Water Resources Research Act Program

Details for Project ID 2019MT159B

Primary controls on nitrate use in lotic systems

Institute: Montana
Year Established: 2019 Start Date: 2019-06-01 End Date: 2019-10-01
Total Federal Funds: $1,000 Total Non-Federal Funds: $440

Principal Investigators: Kimberly Bray

Abstract: Metabolism in aquatic environments has been the focus of many studies because of its ability to link the two major fates of carbon in the natural world: fixation of CO2 and mineralization of organic carbon (Jones and Stanley 2016). Calculating metabolic rates of respiration and production encapsulates much of heterotrophic and autotrophic energy processing and demand within streams (Bernhardt et al. 2018). Metabolism is often described at an ecosystem-scale with gross primary production (GEP), the quantity of carbon fixed through chemoautotrophy and photoautotrophy. Net ecosystem production (NEP) is found through the addition of GPP and ecosystem respiration (ER). An ecosystem is exporting or accumulating organic carbon when GEP is less than ER, whereas it is being imported or consumed and then respired when GEP is more than ER. The mechanisms underlying manifested metabolic rates can be due to hydrology, chemistry, and geology, to name a few. Building on understandings of the linkages between nutrient inputs and instream heterotrophic and autotrophic growth, stream ecologist recently began to explore the relationship between nutrient concentrations and metabolism (Payn et al. 2005, Bernhardt et al. 2018). Many studies focus on the control that limiting nutrients, like nitrogen and phosphorus, can exhibit on respiration and production. In the past decade, the reciprocal relationship between nutrient availability and metabolism has been explored more holistically (Roberts and Mulholland 2007, Roberts et al. 2007, Branch et al. 2018). There is still much to explore about how metabolism, as well as channel characteristics, impact nutrient uptake by biota. Thus, such trends are not well understood across multiple systems and long timeframes. This lack of understanding is primarily due to highly intensive water sampling and measurement that was needed to dissect such relationships. However, with the development of modern sensors that can autonomously detect nutrient and dissolved oxygen concentrations, detailed measurement of metabolism and nutrient dynamics across multiple temporal and spatial scales is now possible. “Metabolic fingerprints†can now be used to describe changing respiration and production rates at fine temporal scales (Bernhardt et al. 2018). Quantifying controls on nutrient uptake is becoming increasingly important in a world with more and more anthropogenic nutrient inputs into streams and rivers with associated algal blooms.