Integrating biogeochemistry and physics to understand hot spots and hot moments for nitrogen transformation in lakes and reservoirs

Washington State University, Pullman WA

Investigators

Abstract

In many waterways around the world, over-enrichment with the nutrient nitrogen is a major and growing concern. In addition to degrading drinking water, high levels damage ecosystems by reducing biodiversity, increasing the frequency of harmful algal blooms, and contributing to low oxygen ("dead zones"). Nitrogen-related problems would be substantially worse if not for the aquatic microbes that live in aquatic ecosystems and remove harmful nitrogen by converting it from a nutrient to a dissolved gas that can return to the atmosphere. This removal process, called denitrification, is important for pollution management, but the conditions that result in high rates of denitrification are not well known in complex systems such as lakes and reservoirs. Progress in understanding has been hampered by the fact that denitrification rates are challenging to measure, and vary greatly in space and time. This project addresses these challenges by combining state-of-the-art physical and biogeochemical techniques in a new way to measure denitrification in lakes. The new flux-gradient measurement technique that will be refined and applied in this project has potential to resolve spatial and temporal variation in denitrification, and will be used to shed new light on the human activities and natural hydrologic processes that probably control denitrification rates. It is expected that this project will improve the ability to measure, explain, predict, and perhaps even control denitrification so that lakes and the rivers draining them will have improved water quality. The proposed research is designed not only to advance fundamental scientific understanding, but also to provide management-relevant results that help address pressing societal concerns. For example, it is hoped that new insights into reservoir nutrient processing will allow managers to improve their management of water resources and associated ecosystems. To help researchers and managers apply the flux-gradient technique, a multi-media website will be developed, explaining the approach and providing detail on important practical and methodological considerations. This project will also have an educational impact: at least 2 doctoral students and 3 undergraduates will be directly supported.