Reframing the Microcystin Problem – a Biogeochemical Cycling Approach

Abstract:

Harmful algal blooms and the cyanotoxins they produce pose a serious threat to aquatic ecosystems and human health. Specifically, the hepatotoxin microcystin (MC), which can be produced by cyanobacteria and prevalent during blooms, is pervasive in nutrient-rich surface waters and harmful to humans. As such, there is a strong interest in understanding and predicting the dynamics of when, where, and how microcystin will be produced, degraded, and accumulated in the environment. Despite microcystin being pervasive in aquatic environments, these important dynamics are largely being studied individually and in disparate fields. Yet fundamentally, microcystin is a molecule that cycles in the environment through pools and fluxes, controlled by internal and external drivers. Reframing the study of microcystin dynamics as a biogeochemical cycle is a tool to identify the important, but potentially cryptic, pathways of human exposure to this toxin. Here we present a literature review of 1,781 papers which synthesize the rates of major pools and fluxes of microcystin into, within, and exported from lakes. Specifically, we collected published estimates of microcystin production, biological uptake, sedimentation, degradation and other fluxes. Through this literature review exercise we have identified knowledge gaps in the dynamics of microcystin movement and accumulation, as well as potential control points that could be targeted for mitigating microcystin exposure to humans.