Fish Distributions and Nutrient Cycling in Streams: Can Fish Create Biogeochemical Hotspots?

Authors

Peter B. McIntyre, Cornell UniversityFollow
Alexander S. Flecker, Cornell University
Michael J. Vanni, Miami University - Oxford
James M. Hood, University of Minnesota
Brad W. Taylor, Dartmouth College
Steven A. Thomas, University of Nebraska-LincolnFollow

Date of this Version

2008

Citation

Ecology, 89(8), 2008, pp. 2335–2346

Comments

Copyright 2008 by the Ecological Society of America

Abstract

Rates of biogeochemical processes often vary widely in space and time, and characterizing this variation is critical for understanding ecosystem functioning. In streams, spatial hotspots of nutrient transformations are generally attributed to physical and microbial processes. Here we examine the potential for heterogeneous distributions of fish to generate hotspots of nutrient recycling. We measured nitrogen (N) and phosphorus (P) excretion rates of 47 species of fish in an N-limited Neotropical stream, and we combined these data with population densities in each of 49 stream channel units to estimate unit- and reach-scale nutrient recycling. Species varied widely in rates of N and P excretion as well as excreted N:P ratios (6–176 molar). At the reach scale, fish excretion could meet >75% of ecosystem demand for dissolved inorganic N and turn over the ambient NH₄ pool in