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USING delta15N OF CHIRONOMIDAE TO HELP ASSESS CONDITION AND STRESSORS IN LAKES, RIVERS AND STREAMS OF THE UNITED STATES.
Citation:
Brooks, J. Renee, J. Compton, A. Herlihy, D. Sobota, J. Stoddard, AND M. Weber. USING delta15N OF CHIRONOMIDAE TO HELP ASSESS CONDITION AND STRESSORS IN LAKES, RIVERS AND STREAMS OF THE UNITED STATES. Presented at Joint Aquatic Sciences Meeting, Portland, OR, May 19 - 23, 2014.
Impact/Purpose:
To assess large-scale ecological conditions efficiently, indicators that can be collected quickly at many sites need to be developed. We explore the utility of delta15N from basal food chain organisms to provide information on N loading and processing in lakes, rivers and streams. Our results suggest that chironomid 15N values can provide information about landscape-level nitrogen inputs and processing in national water quality monitoring efforts.
Description:
To assess large-scale ecological conditions efficiently, indicators that can be collected quickly at many sites need to be developed. We explore the utility of delta 15N from basal food chain organisms to provide information on N loading and processing in lakes, rivers and streams. EPA’s National Aquatic Resource Surveys (NARS) collect numerous measurements at thousands of sites during one-day visits to assess ecological condition; however, processes such as nitrogen cycling are too resource intensive to be measured. Chironomidae delta 15N values help assess aquatic ecological conditions because they indicate sources or processes that affect nitrogen. In NARS, chironomid delta 15N were higher in rivers and streams than in lakes (median = 7.6 ‰ vs. 4.8 ‰, respectively), indicating that nitrogen was processed to a greater degree in lotic than lentic chironomids. For both, delta 15N increased with watershed-level agricultural land cover and nitrogen loading, and decreased as precipitation increased. Watershed-level predictors explained more variance than stream reach, lake, or food web attributes. Our results suggest that chironomid delta 15N values can provide information about landscape-level nitrogen inputs and processing in national water quality monitoring efforts.