PARENT SESSION
Oral Session #65: Aquatic Ecology: Stream and Lake.
Presiding: C. Osenberg
Wednesday, August 7. 1:00 PM to 4:45 PM. Coconino Meeting Room, TCC.

Does nutrient enrichment increase carbon limitation of a detritus-based stream food web?

Rosemond, Amy^*,1, Benstead, Jonathan¹, Suberkropp, Keller², Cross, Wyatt¹, Mulholland, Patrick³, Greenwood, Jennifer¹, Wallace, Bruce¹, ¹ Institute of Ecology, Athens, GA² Department of Biological Sciences, Tuscaloosa, AL³ Environmental Sciences Division, Oak Ridge, TN

ABSTRACT- We enriched a headwater stream with nitrogen (N) and phosphorus (P) for one year to determine effects on carbon flow within a detritus-based food web. Carbon budgets and production of food web components (microbes and macroinvertebrates) were compared between the treatment and a reference stream (Coweeta Hydrologic Laboratory, North Carolina, USA) for one year prior to and following continuous input of N and P. Inputs of dissolved and particulate organic matter did not differ between the streams prior to or following enrichment. Export of dissolved organic matter was also unaffected by nutrient enrichment. However, standing crop of leaf litter was reduced (p<0.0001) and export of fine particulate organic matter was increased (p<0.0001) by nutrient enrichment relative to the reference stream. Annual production of heterotrophic microbes and invertebrate consumers increased following nutrient enrichment. Greater production, coupled with increased system export, likely contributed to carbon limitation of consumers. Our results illustrate the potentially profound effects of increased nutrient input on the resource base and productive capacity of detritus-based ecosystems.

KEY WORDS: nutrients, streams, carbon , limitation