HR: 08:30h
AN: NB21B-01    [Abstracts]
TI: Consumer-Driven Nutrient Recycling and its Effects on Whole-Ecosystem Flux in Tropical Streams
AU: * Cross, W F
EM: crosss@uga.edu
AF: Institute of Ecology, University of Georgia, Athens, GA 30602 United States
AU: Benstead, J P
EM: jpbenstead@mbl.edu
AF: The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543 United States
AU: March, J G
EM: jmarch@washjeff.edu
AF: Biology Department, Washington and Jefferson College, Washington, PA 15301 United States
AU: Ramirez, A
EM: aramirez@ites.upr.edu
AF: Institute for Tropical Ecosystem Studies, University of Puerto Rico, San Juan, PR 00931 United States
AU: McDowell, W H
EM: Bill.McDowell@unh.edu
AF: Department of Natural Resources, University of New Hampshire, Durham, NH 03824 United States
AU: Covich, A P
EM: alanc@uga.edu
AF: Institute of Ecology, University of Georgia, Athens, GA 30602 United States
AB: Recent work has shown that nutrient recycling by benthic consumers can strongly influence whole-ecosystem nutrient flux. This recycling is likely to be most important in ecosystems with high consumer biomass and low ambient nutrient concentrations. We examined rates and ratios of nitrogen:phosphorus (N:P) excretion of freshwater shrimps in two tropical headwater streams that exhibit strongly contrasting levels of shrimp biomass (due to the presence/absence of predatory fish). N and P excretion rates (μmol g^-1 h^-1) did not differ between streams or among species of shrimp. Excretion rates of total dissolved N and P ranged from 2.0 - 17.7 μmol N g^-1 h^-1 and 0.04 - 0.89 μmol P g^-1 h^-1, respectively. Body size was a strong predictor of N (r² = 0.73) and P (r² = 0.91) excretion rates, as well as molar N:P excretion ratios (r² = 0.56). On an areal basis, large between-stream differences in shrimp-mediated nutrient recycling were found (9.8 vs. 0.1 mg N m^-2 d^-1) as a result of contrasting levels of shrimp biomass. Calculations, based on stream nutrient concentrations, discharge and shrimp biomass estimates revealed that up to 50% of dissolved N and P exported from shrimp-dominated tropical streams may be supplied by excretion.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly