HP8 Field Biological Monitoring of Ecosystem Impairment
A105 & A106
1:20 PM - 5:20 PM, Thursday
() The influence of climate-induced changes in dissolved organic material on metal toxicity and UV radiation in Rocky Mountain streams.
Clements, W1, Appel, M2, Baron, J3, Brooks, M1, Kashian, D1, McKnight, D2, Meyer, J4, Zuellig, R1, 1 Dept. of Fishery and Wildlife Bio., Colorado State University, Fort Collins, CO, USA2 Inst. for Arctic and Alpine Res., University of Colorado, Boulder, CO, USA3 Natural Resources Ecology Lab, Colorado State University, Fort Collins, CO, USA4 Dept. of Zoology and Physiology, University of Wyoming
ABSTRACT- Increased levels of atmospheric CO2 and associated global climate change over the next 100 years are expected to have significant impacts on riparian vegetation, biogeochemical cycles and hydrologic processes in the Rocky Mountain region. Benthic communities in high elevation streams of the Rocky Mountains are subjected to intense levels of ultraviolet radiation (UVR) because of shallow depth and naturally low levels of light-attenuating organic materials. Communities are simultaneously exposed to elevated metals from abandoned mines, the toxicity and bioavailability of which are also determined by dissolved organic materials (DOM). The goal of this interdisciplinary research is to investigate the influence of climate-induced changes in stream hydrology and DOM on responses of stream ecosystems to heavy metals and UV-b exposure. We integrated climate and hydrologic modeling with an intensive field monitoring and experimental program to test the hypothesis that changes in DOM increase bioavailability of heavy metals and exposure to UV-B radiation. Our field monitoring program demonstrated that vegetation and hydrologic processes (e.g., snowpack, discharge) regulate the concentration and composition of DOM in streams. Spatiotemporal variation in the amount of fulvic acid and the source of DOM (e.g., terrestrial vs. microbial) have important consequences for metal bioavailability and UV-b penetration in streams. Photodegradation of water collected from several field sites resulted in a 13% decrease in DOM and a corresponding increase in potential UV-b exposure and metal bioavailability. Microcosm experiments conducted in experimental streams showed that combined effects of UV-B and heavy metals on benthic communities were greater than either stressor alone. Finally, results of a field experiment conducted in 12 streams along a gradient of metal contamination showed direct effects of UV-b on structure and function of benthic communities. These results demonstrate that interactions between UV-b and other anthropogenic stressors may structure aquatic communities in Rocky Mountain streams. Changes in the quality and quantity of DOM resulting from climate change may increase the strength of these interactions.
Key words: heavy metals, Rocky Mountain streams, UV-b radiation, dissolved organic carbon