg l^-1. The drinking water guideline (1.5 µg l^-1) was exceeded in 34% of lake water samples but treated water was not tested. Although maximum total anabaenopeptins concentration was almost four times higher (almost 100 µg l^-1) than microcystins, no anabaenopeptin guideline values have been derived as their impact is currently considered to be ecological rather than toxic to humans/animals. These results can be used to evaluate risk from cyanobacterial bioactive metabolites, including toxins, in Lake Erie and aid binational lake management and policy development in the Great Lakes basin.