Invasive crayfish as vectors of mercury in freshwater food webs of the Pacific Northwest

Abstract

Invasive species are important drivers of environmental change in aquatic ecosystems and can alter habitat characteristics, community composition, and ecosystem energetics. Such changes have important implications for many ecosystem processes, including the bioaccumulation and biomagnification of contaminants through food webs. Mercury concentrations were measured in 2 nonnative and 1 native crayfish species from western Oregon (USA). Nonnative red swamp crayfish had mercury concentrations similar to those in native signal crayfish (0.29 ± 0.05 µg/g dry wt and 0.36 ± 0.06 µg/g dry wt, respectively), whereas the nonnative ringed crayfish had lower mercury concentrations (0.10 ± 0.02 µg/g dry wt) than either of the other species. The mean energy content of muscle was similar between the native signal crayfish and nonnative ringed crayfish but was significantly higher in the nonnative red swamp crayfish. Across species, mercury concentrations were negatively correlated with energy density. Such energetic differences could exacerbate changes in mercury transfer through trophic pathways of food webs, especially via alterations to the growth dynamics of consumers. Thus, it is important to consider the role of energy content in determining effective mercury exposure even when mercury concentrations on a per-unit mass basis do not differ between species. Environ Toxicol Chem 2014;33:2639-2645. Published 2014 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US Government work and as such, is in the public domain in the United States of America.

Effects of ontogeny and invasive crayfish on feeding ecology and mercury concentrations of predatory fishes

“…This includes slow post-glacial expansion by a widely distributed species, Faxonius virilis (Phillips et al 2009). Different species of crayfish can have different mercury concentrations and energy densities even when they co-occur, suggesting predation on recently introduced species could alter concentrations in predators (Johnson et al 2014). Work in the United States Midwest shows that lakes invaded by crayfish can have predatory fishes that feed more in the littoral zone and occupy lower trophic positions (Nilsson et al 2012;Kreps et al 2016).…”