Climate displaces deposition as dominant driver of dissolved organic carbon concentrations in historically acidified lakes

Authors: Herreid, Allison; FAZEKAS, HANNAH - Saginaw Valley State University; NELSON, SARAH - Appalachian Mountain Club; WYMORE, ADAM - University Of New Hampshire; MURRAY, DESNEIGES - University Of New Hampshire; VARNER, RUTH - University Of New Hampshire; MCDOWELL, WILLIAM - University Of New Hampshire

Submitted to: Biogeochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2024
Publication Date: 12/21/2024
Citation: Herreid, A.M., Fazekas, H.M., Nelson, S.J., Wymore, A.S., Murray, D., Varner, R.K., Mcdowell, W.H. 2024. Climate displaces deposition as dominant driver of dissolved organic carbon concentrations in historically acidified lakes. Biogeochemistry. 168. Article 5. https://doi.org/10.1007/s10533-024-01193-5.
DOI: https://doi.org/10.1007/s10533-024-01193-5

Interpretive Summary: Lakes are critical sources of fresh water, but their quality is increasingly influenced by complex environmental factors. One important measure of water quality is the concentration of dissolved organic carbon (DOC), which affects both ecosystem health and drinking water safety. The amount of DOC in lakes is influenced by a combination of factors like climate, atmospheric deposition, and the features of the land surrounding the lake. These factors are interconnected and complex, making it hard to pinpoint a single cause for changing DOC levels. This research uses forty years of data to show that climate, especially how it interacts with the features of the land that drains into the lakes, has become the primary factor affecting DOC levels, surpassing the impact of sulfate deposition observed in the past. Specifically, more winter precipitation is falling as rain rather than snow, which leads to higher DOC levels in spring. This information helps us understand how climate change could impact lake ecosystems and drinking water quality in the future. The findings from this study will be valuable to environmental scientists, water resource managers, and policymakers. By understanding the relationship between climate, watershed properties, and DOC levels, they can better predict and manage the effects of climate change on lake water quality.

Technical Abstract: Climate and atmospheric deposition interact with watershed properties to drive dissolved organic carbon (DOC) concentrations in lakes. Because drivers of DOC concentration are inter-related and interact, it is challenging to assign a single dominant driver to changes in lake DOC concentration. Leveraging forty years of data, we used structural equation modeling to show that the impact of climate, as moderated by watershed characteristics, has become more dominant in recent decades, superseding the influence of sulfate deposition that was observed in the 1980s. An increased percentage of winter precipitation falling as rain was associated with elevated spring DOC concentrations, suggesting a mechanistic coupling between climate and DOC increases that will persist in coming decades. Watersheds characterized by more poorly drained soils had greater variability in lake DOC concentrations than watersheds with well-drained soils. Capturing the spatial variability in interactions between climatic impacts and localized watershed characteristics is crucial for forecasting lentic carbon and nutrient dynamics, with implications for lake ecology and drinking water quality.