Mercury in river turtles occupying a predominantly forested rural watershed

Freshwater turtles have faced extreme global population declines in recent decades in association with habitat loss and degradation including from pollution, and the collection of individuals for the pet, food, and traditional medicine trade. Mercury pollution of aquatic environments is a pervasive threat to semi-aquatic and aquatic species including turtles as mercury released into the atmosphere is deposited into aquatic environments, sometimes far from the source, where it becomes bioavailable and can bioaccumulate in organisms. Mercury can cause sublethal effects in turtles, including reduced reproduction and survivorship, negatively impacting the size and overall health of future turtle populations. Consuming turtles as food or traditional medicine can contribute to the accumulation of mercury in humans, leading to adverse effects on human health. We measured the concentration of mercury in scutes collected non-lethally from turtles of various species and size classes from a stream in a predominantly forested rural watershed to assess the extent of bioaccumulation within and among species. Mercury concentrations were elevated and exceeded safety threshold levels for human consumption in all species and sizes classes, including in the smallest size class measured (5.1-8.0 cm plastron length), despite no obvious nearby mercury source. The prevalence of mercury in turtles in a river within a predominantly forested rural watershed emphasizes that efforts are needed to reduce mercury emissions and remediate contamination in aquatic ecosystems. People should be discouraged from consuming turtles to both conserve turtle populations and reduce the risk of mercury-related human health consequences.