Impacts of Riverine Heatwaves on Rates of Ecosystem Metabolism in the United States
Spencer J. Tassone*, Michelle C. Kelly, Olivia N. Beidler, Michael L. Pace, and Amy M. Marcarelli
- SJT is the corresponding author ([email protected])
Tassone, S. J., Kelly, M. C., Beidler, O. N., Pace, M. L., & Marcarelli, A. M. (2025). Impacts of riverine heatwaves on rates of ecosystem metabolism in the United States. Limnology and Oceanography Letters, 10(4), 464-472. https://doi.org/10.1002/lol2.70014
Rivers produce and decompose large amounts of carbon globally due, in part, to high rates of gross primary production (GPP) and ecosystem respiration (ER), collectively known as ecosystem metabolism. Water temperature is a major driver of ecosystem metabolism, and in-stream temperatures are increasing globally, including extreme temperature events called heatwaves. This study used published estimates of daily GPP and ER from 48 stream and river locations in the United States to examine how ecosystem metabolism responds to riverine heatwaves. During low-severity heatwaves, GPP and ER increase proportionally, resulting in no net difference. However, during severe and extreme heatwaves, GPP declined up to 82% while ER increased up to 47%, resulting in greater rates of heterotrophy (ER > GPP). While rivers were typically heterotrophic outside of heatwave conditions, these results suggest that during heatwaves, rivers become stronger sources of carbon dioxide.
The biological processes of primary production and respiration collectively capture and release carbon within rivers and are strongly temperature dependent. Rivers are warming and experiencing a greater frequency of extreme warming events, called heatwaves. Research on heatwave impacts to aquatic ecosystems, particularly in riverine systems, is in an early phase, with few studies considering heatwaves across many systems. This study examined the impact of riverine heatwaves on rates of primary production and respiration throughout the United States, providing evidence that severe heatwaves reduce primary production while increasing respiration. Together these results suggest that rivers may become larger sources of carbon dioxide, a greenhouse gas, to the atmosphere during riverine heatwaves.
The Analysis folder contains the 5 scripts used to develop this manuscript. The scripts are labeled in the order in which they should be run (i.e., 1, 2, 3,...). The data are available at https://doi.org/10.5281/zenodo.14884950