Human activities such as the application of road deicing salts, resource extraction, agriculture, and climate change are increasing the concentration of salts in freshwater systems around the world. The salinization of freshwater affects physics, biogeochemical cycling, and organismal population and community dynamics of streams, lakes and wetlands. This session will showcase new research on ecological and evolutionary impacts of freshwater salinization and how salinization will impact the ecosystem services freshwaters provide. We also welcome presentations on naturally saline systems. Our goal is to promote collaboration and facilitate knowledge exchange among researchers working on different aspects of freshwater salinization through this multidisciplinary session.
Lead Organizer: Shelley Arnott, Queen's University (arnotts@queensu.ca)
Co-organizers:
Steven Brady, Southern Connecticut University (bradys4@southernct.edu)
Lizzie Emch, University of Wisconsin-Madison (eemch@wisc.edu)
Presentations
09:00 AM
DRIVERS AND CONTROLS OF SALINIZATION IN SMALL FARM PONDS (7997)
Primary Presenter: Michael Mensah, University of Regina (mikemenz253@gmail.com)
Small farm ponds are naturally occurring (wetlands) or artificially constructed (dugouts) reservoirs that store water for various agricultural purposes. These ponds trap a suite of substances including sulphate (SO42-). High SO42- suppresses methane production and contributes positively to climate change mitigation, but it is also considered toxic, as it enhances salinization and impacts aquatic ecosystem interactions, with adverse effects on livestock and human well-being. This research explores opportunities to predict SO42- dynamics in ponds by assessing several physical, chemical and biological features to identify key drivers and controls of SO42- in ponds. Forty (40) ponds with SO42- concentrations ranging from 0.3 mg/L to 24637.0 mg/L were studied in Saskatchewan, Canada during the summer months (May to August) of 2021, 2022 and 2023. Evidence of higher SO42- levels in sediment suggests that spatially, SO42- is more concentrated at the pond bottom (5675 ± 4083.4 mg/L) relative to water column (838.0 ± 1933.7 mg/L) and upland soils (1120.2 ± 2062.0 mg/L), suggesting that dredging may be useful in controlling SO42- in ageing ponds. Generalized Linear Models indicate that pore SO42- in upland soils is a key driver of pond SO42- and vegetation serves as a potent control to its migration into ponds. While further work is required to unravel the complexities involved in the identified interactions, these findings highlight the opportunities that environmental features, particularly sediment, but also vegetation offer in addressing the classic issue of pond salinization.
09:15 AM
Salinization of Ohio Rivers: More Chloride, More Problems (7837)
Primary Presenter: Douglas Kane, Heidelberg University (dkane@heidelberg.edu)
Salinization of aquatic ecosystems has a number of negative effects on the biota, water quality, and physical infrastructure and is an emerging environmental problem of the 21st century. Herein, we provide analyses of trends in chloride concentrations in watersheds in the Lake Erie, Ohio River, and Grand Lake St. Marys watersheds using long-term monitoring data obtained through the Heidelberg Tributary Loading Program (some watersheds sampled since 1974). We used simple linear regressions, ANOVAs, and Weighted Regression on Time, Discharge, and Season (WRTDS) to analyze chloride trends. Further, we used relative concentrations of chloride and nitrate to delineate possible sources of chloride (i.e., road salt, fertilizer, animal or human waste) in the Grand Lake St. Marys and Ohio River watersheds. We found that the Cuyahoga River (urban watershed), had the highest watershed yield and mean concentrations of chloride and increased the most with time. In addition, chloride was seasonally greatest in winter and spring when salt is applied as a deicing agent in the Cuyahoga watershed. However, we also found that small streams around Grand Lake St. Marys watershed could also have consistently high chloride values, with the greatest values occurring in the fall. In these agricultural watershed streams it seems likely that animal or septic sources and inorganic fertilizers were likely substantial sources of chloride, as they likely were in an agricultural watershed in the Ohio River watershed.
09:30 AM
FOUR-YEAR STUDY OF OXIC HOT MOMENTS DRIVEN BY SALINIZATION OF A FORMER FRESH WATER HABITAT HIGHLIGHTS BIDIRECTIONAL EXCHANGE BETWEEN SURFACE AND GROUND WATER (8373)
Primary Presenter: Ruby Ghosh, Opti O2 (ghosh@optio2.com)
Human activities, such as engineered barriers, can increase the salinity of freshwater systems, which then affect the biogeochemistry of floodplains and wetlands. Inundations during high water levels can mobilize dissolved oxygen (DO), a driver of biochemical function, towards the subsurface, stimulating microbial activity. This requires insight into the spatiotemporal variability of essential biochemical drivers within coastal habitats. Measuring DO at a sufficient temporal resolution has limited our ability to predict how chronic sea-level rise will impact former freshwater ecosystems functionality due to flooding. We seek to fill this knowledge gap. Following dam removal, the former freshwater habitat at Beaver Creek, Washington, USA is now disturbed by periodic intrusion of saline waters during high tide. Using state-of-the-art probes (Opti O2) we continuously measured subsurface DO over 4 years. This data set is the first measurement in a coastal environment with the requisite temporal resolution to obtain subsurface oxygen consumption time series. Co-located measurements of salinity, surface and groundwater levels, and meteorological parameters let us parse the critical drivers of coastal ecosystem biochemistry. Wavelet analyses elucidate the interactions between DO, salinity and water level during oxygenation events followed by subsequent returns to anoxia. Information theory revealed DO’s relationship with meteorological data. We show the importance of multi-year, continuous measurements to elucidate the non-linear coupling of climate, biochemistry and hydrology.
09:45 AM
Navigating Salinity Shifts: A Multi-Faceted Approach to Understanding Freshwater Salinization in Urban Lakes (8274)
Primary Presenter: Hailey Sauer, St. Croix Watershed Research Station (breisterh@gmail.com)
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.
10:00 AM
Road salt impacts on phytoplankton and periphyton communities in urban ponds (8368)
Primary Presenter: Charlie Loewen, Iowa State University (cloewen@iastate.edu)
Urban ecosystems contend with an array of environmental stressors, including salinization by deicing road salts. While application to city streets and sidewalks helps to reduce accidents in temperate regions that experience winter freezing, salt is readily transported during runoff events and can accumulate in the environment. As urban runoff is often funneled into retention basins to dampen hydrological responses and provide opportunity for contaminants to settle out, stormwater ponds are potential hotspots for freshwater salinization and useful venues for understanding its ecological consequences. To assess the extent of salinization and its impact on the midsummer functioning of urban ponds, we sampled 50 stormwater retention basins in the Greater Toronto Area, Canada. We deployed artificial colonization substrates and collected near-surface grab samples to evaluate periphyton and phytoplankton communities based on their taxonomically diagnostic pigments (chlorophylls and xanthophylls). Pigments were measured using high-performance liquid chromatography and assessed in relation to pond water quality. Depth profiles were also collected at each site to assess water density gradients and the vertical distributions of chlorophyll a and phycocyanin pigments (using a fluorescence sensor). By contrasting how phytoplankton and periphyton respond to variation in chloride concentrations (among other factors), we offer insights into the use of these communities as bioindicators of urban water quality and the risk of salinization facilitating growth of toxin-producing cyanobacteria.
10:15 AM
EXAMINING HOW BASIN CHARACTERISTICS MODULATE SIGNATURES OF RIVER SALINIZATION AT OVER 100 SITES (7781)
Primary Presenter: Lindsay Platt, University of Wisconsin-Madison (lrplatt@wisc.edu)
Long-term increases in salinization can disrupt ecosystem processes such as aquatic organismal development, replenishment of dissolved oxygen during periods of lake mixing, and biogeochemical cycling. In contrast, short-term fluxes in salinity from extreme events can also threaten ecosystem health due to the abrupt changes in environmental conditions and the sensitivity of many aquatic organisms to such swings. The speed, timing, and magnitude of salt transport through a watershed can be influenced by a variety of land uses, hydrologic features, and soil characteristics. In this study, we explored watershed characteristics that may exacerbate or buffer the impact of road salt on rivers in the northeast and midwest United States at 122 different sites. We focused on two salinization mechanisms contributing to in-situ dynamics observed in long-term records: "episodic salinization" resulting from the rapid flushing of salts after a winter storm, and "baseflow salinization" resulting from salt retention and release through subsurface flow paths. We found that under similar road salt application rates, sites exhibit different salinization dynamics due to differences in groundwater influence, hydrology, and land use. The results of this study add to the growing body of research characterizing the spatiotemporal extent and severity of freshwater salinization due to winter road salting, and gives us tools to identify at-risk rivers in order to improve management of roadways during winter months and better balance human safety with ecosystem health.
SS07A - Salinization of Freshwater Habitats
Description
Time: 9:00 AM
Date: 4/6/2024
Room: Hall of Ideas F