Grant: Discovery Grants Program - Individual

Cyanobacterial Harmful Algae Blooms (cHABs) - often dominated by Microcystis aeruginosa (Ma), are increasing in frequency and severity worldwide and are exacerbated by climate change. A total of 9503 harmful algae events, including fish kills, were recorded worldwide as of December 2019. cHABs occurrence and attendant problems are manifest in many Canadian lakes with nearly 150 cHAB incidences. Cyanobacteria are renowned for their negative impacts on aquatic ecosystems, largely owing to the noxious and harmful, secondary metabolites and toxins that they produce and release upon cell lysis. While more than 5000 studies have been published on toxicity of Microcystins (MCs), cyanobacteria also release a mixture of exudates containing various compounds with demonstrated toxicity to aquatic biota. However, the components in these exudates and their specific harmful effects remained unclear. Fish are typically abundant and widespread in lakes, and thus vulnerable to presence of cHABs. Available evidence has implicated cHABs in massive fish kills. Neurotoxicity is one mode of toxicity by which fish may be impacted cHAB compounds as the fish nervous system is particularly sensitive to toxins. However, impacts on fish result from the potentially neuro-toxic metabolites from senescent and lysing cyanobacteria cells have paid less attention. Our recent work in China revealed that a strain of Ma, which produces harmful secondary metabolites in addition to MCs, impairs neurobehavior by affecting neurotransmitters and receptors in an endangered fish species. We then used untargeted metabolomics to identify~400 chemicals in MaE, and employed machine learning to screen nine new priority neurotoxins. Ma strains may be characterized as `MCs-producing or `MCs-free' and they often coexist in nature. More interesting, our current laboratory studies revealed that a MCs-free Ma strain had higher toxicity on animal than MCs-producing strain.  cHABs have emerged as a critical problem in the Great Lakes, which threatens fisheries production. To reveal if cHABs have neurotoxicity on fishes in the Great Lakes, we will explore if exposure to summer cHABs induces toxic conditions that impair the nervous system in yellow perch, Perca flavescens, an important sport and commercial fish species in the Great Lakes. Specifically, we will: 1) investigate the Microcystis population and MC-producing strains proportion in western Lake Erie; 2) compare the metabolome of exudates from MC-producing and MC-free strains of Microcystis dominated in western Lake Erie; 3) assess neurotoxicological risks of mixtures and screen top priority neurotoxins for each Ma strain, then validate them by fish; and 4) investigate the concentrations of screened neurotoxins in fish and water from the western basin of Lake Erie during the cHABs season. This research will enhance understanding of neurotoxicity of cyanobacterial exudates, which may be help for cyanobacterial bloom management and fish protection.