Synthesis of stream ecosystem responses to nutrient enrichment at multiple trophic levels

The goals of this LTER Synthesis Working Group are (1) to initiate and coordinate the integration of data from multiple sites on stream ecosystem responses to nutrient amendment, (2) to synthesize these data with a quantitative evaluation of functional responses at the microbial, primary producer, consumer and whole-stream levels and (3) to promote interaction between LTER and the NEON experiment (Stream Experimental and Observatory Network, STREON): of 10 STREON sites, 6 are located at or near LTER sites. Streams are hotspots of nutrient processing on the landscape, receiving, transforming and cycling inorganic nutrients (nitrogen (N) and phosphorus (P)) that are delivered from the watershed. The cycling of inorganic nutrients is a result of the interactions between geochemical settings and the integrated activity of biota that inhabit streams, including microbial life (bacteria and fungi), primary producers (plants, algae and cyanobacteria) and secondary producers (invertebrates and fish). As such, stream water nutrient concentration is a key driver of stream function at these three trophic levels, and of integrated ecosystem processes like leaf litter decomposition and whole-stream metabolism. Increases in stream nutrient concentrations are occurring globally, as a result of increased nutrient input and runoff from intensifying agricultural and urban land use and atmospheric deposition related to the use of fossil fuels. Nutrient increases may negatively affect stream ecosystem goods and services and exacerbate efforts to conserve stream biota. Aptly, research on the effects of nutrient enrichment in streams (some of it from LTER sites) has expanded. However, consideration of these effects across multiple trophic levels and ecosystem response metrics is limited, and an integrated framework to forecast the long-term nutrient enrichment effects on stream ecosystem health is still lacking. The proposed synthesis effort will address these gaps. We predict that regard