Collaborative Research: LTREB Renewal: Will increases in dissolved organic matter accelerate a shift in trophic status through anoxia-driven feedbacks in an oligotrophic lake?

Lakes can undergo rapid and sustained changes in water quality. These changes, often referred to as regime shifts, can substantially alter the lake environment, including food webs. Regime shifts often occur when conditions cross tipping points, but understanding the feedbacks and attributes that lead to regime shifts can be challenging. Increases in dissolved organic matter in lake water, termed lake browning, are occurring in many regions. Dissolved organic matter regulates water clarity, water temperature, ecosystem respiration, and many other lake attributes, suggesting potentially long-term and substantial impacts. Lake browning may stimulate lake dissolved oxygen losses, termed deoxygenation, that leads to further increases in dissolved organic matter and nutrients, ultimately resulting in sustained water quality impairment. This project seeks to understand the impacts of an anticipated lake regime shift driven by increases in dissolved organic matter and its impact on the lake overall. There may be tipping points associated with the low dissolved oxygen in lake bottom waters, driven by the increases in dissolved organic matter. Broader impacts include undergraduate student research experiences and community outreach activities. Using a sophisticated suite of sensors, manually-collected long-term data spanning multiple decades, experiments, and ecosystem models will help discern the consequences of lake browning and low dissolved oxygen availability in lakes. Studying multiple lakes that vary in dissolved organic matter, nutrients, and oxygen availability will provide the capacity to compare and assess feedbacks and tipping points resulting from rapid increases in dissolved organic matter that may push water quality conditions toward several potential future trajectories. This research will provide a foundation to understand the implications of widespread aquatic deoxygenation through research and data publications and training of early career scientists in the use of sophisticated sensors and other technologies. This project will extend a long-term data set of water quality variables sampled since the late 1980s of Lakes Lacawac and Giles in or near the Lacawac Sanctuary and Biological Field Station, located in northeastern Pennsylvania. The project will support a regional lake monitoring network in Pennsylvania and closely interface with GLEON, the Global Lake Ecological Observatory Network. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.