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SFS Annual Meeting

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PREDICTING EFFECTS OF WARMING ON SECONDARY PRODUCTION IN STREAM FOOD WEBS WITH FIXED DETRITAL RESOURCE SUPPLY

We currently lack experimental tests or predictions of how food-web production will change in freshwater ecosystems due to increasing temperatures. Assuming constant resource supply, metabolic theory predicts a neutral net effect of warming on animal production (P) due to matched opposing effects on community biomass (B, decrease) and turnover (P:B, increase). Although a recent test in an algal-based stream food web confirmed the predicted neutral effect of warming on P, annual gross primary production increased by ~170%, violating assumptions of fixed resource supply. Ecosystems reliant on external supplies of detritus may respond differently, as warming can accelerate carbon loss. We are investigating the effects of temperature in two detritus-based streams in North Carolina, USA, by quantifying monthly invertebrate B, P, and P:B under ambient temperatures (1-yr) and warming (2-yr, ~4°C) of one stream. Under the assumption of a fixed resource supply and a 4°C temperature increase, B is expected to decrease by ~30% (~2.0 to 1.4 g AFDM/m2) while instantaneous P:B will increase 40%, maintaining P at ~10 g AFDM·m-2·y-1. We will test whether B and P:B actually change and/or whether they are further affected by a reduced resource base.

Phoenix Rogers (Primary Presenter/Author), The University of Alabama, parogers@crimson.ua.edu;


Jonathan Benstead (Co-Presenter/Co-Author), The University of Alabama, jbenstead@ua.edu;


Amy Rosemond (Co-Presenter/Co-Author), University of Georgia, rosemond@uga.edu;