HR: 10:45h
AN: NB22A-02 INVITED     [Abstracts]
TI: Effects of Stream Fishes on Benthic Primary Productivity: A Mechanistic Test
AU: * Hargrave, C W
EM: cwhargrave@ou.edu
AF: University of Oklahoma Biological Station and Department of Zoolgy, University of Oklahoma, 710 Van Vleet Oval, Norman, OK 73019 United States
AB: I simultaneously tested three alternative hypotheses (the trophic cascade, nutrient enhancement via terrestrial nutrient translocation, and nutrient enhancement via bioturbation) for consumer regulation of primary productivity (PPR) by three widely distributed stream fish species (Orangethroat Darter, Western Mosquitofish, and Bullhead Minnow). I used stream mesocosms fitted with fish and terrestrial input barriers to address relative importance of localized fish predation versus access to terrestrial inputs for fish consumer effects. Orangethroat Darter, a benthic invertivore, increased PPR through an apparent trophic cascade, by localized reduction of benthic grazing invertebrate densities. Western mosquitofish, a surface feeding insectivore, increased PPR by enhancing nutrients through terrestrial nutrient translocation, and had no effect on benthic grazer invertebrate density. Bullhead Minnow, a benthic omnivore that disturbed sediments during foraging, increased PPR through nutrient enhancement via bioturbation, but within specific stream mesocosm areas two which the fish was restricted it also reduced benthic grazing invertebrates. Thus, suggesting this species may have affected PPR through a combination bioturbation and trophic cascade mechanisms. These mechanistic pathways are likely common processes by which fish affect food web structure and ecosystem function in many stream ecosystems.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly