PARENT SESSION
Oral Session #43: Fish: Ecology and Conservation.
Presiding: B. Harvey
Tuesday, August 6. 1:00 PM to 4:45 PM. Cochise Meeting Room, TCC.

Impacts of removing a single fish species on organic carbon turnover in a diverse tropical stream.

Taylor, Brad^*,1, Flecker, Alexander², Hall, Jr., Robert¹, ¹ University of Wyoming, Laramie, Wyoming² Cornell University, Ithaca, New York

ABSTRACT- We tested the degree to which removing a single fish species from a diverse tropical stream would alter organic carbon turnover. Variation in suspended organic matter transport over the past 6 years was strongly correlated with the abundance of a single fish species, Prochilodus mariae. To experimentally test whether this fish was a major driver of carbon dynamics, we divided a reach of stream longitudinally by installing a 200 meter plastic curtain down the middle and excluded all Prochilodus from one side. We measured striking differences in particulate organic carbon accrual, export, and whole-system respiration after excluding only Prochilodus compared to the side with Prochilodus present and the full complement of fish. Removal of Prochilodus decreased organic matter export by 50%, increased benthic organic matter standing crop from 10 to 1000 grams m², and increased community respiration, which resulted in a decrease in carbon spiralling length. These data show how a single fish species in an ecosystem with more than 100 fish species can be a major driver of organic carbon processing, a fundamental component of stream ecosystem function. Populations of this migratory fish are declining throughout South America, so documenting their importance to ecosystem phenomena will be essential for implementing conservation programs, managing the fishery, and maintaining ecosystem function in headwater Andean streams.

KEY WORDS: streams, metabolism, Venezuela, carbon