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STABLE NITROGEN ISOTOPES AS INDICATORS OF ANTHOPOGENIC ACTIVITIES IN SMALL FRESHWATER SYSTEMS
Citation:
Lake, J L., R A. McKinney, F Osterman, R J. Pruell, J A. Kiddon, S A. Ryba, AND Libby. STABLE NITROGEN ISOTOPES AS INDICATORS OF ANTHOPOGENIC ACTIVITIES IN SMALL FRESHWATER SYSTEMS. CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES 58(5):870-878, (2001).
Description:
Stable nitrogen isotope ratios ( 15N) were measured in fish, mussel, and sediment samples taken from 17 small freshwater sites to examine food chain length and trophic position across sites affected by differing levels of anthropogenic activity. Both shoreline development and fish species composition varied greatly among sites, and a range of up to 11.2? was found for 15N values of largemouth bass (Micropterus salmoides). Fish 15N values were baseline corrected using unionid mussel (Elliptio complanata) 15N values. Predators, such as largemouth bass and chain pickerel (Esox niger), exhibited normalized 15N values that were less variable than those of benthic-feeding fishes. Relationships between 15N and dissolved inorganic nitrogen concentrations indicated that 15N was a valid descriptor of eutrophication at sites with low dissolved inorganic nitrogen concentrations. The fraction of residential land in buffer zones surrounding sites was correlated with fish 15N, indicating that urban development, and presumably human wastewater, resulted in elevated 15N values in these small freshwater systems.