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SFS Annual Meeting

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LONG-TERM TRENDS IN WATER CHEMISTRY IN GEOTHERMALLY-MODIFIED GROUNDWATER INFLUENCED LOWLAND TROPICAL STREAMS

Long-term datasets are useful to understand responses to climate cycles and human stressors on freshwaters. We have collected a ~20-year dataset of stream physical and chemical parameters (temperature, pH, soluble reactive phosphorus (SRP), nitrate (NO3-)) from the La Selva Biological Station, Costa Rica. At La Selva, low elevation streams exhibit higher solute concentrations due to inputs of geothermally modified groundwater (GMW). Here, we use time series methods to assess long-term stream data in relation to climate phenomena across the groundwater-elevation gradient. Low solute and high solute streams exhibited increases in NO3- (tauH = 0.22, tauL = 0.06). Concurrent increases in NO3- and decreases in SRP (tauH = -0.07, tauL = -0.08) across all sites have resulted in increases in [NO3]-:[SRP] (tauH = 0.27, tauH = 0.03). Decreases in SRP in all streams raises interesting questions about SRP cycling in low solute streams, where P is limiting, and high solute streams where P is abundant due to GMW. Continued changes in nutrient and physical conditions reveal potential ecosystem level consequences in response to GMW driven by climate cycles.

Nick Marzolf (Primary Presenter/Author), North Carolina State University, nmarzol@ncsu.edu;


Marcelo Ardon (Co-Presenter/Co-Author), North Carolina State University, mlardons@ncsu.edu;


Alonso Ramirez (Co-Presenter/Co-Author), North Carolina State University, alonso.ramirez@ncsu.edu;


Catherine Pringle (Co-Presenter/Co-Author), Odum School of Ecology, University of Georgia, cpringle@uga.edu;