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
02:00 PM
SITE-SPECIFIC DIFFERENCES, BUT NOT EXPOSURE PROFILES DRIVE THE RESPONSES OF PRIMARY-PRODUCERS TO FRESHWATER SALINIZATION IN A MULTI-SITE MESOCOSM EXPERIMENT (8387)
Primary Presenter: Jose Luis Rodriguez Gil, IISD - Experimental Lakes Area (joseluis.rodriguezgil@gmail.com)
The PRESSUR experiment aimed to characterize the response of model aquatic ecosystems to two different salinity exposure patterns. Fifteen ~500-L, in-lake, closed-bottom, mesocosm were assigned to three treatments (n = 5 each): a control, and two sets of mesocosms treated with NaCl (500 mg CL-/L final concentration) differing on the exposure profile. One received a single spike while the other received the same total amount in 8 events over 21 days. This set up was also replicated at two different locations, an oligotrophic temperate lake (57ºN) and a humic boreal lake (64ºN) both in Sweden. Each mesocosm was outfitted with an array of sensors collecting real time data on temperature, conductivity, pH, dissolved oxygen, chlorophyll-a and phycocyanin fluorescence, and PAR. Other endpoints were also assessed in phyto- and periphyton over the 38 days of the study. Phytoplankton Chll-a fluorescence was reduced by NaCl addition with this effect developing faster in the single application treatment. The gradual application treatment, however, reached similar effect levels after ~2 applications. Interestingly, differences were observed between the two sites, with the northern site showing a late increase in Chll-a 14-20 days post first application (onset earlier in the single-pulse treatment). This late increase on Chll-a levels was not observed in the south site, where Chll-a levels remained low after the initial reduction. This study highlights the importance of original ecosystem characteristics on the sensitivity of aquatic systems to salinization.
02:15 PM
IMPACT OF SALINIZATION RATE ON ZOOPLANKTON COMMUNITY DIVERSITY AT TWO LAKES IN SWEDEN (8359)
Primary Presenter: Erin Ford, Queen's University (erin.sydney.f@gmail.com)
The increasing salinization of freshwater systems is threatening planktonic communities around the globe. However, little is known about how the rate of salinization exposure impacts the response of plankton communities to chloride. Zooplankton can experience ecological and evolutionary rescue when exposed to stress but responses may differ under gradual or abrupt exposure to a toxicant. Further, responses to salinization may be vary across habitats. To assess how differing rates of salinization impact zooplankton community dynamics, and how the responses differ between lakes, we employed in-lake mesocosm experiments at two oligotrophic lakes in northern and southern Sweden. Planktonic communities were exposed to 500 mg Cl-/L in a single dose or at a gradual rate over 22 days. Zooplankton were sampled every 6 days for 36 days by filtering 7-10L of water through 50-um mesh. We found a strong negative effect of salt on zooplankton communities but did not observe an effect of salinization rate. At both sites, total abundance and abundance of taxa decreased in salt treatments relative to controls, but there was no difference between abrupt and gradual treatments. We observed similar results for taxa richness except that at the northern site richness in abrupt treatments was lower than in the gradual treatment. A difference in the dominant species was observed between the gradual and abrupt mesocosms. These findings suggest that local community composition may be more important in determining community response to stress than rate of exposure.
02:30 PM
Response of water quality to short and long-term warming under different salinities and climatic conditions: two synchronized mesocosm experiments in Turkey (7883)
Primary Presenter: Korhan Özkan, MIDDLE EAST TECHNICAL UNIVERSITY / INSTITUTE OF MARINE SCIENCES (korhan.ozkan@gmail.com)
Salinisation due to excessive water use for irrigation in dry landscapes may dramatically affect functioning of shallow lake ecosystems, which may further be complicated by climate warming and heatwave events. We conducted two synchronized experiments for the effects of short and long-term heating at two different salinities (4 and 40 ppt) in 32 identical outdoor mesocosms located in two different climatic zones (semi-arid cold-dry steppe Ankara and Mediterranean Mersin, 16 mesocosms per location) mimicking shallow lake ecosystems. Each mesocosm had 5m3 volume, 1.2 m water depth and inoculated with natural sediment and biotic communities. The first experiment focused on the effects of a short heatwave event (ambient temperature vs a two-week long heatwave of +6 °C) and was conducted between 29 August and 3 November 2022. The second experiment focused on the effects of long-term heating (ambient temperature and constant +4.5 °C heating), conducted between 29 August and 30 November 2023. Temperature treatments in both experiments were crossed with two salinities, all having four replicates. Both experiments revealed significant response in water quality and nutrient concentrations to salinity treatment and climatic zones (between Mersin and Ankara). No pronounced effect of short-term heatwave was observed, whereas long-term heating induced significant response in water quality and nutrient chemistry. Long-term heating decreased chlorophyll-a concentrations, oxygen, and pH, especially at higher salinities and warmer climates. Both mesocosm experiments revealed predominantly negative effects of salinisation and climatic warming on water quality, although latter was conditional on duration of heating.
02:45 PM
MULTISTRESSOR EFFECTS OF CHLORIDE AND CALCIUM ON CANADIAN LAKE ZOOPLANKTON COMMUNITY ASSEMBLAGES (8401)
Primary Presenter: Caelan Johnson, Queen's University (20cj3@queensu.ca)
Salt concentrations (NaCl) associated with road de-icing are increasing in freshwater bodies in Canada and other regions that experience cold winters, posing concern for the health of those ecosystems. Some zooplankton, which play an important role as primary consumers of algae in freshwater bodies, have a high sensitivity to chloride (Cl-) resulting in changes in zooplankton community composition, reduced biomass, and lower richness. Additionally, there is some evidence that zooplankton may be more sensitive to Cl- in soft water conditions (i.e., low [Ca2+] and [Mg2+]), especially in regions where [Ca2+] is declining. We conducted a six week mesocosm experiment to test the interactive effects of Ca2+ (1, 5, and 10 mg/L) and Cl- (gradient from 0.22 to 1500 mg/L) on zooplankton species abundances and community metrics. We found that abundances decrease across all taxonomic groups as Cl- increases. Ca2+ has an ameliorating effect on some taxa like copepods, rotifers, large Cladocera, Monostyla spp., and Chydorus sphaericus. The ameliorative effect of Ca2+ on Daphnia pulicaria is unclear, but we observed higher D. pulicaria abundances at higher Ca2+. We also observed lower small Cladocera (excluding C. sphaericus) abundances at higher Ca2+. These results suggest that zooplankton communities in low Ca2+ environments may be more susceptible to Cl- toxicity, and community dynamics may be influenced by shifts in dominant taxa.
03:00 PM
Intraspecific variation in Daphnia pulicaria/pulex complex response to salt: a multi-region study (8188)
Primary Presenter: Shelley Arnott, Queen's University (arnotts@queensu.ca)
Evaluating the capability of organisms to adapt and persist in face of environmental change is critical for assessing risk of biodiversity loss. Freshwater salinization has severe consequences for lake environments, aquatic organisms, and the services they provide. Although the number of studies investigating the ecological impacts of freshwater salinization is steadily rising, our understanding of the capacity of the adaptive potential of aquatic organisms to increasing freshwater salinity remains limited. We used Daphnia pulicaria/pulex, a ubiquitous herbivorous zooplankter found across North America and Europe, to assess intraspecific variation in tolerance to acute exposures of NaCl. We isolated 95 iso-female lines from 59 lakes and assessed survival after 48-hr exposure to chloride concentrations ranging from 18 to 2700 mg/L. We detected high variation in survival among iso-female lines; LC50 (the chloride concentration where 50% of organisms die) ranged from 675 to 2763 mgCl-/L, and had a coefficient of variation equal to 30%. Survival was influenced by test media chloride concentration and lake chloride concentration. For lakes with multiple iso-female lines, we found that variation within lakes was much less than variation among lakes. High genetic variation in salt tolerance among D. pulicaria across regions suggests that local adaptation to increasing salinity may be possible if dispersal is high enough to allow the movement of salt-tolerant genotypes.
SS07B - Salinization of Freshwater Habitats
Description
Time: 2:00 PM
Date: 4/6/2024
Room: Hall of Ideas F