Lake Erie fish safe to eat yet afflicted by algal hepatotoxins

Microcystin toxins from harmful algal blooms (HABs) can accumulate and persist in fish, raising dual concerns about human health risks from consumption and the potential for detrimental impacts on fish populations. However, there are fundamental unknowns about the relationship between HABs and fish populations driven by a lack of field information on toxin accumulation and retention over space and time. We conducted a field study to assess human health risks from consuming fish caught across all life stages of a HAB and to determine the pervasiveness of potentially harmful levels of microcystins on fish populations. We collected 190 fish in 2015 and 2017 from Lake Erie, a large freshwater ecosystem that is highly productive for fisheries and is an epicenter of HABs and microcystin toxicity events. Muscles and livers were analyzed for total microcystins, which was used to conduct a human health risk assessment for comparison against fish consumption advisory benchmarks available for Lake Erie. We find low human health risk from muscle consumption following the World Health Organizations safety thresholds. However, all fish across capture dates had microcystins in their livers at levels shown to cause adverse effects, suggesting a pervasive and underappreciated toxic stressor. These data demonstrate that microcystins are retained in fish livers well beyond the cessation of HABs and calls for additional research to better understand the effects of sublethal toxic exposures for fish population dynamics, conservation, and related ecosystem services.