Mercury in fish and invertebrates in the Saint John River estuary

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University of New Brunswick


Methylmercury (MeHg) is a common toxin that affects freshwater fish and fish consumers in North America, but its accumulation has not been well studied in estuarine systems. Therefore, the spatial trends of MeHg in biota from fresh to marine waters are poorly understood. This study investigated patterns of MeHg along a salinity gradient ranging from freshwater to brackish water within the Saint John River estuary, New Brunswick, Canada. The objective was to identify how MeHg concentrations in organisms relate to this salinity gradient and other biological or environmental variables. Samples collected in 2015 and 2016 included fourspine stickleback (Apeltes quadracus), Gammarus amphipods, freshwater snails, chironomids, sediments, and water. With increasing salinity, MeHg increased in chironomids but showed no strong correlations for other samples. This research showed that salinity was not strongly associated with MeHg in abiotic and biotic compartments of this estuary and that the risk of MeHg toxicity cannot be identified based on habitat salinity. However, this work is important for building future studies predicting MeHg in estuarine food webs.