PARENT SESSION
Tuesday, August 8, 5:00-6:30 pm
Poster Session 8 - Aquatic ecology
Exhibit Hall, Ballroom Level, Cook Convention Center
Life-history traits determine long-term impacts of nutrient enrichment on macroinvertebrate community dynamics in a detrital-based system.
Davis, John*,1, Rosemond, Amy1, Cross, Wyatt1, Eggert, Sue 1, Wallace, J. Bruce1, 1 University of Georgia, Athens, GA
ABSTRACT- Consumer production in detrital-based systems is a function of food resource quality and quantity. Chronic nutrient enrichment can potentially alter these relationships by increasing nutrient content of food resources while simultaneously decreasing carbon availability. Detritivores may respond differentially to these changes due to variation in their feeding strategies and seasonal life cycles, which both affect their relative susceptibilities to carbon and nutrient limitation. To determine the population responses of stream detritivores, we have continuously added N and P to a detrital-based headwater stream since July 2000 and compared results to a reference stream. Data from the first two years of enrichment showed that total macroinvertebrate production, biomass, and abundance increased with enrichment, and was associated with greater leaf breakdown rates and decreased carbon availability during the summer months. During years 4 and 5, total macroinvertebrate biomass continued to increase, but abundance declined relative to year 2. This increase in consumer biomass was taxon specific. Short-lived taxa that reproduced during the period of greatest resource availability exhibited a positive response to enrichment. Longer-lived taxa that reproduced during periods of low resource availability showed no effect or declined in abundance and biomass. The overall positive response of macroinvertebrate biomass to nutrient enrichment was driven by a limited number of taxa that could capitalize on the changes in detrital food quality and availability. These results indicate that larval development time and feeding strategies may be important factors in helping to predict the ecosystem response to nutrient enrichment.
Key words: headwater stream, detritus, aquatic food webs