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DRAMATIC SEASONAL SHIFTS IN PRIMARY PRODUCERS IN A MID-SIZED PIEDMONT RIVER

Stream flow has a major influence on ecosystem structures, functions and the corresponding services provided by rivers. We are studying the effects of different flow conditions on primary productivity in a mid-sized Piedmont river by measuring biomass of primary producer pools monthly and biomass-specific productivity and respiration rates through chamber studies. Data from the 2016 field season show dramatic shifts in identity and biomass of primary producers from June to November when the Middle Oconee River experienced prolonged drought. Preliminary data suggest patterns in filamentous algal biomass and identity were due, in part, to scouring flows, and that variability in the dominant macrophyte biomass was influenced by desiccation or herbivory during the prolonged drought. These shifts in dominant producers, which have different per-unit mass productivity and respiration rates, may explain patterns in whole-stream metabolism, which change seasonally and under different hydrologic regimes. By modeling productivity in response to biomass changes and antecedent flow conditions, we aim to quantify the effects of different flow conditions, and thus different management strategies and climate scenarios, on ecosystem functions.

Caitlin Conn (Primary Presenter/Author), University of Georgia, caitlin.conn25@uga.edu;


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


Phillip Bumpers ( Co-Presenter/Co-Author), Odum School of Ecology, University of Georgia, bumpersp@gmail.com;


Mary Freeman ( Co-Presenter/Co-Author), US Geological Survey, mcfreeman@usgs.gov;


Kyle McKay ( Co-Presenter/Co-Author), US Army Corps of Engineers, kyle.mckay@usace.army.mil;


Seth Wenger ( Co-Presenter/Co-Author), University of Georgia, sethwenger@fastmail.fm;