TRIAGE · TRophic state Interactions with drivers of Aquatic greenhouse Gas Emissions

Inland waters are an integral component of the carbon cycle as they process, store, transport, and emit significant amounts of carbon. Freshwaters emit carbon in the form of carbon dioxide (CO2) and methane (CH4), both important greenhouse gases (GHG). Lakes subject to a high nutrient load in a process called eutrophication are typically characterized by enhanced primary production and depleted oxygen, variables directly related to GHG production. Therefore, with increasing nutrient load (i.e., trophic state), lakes have the potential to substantially impact GHG emission, but the relationship is poorly constrained. Climate change-induced variations in variables such as temperature and precipitation could alter nutrient loading, primary production and oxygen, which in turn could change the GHG balance of a system. Evidence suggests that lake eutrophication and climate change impacts interact and alter the lake GHG budget in non-linear ways. Moreover, eutrophication may shift the balance toward higher emissions of CH4, a more potent GHG. To date, very few studies have used a systematic approach to understanding the interaction between GHG emissions and eutrophication, which is essential for efficient management of inland waters, particularly in the face of global change. The overall goal of the project is determine how the GHG balance of aquatic systems shift along a trophic gradient and what some of the drivers of these shifts may be. The project will consist of a multi-lake survey throughout central Europe across a large trophic gradient, followed by modeling of the full GHG balance of those lakes and testing of the strength of relevant drivers. Constraining the variables that dictate the GHG balance will help to inform better management practices for mitigating climatic impacts on aquatic systems as well as allow for the development of models capable of predicting the response of aquatic systems to global environmental changes.