Navigating Salinity Shifts: A Multi-Faceted Approach to Understanding Freshwater Salinization in Urban Lakes

The salinization of freshwater poses a significant threat to water quality, ecosystem health, and biodiversity globally. Despite the existence of chloride toxicity standards set by the United States Environmental Protection Agency, many lakes across the U.S. have salinity levels above those intended to safeguard aquatic life. Among these are metropolitan lakes in Minnesota, USA – where it is estimated that 78% of the 350,000 annual tons of applied road salt remains in lake ecosystems. Here we’ve examined the intricate dynamics of freshwater salinization in 15 lakes across a variety of urbanized landscapes. Using high-frequency monitoring, paleolimnology, genomics, and lake modeling, we’ve aimed to address how water quality and aquatic food webs have historically and are currently responding to salinity stress. Our initial findings of this multi-year study highlight the nuanced and potential compounding effects salinity stress plays on nutrient enrichment and internal nutrient loading. Our research further suggests that shifts in lake ecosystems due to salinization could have far-reaching implications for aquatic biodiversity and ecosystem services (e.g., decline in recreational value, impaired drinking water). Insights gained from this study underscore the importance of developing comprehensive salt mitigation strategies that not only address the immediate impacts of chloride on freshwater systems but also consider resilience and the long-term ecological consequences of salinization.

Primary Presenter: Hailey Sauer, St. Croix Watershed Research Station (breisterh@gmail.com)

Authors:

Mari Leland, St. Croix Watershed Research Station  (mleland@smm.org)

Matthew Wersebe, St. Croix Watershed Research Station  (mwersebe@smm.org)

Jason Ulrich, St. Croix Watershed Research Station  (julrich@smm.org)

Joy Hobbs, St. Croix Watershed Research Station  (jramstack@smm.org)

Amy Myrbo, St. Croix Watershed Research Station  (amyrbo@smm.org)

Adam Heathcote, St. Croix Watershed Research Station  (aheathcote@smm.org)

Mark Edlund, St. Croix Watershed Research Station  (medlund@smm.org)