Inorganic Contaminants from Past Mining Activity: Community Structure, Foodweb Dynamics and Bioaccumulation in Fish and Aquatic Macro-invertebrates, Southeastern Arizona.

Authors: Jessica E. Gwinn, John Chesley, David L. Dettman, Peter N. Reinthal

Year: 2013 (xlv)

Abstract

Mine drainages in the Patagonia Mountains, Arizona can impact aquatic ecosystems because acidic, metal-laden water periodically discharges into Sonoita Creek, with a rich native fish assemblage, and Patagonia Lake, a popular sport fishery. We examined water quality and foodweb dynamics using nitrogen and carbon stable isotopes in three streams with varying degrees of abiotic impairment; (1) Alum Gulch with elevated metal contaminants levels and low pH, (2) Humboldt Canyon with trace metal contaminants and low pH, and (3) Middle Harshaw Creek with low metal levels and neutral pH. Impaired stream reaches, especially in Alum Gulch, were found to have an overall decrease in both abundance and diversity of macro-invertebrates, especially pollution sensitive taxa and an increase in predatory invertebrates. Middle Harshaw Creek was found to have the greatest diversity of macro-invertebrates and increased foodweb complexity. Stable carbon and nitrogen isotopic results showed a loss of lower trophic levels in the impaired streams. Additionally, to identify extent, sources, bioaccumulation and transportation of metal contaminants in these aquatic systems, we collected fish and aquatic macro-invertebrates from lakes and streams and used High Resolution Inductive Coupled Plasma Mass Spectrometry (HR-ICP-MS) to analyze tissues for 59 inorganic contaminants. Lead isotopic analysis was conducted with soil, water, and aquatic biota samples as a possible method to determine point source pollution locations in relation to known mine locations. Numerous contaminants were found in very high levels in both invertebrates and fish which were geographically near historic mining areas. Lead (Pb) and mercury (Hg) were elevated in predatory invertebrates and predatory sport fish, with largemouth bass (Micropterus salmoides) and channel catfish (Ictalurus punctatus), having the highest levels of Hg and Pb.