HR: 09:00h
AN: NB21B-03 INVITED     [Abstracts]
TI: Linking Invertebrates With Ecosystem Nitogen Cycling in a Tropical Stream
AU: * Hall, R O
EM: bhall@uwyo.edu
AF: Dept. of Zoology and Physiology, University of Wyoming, Laramie, WY 82071 United States
AU: Behn, K
EM: Kate_Behn@myrealbox.com
AF: Dept. of Zoology and Physiology, University of Wyoming, Laramie, WY 82071 United States
AU: Taylor, B W
EM: btaylor@uwyo.edu
AF: Dept. of Zoology and Physiology, University of Wyoming, Laramie, WY 82071 United States
AU: Flecker, A S
EM: asf3@cornell.edu
AF: Dept. of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853 United States
AB: Invertebrates can regulate stream nitrogen (N) cycles by excreting biologically available ammonium and by serving as a sink for benthic N in their biomass. Typically invertebrates have been considered to play a small role in stream N cycling because their biomass is low relative to other benthic stocks of N. However, if their production and excretion rates are high relative to N uptake and regeneration rates, then they may strongly regulate the N cycle in a stream. We investigated this idea in a tropical Venezuelan stream that has a high density and diversity of fishes. We measured N uptake, storage and regeneration using isotope tracers. Concurrently, we measured secondary production of invertebrates. We also measured ammonium excretion rates of several invertebrate taxa and compared these to whole ecosystem rates. Invertebrate excretion constituted one-fourth of ammonium uptake. High growth rates (up to 0.3 /d for some mayflies) contributed to high secondary production which equaled the excretion rate, thus invertebrates sequestered N at one-fourth of the cycling rate. Despite low biomass (< 1 g dry mass/m2) invertebrate activity constituted a substantial fraction of whole-stream N cycling rates.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly