Contrasting food web linkages for the grazing pathway in three temperate forested streams using ¹⁵N as a tracer

Abstract

Nitrogen is a critical element controlling the productivity and dynamics of stream ecosystems and many streams are limited by the supply of biologically available nitrogen (e.g. Grimm & Fisher 1986, Lohman et al. 1991). We are learning more about the fate of inorganic nitrogen entering streams through ¹⁵N tracer additions (Peterson et al. 1997). The Lotic Intersite Nitrogen eXperiment (LINX) is studying the uptake, cycling, and fate of ¹⁵N-NH₄ in the stream food web of 10 streams draining different biomes. Using the ¹⁵N tracer method and data from three sites in the study, w can differentiate patterns in the cycling of nitrogen through the grazing pathway (N from the epilithon to grazing macroinvertebrates) for three temperate forested streams. Here, we quantify the relationship between the dominant grazer and its proposed food resource, epilithon, by comparing ¹⁵N levels of grazers with those of the epilithon, as well as the biomass, nitrogen content, and chlorophyll a standing stocks of the epilithon in three streams.

Citation

Tank, J.L.; Mulholland, P.J.; Meyer, J.L.; Bowden, W.B.; Webster, J.R.; Peterson, B.J. 2000. Contrasting food web linkages for the grazing pathway in three temperate forested streams using ¹⁵N as a tracer. Verh. Internat. Verein. Limnol., Vol. 27: 2832-2835