LTREB: Evaluation of Geothermally-modified Runoff and Nutrient Cycling in a Lowland Tropical Stream

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9528434 Pringle Previous research focused on the linkage between geothermally-introduced solutes and stream ecology in lowland rain forests of Costa Rica. Results indicated that phosphorus-rich streams exist 'side-by-side' with phosphorus poor streams. The source of the high phosphorus is geothermally-modified groundwater that creates a high spatial variability in stream solute chemistry. These findings represent patterns among streams draining much of the volcanic spine of Central America. This research will build on these previous findings. The current project will evaluate stream solute chemistry and incorporate important geomorphic features associated with local watershed runoff and geothermal inputs along two major stream drainages in Costa Rica. The hypothesis to be tested states that spatial and temporal patterns in solute chemistry of surface- and ground-water are related to three major geomorphic features of the volcanic landscape. Process oriented studies in one of the study drainages will allow the linkage of stream solute chemistry and transport to ecosystem- and landscape-level processes. Experiments and stream monitoring will test the hypothesis that spatial and temporal patterns in nutrient limitation of algal growth and leaf litter decomposition in surface waters are controlled by the presence or absence of geothermally-introduced phosphorus, along with physical/hydrological characteristics of the stream channel. Results from this project will comprise the only long-term data set on stream solute chemistry for primarily lowland tropical rainforest in Central America. Stream solute chemistry and process-oriented data are of fundamental importance to scientists seeking to understand and manage tropical forests and to predict the effects of regional environmental change on these threatened ecosystems.