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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Food webs 2
Spatial and temporal dynamics of marine-derived nutrients in the food web of a Scottish Highland stream
B.P. Kennedy1, K.H. Nislow2, P. Collen3, J. Keay3, and J.D. Armstrong3. 1Dept of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-1063, 2USDA Forest Service Northeastern Research Station, Amherst, MA 01003, 3Scottish Fisheries Service Freshwater Laboratory, Faskally, UK PH16 5LB
Interest in the changing nutrient budgets of streams has led to an appreciation of migratory fish as agents of transport. While studies have documented incorporation of marine-derived nutrients (MDNs) from salmonids, few have tracked the spatial and temporal dynamics of nutrient transfer from carcasses into stream food webs. As a result, we have little understanding of how the phenology of stream communities affects MDN retention and, in turn, how carcasses can influence the feeding and drift behavior of macroinvertebrates over a growing season. We stocked carcasses of adult Atlantic salmon in an oligotrophic stream in Scotland, and measured the incorporation of marine-derived nitrogen (N) and carbon (C) isotopes in periphyton, macroinvertebrates, and juvenile salmonids at successive transects. Upstream of carcasses, taxa exhibited little variability in freshwater isotopic values, whereas downstream, taxa were significantly enriched with marine N and C throughout the entire 400 m study reach. High variability in the spatial incorporation of MDNs appears to be the result of interspecific differences in both downstream movements and macroinvertebrate feeding habits of macroinvertebrates. Finally, incorporation of MDNs was highly time-dependent, with little uptake (and little loss of carcass tissue) over the winter, followed by rapid incorporation during the spring.
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