Recognition of an Important Water Quality Issue at Zoos: Prevalence and Potential Threat of Toxic Cyanobacteria
Cyanobacterial toxins have been implicated in numerous wildlife mortality events involving a wide array of animal species.1-3 Zoo animals may be particularly vulnerable to water sources contaminated with cyanobacteria and their associated toxins given their non-voluntary close association with this resource. However, the prevalence and potential threat of toxic cyanobacteria to zoo moat water quality is unknown. Several otherwise unexplained turtle (Trachemys scripta scripta) deaths were documented in a moat with a bloom of the toxic cyanobacterium, Microcystis aeruginosa. Furthermore, an extremely high and potentially lethal concentration of the hepatotoxin, microcystin (166 ng/g dry mass), was found in the liver of one necropsied turtle that died in this moat. A subsequent 7-mo survey of water quality across 10 moats revealed detectable concentrations of microcystin in all moats (0.0001 to 7.5 µg/L), with the concentrations in 3 of the moats being significantly higher than the threshold for safe drinking water (1 µg/L) set by the World Health Organization.4 These results demonstrate that cyanobacterial blooms are an important water quality issue in zoos, and future research is necessary to identify potential associations between water quality and zoo animal health.
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