Quantifying Biologically Mediated Fluxes of Stream Metals to Riparian Food Webs

Research Task: 


Task Manager: 

Johanna Kraus

Trace-metal contamination of aquatic ecosystems is a major health and environmental concern globally, leading to alterations of aquatic communities, decreased fisheries, and bioaccumulation in higher trophic levels. In the Rocky Mountains, metals mobilized from the mineralized bedrock underlying watersheds are one of the major factors shaping aquatic communities in perennial streams. The geologic processes that affect distribution of metals within central Colorado streams, such as mining and mineralization, are well characterized, but little is known about the about the repercussions of these effects for neighboring terrestrial ecosystems. Aquatic insects, which represent a large component of stream food webs as larvae, emerge from streams as adults where they are consumed by terrestrial predators such as spiders. Thus, insects can transport metals from aquatic to terrestrial food webs by carrying them within their adult bodies. The primary objectives of this research are to (1) establish the relationship between metal accumulation in riparian predators (i.e., spiders), stream trace-metal concentrations, and underlying rock type; (2) measure insect emergence, production, and metal flux during the growing season; and (3) test how fish, an important top predator, alter metal flux to riparian food webs in contaminated streams. Data from this multi-disciplinary study will be used to construct a predictive framework based on geology, toxicology, and ecology for understanding when and where fluxes of aquatically derived metals to terrestrial food webs are important. The outcomes of this research will have large implications for stream restoration and management in the national forests and parks where this study takes place, since decisions about aquatic ecosystems could have ramifications for metal transfer to riparian food webs.

For more information contact:

Johanna Kraus

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