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
04:00 PM
Impact of Freshwater Salinizaition on Wood Frog sperm Performance (8182)
Primary Presenter: Sean Keane, Southern Connecticut State University (keanes2@southernct.edu)
Freshwater salinization poses threats to many aquatic ecosystems, particularly those polluted by salt from deicing practices in the North American snowbelt region. Much attention has focused on salinization of rivers and lakes, but less has been given to smaller water bodies such as vernal pools, which are critical for a suite of species found nowhere else. Because such pools are relatively small in volume, these habitats can reach high salinity, especially when situated besides roads or in developed landscapes. Beyond immediate ecological consequences, deicing salt can also act as an agent of natural selection, driving population divergence across gradients of salinization. Theory predicts that local populations with a lineage of exposure to elevated salinity should evolve higher tolerance over time. Indeed, experimental reciprocal transplant experiments have found that road adjacent populations of one amphibian, the spotted salamander, appear to have evolved increased tolerance to high-salinity roadside ponds. Curiously, co-habiting populations of a different amphibian, the wood frog, have consistently shown reduced embryonic and larval tolerance to high-salinity roadside ponds, consistent with local maladaptation. We hypothesize that tradeoffs might mediate this maladaptive outcome, where embryonic and larval disadvantages are offset by advantages found at other life history stages. Here, we use data from an artificial fertilization experiment to investigate whether sperm performance and fertility differ between populations across a salinity pollution gradient. Specifically, we predict that roadside populations will harbor adaptive sperm motility variation that improves fertilization, potentially supporting a tradeoff between reproductive success and offspring performance. The results of this analysis underscore the nuanced impacts of environmental stressors on amphibian species, highlighting both maladaptive and adaptive responses across different life stages.
04:15 PM
Salty parasites: Can salinization modify the role of parasites in nutrient cycling? (8094)
Primary Presenter: Jessica Hua, University of Wisconsin- Madison (jhua23@wisc.edu)
By modifying ecological interactions, salinization has complex consequences on freshwater ecosystems. Notably, growing evidence suggests that parasites play important roles in mediating nutrient flow and shaping nutrient cycling via their hosts (animal mediated nutrient cycling). However, despite the rapid rate of anthropogenic environmental change across the globe, how factors like salinization influence the contribution of parasites to nutrient cycling remains a gap. Using an amphibian host-virus model system, we present an interdisciplinary framework that integrates microbiology, disease ecology, ecotoxicology, and ecosystem ecology to evaluate how salinization can influence the role of parasites in nutrient cycling of aquatic systems. First, using a combination of cell/viral culture techniques, toxicological lab assays, and field disease surveys, we asked: How does a common virus respond to environmentally relevant levels of salinity? Second, using lab infection and excretion assays, we asked: How does viral infection influence host excretion? Lastly, we integrated experimental data on a) viral responses to salinity and b) host excretion responses to viral infection with chloride field data from ponds in Madison, WI to parameterize a model that explores and visualizes how salinization can influence the contribution of parasites to nutrient cycling. Collectively, this work offers a framework for integrating an ecological perspective across multiple organizational levels and disciplines to facilitate our understanding of the complex effects of freshwater salinization.
04:30 PM
Salt belt index (SBI): a biotic index for streams within the North American “salt belt,” with newly proposed baseline chloride thresholds (8300)
Primary Presenter: Sam Miess, Oklahoma State University (smiess@okstate.edu)
Road salt (commonly NaCl, CaCl2, and MgCl2) is widely used in the northern United States as a deicing agent for roadways and other byways. Millions of tons of road salt are used annually in the United States, resulting in drastic increases in freshwater salinity. This study aims to determine the chloride optima and tolerance ranges of macroinvertebrates using publicly accessible stream monitoring data from the US EPA. We assigned taxa region-specific tolerance values, which we then used to calculate the Salt Belt Index (SBI). In addition to the SBI, we determined new, region-specific, chronic Cl- thresholds, based on macroinvertebrate community response to salinity. Using generalized linear models, we found the SBI was highly accurate at estimating chloride concentration (mg/L Cl-) across the salt belt states (β=0.349+/-0.011, t=32.3, p<2e-16, r2=0.49). Macroinvertebrate community richness exhibited a significant negative relationship with increasing chloride concentrations (β=-0.132 +/-0.004, z=-32.6, p < 2e-16). Newly proposed chloride thresholds, based on the richness-chloride relationship, were far lower than current thresholds. The SBI was able to differentiate between Low-, Medium-, and High-Impact sites, grouped based on proposed chloride thresholds (F=191.5, dfdenom= 697.5, p<2e-16). Based on our findings, it is clear current salinity thresholds are too high, and management practices should factor in regional variability, taxon-specific physiology, and historical instream chemistry when implementing salinity thresholds.
04:45 PM
Designing a Lower Salt Future (8175)
Primary Presenter: Carolyn Dindorf, Bolton & Menk, Inc. (carolyn.dindorf@bolton-menk.com)
Chloride, found in road salt used to combat icy conditions, is a growing pollutant of concern across the snowbelt. This permanent pollutant contaminates drinking water, is toxic to aquatic life, affects lake turnover, reduces phosphorus removal in treatment ponds, ruins our infrastructure, and harms vegetation. Removal of chloride once it contaminates surface water is infeasible. Prevention is the key. In Minnesota and other states, we have worked to train thousands of winter maintenance professionals on salt reduction strategies and learned of the design challenges that require higher salt use. A significant driver of salt use is the meltwater sprawl and refreeze cycles. As our climate changes, so does the number of thaw/freeze cycles, influencing our need for salt. Winter weather offers many challenges but also provides a few key opportunities that can be harnessed to lower our salt use. In this presentation, attendees will learn about the chloride crisis, the challenges presented to winter maintenance operations, the chloride challenges for stormwater management, and the opportunities designers, architects, and planners have to change our designs for lower salt use and better winter performance.
05:00 PM
Reducing Salt Pollution through Advocacy, Education, and Outreach (7921)
Primary Presenter: Allison Madison, Capital Area Regional Planning Commission (AllisonM@capitalarearpc.org)
Over the last 50 years, salt’s use as a chemical deicer has ballooned, largely unchecked. Salt is cheap, effective, and “disappears” after use. Its (over)application has spread from highways and interstates to parking lots and sidewalks. Changing current norms around salt use involves training winter maintenance professionals on best practices and educating the broader public on the full cost of salt use: damage to infrastructure, vegetation, soils, drinking water supplies, and freshwater ecosystems. Wisconsin Salt Wise (wisaltwise.com) was established in 2015 with an aim of reducing salt pollution through advocacy, education, and outreach. Since then, Salt Wise has been effective in bringing together scientists, multiple agencies, maintenance professionals, and community members to tackle salt pollution. Science-based communication has been instrumental in Salt Wise’s successes in Wisconsin across multiple levels of organization, from working with private applicators to lobbying for legislative change to liability laws. Continued collaboration with research scientists is needed to accurately communicate the status and threats to our freshwater and reduce further degradation of freshwater resources.
SS07C - Salinization of Freshwater Habitats
Description
Time: 4:00 PM
Date: 4/6/2024
Room: Hall of Ideas F