EFFECTS OF RIPARIAN RHODODENDRON REMOVAL AND TOP-DOWN CONTROL BY CRAYFISH ON DIATOM COMMUNITY STRUCTURE IN SOUTHERN APPALACHIAN STREAMS
Primary producers in headwater streams are controlled by both bottom-up (e.g., light, nutrients) and top-down (e.g., stream consumers) factors. In the southern Appalachians, Rhododendron maximum is a pervasive evergreen shrub in headwater riparian zones that severely limits light availability to algal communities year-round. Previous studies indicate that increased light conditions after rhododendron removal had a positive effect on algal growth, although algal consumption by macroconsumers mediated this effect. In this study, we examine how top-down control by crayfish interacts with increased light availability created by reach-scale removal of riparian rhododendron to influence diatom community structure. We experimentally excluded crayfish from localized benthic areas using electric “fences.” Crayfish exclosure treatments were paired with crayfish access controls. We ran two 32-day experiments, pre-rhododendron/post-rhododendron removal, whereby diatoms were sampled weekly. Preliminary analyses indicate that pre-rhododendron removal, diatom communities were dominated by adnate forms (e.g., Eunotia and Nupela spp.) and crayfish exclusion had little effect on diatom community composition. Post rhododendron removal, crayfish exclusion shifted diatom community composition from adnate diatoms (e.g., Eunotia and Achnanthidium spp.) in access plots to upright diatoms (e.g., Gomphonema and Encyonema spp.) in exclusion plots.
Kelsey Solomon (Primary Presenter/Author), Odum School of Ecology, University of Georgia, firstname.lastname@example.org;
Maura Dudley (Co-Presenter/Co-Author), Oglethorpe University, email@example.com;
Rebecca Bixby (Co-Presenter/Co-Author), University of New Mexico, firstname.lastname@example.org;
Catherine Pringle (Co-Presenter/Co-Author), Odum School of Ecology, University of Georgia, email@example.com;