Inorganic Contaminants and Stable Isotopic Food Web Analyses of Bioaccumulation in Aquatic Communities in Southern Arizona

Authors: Betsy Grube, Floyd Gray, Peter Reinthal

Year: 2017 (xlix)

Abstract

In the arid southwest, Acid Mine Drainages (AMD) alter watershed characteristics via input of acidic and metal-laden waters from abandoned mines and tailings In the Santa Cruz River watershed, many geologic workings, tailings, and drainages periodically discharge metal-rich, acidic water, and leachates into surrounding systems Most research focuses on single species responses to individual elemental contaminants Here we combine contaminant and stable isotope analyses to look at bioaccumulation of multiple contaminants and food web dynamics in desert streams and lakes We examine contamination of seven toxic metals (arsenic, cadmium, copper, mercury, lead, selenium and uranium) in samples of invertebrates, and sport and native fish species using both muscle and liver tissues collected in the Upper Santa Cruz watershed, Patagonia Lake, and Pena Blanca Lake We determine food web structure using stable carbon and nitrogen isotopes By combining these analytical methods with regression and multivariate methods, we present a novel approach of testing whether metal contamination occurs from consumption of different food resources or through bioaccumulation We find community level responses to a suite of contaminants Our results indicate that there is great variation in different contaminants in both invertebrate and fish species Contaminants accumulate in different species primarily due to alternate resource utilization as indicated by ‰ C However, some species at higher trophic levels (> 4 ‰ N) demonstrate a trophic expansion to the consumption of a wider range of food items in degraded low pH, high metal systems These results support the conclusion that impacts from degraded systems (low pH and high metals) are not just species specific but that trophic interactions among species and food web dynamics are significantly altered