John Wiley & Sons, Ltd.

Natural stressors in uncontaminated sediments of shallow freshwaters: The prevalence of sulfide, ammonia, and reduced iron

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Potentially toxic levels of three naturally occurring chemical stressors (dissolved sulfide, ammonia, and iron) can occur in freshwater sediments, although their roles in shaping ecosystem structure (i.e., plant and animal communities) and function (e.g., biologically mediated elemental cycles) have received little study. This critical review discusses the prevalence and ecological effects of potentially toxic concentrations of sulfide, ammonia, and iron in uncontaminated freshwater sediments, including review of the literature as well as a case study presenting previously unpublished data on sediment pore waters from a diverse set of shallow (< 2 m) freshwater ecosystems in southwest Michigan. Measured concentrations are compared to surface water quality criteria established by the U. S. Environmental Protection Agency (EPA) and to acute and chronic toxic thresholds in the published literature where available. Based on EPA criteria for aquatic life for these three stressors, the benthic environment of almost every freshwater ecosystem sampled was theoretically stressful to some component of aquatic life in some area or at some time (i.e., in at least one sample), and 54% of samples exceeded more than one criterion simultaneously. Organismal tolerances to chemical stressors vary, so the observed concentrations are likely shaping benthic animal communities and influencing rates of ecosystem processes. It is important to consider the role of natural chemical stressors in shaping freshwater benthic environments, and when developing bioassessments, restoration goals, and remediation plans. Environ Toxicol Chem © 2014 SETAC

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