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SFS Annual Meeting

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CHRONIC PHOSPHORUS ENRICHMENT PRESSES STREAM ECOSYSTEMS INTO A NUISANCE FILAMENTOUS ALGAL REGIME

We demonstrate that chronic over-enrichment of phosphorus triggers a regime shift from biofilm-based stream ecosystems to ones dominated by nuisance filamentous green algae. We sampled reaches bimonthly for 2 y from 35 temperate, open-canopy, moderate-gradient streams that spanned a continuum of total phosphorus (TP) from <10 to 150 µg/L. Streams with TP < 25 µg/L supported relatively high biomass of biofilms that were predominantly comprised of diatoms and cyanobacteria. However, streams with TP > 25-35 µg/L shifted to a regime dominated by the filamentous green alga Cladophora glomerata. Most streams with TP > 25-35 µg/L experienced multiple blooms and sustained relatively high levels of C. glomerata biovolume, even during non-bloom periods. Blooms re-occurred in year 2 despite frequent spates, including a widespread bloom just 2 mo after a 500-y flood. Chronic P enrichment above threshold levels reported in this study is likely to press ecosystems into a nuisance filamentous algal regime, even in the face of frequent, intense hydrological disturbance.

Ryan S. King (Primary Presenter/Author), Baylor University, Ryan_S_King@baylor.edu;


Stephen C. Cook (Co-Presenter/Co-Author), Baylor University, Stephen_Cook@baylor.edu;


Jeffrey A. Back (Co-Presenter/Co-Author), Baylor University, Jeff_Back@baylor.edu;


Morgan W. Bettcher (Co-Presenter/Co-Author), Baylor University, Morgan_Bettcher@baylor.edu;


Stephen Elser (Co-Presenter/Co-Author), Arizona State University, selser2014@gmail.com;


Katherine V. Hooker (Co-Presenter/Co-Author), University of Oklahoma, khooker@ou.edu;


Lauren Housley (Co-Presenter/Co-Author), Baylor University, Lauren_Housley@baylor.edu;


Caleb J. Robbins (Co-Presenter/Co-Author), Baylor University, Caleb_Robbins@baylor.edu;