Decreasing Groundwater Supply Can Exacerbate Lake Warming and Trigger Algal Blooms. Issue 9 (22nd September 2021)

• Record Type: Journal Article
• Authors: Safaie, Ammar; Litchman, Elena; Phanikumar, Mantha S.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 9(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-22
• Subjects: eutrophication -- algal blooms -- groundwater -- lake warming -- climate change; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2021JG006455
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: As groundwater depletion becomes a global phenomenon, inland lake ecosystems are being impacted by decreasing groundwater supply. While the current trend of rapid surface warming of inland lakes continues, the deep waters can resist changes, depending on the nature of surface water — groundwater interactions. However, the effects of these interactions on lake processes are not fully understood. Here we investigate the role of groundwater on coupled biophysical processes in a deep, dimictic, groundwater‐fed lake using mechanistic models combined with data from field observations. Although excess nutrient inputs are the most commonly cited reason for algal blooms, here we show that algal blooms in inland lakes can also appear due to a decreasing groundwater supply while all other factors remain the same. Results indicate that decreasing groundwater supply to lakes leads to elevated hypolimnetic temperatures, enhanced algal growth rates and algal blooms, and oxygen depletion, thus exacerbating the negative effects of surface warming. Our work suggests that globally declining groundwater supplies may have a significant negative effect on water quality of inland lakes by accelerating water column warming and stimulating algal growth, especially when the groundwater contribution to the lake system is significant compared to riverine discharge. The work provides insights for management efforts to improve the resilience of groundwater‐dependent ecosystems in the face of external stressors. Plain Language Summary: Harmful algal blooms in inland lakes and reservoirs contribute to significant economic losses annually while posing a range of health risks; however, the exact causes for the blooms are not always known. Using mechanistic models and field data, we reveal a link between groundwater supply and algal blooms in an inland lake. While previous research has demonstrated that excess nutrient inputs via both surface and subsurface discharges cause algal blooms, our work shows that decreasing groundwater supply alone could trigger algal blooms in inland lakes by exacerbating lake warming while all other factors remain the same. Our results have implications for management efforts to mitigate the current trends of lake surface warming and declining groundwater levels in major aquifers throughout the world. Key Points: Groundwater plays a significant role in key biophysical processes in an inland lake Deep waters in the lake can resist changes induced by surface warming Decreasing groundwater supply to inland lakes could cause deep water warming and trigger algal blooms