 |
Tuesday, May 19, 2009 - 9:15 AM
130
Integrating empirical and observational studies to demonstrate causal relationships between contaminants and benthic community responses: An information-theoretic approach
William H. Clements, Department of Fish, Wildlife, & Conservation Biology, Colorado State University, Fort Collins, CO 80523
Field surveys designed to assess effects of contaminants on benthic communities implicitly assume a causal relationship between chemical stressors and community responses. Because responses of benthic communities in the field are often confounded by multiple and interacting factors, this untested assumption is risky in the absence of supporting experimental evidence. In this research data from a long-term (19 year) field survey of a metal-contaminated stream (the Arkansas River, CO) showed that benthic community responses to heavy metals were strongly influenced by other physicochemical variables. In addition, recovery of these communities following improvements in water quality varied spatially and temporally. I used an information-theoretic approach based on Akaike’s Information Criteria (AIC) to develop predictive models showing the relationship between macroinvertebrate community metrics, heavy metals and physicochemical characteristics. Results of microcosm experiments provided critical support for a causal relationship between metals and benthic community responses and identified threshold concentrations where contaminants were expected to have ecological adverse effects. Experimental results also showed increased metal-tolerance of benthic communities from polluted sites compared to reference sites, providing additional support for causation. These findings demonstrate that experimental studies can complement field surveys to develop causal relationships in benthic ecology.
Web Page: AIC, causation, information-theoretic, microcosms