Measuring nitrogen transformation rates in large lakes: challenges, solutions, and future needs

Session: 49. - Big Lakes - Small World: IAGLR Teams with the European Large Lakes Symposium in 2018

Mark McCarthy, Wright State University, [email protected]
Silvia Newell, Wright State University, [email protected]
Wayne Gardner, UTMSI, [email protected]

Abstract

Population growth and climate change are increasing anthropogenic pressure on aquatic systems, while our dependence on the health of these systems also increases. Impacted systems are often monitored intensively for evidence and mitigation of anthropogenic, nutrient-related impacts, such as hypoxia and harmful algal blooms. ‘Snapshot’ nutrient concentration monitoring is common, but the most bioavailable nutrient forms (e.g., ammonium and reactive phosphorus), cycle rapidly within systems, which limits the usefulness of concentration measurements. For ammonium, and nitrogen (N) in general, the result is underappreciation of its importance due to low in situ concentrations. Understanding N dynamics and its importance to contributing to detrimental impacts requires quantification of the rates at which various N forms are assimilated, recycled, and ultimately removed. These measurements require labor and analytically intensive incubations necessitating the use of stable isotopes, expensive analyses, and multidisciplinary collaborations. Once quantified, the challenge shifts toward interpretation and scaling of results for use in data-based regulatory and mitigation actions. Here, experiences from 20 years of conducting these measurements in large lakes around the world will be presented in the context of resolving these challenges and meeting future research needs to effectively manage the vital resources and ecosystem services provided by large lakes.

1. Keyword
eutrophication

2. Keyword
harmful algal blooms

3. Keyword
nutrients

4. Additional Keyword
nitrogen

5. Additional Keyword
large lakes