HR: 08:45h
AN: NB21B-02 INVITED     [Abstracts]
TI: Alteration of the Fates and Fluxes of Nitrogen by Detritivorous Fish: a Whole-Stream Manipulation and a ¹⁵N-tracer Addition
AU: * Taylor, B W
EM: btaylor@uwyo.edu
AF: University of Wyoming, Department of Zoology and Physiology, Laramie, WY 82071 United States
AU: Hall, R O
EM: bhall@uwyo.edu
AF: University of Wyoming, Department of Zoology and Physiology, Laramie, WY 82071 United States
AU: Flecker, A S
EM: asf3@cornell.edu
AF: Cornell University, Department of Ecology and Evolutionary Biology, Ithaca, NY 14853 United States
AU: Fisher, C A
EM: chrisfish@yahoo.com
AF: University of Wyoming, Department of Zoology and Physiology, Laramie, WY 82071 United States
AU: Grant, M B
EM: maymegrant@yahoo.com
AF: University of Wyoming, Department of Zoology and Physiology, Laramie, WY 82071 United States
AU: Jeffs, L
EM: ljeffs@colostate.edu
AF: Colorado State University, Department of Natural Sciences, Fort Collins, CO 80521 United States
AU: Richmond, E L
EM: erichmond10@hotmail.com
AF: University of Wyoming, Department of Zoology and Physiology, Laramie, WY 82071 United States
AU: Thomas, S A
EM: sat43@cornell.edu
AF: Cornell University, Department of Ecology and Evolutionary Biology, Ithaca, NY 14853 United States
AB: The key roles played by a few species and the non-random order of human-induced biodiversity loss provide compelling reasons for predicting the consequences of individual species losses on ecosystem functioning. This is especially true for vertebrates such as fish that are more vulnerable to extinction and are often over-harvested. Here we test the consequences of losing a single detritivorous fish species, Prochilodus mariae that constitutes 80% of the South American freshwater fishery and is declining. We used a large-scale experimental approach to remove Prochilodus from a diverse assemblage, and measured the effects of its loss on the stream nitrogen cycle using a ¹⁵NH₄-N addition during years with high and low fish abundance. There was no difference in gross uptake of dissolved ¹⁵NH₄-N, but when detritivorous fish were present nitrification was 30% higher. The flux of nitrogen into fine benthic particulate compartments was 46% greater when detritivorous fish were removed, but long-term N loss was much higher from these compartments. In contrast, in the presence of detritivorous fish N was retained by more stable epilithic biofilms. In the ecologically intact system, detritivorous fish influence the fates and fluxes of N, which increases N storage by this headwater stream.
DE: 4804 Benthic processes/benthos
DE: 4805 Biogeochemical cycles (1615)
DE: 4845 Nutrients and nutrient cycling
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly