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Rapid evolution of tolerance to road salt in zooplankton

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Abstract

Organisms around the globe are experiencing novel environments created by human activities. One such disturbance of growing concern is the salinization of freshwater habitats from the application of road deicing salts, which creates salinity levels not experienced within the recent evolutionary history of most freshwater organisms. Moreover, salinization can induce trophic cascades and alter the structure of freshwater communities, but knowledge is still scarce about the ability of freshwater organisms to adapt to elevated salinity. We examined if a common zooplankton of freshwater lakes (Daphnia pulex) could evolve a tolerance to the most commonly used road deicing salt (sodium chloride, NaCl). Using a mesocosm experiment, we exposed freshwater communities containing Daphnia to five levels of NaCl (15, 100, 200, 500, and 1000 mg Cl− L−1). After 2.5 months, we collected Daphnia from each mesocosm and raised them in the lab for three generations under low salt conditions (15 mg Cl− L−1). We then conducted a time-to-death experiment with varying concentrations of NaCl (30, 1300, 1500, 1700, 1900 mg Cl− L−1) to test for evolved tolerance. All Daphnia populations exhibited high survival when subsequently exposed to the lowest salt concentration (30 mg Cl− L−1). At the intermediate concentration (1300 mg Cl− L−1), however, populations previously exposed to elevated concentrations (i.e.100–1000 mg Cl− L−1) had higher survival than populations previously exposed to natural background levels (15 mg Cl− L−1). All populations survived poorly when subsequently exposed to the highest concentrations (1500, 1700, and 1900 mg Cl− L−1). Our results show that the evolution of tolerance to moderate levels of salt can occur within 2.5 months, or 5–10 generations, in Daphnia. Given the importance of Daphnia in freshwater food webs, such evolved tolerance might allow Daphnia to buffer food webs from the impacts of freshwater salinization.

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... Further, shifts in zooplankton biomass with increased salinity often follow nonlinear patterns, with substantial variability in salt tolerance thresholds within and among species (Jeppesen et al. 2007;Corsi et al. 2010;). Factors such as exposure history and regional connectivity may decrease salt sensitivity through adaptive change or increased diversity (Thompson and Shurin 2012;Coldsnow et al. 2017;. Further, salt toxicity may be modulated by water chemistry; for example, studies have found that freshwater zooplankton are more sensitive to salt when calcium concentrations are low (Elphick et al. 2011;Arnott et al. 2020). ...
... Variation in responses to salinization by plankton have been linked to predation, disturbance, adaptation, dispersal, and water chemistry (Waterkeyn et al. 2011;Thompson and Shurin 2012;Coldsnow et al. 2017;. While the mechanisms behind the relatively high salt tolerance of zooplankton here are unknown, mediation of salt toxicity by the relatively high calcium concentrations in our study lake is a plausible explanation. ...
... The regional context may also be an important factor in determining zooplankton salt tolerance. Dispersal from nearby waterbodies may rapidly moderate zooplankton responses to salinity (e.g., in 2.5 months; Coldsnow et al. 2017;). However, our study lake is not saline, and contains few species known to tolerate a broad range of salinities (Hammer and Forró 1992;Lee and Petersen 2002). ...
Article
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Runoff containing road salt (sodium chloride, NaCl) causes the salinization of inland freshwaters, with potentially severe impacts on aquatic species. We performed a mesocosm experiment to test the effects of salinization on plankton community structure in an oligotrophic mountain lake with a limited history of elevated salt concentrations. We exposed plankton communities to a gradient of 30 salt concentrations ranging from 1 to 2900 Cl− mg L−1 for 6 weeks. Adding salt increased zooplankton biomass at concentrations < 500 mg Cl− L−1 while reducing phytoplankton biomass. Zooplankton biomass declined precipitously at higher concentrations, with phytoplankton biomass showing a mirror image increase. The initial increase in zooplankton biomass with salt addition suggests that zooplankton are salt‐limited at low ionic concentrations. Additionally, the inverse response of zooplankton and phytoplankton suggests that salinity mainly affects phytoplankton biomass via changes in top‐down regulation by grazers.
... For example, roadside populations of amphibians can be locally adapted to high salinity resulting from road salt applications [30,31]. Recently, researchers demonstrated the experimental evolution of a ubiquitous species of zooplankton (Daphnia pulex), resulting in higher NaCl tolerance after multi-generational exposure to NaCl [32]. This was an important discovery because Daphnia are a critical component of freshwater food webs, responsible for transferring energy from primary producers to higher trophic levels [33]. ...
... We addressed these questions using one naive population and two NaCl-evolved populations of Daphnia in an outdoor mesocosm experiment. Two Daphnia populations used in our study evolved a tolerance to NaCl road salt in a prior mesocosm experiment [18] and we confirmed this increased tolerance in a follow-up experiment [32]. We maintained Daphnia from the original experiment [18] in low-salt (approx. ...
... Our goal was to include one concentration that was sublethal and another that approached a lethal level. The Daphnia population types were a naive population with no prior exposure to elevated NaCl concentrations and the two other Daphnia populations that evolved tolerance to 833 mS cm 21 (250 mg Cl 2 l 21 ; Population 1 [P1]) and 2662 mS cm 21 (1000 mg Cl 2 l 21 ; Population 2 [P2]) of NaCl [18,32]. The 21 treatment combinations were replicated four times for a total of 84 experimental mesocosms. ...
Article
Recent discoveries have documented evolutionary responses to freshwater salinization. We investigated if evolutionary responses to salinization exhibit life-history trade-offs or if they can mitigate ecological impacts such as cascading effects through mechanisms of tolerance and cross-tolerance. We conducted an outdoor mesocosm experiment using populations of Daphnia pulex —a ubiquitous algal grazer—that were either naive or had previously experienced selection to become more tolerant to sodium chloride (NaCl). During the initial phase of population growth, we discovered that evolved tolerance comes at the cost of slower population growth in the absence of salt. We found evolved Daphnia populations maintained a tolerance to NaCl approximately 30 generations after the initial discovery. Evolved tolerance to NaCl also conferred cross-tolerance to a high concentration of CaCl 2 (3559 µS cm ⁻¹ ) and a moderate concentration of MgCl 2 (967 µS cm ⁻¹ ). A higher concentration of MgCl 2 (2188 µS cm ⁻¹ ) overwhelmed the cross-tolerance and killed all Daphnia . Tolerance to NaCl did not mitigate NaCl-induced cascades leading to phytoplankton blooms, but cross-tolerance at moderate concentrations of MgCl 2 and high concentrations of CaCl 2 mitigated such cascading effects caused by these two salts. These discoveries highlight the important interplay between ecology and evolution in understanding the full impacts of freshwater salinization. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.
... Most studies investigating intraspecific variation in freshwater zooplankton tolerance to salinity were performed in laboratories and were focused on individual-or population-level responses of cladoceran or rotifer species, often at lethal concentrations of chloride (Cl À ), a common tracer of salinity (Loureiro et al. 2012;Coldsnow et al. 2017;Venâncio et al. 2018;Adamczuk and Mieczan 2019). These studies have shown that genetic adaptation (Coldsnow et al. 2017), phenotypic plasticity (Adamczuk and Mieczan 2019), epigenetics (Jeremias et al. 2018), and maternal effects (Venâncio et al. 2018) can be important adaptive strategies for freshwater zooplankton in response to salinization. ...
... Most studies investigating intraspecific variation in freshwater zooplankton tolerance to salinity were performed in laboratories and were focused on individual-or population-level responses of cladoceran or rotifer species, often at lethal concentrations of chloride (Cl À ), a common tracer of salinity (Loureiro et al. 2012;Coldsnow et al. 2017;Venâncio et al. 2018;Adamczuk and Mieczan 2019). These studies have shown that genetic adaptation (Coldsnow et al. 2017), phenotypic plasticity (Adamczuk and Mieczan 2019), epigenetics (Jeremias et al. 2018), and maternal effects (Venâncio et al. 2018) can be important adaptive strategies for freshwater zooplankton in response to salinization. Moreover, among natural populations of zooplankton along salinity gradients, there is evidence for genetically based adaptation in salinity tolerance in Daphniidae (Weider and Hebert 1987;Teschner 1995;Loureiro et al. 2012;Liao et al. 2015). ...
Article
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The salinization of freshwaters is a global threat to aquatic biodiversity. We quantified variation in chloride (Cl−) tolerance of 19 freshwater zooplankton species in four countries to answer three questions: (1) How much variation in Cl− tolerance is present among populations? (2) What factors predict intraspecific variation in Cl− tolerance? (3) Must we account for intraspecific variation to accurately predict community Cl− tolerance? We conducted field mesocosm experiments at 16 sites and compiled acute LC50s from published laboratory studies. We found high variation in LC50s for Cl− tolerance in multiple species, which, in the experiment, was only explained by zooplankton community composition. Variation in species‐LC50 was high enough that at 45% of lakes, community response was not predictable based on species tolerances measured at other sites. This suggests that water quality guidelines should be based on multiple populations and communities to account for large intraspecific variation in Cl− tolerance.
... For instance, Nielsen et al. (2003) described decreased diapausing eggs' emergence of zooplankton and richness related to slight increases in water salinity. According to Coldsnow et al. (2017), increasing salinity generally results in a decrease of cladocerans and copepods, and an increase of rotifers, which facilitates the increase of phytoplankton blooms and the alteration of functional ecosystem parameters. Furthermore, salinity can induce changes in species competition patterns and alter predation regimes, which affect population dynamics and the structure of freshwater communities (Hintz et al., 2018;Bracewell et al., 2019). ...
... Some authors have argued that such structural changes in the zooplankton community are characteristic of brackish lagoons during high osmotic pressure periods, and are a consequence of reduced fitness of Cladocera and competitive exclusion by well adapted copepods (Brucet et al., 2009;Jensen et al., 2010). Other studies have demonstrated that short rises of salinity can result in the dominance of few Rotifera taxa (Schallenberg et al., 2003;AntonÀPardo and Armengol, 2012;Coldsnow et al., 2017). Our experiment shows that at 20 C, salinity resulted in a notable increase of Brachionus quadridentatus and a decrease of Anuraeopsis sp. (Fig. 4). ...
Article
Temperature increase, salinity intrusion and pesticide pollution have been suggested to be among the main stressors affecting the biodiversity of coastal wetland ecosystems. Here we assessed the single and combined effects of these stressors on zooplankton communities collected from a Mediterranean coastal lagoon. An indoor microcosm experiment was designed with temperature variation (20 °C and 30 °C), salinity (no addition, 2.5 g/L NaCl) and the insecticide chlorpyrifos (i.e., no addition, 1 μg/L) as treatments. The impact of these stressors was evaluated on water quality variables and on the zooplankton comunity (structure, diversity, abundance and taxa responses) for 28 days. This study shows that temperature is the main driver for zooplankton community change, followed by salinity and chlorpyrifos. The three stressors contributed to a decrease on zooplankton diversity. The increase of temperature contributed to an increase of zooplankton abundance. Salinity generally affected Cladocera, which resulted in a Copepoda increase at 20 °C, and a reduction in the abundance of all major zooplankton groups at 30 °C. The insecticide chlorpyrifos affected primarily Cladocera, altough the magnitude and duration of the direct and indirect effects caused by the insecticide substantially differed between the two temperature scenarios. Chlorpyrifos and salinity resulted in antagonistic effects on sensitive taxa (Cladocera) at 20 °C and 30 °C. This study shows that temperature can influence the direct and indirect effects of salinity and pesticides on zooplankton communities in Mediterranean coastal wetlands, and highlights vulnerable taxa and ecological responses that are expected to dominate under future global change scenarios.
... Expression of circadian clock genes have recently come into focus in Daphnia (Tilden et al., 2011;Schwarzenberger and Wacker, 2015;Bernatowicz et al., 2016;Rund et al., 2016;Coldsnow et al., 2017). The highest gene expression of genes of D. pulex's core clock (i.e. ...
... In constant darkness, such patterns have a rhythmicity of 24 hours but show an unusual 28 -h rhythm in D. magna under constant illumination (Harris, 1963). It has been demonstrated that Daphnia pulex possesses circadian clock genes (Tilden et al., 2011) which are cyclically expressed over a 24 -h day-night cycle (Schwarzenberger and Wacker, 2015;Bernatowicz et al., 2016;Rund et al., 2016;Coldsnow et al., 2017), with a peak of gene expression one hour after the beginning of the dark phase (Schwarzenberger and Wacker, 2015). However, until now it has been unclear whether other Daphnia species show the same pattern of gene expression and whether their clock acts truly circadian (i.e. ...
Article
Nearly all organisms show daily and seasonal physiological and behavioural responses that are necessary for their survival. Often these responses are controlled by the rhythmic activity of an endogenous clock that perceives day length. Day length differs not only between seasons but also along latitudes, with different seasonal day lengths between the north and the south. Both seasonal and latitudinal differences in day length are discussed to be perceived/processed by the endogenous clock. Some species are distributed over a wide range of latitudes; it should be highly adaptive for these species to be able to time physiological responses (e.g. migration behaviour and diapause) according to the organisms’ respective photoperiod, i.e. their respective seasonal and latitudinal day length. The mediator of day length is the indoleamine hormone melatonin which is synthesized by melatonin-producing enzymes (AANAT and HIOMT). These enzymes are in turn controlled by an endogenous clock. The ubiquitous aquatic keystone organism Daphnia possess clock and melatonin synthesis genes that are rhythmically expressed over 24 hours. We were able to show that the 24-hour rhythm of D. magna’s clock persists in constant darkness and is thus truly circadian. In one particular photoperiod, all D. magna clones produced a similar melatonin concentration due to a fixed AANAT activity. However, we have demonstrated that clones originating from different latitudes are adapted to their respective photoperiod by showing a geographic cline in clock and downstream melatonin synthesis gene expression. These findings hint at the problem locally adapted organisms face when they are forced to leave their respective photoperiod, e.g. because of climate change-driven range-expansion. If such a species is incapable of adjusting its endogenous clock to an unknown photoperiod, it will likely become extinct.
... Salinization of freshwaters presents a growing environmental threat globally (Baek et al. 2014;Cañedo Argüelles et al. 2013;Coldsnow et al. 2017;Fay and Shi 2012;Kefford et al. 2016;Ziemann and Schulz 2011). Salinization is a process where the total concentration of dissolved salts increase (Williams 1987) and is generally associated with eight major inorganic ions: Na + , K + , Mg 2+ , Ca 2+ , Cl − , SO 4 2− , CO 3 2− , and HCO 3 − (Ziemann and Schulz 2011). ...
... As a result of the short and pulsed nature of runoff expected with snow-melt events (Coldsnow et al. 2017), periodic measurements of stream salinity are highly likely to severely underestimate peak salinity concentrations. Thus, electrical conductivity (EC) data loggers (HOBO U24-001) were deployed at each site on the salted-road streams between May 2016 and May 2019 to collect EC (µS cm −1 @ 25 °C) and water temperature (°C) data at 15-min intervals with 83% of the timeseries continuous. ...
Article
Full-text available
The application of road de-icing salts has the potential to salinize fresh waters and degrade habitat for aquatic organisms. In the Australian Alps, the ecological effects of even small salinity increases from de-icing may be different than in North America and Europe because of (1) differences in the evolutionary history, and (2) areas with de-icing in Australia are not located in urbanized landscapes where de-icing has been largely studied elsewhere. In this study, we tried to determine the salinity increases attributable to de-icing in Australia and the effects of this increase in salinity to stream macroinvertebrates. We observed increased salt concentrations (as measured by continuous measurements of electrical conductivity (EC) and periodic measurements of chloride concentrations) in streams near two Australian ski resorts, during the snow seasons (June to September) of 2016 to 2018. The maximum EC observed in streams in salted sites near Perisher, New South Wales, was 390 µS cm−1 compared with a maximum of 26.5 µS cm−1 at unsalted sites. Lower EC values (i.e., maximum 61.1 µS cm−1) and short durations of salinity increases in streams near Falls Creek, Victoria, were not expected to cause an adverse biological response. Salt storage in the landscape was evident at salted sites near Perisher where EC was above background levels during periods of the year when no salt was applied to roads. Stream macroinvertebrate community composition differed at sites receiving run-off from road salting activities near Perisher. Abundances of Oligochaeta (worms) (up to 11-fold), Dugesiidae (flat worms) (up to fourfold), and Aphroteniinae (chironomids) (up to 14-fold) increased, whereas Leptophlebiidae (mayflies) decreased by up to 100% compared with non-salted sites. The taxa that were less abundant where de-icing salts were present tended to be the same taxa that toxicity testing revealed to be relatively salt sensitive species. This study demonstrates a causal link between de-icing salts, elevated stream salinity, and altered macroinvertebrate community composition in streams that received run-off from road de-icing activity in the Australian Alps.
... Earthworms (Lumbricus rubellus) are well able to tolerate contaminants in soil (Kille et al. 2013). The water flea Daphnia has adapted to cyanobacteria (Hairston et al. 2001, Ger et al. 2014, thermal environments (Brans et al. 2017b(Brans et al. 2017a, and road salt (Coldsnow et al. 2016). The white-footed mouse (Peromyscus leucopus), a common resident of New York City's forest fragments, carries the bacteria for Lyme disease and exhibits signatures of directional selection . ...
... Daphnia galatea have shown rapid adaptation to road salt. The evolved tolerance of D. galatea to road salt could mitigate trophic cascades due to the impact of lake salinization that would otherwise lead to elevated phytoplankton levels (Coldsnow et al. 2016). ...
Article
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Urbanization is changing Earth's ecosystems by altering the interactions and feedbacks between the fundamental ecological and evolutionary processes that maintain life. Humans in cities alter the eco-evolutionary play by simultaneously changing both the actors and the stage on which the eco-evolutionary play takes place. Urbanization modifies land surfaces, microclimates, habitat connectivity, ecological networks, food webs, species diversity, and species composition. These environmental changes can lead to changes in phenotypic, genetic, and cultural makeup of wild populations that have important consequences for ecosystem function and the essential services that nature provides to human society, such as nutrient cycling, pollination, seed dispersal, food production, and water and air purification. Understanding and monitoring urbanization-induced evolutionary changes is important to inform strategies to achieve sustainability. In the present article, we propose that understanding these dynamics requires rigorous characterization of urbanizing regions as rapidly evolving, tightly coupled human–natural systems. We explore how the emergent properties of urbanization affect eco-evolutionary dynamics across space and time. We identify five key urban drivers of change—habitat modification, connectivity, heterogeneity, novel disturbances, and biotic interactions—and highlight the direct consequences of urbanization-driven eco-evolutionary change for nature's contributions to people. Then, we explore five emerging complexities—landscape complexity, urban discontinuities, socio-ecological heterogeneity, cross-scale interactions, legacies and time lags—that need to be tackled in future research. We propose that the evolving metacommunity concept provides a powerful framework to study urban eco-evolutionary dynamics.
... These studies indicate that zooplankton, especially cladocerans, are one of the most sensitive groups (see Evans andFrick, 2001 and for a review on organism tolerance). Zooplankton can experience declines after short-term (1-2 days) exposures to concentrations around 2000 mg Cl − /L of NaCl and after long-term (>7 days) exposures to concentrations between 500 and 1000 mg Cl − /L of NaCl (Coldsnow et al., 2017a;Dananay et al., 2015;Jones et al., 2017;Lind et al., 2018;Van Meter and Swan, 2014;Van Meter et al., 2011). Recent research has even indicated that sublethal (e. g., effects on reproduction) and lethal effects might occur at much lower concentrations (e.g., <145 mg Cl − /L; Arnott et al., 2020). ...
... By the end of the experiment, only cladocerans were affected and only by the high MgCl 2 treatment (although CaCl 2 and MgCl 2 were not significantly different). Previous studies have shown that a common cladoceran, Daphnia pulex, can rapidly evolve salt tolerance to NaCl (Coldsnow et al., 2017a), which might explain the recovery of cladocerans and possibly copepods in our NaCl and CaCl 2 treatments. Stream invertebrate abundance has also been shown to quickly recover from salinity increases caused by mining contamination (predominantly NaCl); however, differences in community composition still existed at the end of the experiment (Cañedo-Argüelles et al., 2014). ...
Article
Because of environmental and societal concerns, new strategies are being developed to mitigate the effects of road salt. These include new deicers that are alternatives to or mixtures with the most common road salt, sodium chloride (NaCl), improved techniques and equipment, and biotic mitigation methods. Using outdoor mesocosms, we investigated the impacts of NaCl and two common alternatives, magnesium chloride (MgCl2) and calcium chloride (CaCl2) on freshwater communities. We also investigated the mitigation ability of a common macrophyte, Elodea. We hypothesized that road salt exposure reduces filamentous algae, zooplankton, and macrocrustaceans, but results in increases in phytoplankton and gastropods. We also hypothesized that MgCl2 is the most toxic salt to communities, followed by CaCl2, and then NaCl. Lastly, we hypothesized that macrophytes mitigate some of the effects of road salt, specifically the effects on primary producers. We found that all three salts reduced filamentous algal biomass and amphipod abundance, but only MgCl2 reduced Elodea biomass. MgCl2 had the largest and longest lasting effects on zooplankton, specifically cladocerans and copepods, which resulted in a significant increase in phytoplankton and rotifers. CaCl2 increased ostracods and decreased snail abundance, but NaCl increased snail abundance. Lastly, while we did not find many interactions between road salt and macrophyte treatments, macrophytes did counteract many of the salt effects on producers, leading to decreased phytoplankton, increased filamentous algae, and altered abiotic responses. Thus, at similar chloride concentrations, NaCl alternatives, specifically MgCl2, are not safer for aquatic ecosystems and more research is needed to find safer road management strategies to protect freshwater ecosystems.
... In light of this, with continued application of road salts, Clconcentrations in lakes, streams, ponds, and wetlands can possibly increase, as documented in the USA, UK, Canada, Italy, and Sweden (Rogora et al. 2015;Rivett et al. 2016;Wyman and Koretsky 2018;Kelly et al. 2019). For example, Cllevels of 51% of stream sampled during cold seasons in the northern USA exceeded the chronic (230 mg/L) threshold 2 established by the U.S. Environmental Protection Agency (EPA) for the protection of freshwater habitats (Corsi et al. 2010;Coldsnow et al. 2017). The effects of road salt exposure have been also reported in groundwater as well; in the Chicago, Illinois metropolitan area, Clin groundwater increased from 6 mg/L prior to 1950 to a median value of 20 mg/L in 1990-2005 (Williams et al. 1999;Kelly 2008;Harte and Trowbridge 2010;Cassanelli and Robbins 2013;Perera et al. 2013;Cooper et al. 2014;McNaboe et al. 2017;Howard and Gerber 2018). ...
... The Cllevels in Fig 3. indicate that about 60% of Hamedan's stations are beyond the CCME threshold (208 mg/L) and thus can be toxic to aquatic organisms, which are typically adapted to low salt contents (0-20 mg Cl -L -1 ; Coldsnow et al. 2017). Furthermore, by using such waters, a large amount of Clmay be compacted in the agricultural soils No . ...
Article
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This study explores the contamination potential of groundwater due to the use of sodium chloride (NaCl) in the wintertime. The research was conducted in two Iranian cities, Malayer and Hamedan, where groundwater is the major source of water for drinking and irrigating purposes. However, the amount of deicing salt used in the former is about 10 times less than that used in the latter. The assessment of geochemical dataset from 2004 to 2018 revealed no significant trend in the groundwater characteristics of Malayer where the water quality indices were in the range of WHO and USEPA permissible limits. In contrast, the indices had a continually increasing trend (~ 2.3% annually) in Hamedan’s supply wells over the same period and particularly near the urban areas that showed higher levels (> 5 times on average) than those observed in Malayer. This could mainly be ascribed to the influx of halite. Based on the USSL diagram, the water samples retrieved from the latter system were mostly classified as C3-S1 (decreasing the soil fertility) and even as C4-S2 (harmful for agriculture activities). Chloride contamination rates also reached 250 mg/L, which could negatively affect the water potability and threaten the aquatics microorganisms. In this region, a rather similar distribution of NaCl and arsenic was observed, implying mobilization of toxic trace metals with the increased salt encroachment into the aquifer. Based on such findings, it is suggested that in snow-influenced cities (e.g., Hamedan), new approaches for winter maintenance be considered to prevent the gradual deterioration of water resources.
... Diverse communities are also more resistant to change than lower diversity communities (Elmqvist et al., 2003;Shurin et al., 2007;Yachi & Loreau, 1999). Additionally, there is evidence that some zooplankton species can rapidly evolve tolerance after constant exposure to elevated chloride (Coldsnow, Mattes, Hintz, & Relyea, 2017). Therefore, zooplankton communities that have been exposed to higher concentrations of chloride, such as communities from lakes or streams near roads, could be more resistant when faced with further increases. ...
... This apparent variation in intraspecific sensitivity between community treatments could be due to differences in the road salt exposure histories of Long Lake, which is relatively isolated, versus that of Loughborough Lake, which is intersected by a two-lane highway. Zooplankton can adapt to elevated salt concentrations after short periods of exposure (e.g., Coldsnow et al., 2017), and local salinity conditions can drive differences in tolerance between genotypes (e.g., Latta, Weider, Colbourne, & Pfrender, 2012;Weider & Hebert, 1987). Applications of road salt on the highway intersecting Loughborough Lake might have exposed the species within this community to a broader range of salt concentrations, selecting for more salt-tolerant genotypes. ...
Article
• Salt, primarily NaCl, is commonly used to de‐ice winter roads. The usage of road salt is steadily increasing as the area of urbanised land expands, and chloride concentrations in many lakes and flowing waters near roads have been steadily increasing through time. In some waterbodies, these concentrations are reaching levels that are toxic to freshwater organisms, such as zooplankton which are integral to the structure and function of freshwater communities. • We currently have a poor understanding of the impact of road salt contamination on zooplankton communities, and particularly the variation in response among lakes. Zooplankton communities differ in factors that could influence the impacts of elevated chloride, such as local species composition, exposure history and regional connectivity. Assessing and predicting how increasing road salt usage affects natural, freshwater zooplankton communities requires studies that investigate how communities vary in the impacts of elevated chloride, and in their response to dispersal. • We conducted a field mesocosm experiment that examined the effects of salt (NaCl) addition on two different zooplankton communities, which were also subjected to repeated introductions of zooplankton dispersers from the regional species pool. These treatments allowed us to determine whether communities differed in the impacts of salt, and how the effects of salt differed between communities that did and did not receive zooplankton dispersers. • We found variation in the effects of salt and dispersal between our experimental communities. For one lake community, salt drove zooplankton species composition towards dominance by littoral cladocerans. Zooplankton dispersal into this community ameliorated these impacts of salt by returning species composition to a state more similar to our “Control” communities. Conversely, for the other lake community, salt alone had minimal effects on zooplankton, while the combination of salt and dispersal led to declines in adult copepods. • Our experiment found that the impacts of salt varied between two zooplankton communities, causing a range of negative, positive and neutral community effects, and that dispersal from the regional species pool could serve as an ameliorating or exacerbating influence. Efforts to understand and predict the impacts of road salt on freshwater communities would therefore benefit from an evaluation of the potential role played by local (e.g., exposure history and biotic interactions) and regional (e.g., connectivity to possible sources of immigrants) context in the response of communities to elevated chloride.
... Such acclimation responses are most likely to occur in scenarios of gradual and/or sublethal levels of salinization, and have been documented for a wide range of organisms including algae and cyanobacteria (Venâncio et al., 2017b(Venâncio et al., , 2019a, cladocerans (e.g. Loureiro et al., 2015;Coldsnow et al., 2017;Venâncio et al., 2018), fish (e.g. Boeuf & Payan, 2001;Harper, Farag & Brumbaugh, 2008), frogs (e.g. ...
... The higher or similar toxicity of NaCl means that decisions based on its toxicity will represent a conservative approach, for both soil and freshwater compartments. The applicability of toxicity data for NaCl to early stages of risk assessment of salinization scenarios provoked by SW intrusion is advantageous, given the wide availability of toxicity data for NaCl, mainly derived from studies related to its use as a road deicer (Dougherty & Smith, 2006;Denoël et al., 2010;Van Meter et al., 2012;Coldsnow et al., 2017). We found more than twice as many reports regarding NaCl than for SW toxicity. ...
Article
Seawater intrusion into low‐lying coastal ecosystems carries environmental risks. Salinity levels at these coastal ecosystems may vary substantially, causing ecological effects from mortality to several sublethal endpoints, such as depression of rates of feeding, somatic growth, or reproduction. This review attempts to establish safe salinity levels for both terrestrial and freshwater temperate ecosystems by integrating data available in the literature. We have four specific objectives: (i) to identify the most sensitive ecological taxa to seawater intrusion; (ii) to establish maximum acceptable concentrations–environmental quality standards (MAC‐EQSs) for sea water (SW) from species sensitivity distributions (SSDs); (iii) to compile from the literature examples of saline intrusion [to be used as predicted environmental concentrations (PECs)] and to compute risk quotients for the temperate zone; and (iv) to assess whether sodium chloride (NaCl) is an appropriate surrogate for SW in ecological risk assessments by comparing SSD‐derived values for NaCl and SW and by comparing these with field data. Zooplankton, early life stages of amphibians and freshwater mussels were the most sensitive ecological receptors for the freshwater compartment, while soil invertebrates were the most sensitive ecological receptors for the terrestrial compartment. Hazard concentration 5% (HC5) values, defined as the concentration (herein measured as conductivity) that affects (causes lethal or sublethal effects) 5% of the species in a distribution, computed for SW were over 22 and 40 times lower than the conductivity of natural SW (≈ 52 mS/cm) for the freshwater and soil compartment, respectively. This sensitivity of both compartments means that small increments in salinity levels or small SW intrusions might represent severe risks for low‐lying coastal ecosystems. Furthermore, the proximity between HC5 values for the soil and freshwater compartments suggests that salinized soils might represent an additional risk for nearby freshwater systems. This sensitivity was corroborated by the derivation of risk quotients using real saline intrusion examples (PECs) collected from the literature: risk was >1 in 34 out of 37 examples. By contrast, comparisons of HC5 values obtained from SSDs in field surveys or mesocosm studies suggest that natural communities are more resilient to salinization than expected. Finally, NaCl was found to be slightly more toxic than SW, at both lethal and sublethal levels, and, thus, is suggested to be an acceptable surrogate for use in risk assessment.
... Taxonomic groups Recent studies have mostly focused on aquatic invertebrates [83,84], (63 on macroinvertebrates and 46 on zooplankton; Figure 3). Despite their key role for ecosystem functioning (e.g., nutrient cycling), microorganisms have received less attention (30; Figure 3). ...
... For example, the effects on performance of species within the community (e.g., predation efficiency, stressor crosstolerance) are still not fully elucidated. Salinity is a strong evolutionary pressure [90][91][92], but shortor mid-term adaptations can result in a cost for species fitness [84]. These adaptive costs add pressure to aquatic communities exposed to salinisation, potentially leading to loss of genetic diversity [93]. ...
Article
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The widespread salinisation of freshwater ecosystems poses a major threat to the biodiversity, functioning, and services that they provide. Human activities promote freshwater salinisation through multiple drivers (e.g., agriculture, resource extraction, urbanisation) that are amplified by climate change. Due to its complexity, we are still far from fully understanding the ecological and evolutionary consequences of freshwater salinisation. Here, we assess current research gaps and present a research agenda to guide future studies. We identified different gaps in taxonomic groups, levels of biological organisation, and geographic regions. We suggest focusing on global- and landscape-scale processes, functional approaches, genetic and molecular levels, and eco-evolutionary dynamics as key future avenues to predict the consequences of freshwater salinisation for ecosystems and human societies.
... More recently (2011-2017), intraspecific variations in salinity tolerance have been suggested by some studies [42][43][44], and progressive (i.e. multi-generational) adaptation to increased salinity (in the form of NaCl) has been documented for Daphnia [44,45]. However, other investigations have shown little variation in the salt sensitivity of populations of aquatic insects coming from streams with different background conductivities [46 -48] and no evidence that previous salinity exposure could affect salt sensitivity in Daphnia [49]. ...
... Thus, the existence of intraspecific differences in salt sensitivity according to previous salt exposure is still under debate. Moreover, the mechanisms behind possible acclimation or adaptation to salinization by freshwater organisms remain unclear [45]. ...
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Human activities have globally increased and altered the ion concentration of freshwater ecosystems. The proliferation of potash mines in Germany (especially intense in the early 1900s) constitutes a good example of it. The effluents and runoff coming from potash mines led to extreme salt concentrations (e.g. 72 g l–1 of total salt content, approx. 149 mS cm–1) in surrounding rivers and streams, causing ecosystem degradation (e.g. massive algal blooms and fish kills). This promoted scientific research that was mostly published in German, thereby being neglected by the wide scientific community. Here, the findings of the German literature on freshwater salinization are discussed in the light of current knowledge. German studies revealed that at similar ion concentrations potassium (K+) can be the most toxic ion to freshwater organisms, whereas calcium (Ca2+) could have a toxicity ameliorating effect. Also, they showed that salinization could lead to biodiversity loss, major shifts in the composition of aquatic communities (e.g. dominance of salt-tolerant algae, proliferation of invasive species) and alter organic matter processing. The biological degradation caused by freshwater salinization related to potash mining has important management implications, e.g. it could prevent many European rivers and streams from reaching the good ecological status demanded by the Water Framework Directive. Within this context, German publications show several examples of salinity thresholds and biological indices that could be useful to monitor and regulate salinization (i.e. developing legally enforced salinity and ion-specific standards). They also provide potential management techniques (i.e. brine collection and disposal) and some estimates of the economic costs of freshwater salinization. Overall, the German literature on freshwater salinization provides internationally relevant information that has rarely been cited by the English literature. We suggest that the global editorial and scientific community should take action to make important findings published in non-English literature more widely available. Free access until end of January 2019 here: http://rstb.royalsocietypublishing.org/content/374/1764
... extreme climate phenomena) and continued exposure (e.g. through groundwater intrusion) are of relevance, especially for short-lived and multivoltine biota. Therefore, it is important to understand if organisms are capable to acclimate to increased salinity, a phenomenon already reported for algae [23] and daphnids [18,25]. To better cope with salinization episodes, acclimation may occur via short-term compensatory physiological/osmoregulatory changes within their life cycle, like vacuolar compartmentalization or ion sequestration in producers [26], or the triggering of an osmoregulatory reaction in cladocerans [27]. ...
... In a few cases, an increase in tolerance was observed after multigenerational exposure to low levels of salinity (for instance, Cy. raciborskii growth and D. longispina mortality, feeding and reproduction). Previous studies have already reported the ability of Daphnia spp. to increase salinity tolerance over a few generations, namely after 5-10 generations (D. pulex; [25]) and after a 3 generation period (D. longispina clonal lineages; [24]) and, more, that tolerance can be maintained over a 30 generation period (e.g. [74]). ...
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Salinization of coastal freshwater ecosystems is already occurring in some regions of the world. This phenomenon raises serious concerns on the protection of coastal freshwater ecosystems, since many of them support and shelter a large number of species and are considered hotspots of biodiversity. This work intended to assess the adverse effects that salinization, caused by the intrusion of seawater (SW), may pose to freshwater organisms. In this study, three specific goals were addressed: (i) to assess if sodium chloride (NaCl) may be used as a surrogate of natural SW at early-stages of risk assessment; (ii) to identify the most sensitive freshwater species to salinity NaCl; and (iii) to determine if increased tolerance to salinity may be acquired after multigenerational exposure to low levels of salinization (induced with NaCl). A total of 12 standard monospecific bioassays were carried out by exposing organisms from different taxonomic groups (Cyano-bacteria: one species, Tracheophyta: two species, Rotifera: one species, Arthropoda: two species and Mollusca: one species) to a series of concentrations of NaCl (ranging from 0.95 to 22.8 mS cm–1) or dilutions of SW (ranging from 1.70 to 52.3 mS cm²¹). In general, NaCl exerted similar or higher toxicity than SW, both at lethal and sublethal levels, suggesting that it may be proposed as a protective surrogate of SW for first tiers of salinization risk assessment. Among all tested species, the cyanobacterium Cylindrospermopsis raciborskii, the daphnid Daphnia longispina and the rotifer Brachionus plicatilis were the most sensitive taxa to salinization (EC50 4.38 mS cm²¹). Given their position at the basis of the food web, it is suggested that small increments of salinity may be enough to induce structural changes in freshwater communities or induce changes in trophic relations. No clear evidences of increased tolerance after multigenerational exposure to low levels of salinity were found. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’. © 2018 The Author(s) Published by the Royal Society. All rights reserved.
... Recent research shows evolutionary responses by zooplankton can occur in the form of an increased tolerance to NaCl (59). It is unclear whether rapid evolution of tolerance is widespread in natural communities and if such a tolerance could buffer zooplankton from the impacts of various sources of salinization such as road salts over the long term. ...
... It is unclear whether rapid evolution of tolerance is widespread in natural communities and if such a tolerance could buffer zooplankton from the impacts of various sources of salinization such as road salts over the long term. While traits leading to the tolerance can change over short time periods [e.g., a few generations in Daphnia (60)], the durations of our 16 experiments were not long enough to account for evolved responses demonstrated in other studies (59). Nevertheless, while an evolved tolerance to NaCl and cross-tolerance to other salt types could potentially buffer declines in cladoceran abundance to repeated salt exposure, these evolved responses do not always mitigate the cascading effect we observed here (e.g., ref. 61). ...
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Significance The salinity of freshwater ecosystems is increasing worldwide. Given that most freshwater organisms have no recent evolutionary history with high salinity, we expect them to have a low tolerance to elevated salinity caused by road deicing salts, agricultural practices, mining operations, and climate change. Leveraging the results from a network of experiments conducted across North America and Europe, we showed that salt pollution triggers a massive loss of important zooplankton taxa, which led to increased phytoplankton biomass at many study sites. We conclude that current water quality guidelines established by governments in North America and Europe do not adequately protect lake food webs, indicating an immediate need to establish guidelines where they do not exist and to reassess existing guidelines.
... A similar observation was made recently by Hintz et al. (2017) who tracked zooplankton abundance over time, and a follow-up study provided the underlying explanation. In the case of cladocerans, Coldsnow et al. (2017) found that large populations that experience high concentrations of salt are initially greatly reduced in abundance but not completely eliminated. The few that persist possess salt tolerance and, over time, these salttolerant cladocerans reproduce and ultimately rise to an abundance that is similar to the abundance of cladocerans that were never exposed to salt. ...
... For example, the striking negative effects of NaCl road salt on macroalgae suggest that many other macroalgae species, and perhaps many aquatic plant species that are adapted to low salinities, may be highly susceptible to road salt pollution in freshwater ecosystems. The rebounding of both cladocerans and copepods after initial declines following salt exposure suggests evolved tolerance, but our current insights into this possibility are limited to only one species of cladoceran (Coldsnow et al. 2017). There has also been growing interest in using other road salts (or mixtures of salts) for deicing roads including MgCl 2 and CaCl 2 . ...
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The quality of freshwater ecosystems is decreasing worldwide because of anthropogenic activities. For example, nutrient over‐enrichment associated with agricultural, urban, and industrial development has led to an acceleration of primary production, or eutrophication. Additionally, in northern areas, deicing salts that are an evolutionary novel stressor to freshwater ecosystems have caused chloride levels of many freshwaters to exceed thresholds established for environmental protection. Even if excess nutrients and road deicing salts often contaminate freshwaters at the same time, the combined effects of eutrophication and salinization on freshwater communities are unknown. Thus by using outdoor mesocosms, we investigated the potentially interactive effects of nutrient additions and road salt (NaCl) on experimental lake communities containing phytoplankton, periphyton, filamentous algae, zooplankton, two snail species (Physa acuta and Viviparus georgianus), and macrophytes (Nitella spp.). We exposed communities to a factorial combination of environmentally relevant concentrations of road salt (15, 250, and 1000 mg Cl−/L), nutrient additions (oligotrophic, eutrophic), and sunlight (low, medium, and high) for 80 d. We manipulated light intensity to parse out the direct effects of road salts or nutrients from the indirect effects via algal blooms that reduce light levels. We observed numerous direct and indirect effects of salt, nutrients, and light as well as interactive effects. Added nutrients caused increases in most producers and consumers. Increased salt (1000 mg Cl−/L) initially caused a decline in cladoceran and copepod abundance, leading to an increase in phytoplankton. Increased salt also reduced the biomass and chl a content of Nitella and reduced the abundance of filamentous algae. Added salt had no effect on the abundance of pond snails, but it caused a decline in banded mystery snails, which led to an increase in periphyton. Low light negatively affected all taxa (except Nitella) and light levels exhibited multiple interactions with road salt, but the combined effects of nutrients and salt were always additive. Collectively, our results indicate that eutrophication and salinization both have major effects on aquatic ecosystems and their combined effects (through different mechanisms) are expected to promote large blooms of phytoplankton and periphyton while causing declines in many species of invertebrates and macrophytes.
... Hintz et al. (2017) also showed that concentrations of 1,000 mg Cl − /L and fish predation had a negative synergistic effect on the richness and abundance of experimental zooplankton communities. Although this effect triggered a trophic cascade leading to phytoplankton blooms, the authors found few effects in the absence of fish predation on zooplankton communities, perhaps due to rapid adaptation of zooplankton to the salt concentrations (Coldsnow, Mattes, Hintz, & Relyea, 2017;Hintz, Jones, & Relyea, 2019). Road salt concentrations ≥860 mg Cl − /L and non-consumptive predatory stress can also negatively affect zooplankton abundance in an additive way, and natural stress responses by zooplankton to predators (e.g. ...
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• Freshwater ecosystems worldwide are threatened by salinisation caused by human activities. Scientific attention on the ecological impacts of salinisation from road deicing salts is increasing exponentially. • Spanning multiple trophic levels and ecosystem types, we review and synthesise the ecological impacts of road salt in freshwater ecosystems to understand species‐, community‐, and ecosystem‐level responses. In our review, we identify knowledge gaps that we hope will motivate future research directions. • We found that road salts negatively affect species at all trophic levels, from biofilms to fish. The concentration at which road salt triggered an effect varied considerably. Species‐level impacts were generally sub‐lethal, leading to reductions in growth and reproduction, which can be magnified by natural stressors such as predation. Community‐level impacts including reductions of biodiversity were common, leading to communities of salt‐tolerant species, which may have implications for disease transmission from enhanced recruitment of salt‐tolerant host species such as mosquitoes. At the ecosystem level, road salts alter nutrient and energy flow. Contaminated wetlands could see greater export of greenhouse gases, streams will probably export more nitrogen and carbon, and lakes will encounter altered hydrology and oxygen dynamics, leading to greater phosphorus release from sediments. • While it is necessary to keep roads safe for humans, the costs to freshwater ecosystems may be severe if actions are not taken to mitigate road salt salinisation. Cooperation among policy makers, environmental managers, transportation professionals, scientists, and the public will be crucial to prevent a loss of ecosystem services including water clarity, drinkable water, recreation venues, and fisheries.
... Freshwater ecosystems are now becoming increasingly threatened, partly due to the rise in salinity of groundwater (i.e., from seawater intrusion) and, water regime modifications which reduce the frequency of high-flow, flushing events (Iannacone & Alvarino, 2002;Ca~nedo-Arguelles et la., 2016;Kayla et al., 2017) and, these will significantly impact both the survival rate (Rahma et al., 2017) and, reproduction (Grezesiuk and Mikulski, 2006;Bezirci et al., 2012;Rahma et al., 2017) of M. ...
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Salinity is a known factor which shapes population dynamics and community structure through direct and indirect effects towards aquatic ecosystems. The responses of Moina macrocopa (Cladocera) collected from Setiu Wetland lagoon (Terengganu) were evaluated through manipulative laboratory experiments to understand the ability of M. macrocopa to tolerate under high salinity stress. Specifically, the fatty acid composition, growth, survival and reproduction of this cladocerans species were examined. Sodium chloride (NaCl) were used in the treatments water with the concentration 0, 4, 6, 8, 12, and 15psu. Fatty acid levels were determined using Gas Chromatography and Mass Spectrophotometry (GC-MS). Results clearly indicate that normal conditions give the highest content of fatty acid, especially the polyunsaturated fatty acid content like EPA (eicosapentaenoic acid), ALA (alpha-linoleic acid), ARA (arachidonic acid) and DHA (docosahexaenoic acid). Furthermore, M. macrocopa survival also was best at 0psu, with percentage reached 98%, whereas the opposite occurred at 15psu, with approximately 9% of viable animals survived. On other aspects, M. macrocopa also showed the highest reproduction rate at 0psu (e.g. average initial age of reproduction, 4.33±0.58 days) compared with other salinities level. Interestingly, the difference in terms of growth at different salinities was unapparent, an unexpected outcome when adverse effects such as osmoregulation pressure on the organism are considered. Based on the results, we conclude that M. macrocopa can only tolerate salinity below 8psu and, is unable to withstand stressful environmental condition engendered with salinities above 8psu.
... It is difficult to evaluate the first assumption without field studies in the region of interest, as published studies on zooplankton dispersal differ widely in their conclusions about dispersal rates (Audet et al., 2013;Cohen & Shurin, 2003;Havel & Shurin, 2004;Jenkins & Underwood, 1998;Jenkins, 1995;Márquez & Kolasa, 2013;Vanschoenwinkel et al., 2008b). A few past studies support the second assumption, as there is evidence that zooplankton can evolve to tolerate higher salinity levels (Coldsnow et al., 2017;Hintz et al., 2018) and that there are differences in salinity tolerance both within and among species (EPA, 1988;Weider & Hebert, 1987). Manipulative experiments also provide some support for the idea that dispersal can act to buffer against community change in the case of small increases in salinity (Symons & Arnott, 2013;Thompson & Shurin, 2012) or when zooplankton are exposed to other stressors such as nutrient enrichment (Forrest & Arnott, 2006), acidification (Steiner et al., 2011) and introduced predators (Howeth & Leibold 2010). ...
Article
• The North American Great Plains contains thousands of lakes that vary in salinity from freshwater to hypersaline. Paleolimnological studies show that salinity levels in these lakes are tightly linked with climate, and current projections point to a more arid future in the region due to natural and anthropogenic climate change, potentially influencing lake salinity. • Many zooplankton species are sensitive to changes in salinity, and their position near the base of the aquatic food web makes it important to understand how they might respond to increasing salinity levels. Zooplankton communities in lakes with rising salinity levels may exhibit changes in structure, including a shift toward more salinity‐tolerant species and a reduction in abundance, species richness, and diversity. However, it is possible that dispersal of zooplankton among lakes could mitigate such community changes when migrant populations replace sensitive zooplankton with those that are locally adapted to higher salinities. • To test if dispersal could reduce salinity‐induced changes in zooplankton communities, we ran a field enclosure experiment at a freshwater lake in southern Saskatchewan where we manipulated salinity levels and zooplankton dispersal. We evaluated how salinity and dispersal influenced species identities and relative abundances (community structure) using multivariate statistics and comparing taxonomic and functional compositions among the different treatments (richness, diversity, and evenness). • We found that increasing salinity levels in our enclosures above that in our study lake resulted in lower zooplankton abundances and species richness levels, primarily due to the loss of cladoceran species. However, patterns in our multivariate analyses suggested that cladocerans were maintained in enclosures with salinity levels of 2.5 and 5.0 g/L when those enclosures received immigration from nearby lakes. • In contrast, our univariate analyses failed to find evidence that immigration affected community structure (richness, diversity, evenness). The lack of significant statistical differences could suggest that dispersal does not have an effect, or it may have been a problem with statistical power, as a power analysis suggested that fairly large effect sizes would have been required to achieve statistical significance. • Based on our results, we were unable to reach a definitive conclusion on the role that dispersal might play in buffering zooplankton communities against salinity‐driven changes. However, our study provides two important insights for planning future work. First, our power analyses indicated that more replication may be needed given the variability among our experimental enclosures. Second, the patterns in our multivariate analyses suggested that cladocerans could be maintained in lakes undergoing salinity increases if they receive immigration from surrounding lakes with higher salinities. Future work examining how inter‐ and intraspecific salinity tolerance varies across lakes with a gradient of salinities would be helpful for understanding the role that dispersal might play in buffering against salinity‐driven losses of cladoceran zooplankton.
... Based on the proximity of the study area to six major industries in southern Nigeria, the researchers attributed the elevated heavy metal concentrations in these catfish to industrial pollution. While numerous studies have investigated the negative effects of aquatic toxicants on target organisms like fish, Coldsnow et al. (2016) noted that less attention has been paid to the effects of these toxins on zooplankton taxa, such as Cladocerans in their natural environments. ...
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Salinity levels of some freshwater systems have been altered by humans, posing a threat to aquatic life. We hypothesized that a Daphnia magna population pre-treated with a low concentration of NaCl would develop greater salinity tolerance than an untreated population. Two Daphnia magna cultures with 60 individuals each were established, one started with 1.00 ppt NaCl and increased by 0.20 ppt weekly, and the other with pure spring water. After 4 weeks, 40 neonates from each culture were individually placed in a solution of 2.30 ppt NaCl (separately determined to be the LC50) for 48 hours. Survival was significantly greater for the experimental group (LR = 7.5, df = 1, p < 0.05) and significantly exceeded the expected 50% survival rate (χ2 = 6.4, df = 1, p < 0.05). This finding suggests that Daphnia populations can evolve or acclimatize to increase their survival in high salinity habitats.
... As a result, predicted mean abundance for both species was likely overestimated compared to typical abundances at these chloride concentrations. Presence of these species at this wetland suggests the potential for local adaptation to offset some effects of persistent chloride contamination, as documented for a wide range of amphibians and other freshwater species (e.g., Kearney et al., 2012;Hopkins and Brodie, 2015;Coldsnow et al., 2017). However, the leopard frog larvae in this wetland were lethargic and easily caught by hand. ...
Article
To inform sustainable energy development, it is important to understand the ecological effects of historical and current production practices and the persistence of those effects. The Williston Basin is one of North America's largest oil production areas and overlaps the Prairie Pothole Region, an area densely populated with wetlands that provide important wildlife habitat. Although historical disposal practices that released chloride-rich waters (brines) produced during oil extraction into the environment are no longer used, brine spills still occur frequently. We sampled 33 wetlands for three amphibian species in Montana and North Dakota during 2015-2017, primarily on National Wildlife Refuges, and used N-mixture models to determine how abundance varied with evidence of brine contamination. To provide insight into effects of historical versus contemporary contamination , we also estimated the association of well density and age with water quality and amphibian abundance. Abundance of boreal chorus frog (Pseudacris maculata) larvae declined most rapidly in response to increased chloride (range: 0.04-17,500 mg/L), followed by the northern leopard frog (Lithobates [Rana] pipiens) and barred tiger salamander (Ambystoma mavortium). Water quality and population-and community-level abundance of amphibians were more strongly related to nearby wells (≤800 m) installed before 1982 than to wells installed since 1982. These results suggest historical brine management practices were the primary driver of contamination and reduced amphibian abundance in wetlands we sampled, reflecting multi-decadal ecological effects. These persistent effects also underscore the critical need for tools to restore landscapes affected by brine contamination.
... Despite Brown and Yan's (2015) finding of limited tolerance of Daphnia to salinity (LC 50 5 55-248 mg/L Cl 2 ), the observed increase in the relative abundance of Daphnia in our study agrees with previous paleolimnological research showing that multi-specific groups have wider tolerances (Bos et al. 1996), and that this Daphnia pulex group in particular (D. pulex, D. schødleri, and D. pulicaria) can occur across a relatively-wide range of salinity (Reynolds 1979, Bos et al. 1996, Derry et al. 2003). In addition, Coldsnow et al. (2016) showed that D. pulex was able to rapidly (2.5 mo or within 10-15 generations) acquire an increased tolerance to road salt, and many studies have shown that daphniids living at higher salinity levels have higher tolerances to salt than populations living at lower concentrations (Weider and Hebert 1987, Teschner 1995, Latta et al. 2012, Liao and Faulks 2015. Tooke, Wolfkin, and Penfold lakes recorded an increase in the relative abundance of the D. pulex complex, suggesting that some clonal ...
Article
Road-salt application is an integral part of winter road maintenance and safety in many cold regions. However, chloride (Cl 2) runoff from salting activities may have adverse ecological effects. Lakes affected by road salt, particularly in urban areas, may have Cl 2 concentrations up to 300% higher than natural conditions. Zoo-plankton are sensitive to changes in water chemistry; however, little research has been conducted thus far into the biological effects of elevated Cl 2 concentrations from road-salt runoff. Using paleolimnological analyses, we studied the long-term effects of Cl 2 from road salt runoff on shallow, soft-water lakes within the southern Cana-dian Shield. Specifically, we examined Cladocera subfossils in dated sediment cores from 6 lakes within the Muskoka River Watershed of south-central Ontario, Canada. We compared long-term changes in cladoceran assemblages in the 5 lakes with the highest regional Cl 2 concentrations (32.8-90.9 mg/L) with a reference lake (0.91 mg/L). Prior to salting (ca. 1950), all of the lakes were dominated by Bosmina spp., and cladoceran assemblages showed little variation over time. After salting began, species assemblages in the 5 impacted lakes showed distinct taxonomic shifts, including increases in relative abundances of Chydorus brevilabris (Frey, 1980), Eurycercus spp., and the Daphnia pulex complex, and decreases in the relative abundance of Bosmina spp. and Alona spp. In 2 of the lakes, these changes were distinct and coincided with the onset of salting activities. In contrast to the species changes observed in the affected lakes, we recorded minimal directional changes in cladoceran assemblages in the nearby reference site. Overall, biological changes in the impacted lakes were best explained by changing Cl 2 concentrations associated with road-salt application. Among lakes, the severity of impact may have been indirectly mediated by differences in food quantity through its effect on Cl 2 toxicity.
... Urban populations are also characterized by a reduced activity of antioxidant enzymes (SOD and CAT), while oxidative damage to lipids did not differ, indicative of more effective defence responses or investment in other defence proteins. In general, these results are in line with earlier findings on the evolutionary and acclimatory responsiveness of Daphnia when exposed to human-associated toxicants such as heavy metals and pesticides [62,63] and natural toxicants such as cyanotoxins [64]. The results of our study reinforce earlier observations on genetic differentiation in D. magna populations in response to urbanization, which involved both heat tolerance [43] and life-history traits [35]. ...
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Natural and human-induced stressors elicit changes in energy metabolism and stress physiology in populations of a wide array of species. Cities are stressful environments that may lead to differential selection on stress-coping mechanisms. Given that city ponds are exposed to the urban heat island effect and receive polluted run-off, organisms inhabiting these ecosystems might show genetic differentiation for physiological traits enabling them to better cope with higher overall stress levels. A common garden study with 62 Daphnia magna genotypes from replicated urban and rural populations revealed that urban Daphnia have significantly higher concentrations of total body fat, proteins and sugars. Baseline activity levels of the antioxidant defence enzymes superoxide dismutase (SOD) and glutathione-S-transferase (GST) were higher in rural compared with city populations, yet urban animals were equally well protected against lipid peroxidation. Our results add to the recent evidence of urbanization-driven changes in stress physiology and energy metabolism in terrestrial organisms. Combining our results with data on urban life history evolution in Daphnia revealed that urban genotypes show a structured pace-of-life syndrome involving both life-history and physiological traits, whereas this is absent in rural populations.
... Urban populations are also characterized by a reduced activity of antioxidant enzymes (SOD and CAT), while oxidative damage to lipids did not differ, indicative of more effective defence responses or investment in other defence proteins. In general, these results are in line with earlier findings on the evolutionary and acclimatory responsiveness of Daphnia when exposed to human-associated toxicants such as heavy metals and pesticides [62,63] and natural toxicants such as cyanotoxins [64]. The results of our study reinforce earlier observations on genetic differentiation in D. magna populations in response to urbanization, which involved both heat tolerance [43] and life-history traits [35]. ...
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1.Multiple species show significant trait shifts in response to urbanization. Yet, the impact of anthropogenic warming linked to the urban heat island effect is remarkably understudied. Additionally the relative contributions of phenotypic plasticity and genetic change underlying trait shifts in response to urbanization are poorly known. 2.A common garden study with the water flea Daphnia magna revealed that both genetic differentiation in response to urbanization and phenotypic plasticity in response to higher rearing temperature (24 °C) induced significant parallel multivariate shifts in life history strategy along the slow‐fast pace‐of‐life axis. 3.Urban animals and animals reared at higher temperatures are characterized by fast maturation, early release of progeny, a smaller size at maturity, increased fecundity, and higher performance (given by maximal population growth rate r) compared to genotypes isolated from rural ponds and animals reared at lower temperatures respectively. 4.Evolution in response to urbanization accounted for 30% of the total observed shift in life history and caused a significant change in mean trait values, while plasticity responses to experimental warming were unaltered between urban and rural populations. The total trait change achieved through both plasticity and evolution ranged from 8 to 56% depending on the trait. 5.Our results provide clear evidence for evolution underlying an increase in pace‐of‐life of populations in response to urbanization. Given the pivotal role of Daphnia in aquatic ecosystems, this shift potentially feeds back to population structure, top‐down control of algae, and food web dynamics in urban freshwater ecosystems. Additionally, we argue that adaptation to urban heat islands might render these populations pre‐adapted in a context of future climate change. This article is protected by copyright. All rights reserved.
... For example, since our mesocosms were isolated, recolonization via dispersal was not possible (Hintz and Relyea, 2019;Sinclair and Arnott, 2018) as it was in other studies conducted in natural ecosystems along salinity gradients (Gutierrez et al., 2018;Jeppesen et al., 2007b;Vidal et al., 2021). We also did not account for the adaptation responses to increased salinity due to the short duration of the experiment (6 weeks), although adaptation was possible after 2.5 months (Coldsnow et al., 2017). Longer experiments are needed at the community level to understand the evolutionary adaptation dynamics. ...
Article
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Freshwater ecosystems are becoming saltier due to human activities. The effects of increased salinity can lead to cascading trophic interactions, affecting ecosystem functioning and energy transfer, through changes in community and size structure. These effects can be modulated by other environmental factors, such as nutrients. For example, communities developed under eutrophic conditions could be less sensitive to salinization due to cross-tolerance mechanisms. In this study, we used a mesocosm approach to assess the effects of a salinization gradient on the zooplankton community composition and size structure under eutrophic conditions and the cascading effects on algal communities. Our results showed that zooplankton biomass, size diversity and mean body size decreased with increased chloride concentration induced by salt addition. This change in the zooplankton community did not have cascading effects on phytoplankton. The phytoplankton biomass decreased after the chloride concentration threshold of 500 mg L⁻¹ was reached, most likely due to direct toxic effects on the osmotic regulation and nutrient uptake processes of certain algae rather than as a response to community turnover or top-down control. Our study can help to put in place mitigation strategies for salinization and eutrophication, which often co-occur in freshwater ecosystems.
... This could be a result of evolved tolerance to CaCl 2 . Daphnia pulex, a common cladoceran and model organism, has been shown to evolve tolerance to NaCl road salt in 2.5 months, or 5-10 generations, in a similar mesocosm setting (Coldsnow et al. 2017). Increased salt tolerance also occured in Daphnia in a number of other circumstances, including seawater intrusion (Weider and Hebert 1987;Latta et al. 2012;Loureiro et al. 2012;Liao et al. 2015;Venâncio et al. 2019). ...
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Invasive bivalves can drastically alter freshwater ecosystems and affect ecosystem services, but they can be influenced by external factors including calcium concentrations. When a common road salt, calcium chloride (CaCl2), enters freshwater ecosystems, it may be toxic to organisms or facilitate bivalves by serving as a calcium source. Therefore, CaCl2 could benefit invasive mollusks tolerant to chloride that require calcium to grow. We used mesocosms to investigate the impacts of CaCl2 (35–187 mg Ca²⁺ L⁻¹) and invasive bivalves (Asian clams, Corbicula fluminea; zebra mussels, Dreissena polymorpha) on a native lake food web. We hypothesized that invasive bivalves facilitate benthic algae because they reduce phytoplankton and excrete waste. These changes in primary producers would subsequently impact consumers. We also hypothesized that low to moderate CaCl2 concentrations promote the survival, growth, and reproduction of native and invasive mollusks, while causing few toxic effects. If so, we hypothesized that invaded communities exposed to CaCl2 experience stronger impacts from the invasive bivalves. We found that invasive bivalves decreased phytoplankton, which led to decreases in periphyton, zooplankton, and native clams. They caused increases in filamentous algae and isopods. While zebra mussels survived poorly in all treatments, moderate concentrations of CaCl2 substantially reduced Asian clams, which reduced their community effects. Our highest CaCl2 treatments also reduced zooplankton densities. Thus, while freshwater salinization from road salts poses a concern, we observed no indication that CaCl2 road salt will benefit Asian clams and zebra mussels. However, the community-wide consequences from Asian clams at low CaCl2 emphasize the extensive effects that invasive bivalves can have on freshwater communities and the immense concern surrounding their invasions.
... Cl À ), recent work suggests that they can have very different effects on aquatic organisms due to difference in cations (Schuler et al., 2017). Moreover, there is increasing evidence that aquatic plants and animals might evolve tolerance to chronic salt contamination that is characteristic of many freshwater systems near roadways and other human development (Coldsnow, Mattes, Hintz, & Relyea, 2017;Daley, Potter, & McDowell, 2009;James, Cant, & Ryan 2003). ...
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• Around the world, freshwater ecosystems are subjected to numerous stressors that can alter community composition in favour of stress‐tolerant species. Because combinations of stressors often result in non‐additive interactions, elucidating responses to isolated and combined stressors is important to understand the ecological responses to anthropogenic disturbance. • In this study, we explored the responses of common macrophyte species to two stressors of increasing concern: elevated salinity from road salt applications and turbidity from human recreational activities and shoreline development. The independent and interactive effects of environmentally relevant salt concentrations and turbidity on macrophyte productivity have received little attention. We hypothesised that both stressors in isolation would reduce macrophyte productivity and that the two stressors combined will lead to a greater (i.e. synergistic) reduction in productivity. • To test these hypotheses, we conducted dark‐ and light‐bottle experiments on seven species of native and invasive macrophytes under a factorial combination of three salt concentrations (0, 500 and 3,000 added mg Cl⁻ L⁻¹) and two turbidity conditions (clear and turbid via a disturbance to the sediment). • On average, macrophytes exhibited reduced productivity in response to increased salt, but results were highly species‐specific. Several species exhibited a unimodal response to elevated salinity, whereas Elodea canadensis exhibited a positive response to the high‐salt treatment. Similarly, macrophytes exhibited an average reduction in productivity under turbid conditions, but analysis of species‐specific responses revealed both neutral and negative responses. Combining the two stresses yielded non‐additive responses for some species. Specifically, Myriophyllum spicatum appeared to suffer from the combination of salt and turbidity, whereas Elodea canadensis and Ceratophyllum demersum benefited from the combination. • Our results suggest that increased anthropogenic disturbance of freshwater ecosystems can dramatically alter macrophyte species metabolism and might stimulate the growth of some species while deterring the growth of others.
... The resulting salinization of these water bodies raises the question of whether freshwater populations can adapt to the selective pressure imposed by this new water chemistry regime. Indeed, populations of the freshwater cladoceran zooplankton Daphnia, a critical link in most freshwater lake food webs, can adapt to higher (albeit not extreme) salinities in 5-10 generations (Coldsnow et al., 2017). ...
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Rapid evolution is ubiquitous in nature. We briefly review some of this quite broadly, particularly in the context of response to anthropogenic disturbances. Nowhere is this more evident, replicated and accessible to study than in cancer. Curiously cancer has been late - relative to fisheries, antibiotic resistance, pest management and evolution in human dominated landscapes - in recognizing the need for evolutionarily informed management strategies. The speed of evolution matters. Here, we employ game-theoretic modeling to compare time to progression with continuous maximum tolerable dose to that of adaptive therapy where treatment is discontinued when the population of cancer cells gets below half of its initial size and re-administered when the cancer cells recover, forming cycles with and without treatment. We show that the success of adaptive therapy relative to continuous maximum tolerable dose therapy is much higher if the population of cancer cells is defined by two cell types (sensitive vs. resistant in a polymorphic population). Additionally, the relative increase in time to progression increases with the speed of evolution. These results hold with and without a cost of resistance in cancer cells. On the other hand, treatment-induced resistance can be modeled as a quantitative trait in a monomorphic population of cancer cells. In that case, when evolution is rapid, there is no advantage to adaptive therapy. Initial responses to therapy are blunted by the cancer cells evolving too quickly. Our study emphasizes how cancer provides a unique system for studying rapid evolutionary changes within tumor ecosystems in response to human interventions; and allows us to contrast and compare this system to other human managed or dominated systems in nature.
... Vol.: (0123456789) 2020; Derry et al., 2003;Elphick et al., 2011;Gonçalves et al., 2007) and may depend on history of exposure (Coldsnow et al., 2017. History of exposure, or lack thereof, alters sensitively of many Cladocera species . ...
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Salinization of freshwater lakes, largely linked to road salt (NaCl) runoff, is a serious threat to zooplankton across North America and Northern Europe. Chloride (Cl⁻) can be toxic to many freshwater species, and so water quality guidelines have been created to regulate it and protect aquatic life. However, these guidelines may not adequately protect organisms in low-nutrient, softwater lakes. To evaluate this issue, two Cladocera species that are common in softwater lakes (Bosmina longirostris and Chydorus brevilabris) were selected as test organisms for an experimental study. Fourteen-day bioassays were conducted with eight different Cl⁻ treatments (ranging from 0.4 to 1200 mg/L) using a soft water medium, which reflects chemical conditions observed in Precambrian Shield lakes. We calculated 14-day Cl⁻ LC50 values for both B. longirostris and C. brevilabris below the water quality guidelines for Cl⁻ (LC50 = 24.3 mg/L and 60.3 mg/L, respectively), and a significant reduction in neonate production was observed for both taxa at a Cl⁻ concentration of 15 mg/L. Our work illustrates the need to re-evaluate the current water quality guidelines for the protection of aquatic life.
... In the intermediate and high chloride mesocosms, the eukaryote community was almost entirely reduced to phytoplankton or fungal species, and zooplankton were almost entirely lost. While other studies have found that certain zooplankton persist higher chloride levels up to 1300 mg Cl À L À1 (Coldsnow et al. 2017;Moffett et al. 2021), this was not the case in our study where cladocerans, copepods, and rotifers were all sensitive to increasing freshwater salinity. The simplification of the planktonic eukaryote community detected in our experiment has the potential to modify ecosystem function and productivity in salt-naïve freshwater lakes, if the responses that we measured in experimental mesocosms extend to the whole ecosystem scale in lakes (energy pathways: Sherwood et al. 2011;O'Gorman et al. 2019;productivity: Liess et al. 2009;Higgins et al. 2014;and food web stability: Fussmann et al. 2014;Binzer et al. 2016;Mo et al. 2021). ...
Article
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Freshwater salinization is a widespread issue, but evidence of ecological effects on aquatic communities remains scarce. We experimentally exposed salt‐naive plankton communities of a north‐temperate, freshwater lake to a gradient of chloride (Cl−) concentration (0.27–1400 mg Cl L−1) with in situ mesocosms. Following 6 weeks, we measured changes in the diversity, composition, and abundance of eukaryotic 18S rRNA gene. Total phytoplankton biomass remained unchanged, but we observed a shift in dominant phytoplankton groups with increasing salt concentration, from Cryptophyta and Chlorophyta at lower chloride concentrations (< 185 mg Cl− L−1) to Ochrophyta at higher chloride concentrations (> 185 mg Cl− L−1). Crustacean zooplankton and rotifers were sensitive to the salinity, and disappeared at low chloride concentrations (< 40 mg Cl− L−1). While ciliates thrived at low chloride concentrations (< 185 mg Cl− L−1), fungal groups dominated at intermediate chloride concentrations (185–640 mg Cl− L−1), and only phytoplankton remained at the highest chloride concentrations (> 640 mg Cl− L−1).
... Local environmental conditions may also modulate zooplankton responses to salinization. Notably, historic chloride levels at which communities have evolved may influence tolerance to contamination events (Coldsnow et al. 2017). Naturally-occurring calcium (Elphick et al. 2011) and phytoplankton availability (Brown and Yan 2015) may also mitigate chloride toxicity. ...
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Human-induced salinization increasingly threatens inland waters; yet we know little about the multifaceted response of lake communities to salt contamination. By conducting a coordinated mesocosm experiment of lake salinization across 16 sites in North America and Europe, we quantified the response of zooplankton abundance and (taxonomic and functional) community structure to a broad gradient of environmentally relevant chloride concentrations, ranging from 4 to ca. 1400 mg Cl/L. We found that crustaceans were distinctly more sensitive to elevated chloride than rotifers; yet, rotifers did not show compensatory abundance increases in response to crustacean declines. For crustaceans, our among-site comparisons indicate: (1) highly consistent decreases in abundance and taxon richness with salinity; (2) widespread chloride sensitivity across major taxonomic groups (Cladocera, Cyclopoida, and Calanoida); and (3) weaker loss of functional than taxonomic diversity. Overall, our study demonstrates that aggregate properties of zooplankton communities can be adversely affected at chloride concentrations relevant to anthropogenic salinization in lakes.
... Also, several studies demonstrated the negative effect of road salts on the structure of food webs (Meter et al. 2011;Schuler et al. 2017), predator-prey relationships , and mortality and decreased fertility of Daphnia (Arnott et al. 2020), even at a relatively low level of salt pollution. Even though several recent studies demonstrated that freshwater Daphnia could rapidly adapt to elevated salinity (Coldsnow et al., 2017;Hintz et al., 2019), up to 2 g L -1 of chlorine, this salinity is still below the values of critical salinity. ...
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The salinization of freshwaters due to the use of deicing road salts is a serious anthropogenic threat. We investigated the effects of the road deicer, which is mostly composed (ca. 70%) of NaCl, on the life cycle parameters of the cladoceran Moina macrocopa in acute and chronic toxicity tests and on the hatching success of resting eggs exposed to sediments contaminated with the road salt. The negative effects of the road salt on survival and life cycle parameters of animals were observed at concentrations above 5 g L−1. The 6-month exposure of resting eggs to contaminated sediments had a consistent but relatively weak effect on the postexposure hatching of resting eggs. Experiments demonstrated that the concentration of the deicer in the top water layer in the water-sediment systems is more important for the hatching success of resting eggs than the salt content in the sediment. Only 2.2 ± 1.9% of resting eggs hatched when the deicer content in the top water layer was equal to 12 g L−1. Lethal effects on hatchlings were observed starting from the deicer content in the water equal to 1 g L−1, and 97.0 ± 0.8% of hatchlings were dead at the deicer content in the water equal to 5 g L−1. Thus, the resilience of resting eggs to the contaminated sediments can ensure the replenishment of the population from the egg bank after the salinity disturbance is diminished but the negative effects of the elevated salt content in surface waters on active population will be manifested at lower salinities.
... However, long exposure to Cl could promote resistance in the zooplankton community. Coldsnow et al. (2017) found that Daphnia were able to adapt to higher salt concentration. During phase I of a 2.5month experiment, individual Daphnia pulex were first exposed to chloride concentrations from 100 to 1000 mg/L over the course of 5-10 generations. ...
Article
Road salt (mainly NaCl) is commonly used during the winter to ensure road and pavement safety; however, the long-term application of NaCl has negative consequences on soil and the water environment. The aims of the present review were to evaluate the impact of road salt on catchment processes which accelerate the eutrophication of waters, and to identify a possible approach for reducing the impact of winter salt treatments of roads and sidewalks, on water body quality. The objectives were implemented in accordance with the ecohydrological approach, which recommends using hierarchical steps to solve problems. The first step was the monitoring of threats, in which the causes of high chloride (Cl) concentrations in groundwater and surface water were identified. The results indicate that long-term winter application of road salt increases the annual mean concentrations of Cl in rivers and lakes, due to Cl entering groundwater. The second step was a cause-effect analysis of the impact of NaCl on the abiotic processes in soil and water, and on the biotic response to chloride exposure. Chlorides appear to decrease the biodiversity of aquatic animals and plants but favour the growth of phytoplankton, especially cyanobacteria. Moreover, Cl reduces the self-purification processes of water by decreasing nutrient accumulation in macrophytes, decreasing the denitrification rate and reducing organic matter decomposition. The third step was to evaluate possible solutions for reducing the negative impact of NaCl on the environment, and to improve the effectiveness of alternative de-icing agents. An analysis of available literature indicates that a system-based approach integrating engineering knowledge with an understanding of biological and hydrological processes is necessary to indicate solutions for reducing environmental risks from road salt use.
... Consensus among researchers is that freshwater salinization is a threat to aquatic organisms as well as water potability (Godwin et al., 2003;. However, research illustrates that Daphnia species can rapidly develop a tolerance to road salts within as few as 2.5 months or 5-10 generations of exposure to high levels of chloride in lake waters (Coldsnow et al., 2017;. In the high Cl lakes group, Daphnia body length increased by 12% from 1986 to 2004 despite a 200% increase in Cl (Figure 3b). ...
Article
Since the Clean Air Act Amendments of 1990, lakes in Maine and much of the Northeastern US have seen significant shifts in response to reduced atmospheric deposition as well as climate change. The organisms that inhabit lakes are susceptible to environmental change, but our understanding about how biological communities react to simultaneous changes in geochemistry and climate is incomplete. This research investigates how zooplankton communities respond to geochemical changes and warming, on both long-term and seasonal scales. These small organisms are sensitive to changes in physical lake conditions, and variation within zooplankton communities could indicate larger ecosystem shifts. We evaluated historical water chemistry and zooplankton composition data from 143 lakes throughout the northeastern US from the EPA’s Eastern Lake Survey (ELS) to understand how recovery from acidification and subsequent chemical shifts influenced zooplankton. Surface water sulfate concentrations decreased by 22% between the two sample years of 1986 and 2004. Sites with closer proximity to development saw significant increases in chloride concentration likely due to increased use of road deicers, which caused a subsequent increase in calcium and magnesium base cations. Zooplankton body size increased significantly between 1986 and 2004 and Daphnia species, which have high calcium requirements, increased in correlation with increases in calcium. Zooplankton community structure, however, was most strongly influenced by variation in ANC, sulfate, and dissolved organic carbon (DOC). Our findings indicate that, though surface water acidity influences zooplankton community structure, recovery of zooplankton populations to a pre-acidification composition is unlikely because other chemical shifts along with changes in climate and land-use, are also eliciting responses in zooplankton communities. A significant result of climate change is shifts in the timing of seasonally reoccurring events which have already been observed in Northeastern lakes including earlier ice break-up and longer periods of thermal stratification. Biotic responses to shifting seasons in lakes depends on species specific life-history traits and the seasonal events that drive them. We examined zooplankton phenology in lakes across a range of elevation and climate zones in Maine to understand the importance of spring surface water warm-up in high elevation versus low elevation sites. We collected zooplankton, chlorophyll-a, and water temperature in eight remote Maine lakes from the extremes of elevations (94m – 955m above sea level), representing the endmembers of climate variability in the state. High elevation lakes were distinguished by a short and rapid period of spring warming compared to more gradual warm-up in low elevation lakes. Zooplankton abundances increased in correlation with spring warm-up, most significantly in high elevation lakes. The link between surface water warming and zooplankton phenology varied among taxa, with rotifers and calanoid copepods more dependent on spring temperature than cladocerans and cyclopoid copepods. The variable response among zooplankton taxonomic groups to spring water warmup indicates that responses to climate change will be taxa specific. Disentangling the drivers of zooplankton populations will help provide a mechanistic understanding of longer-term climate and geochemical shifts observed in northeastern lake ecosystems and potential consequences of climate change.
... In megalopolises, a range of negative anthropogenic factors promotes the accumulation of pollutants in the soil. De-icing agents are among the most environmentally hazardous (Yakubov and Nikolayevskiy, 2001;Coldsnow et al., 2017;Nutile and Solan, 2019). De-icing agents are chemical reagents applied to prevent ice and snow deposits on the roads and increase human safety for those traveling during dangerous winter conditions. ...
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De-icing agents (ice and snow control materials) are applied to prevent ice and snow deposits on the roads in winter period. The extensive use of de-icing agents in countries with cold climate creates problems for the environment. In this study, the dynamics of de-icing salt concentrations in sod-podzolic soil was revealed in laboratory and field experiments. Twelve de-icing agents of different chemical groups (chlorides, acetates and formates) were studied. Under laboratory conditions, application of high doses of chloride reagents led to an increase of salt concentration in soil up to a level of slightly saline soils. Contaminated soils had salt levels high enough to be toxic to plants and soil microorganisms. However, under field conditions, soil salinity eventually decreased due to salt washout by atmospheric precipitation. By the end of the growing season, salt concentration corresponded to a background level. The decrease in salt concentration was accompanied by a decrease in soil toxicity. Acetate and formate de-icing agents demonstrated the least environmental effect. Our results suggest that magnesium chloride was the least harmful among the de-icers of chloride group while the most commonly used road de-icing salt sodium chloride was the most persistent and toxic to terrestrial plants and soil microbiota.
... For instance, laboratory selection in response to declining salinity (15 to 0 PSU) for 6-10 generations in the copepod E. affinis complex revealed rapid evolution of increased low salinity tolerance (Lee et al. 2007), evolutionary shifts in ion transport activity (Lee et al. 2011), and genome-wide signatures of selection, especially at ion transport related genes (Stern et al. 2022). In terms of evolutionary responses to elevated salinity, the freshwater water flea Daphnia pulex reared at elevated salinities for 5-10 generations in mesocosms displayed rapid evolution of tolerance of increased salinity (Coldsnow et al. 2017). In particular, D. pulex treatments that experienced selection at high salinities were subsequently able to survive higher salinities (1300 mg Cl -L -1 ≈ 2.3 PSU salinity) relative to control treatments reared at their natural low salinity conditions (15 mg Cl -L -1 ≈ 0 PSU salinity). ...
Article
Climate change is causing habitat salinity to transform at unprecedented rates across the globe. While much of the research on climate change has focused on rapid shifts in temperature, far less attention has focused on the effects of changes in environmental salinity. Consequently, predictive studies on the physiological, evolutionary, and migratory responses of organisms and populations to the threats of salinity change are relatively lacking. This omission represents a major oversight, given that salinity is among the most important factors that define biogeographic boundaries in aquatic habitats. In this perspective, we briefly touch on responses of organisms and populations to rapid changes in salinity occurring on contemporary time scales. We then discuss factors that might confer resilience to certain taxa, enabling them to survive rapid salinity shifts. Next, we consider approaches for predicting how geographic distributions will shift in response to salinity change. Finally, we identify additional data that are needed to make better predictions in the future. Future studies on climate change should account for the multiple environmental factors that are rapidly changing, especially habitat salinity.
... For example, a 35% decrease in the abundance of zooplankton 511 was seen at a concentration of 120 mg Cl -/L, which is the limit of chronic exposure to chloride in 512 fresh water according to Canadian water quality guidelines (170). 513 mg Cl -/L showed that the species could evolve a tolerance to moderate salinity within 5-10 516 generations (171). According to Hintz et al. (172), the evolved tolerance of zooplankton to 517 moderate MgCl2 concentration (967 μS/cm) and high CaCl2 concentration (3559 μS/cm) can last 518 up to one year or 30 generations. ...
Article
During winter, snow and ice on roads in regions with cold weather can increase traffic crashes and casualties, resulting in travel delays and financial burdens to society. Anti‐icing or deicing the roads can be a cost‐effective method to significantly reduce such risks. Although traditionally the main priorities of winter road maintenance (WRM) have been level of service, cost‐effectiveness, and corrosion, it is increasingly clear that understanding the environmental impacts of deicers is vital. One of the most important problems in this regard is environmental contamination caused by cumulative use of deicers, which has many detrimental effects on the aquatic systems. Among the deicers, the chloride‐based ones raise the most toxicological concerns because they are highly mobile, can migrate quickly in the environment and have cumulative effects over time. In this review, we summarize and organize existing data, including the latest findings about the adverse effects of deicers on surface water and groundwater, aquatic species, and human health, and identify future research priorities. In addition, the data provided can be used to provide a framework for quantifying some of the variables that stakeholders and agencies use when preparing guidelines and standards for WRM systems.
... Freshwater ecosystems are becoming increasingly threatened, partly due to the rise in the salinity of groundwater (i.e., from seawater intrusion) and water regime modifications, which reduce the frequency of high flow flushing events [25,35,36] These changes will significantly impact both the survival rate [37] and reproduction [37,38] of M. macrocopa. This study demonstrated how the increase of salinity, especially sodium chloride (NaCl) affects survival and life history traits of a freshwater cladoceran species through an examination of effects on M. macrocopa, which may be representative the of impact to other members of zooplankton communities. ...
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Salinity is a known factor in shaping population dynamics and community structure through direct and indirect effects on aquatic ecosystems. Salinity changes further influence food webs through competition and predation. The responses of Moina macrocopa (Cladocera) collected from Setiu Wetland lagoon (Terengganu) was evaluated through manipulative laboratory experiments to understand the ability of M. macrocopa to tolerate high salinity stress. Specifically, the fatty acid composition, growth, survival, and reproduction of this cladocerans species was examined. Sodium chloride (NaCl) as used in the treatments water with the concentration 0, 4, 6, 8, 12, and 15 salinity. Fatty acid levels were determined using Gas Chromatography and Mass Spectrophotometry (GC-MS). The results indicated that optimal conditions produced the highest fatty acid content, especially the polyunsaturated fatty acid content, such as EPA (eicosapentaenoic acid), ALA (alpha-linoleic acid), ARA (arachidonic acid), and DHA (docosahexaenoic acid). Furthermore, M. macrocopa survival was best at salinity 0, with a percentage of 98%, whereas the opposite occurred at salinity 15, with approximately 20% of viable animals surviving. Besides, M. macrocopa also showed the highest reproduction rate at salinity 0 (e.g., average initial age of reproduction, 4.33 ± 0.58 days) compared with other salinities level. Interestingly, the difference in growth at different salinities was not evident, an unusual finding when considering adverse effects such as osmoregulation pressure on the organism. Based on the results, we conclude that M. macrocopa can only tolerate salinity below salinity 8 and cannot withstand stressful environmental conditions associated with salinities above 8.
... To understand how changes in salinity affect the physiology and fitness of aquatic organisms, it is important to ask how well aquatic organisms can acclimate to changing salinity regimes. This question has been studied in daphnids [46,47] and mayflies [48,49], but only in terms of increasing salinity. Studies with the baetid mayfly, Neocloeon triangulifer (which has been recently established as a useful model for ecological [50], toxicological [51][52][53][54][55][56] and physiological [20,57,58] studies) have provided evidence of ion-specific physiological plasticity and ion-specific toxicity mechanisms in high-salinity waters [49]. ...
Article
Relative to a growing body of knowledge about the negative consequences of freshwater salinization, little is known about how aquatic insects respond to progressively ion-poor conditions. Here, we examined life-history and physiological acclimation in Neocloeon triangulifer by rearing nymphs from 1-day post-egg hatch to adulthood across a gradient of decreasing Na concentrations (15, 8, 4, 2 and 1 mg l ⁻¹ Na). We found no significant changes in survival, growth, development time and whole-body Na content across these treatments. Radiotracer data revealed that nymphs acclimated to their dilute exposures by increasing their rates of Na uptake and were able to maintain a relatively narrow range of uptake rates (±s.e.m.) of 38.5 ± 4.2 µg Na g ⁻¹ h ⁻¹ across all treatments. By contrast, the Na uptake rates observed in naive nymphs were much more concentration dependent. This acclimatory response is partially explained by differences in ionocyte counts on the gills of nymphs reared under different salinities. Acclimated nymphs were surprisingly less retentive of their sodium composition when subjected to deionized water challenge. By contrasting our findings with a previous N. triangulifer salinity acclimation study, we show a physiological affinity for dilute conditions in this emerging mayfly model.
... Overall, although there was no change in total phytoplankton biomass, a transition from Cryptophyta and Chlorophyta to Ochrophyta dominance with increasing salinity was present. Combined with the disappearance of rotifers and zooplankton, these results are consistent with several studies that affirm the sensitivity of zooplankton to salinity [7][8][9][10], both following sudden and gradual exposure [11], although the development of tolerance is possible [12,13] and each species has its salinity optimum [14]. ...
Article
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Each year, millions of tons of sodium chloride are dumped on roads, contributing to the salinization of freshwater environments. Thus, we sought to understand the effect of sodium chloride (NaCl) on freshwater lake prokaryotic communities, an important and understudied component of food webs. Using mesocosms with 0.01–2.74 ppt NaCl (0.27–1110.86 mg/L Cl−), we evaluated the effect generated on the diversity and absolute abundance of prokaryotic populations after three and six weeks. A positive relationship between Cl− values and absolute bacterial abundance was found after three weeks. The influence of eukaryotic diversity variation was observed as well. Significant differentiation of bacterial communities starting at 420 mg/L Cl− was observed after three weeks, levels lower than the Canadian and US recommendations for acute chloride exposure. The partial recovery of a “pre-disturbance” community was observed following a drop in salinity at the threshold level of 420 mg/L Cl−. A gradual transition of dominance from Betaproteobacteria and Actinobacteria to Bacteroidia and Alphaproteobacteria was observed and is overall similar to the natural transition observed in estuaries.
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Phenotypic plasticity is central to an organism’s ability to adapt to variable environmental conditions. For aquatic organisms, exposure to elevated salt levels poses a challenge and organisms may fail to tolerate or survive much higher levels short-term. Here we demonstrate, for the first time, in a laboratory study of Daphnia magna that exposure to levels of salinity higher than those previously shown to lead to apparent death (paralysis) can be reversed following a transfer to optimal conditions. We established experimental populations from one clone of D. magna , each with five replicates, that were exposed to different short periods of three different lethal levels of salinity (12.27 PSU [45, 60, 90 and 120 min], 18.24 PSU [45, 60 and 90 min] and 24.22 PSU [45, 60 and 90 min]). In all populations, all individuals were paralysed at the end of their exposure, usually classified in the literature as dead. Subsequently, all individuals were transferred to optimal conditions. However, after the transfer, a proportion of the individuals not only came back from the verge of death (i.e. were revitalised), but also showed afterwards differential reproductive success over a period of 20 days, depending on the level and the length of exposure before revitalisation. Both exposure level and time had an overall negative effect on population size that differed across all treatments. Revitalisation occurred within an hour after the transfer to optimal conditions for 18.24 PSU but took 14–16 h for 12.27 PSU. There was no instantaneous revitalisation nor was there any revitalisation after 16 h no matter how long the paralysed Daphnia individuals were left in the optimal conditions. Our findings cast new light on resilience in cladocerans and suggest that abrupt environmental change can reveal novel plastic responses to extreme conditions.
Article
Elevated lake chloride concentration has been observed in many regions, due to human activities such as mining, agriculture, and urbanisation. Meanwhile, lakes are also experiencing increasing frequency and intensity of heatwaves. The combination of elevated salinity and heatwaves has not been thoroughly studied in freshwater communities, limiting our ability to predict outcomes of future disturbances. We conducted a mesocosm experiment to investigate the individual and interactive effects of increased salinity and heatwaves on a freshwater zooplankton community. The combined effects of the two stressors were examined in two scenarios: when they occurred simultaneously and when a heatwave was preceded by an 8‐week increase in salinity. We expected to see a synergistic effect when the two stressors were applied simultaneously, as organisms might experience energy deficiency due to physiological changes caused by salinity stress and be overwhelmed by the heat treatment. When the two stressors were applied sequentially, we expected them to act independently as the two stressors trigger different physiological responses and physiological homeostasis may have already recovered from previous salt exposure and not influence an organism's response to a subsequent stressor. Individually, increased salinity and heatwave conditions both impaired zooplankton communities with largest effects on copepod nauplii and cladocerans. Together, these stressors caused antagonistic effects on total zooplankton abundance and biomass in both the simultaneous and sequential scenarios, with the combined effects being similar to the salt‐only effects. Our experiment illustrates the potential for heatwaves to have hidden effects when they occur in lakes experiencing salinisation. The findings suggested that the two stressors negatively impacted some zooplankton taxonomic groups, and at the community level, they acted antagonistically such that the occurrence of a 3‐day heatwave did not cause any additional loss of abundance or biomass regardless of whether the community was exposed to the sequential or simultaneous scenario. Our findings also illustrated that even when the two stressors were decoupled in time, the community could still be influenced by a previous stressor.
Article
While de-icing salts improve safety on roads and sidewalks during winter, they have a negative impact on the environment. This has spurred the search for more environmentally-friendly alternatives. The present study tests the impact of NaCl and six other de-icing salts (pure CaCl2, CaCl2+NaCl, “eco-label” CaCl2, MgCl2, solid and liquid CH3COOK), promoted as more eco-friendly alternatives to NaCl, on four zooplankton species from biotests: Ceriodaphnia dubia (Ceriodaphtokit), Daphnia magna (Daphtoxkit), Brachionus calyciflorus (Rotoxkit) and Thamnocephalus platyurus (Thamnotoxkit). 24-h EC50 evaluation showed that only solid CH3COOK was less toxic for all tested species than NaCl. The other tested de-icing salts had similar or even higher toxicity, with CaCl2, MgCl2 and liquid CH3COOK being significantly more toxic for all species than NaCl. Of the tested species, Thamnocephalus platyurus demonstrated toxicity response at significantly lower concentration of all used de-icing salts, while Daphnia magna had significantly the highest concentrations of toxicity response. Our findings demonstrate that these alternatives are not less toxic in this regard than the commonly-used NaCl and underline the need to verify the accuracy of the term “eco-friendly” on the labels of these products.
Article
Epigenetic mechanisms have been found to play important roles in environmental stress response and regulation. These can, theoretically, be transmitted to future unexposed generations, yet few studies have shown persisting stress-induced transgenerational effects, particularly in invertebrates. Here, we focus on the aquatic microcrustacean Daphnia, a parthenogenetic model species, and its response to salinity stress. Salinity is a serious threat to freshwater ecosystems and a relevant form of environmental perturbation affecting freshwater ecosystems. We exposed one generation of D. magna to high levels of salinity (F0) and found that the exposure provoked specific methylation patterns that were transferred to the three consequent non-exposed generations (F1, F2 and F3). This was the case for the hypomethylation of six protein-coding genes with important roles in the organisms’ response to environmental change: DNA damage repair, cytoskeleton organization and protein synthesis. This suggests that epigenetic changes in Daphnia are particularly targeted to genes involved in coping with general cellular stress responses. Our results highlight that epigenetic marks are affected by environmental stressors and can be transferred to subsequent unexposed generations. Epigenetic marks could therefore prove to be useful indicators of past or historic pollution in this parthenogenetic model system. Furthermore, no life history costs seem to be associated with the maintenance of hypomethylation of across unexposed generations in Daphnia following a single stress exposure.
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Widespread use of NaCl for road de-icing has caused increased chloride concentrations in lakes near urban centers and areas of high road density. Chloride is toxic, and water quality guidelines have been created to regulate it and protect aquatic life. However, these guidelines may not adequately protect organisms in low nutrient, soft water lakes such as those underlain by Precambrian Shield. We tested this hypothesis by conducting laboratory experiments on 6 Daphnia species, using a soft water culture medium. We also examined temporal changes in cladoceran assemblages in the sediments of two small lakes on the Canadian Shield; one near a highway and the other > 3 km from roads where salt is applied in the winter. Our results showed that Daphnia were sensitive to low chloride concentrations with decreased reproduction and increased mortality occurring between 5 and 40 mg Cl-/L. Analysis of cladoceran remains in lake sediments revealed changes in assemblage composition that coincided with the initial application of road salt in this region. In contrast, there were no changes detected in the remote lake. We found that 22.7% of recreational lakes in Ontario have chloride concentrations between 5 and 40 mg/L suggesting that cladoceran zooplankton in these lakes may already be experiencing negative effects of chloride.
Article
Increasing chloride concentrations from road salt applications are an emerging threat to freshwater diversity in cold weather regions. Few studies have focused on how road salt affects freshwater biota and even fewer have focused on how the rate of exposure alters organism responses. We hypothesized that road salt concentrations delivered gradually would result in slower population declines and more rapid rebounds due to evolved tolerance. To test this hypothesis, we examined the responses of freshwater lake organisms to four environmentally relevant salt concentrations (100, 230, 860, and 1600 mg Cl⁻/L) that differed in application rate (abrupt vs. gradual). We used outdoor aquatic mesocosms containing zooplankton, filamentous algae, phytoplankton, periphyton, and macroinvertebrates. We found negative effects of road salt on zooplankton and macroinvertebrate abundance, but positive effects on phytoplankton and periphyton, likely resulting from reduced grazing. Only rarely did we detect a difference between abrupt vs gradual salt applications and the directions of those differences were not consistent. This affirms the need for additional research on how road salt pollution entering ecosystems at different frequencies and magnitudes will alter freshwater communities.
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Freshwater salinization is a rapidly emerging ecological issue and is correlated with significant declines in aquatic biodiversity. It remains unclear how changing salinity regimes affect the physiology of sensitive aquatic insects. We used the parthenogenetic mayfly, Neocloeon triangulifer, to ask how ionic exposure history alters physiological processes and responses to subsequent major ion exposures. Using radiotracers (²²Na, ³⁵SO4, and ⁴⁵Ca), we observed that mayflies chronically reared in elevated sodium or sulfate (157 mg L⁻¹ Na or 667 mg L⁻¹ SO4) had 2-fold (p<0.0001) and 8-fold (p<0.0001) lower ion uptake rates than mayflies reared in dilute control water (16 mg L⁻¹ Na and 23 mg L⁻¹ SO4) and subsequently transferred to elevated salinities, respectively. These acclimatory ion transport changes provided protection in 96-hour toxicity bioassays for sodium, but not sulfate. Interestingly, calcium uptake was uniformly much lower and minimally influenced by exposure history, but was poorly tolerated in the toxicity bioassays. With qRT-PCR, we observed that the expression of many ion transporter genes in mayflies was influenced by elevated salinity in an ion-specific manner (upregulation in response to sulfate, downregulation in response to calcium). Elevated sodium exposure had minimal influence on the same genes. Finally, we provide novel light microscopic evidence of histomorphological changes within the epithelium of the Malpighian tubules (insect primary excretory system) that undergoes cellular degeneration and necrosis secondary to calcium toxicity. We conclude that physiological plasticity to salinity stress is ion-specific and provide evidence for ion-specific toxicity mechanisms in N. triangulifer.
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The Great Plains of North America are projected to become more arid over the next century. Paleolimnological studies show that lake salinity levels in this region are tightly linked with climate, and that lakes will become more saline as the climate becomes drier. One group of organisms that might be affected by increased salinity levels are the zooplankton. Although recent studies suggest that zooplankton can evolve to tolerate small increases in salinity over short time periods, few studies have examined how they respond when experiencing large increases over longer time frames. For this study, we used resurrection ecology to examine how a common zooplankter, Ceriodaphnia dubia, has responded to long‐term salinity change in Moon Lake, North Dakota over the last 150 yrs. We ran experiments to determine the salinity levels that induced C. dubia eggs to hatch and we ran toxicity experiments to determine the salinity tolerance of adults. These experiments showed that C. dubia eggs hatched in saltier water during periods of drought and in fresher water during wet periods. Similarly, our toxicity experiments showed that EC50 values for C. dubia were higher during episodes of drought. The presence of C. dubia eggs throughout the sediment core during the last 150 yrs combined with their ability to adapt to changing salinity levels, suggests that they will likely be able to persist through coming droughts. Further studies will be needed to determine if other common zooplankton species in Great Plains' lakes are similarly adaptable.
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The salinization of the global freshwater system caused by various human activities and climate change has become a common problem threatening freshwater biodiversity and resources, which may affect a variety of species of cladocerans at individual and population levels. In order to comprehensively evaluate the impact of salinization on different-sized cladocerans at individual and population levels, we exposed two species of cladocerans with obvious body size difference, Daphnia magna and Moina macrocopa, to seven salinities (0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12 M), recorded individual life history traits and population growth dynamics, and used multiple mechanistic models to fit the data. At the individual level, the median effect concentration of survival time, total offspring per female, and number of broods of D. magna were significantly higher than those of M. macrocopa. At the population level, the decrease in carrying capacity of D. magna with increasing salinity was significantly less than that of M. macrocopa. At the same salinity treatment, the integrated biomarker response indexes value of M. macrocopa is higher than that of D. magna. Therefore, it was further inferred that the sensitivity of small-sized species M. macrocopa to salinity stress is significantly higher than that of big-sized species D. magna. Thus, freshwater salinization may result in the replacement of smaller salt-intolerant cladocerans with larger salt-tolerant cladocerans, which may have dramatic effects on freshwater communities and ecosystems. Additionally, the increase of salinity had a greater impact on the population level of D. magna and M. macrocopa than on the individual level, indicating that population level of cladocerans was more susceptible to salinity stress. Experiments only based on individuals may underestimate the ecologically related changes in populations and communities, thus understanding the impact of salinization on freshwater systems needs to consider multiple ecological levels.
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Cladocerans of the genus Daphnia are keystone pelagic filter feeders in many temperate ponds and lakes. They have also become popular model organisms in various biological disciplines, from aquatic ecology to biomedical sciences. The crucial features that make these organisms excellent experimental models are their cyclical parthenogenetic life cycle together with easy culturing and handling. Thanks to these characteristics, the number of publications dealing with Daphnia is rapidly growing. The special insert to the Journal of Limnology on Daphnia biology contains contributions that deal directly or indirectly with the reproduction and development of these water fleas, in relation to various ecological factors. These include predator-prey interactions and their impact on morphology, population dynamics, or senescence-related traits, growth of daphnids on a diet consisting of invasively spreading cyanobacteria, and also the impact of extreme floods on a Daphnia population (and particularly on its dormant ephippial egg bank) in a reservoir. Here, we discuss these presented works, and point out the potential lines of research that may improve the generalisation of their findings.
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Despite growing recognition of the importance of ecosystem services and the economic and ecological harm caused by invasive species, linkages between invasions, changes in ecosystem functioning, and in turn, provisioning of ecosystem services remain poorly documented and poorly understood. We evaluate the economic impacts of an invasion that cascaded through a food web to cause substantial declines in water clarity, a valued ecosystem service. The predatory zooplankton, the spiny water flea (Bythotrephes longimanus), invaded the Laurentian Great Lakes in the 1980s and has subsequently undergone secondary spread to inland lakes, including Lake Mendota (Wisconsin), in 2009. In Lake Mendota, Bythotrephes has reached unparalleled densities compared with in other lakes, decreasing biomass of the grazer Daphnia pulicaria and causing a decline in water clarity of nearly 1 m. Time series modeling revealed that the loss in water clarity, valued at US$140 million (US$640 per household), could be reversed by a 71% reduction in phosphorus loading. A phosphorus reduction of this magnitude is estimated to cost between US$86.5 million and US$163 million (US$430-US$810 per household). Estimates of the economic effects of Great Lakes invasive species may increase considerably if cases of secondary invasions into inland lakes, such as Lake Mendota, are included. Furthermore, such extreme cases of economic damages call for increased investment in the prevention and control of invasive species to better maximize the economic benefits of such programs. Our results highlight the need to more fully incorporate ecosystem services into our analysis of invasive species impacts, management, and public policy.
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Anthropogenic salinization of rivers is an emerging issue of global concern, with significant adverse effects on biodiversity and ecosystem functioning. Impacts of freshwater salinization on biota are strongly mediated by evolutionary history, as this is a major factor determining species physiological salinity tolerance. Freshwater insects dominate most flowing waters, and the common lotic insect orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) are particularly salt-sensitive. Tolerances of existing taxa, rapid adaption, colonization by novel taxa (from naturally saline environments) and interactions between species will be key drivers of assemblages in saline lotic systems. Here we outline a conceptual framework predicting how communities may change in salinizing rivers. We envision that a relatively small number of taxa will be saline-tolerant and able to colonize salinized rivers (e.g. most naturally saline habitats are lentic; thus potential colonizers would n
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Many human activities—like agriculture and resource extraction—are increasing the total concentration of dissolved inorganic salts (i.e., salinity) in freshwaters. Increasing salinity can have adverse effects on human health (1); increase the costs of water treatment for human consumption; and damage infrastructure [e.g., amounting to $700 million per year in the Border Rivers catchment, Australia (2)]. It can also reduce freshwater biodiversity (3); alter ecosystem functions (4); and affect economic well-being by altering ecosystem goods and services (e.g., fisheries collapse). Yet water-quality legislation and regulations that target salinity typically focus on drinking water and irrigation water, which does not automatically protect biodiversity. For example, specific electrical conductivities (a proxy for salinity) of 2 mS/cm can be acceptable for drinking and irrigation but could extirpate many freshwater insect species (3). We argue that salinity standards for specific ions and ion mixtures, not just for total salinity, should be developed and legally enforced to protect freshwater life and ecosystem services. We identify barriers to setting such standards and recommend management guidelines.
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Anthropogenic stressors are ubiquitous and have been implicated in worldwide declines of terrestrial and aquatic species. Pesticides are one such stressor that can have profound effects on aquatic communities by directly affecting sensitive species and indirectly affecting other species via trophic cascades, which can alter ecosystem function. However, there is growing evidence that non-target species can evolve increased resistance. When such species are important drivers of the food web, then evolved resistance should help buffer communities from the effects of pesticides. To examine this possibility, we cultured four populations of the common zooplankton Daphnia pulex that we previously demonstrated were either sensitive or resistant to a common insecticide (i.e., chlorpyrifos) due to their proximity to agriculture. Using outdoor mesocosms that contained identical aquatic communities of phytoplankton, periphyton, and leopard frog tadpoles (Lithobates pipiens), we manipulated four D. pulex populations and four insecticide concentrations. As we monitored the communities for nearly 3 months, we found that the insecticide caused direct mortality of D. pulex in communities containing sensitive populations, and this led to a bloom of phytoplankton. In contrast, the insecticide caused much less direct mortality in communities containing resistant D. pulex populations, and the trophic cascade was prevented under low to moderate insecticide concentrations. Across all insecticide treatments, survivorship of leopard frogs was approximately 72 % in communities with resistant D. pulex but only 35 % in communities with sensitive D. pulex. To our knowledge, this is one of the first studies to use naturally occurring population variation in insecticide resistance to show that the evolution of pesticide resistance in zooplankton can mitigate the effects of insecticide-induced trophic cascades, and that this outcome can have far-reaching community effects.
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The R Commander graphical user interface to R is extensible via plug-in packages, which integrate seamlessly with the R Commander's menu structure, data, and model handling. The paper describes the RcmdrPlugin.survival package, which makes many of the facilities of the survival package for R available through the R Commander, including Cox and parametric survival models. We explain the structure, capabilities, and limitations of this plug-in package and illustrate its use.
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Embryos, larvae, and adults of Palaemonetes argentinus tolerate a wide range of salinities (1 to 25 parts per thousand). While osmoregulatory capacities have previously been demonstrated in all postembryonic stages, little is known about the occurrence of osmoregulation during the embryonic phase. We examined ontogenetic and salinity-induced changes in the activity of a key enzyme involved in osmoregulation, Na+,K+-ATPase. Its activity was studied in: (1) eggs at an early (SI), an intermediate (SII), and a late stage of embryonic development (SIII); (2) in newly hatched larvae (Zoea-I, ZI); and in homogenates of (3) whole adults and (4) isolated gill tissue. All stages were directly exposed to 1, 15, or 25%., and Na+,K+-ATPase activity was chemically determined 24 h (embryos, larvae) or 48 h later (adults). Enzyme activity was detected in all developmental stages, being low in SI and SII, maximum in SIII, and intermediate in ZI and adults. Maximum salinity-induced activity changes prior to hatching (SIII) suggest that hyper-osmoregulatory functions are expressed by the end of the embryonic phase. The ontogenetic activity maximum at this stage, however, may also be related to the hatching process. Comparing different salinities, Na+,K+-ATPase activity in SIII was always highest at 15 parts per thousand, whereas the activity in gills was higher at both 15 and 25 parts per thousand than at 1 parts per thousand. While gills are absent in the embryonic and early larval stages, ion-transporting cells Must be located elsewhere during these early ontogenetic stages, probably in the brachiostegites.
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Understanding population responses to rapid environmental changes caused by anthropogenic activities, such as pesticides, is a research frontier. Genetic assimilation (GA), a process initiated by phenotypic plasticity, is one mechanism potentially influencing evolutionary responses to novel environments. While theoretical and laboratory research suggest that GA has the potential to influence evolutionary trajectories, few studies have assessed its role in the evolution of wild populations experiencing novel environments. Using the insecticide, carbaryl, and 15 wood frog populations distributed across an agricultural gradient, we tested whether GA contributed to the evolution of pesticide tolerance. First, we investigated the evidence for evolved tolerance to carbaryl and discovered that population-level patterns of tolerance were consistent with evolutionary responses to pesticides; wood frog populations living closer to agriculture were more tolerant than populations living far from agriculture. Next, we tested the potential role of GA in the evolution of pesticide tolerance by assessing whether patterns of tolerance were consistent with theoretical predictions. We found that populations close to agriculture displayed constitutive tolerance to carbaryl whereas populations far from agriculture had low naïve tolerance but high magnitudes of induced tolerance. These results suggest GA could play a role in evolutionary responses to novel environments in nature.This article is protected by copyright. All rights reserved.
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A distributional survey of obligately parthenogenetic clonal groups belonging to the Daphnia pulex complex was conducted on rock bluff and tundra ponds near Churchill, Manitoba. Clonal distributions were spatially heterogeneous. The clonal patterns of microgeographic heterogeneity suggested a strong association of Daphnia clonal type with salinity/conductivity gradients in pond habitats that varied in their proximity to Hudson Bay. Acute salinity tolerance experiments showed significant differences in survivorship of six clonal isolates at salinities encountered in nature. Clones from high-salinity ponds had greater survivorship at high salinities than clones from low-salinity ponds. There were no significant differences in clonal survivorship at low salinities. Clonal differences were also found in hatching success of ephippial eggs at different salinities. Laboratory measurements of hemolymph osmolality from these clones indicated significant differences in oscmoregulatory capacity. Coupled with morphological and electrophoretic data, the ecophysiological differences among D. pulex clones from Churchill suggest strongly that this Daphnia complex consists of physiologically different @'ecotypes.@' The ecological and evolutionary implications of these data are discussed.
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Identifying the relative importance of stressors is critical for effectively managing and conserving fresh-water aquatic ecosystems. However, variability in natural ecosystems and the potential for multiple stressors make understanding the effects of stressors challenging in the field. To address these challenges, we assessed four common stressors in the northeastern USA including acidification (pH), climate change (water temperature), salinization (Na and Cl), and nutrient addition using laboratory mesocosms. Each stressor was evaluated in-dependently, with ten mesocosms assigned across a gra-dient of concentrations for each stressor (total N=40). We then monitored the effects of the stressors on a model community consisting of periphyton, zooplankton, Northern watermilfoil (Myriophyllum sibericum), American ribbed fluke snail (Pseudosuccinea columella), and larval American bullfrogs (Lithobates catesbeianus). Aquatic stressors varied in the strength of their effects on community structure: Nutrient addition was the least influential stressor, with no significant effects. Acidification influenced periphyton biomass, but not higher trophic levels. Water temperature influenced pri-mary productivity and survival of amphibian larvae, but not intermediate trophic levels. Finally, road salt led to decreases in productivity for all trophic levels included in our model systems. Our results support the findings of prior research, although the effects of acidification and nutrient addition were less pronounced in our study. Importantly, we found that road salt had the most far-reaching effects on a model aquatic community. Given that road salt is the most easily managed of the stressors we compared, our results indicate that improving the condition of freshwater aquatic ecosystems in the north-eastern USA may be a feasible objective.
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Small fragmented populations can lose genetic variability, which reduces population viability through inbreeding and loss of adaptability. Current and previous environmental conditions can also alter the viability of populations, by creating local adaptations that determine responses to stress. Yet, most studies on stress tolerance usually consider either the effect of genetic diversity or the local environment, missing a more holistic perspective of the factors contributing to stress tolerance among natural populations. Here, we studied how salinity stress affects population growth of Daphnia longispina, Daphnia magna, and Daphnia pulex from rock pools with varying degrees of population isolation and salinity conditions. Standing variation of in situ rock pool salinity conditions explained more variation in salt tolerance than the standing variation of population isolation or genetic diversity, in both a pulse and a press disturbance experiment. This indicates that the level of stress, which these natural populations experience, influences their response to that stress, which may have important consequences for the conservation of fragmented populations. However, long-term population stability in the field decreased with population isolation, indicating that natural populations experience a variety of stresses; thus, population isolation and genetic diversity may stabilize population dynamics over larger spatiotemporal scales.
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We integrated the evidence for evolutionary and plastic trait changes in situ in response to climate change in freshwater invertebrates (aquatic insects and zooplankton). The synthesis on the trait changes in response to the expected reductions in hydroperiod and increases in salinity indicated little evidence for adaptive, plastic, and genetic trait changes and for local adaptation. With respect to responses to temperature, there are many studies on temporal trait changes in phenology and body size in the wild that are believed to be driven by temperature increases, but there is a general lack of rigorous demonstration whether these trait changes are genetically based, adaptive, and causally driven by climate change. Current proof for genetic trait changes under climate change in freshwater invertebrates stems from a limited set of common garden experiments replicated in time. Experimental thermal evolution experiments and common garden warming experiments associated with space-for-time substitutions along latitudinal gradients indicate that besides genetic changes, also phenotypic plasticity and evolution of plasticity are likely to contribute to the observed phenotypic changes under climate change in aquatic invertebrates. Apart from plastic and genetic thermal adjustments, also genetic photoperiod adjustments are widespread and may even dominate the observed phenological shifts.
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The role of plasticity in shaping adaptations is important to understanding the expression of traits within individuals and the evolution of populations. With increasing human impacts on the environment, one challenge is to consider how plasticity shapes responses to anthropogenic stressors such as contaminants. To our knowledge, only one study (using mosquitoes) has considered the possibility of induced insecticide tolerance. Using populations of wood frogs (Lithobates sylvaticus) located close to and far from agricultural fields, we discovered that exposing some populations of embryos and hatchlings to sublethal concentrations of the insecticide carbaryl induced higher tolerance to a subsequent lethal concentration later in life. Interestingly, the inducible populations were located >800 m from agricultural areas and were the most susceptible to the insecticide. In contrast, the noninducible populations were located close to agricultural areas and were the least susceptible. We also found that sublethal concentrations of carbaryl induced higher tadpole AChE concentrations in several cases. This is the first study to demonstrate inducible tolerance in a vertebrate species and the pattern of inducible and constitutive tolerance among populations suggests the process of genetic assimilation.
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In order to conduct experiments on interactions between animals and food organisms, it is necessary to develop a medium that adequately supports the growth of both algae and zooplankton without the need to alter the medium to accommodate either the algae or the animals. We devised a freshwater medium, named COMBO, that supports excellent growth of both algae and zooplankton. Two types of algae, Ankistrodesmus falcatus and Stephanodiscus hantzschii, were reared in COMBO and their growth rates were not significantly different from those of algae grown in a reference medium (WC). One of these algae, A. falcatus, was then fed to a cladoceran, Daphnia pulicaria, which was also cultured in COMBO, and the resulting fecundities of D. pulicaria were compared to those of animals reared in natural surface water. We also determined whether the value of COMBO as a medium for D. pulicaria was affected by modifications in nitrogen or phosphorus concentration to evaluate whether the new medium will be useful in nutritional research. Lowering the N or P content of COMBO did not affect the reproductive performance of D. pulicaria. Other researchers have also reported excellent growth and reproduction by numerous algae and zooplankton reared in COMBO. Our results suggest that COMBO is an effective artificial, defined culture medium capable of supporting robust growth and reproduction of both freshwater algae and zooplankton.
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Intermittent saline intrusions are a common feature of many coastal lakes and wetlands. These ecosystems are often important sites of biodiversity, biological productivity, and ecosystem services such as the removal of sediment, nutrients, and contaminants from inflowing rivers. Predicted effects of global climate change, including sea level rise, are likely to intensify saline intrusions into such ecosystems. Analyses of taxonomic diversity and abundance of zooplankton at different salinities in Lake Waihola, South Island, New Zealand, are supported by results of laboratory studies of salinity tolerances of 3 crustacean taxa Gladioferens pectinatus, Boeckella hamata and Daphnia carinata obtained from the lake. The field and laboratory analyses show that severe perturbations of zooplankton community structure and abundance are caused by even minor saline intrusions into Lake Waihola that raise the salinity to >1.2 psu. Our analyses of Lake Waihola, and data from brackish ecosystems around the world, show that even relatively small increases in salinity levels can drive such systems to a state of depleted biodiversity and abundance, altering ecosystem functioning.
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Limnologistas han venido estudiando patrones de la productividad primaria en los lagos por mas de 60 anos. En lo relativo a la entroficacion a puesto la atencion en el suministro de nutrientes como un regulador de la productividad del lago. Sin embargo la adicion de nutrientes no siempre explica la variacion de la productividad primaria de todos los lagos del mundo. Este articulo se refiere a algunos casos practicos
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We studied the winter to spring transition in Third Sister Lake (TSL), a small glacial lake in southeastern Michigan, to determine the effect of mixing regime on nutrient dynamics and community structure in an urban temperate lake. After ice-off, the oxycline was mixed downward from 3 to 6 m depth, resulting in addition of 5 mg m P-SRP, 857 mg m N-NH4 , and 400 mg m N-NO3 to the epilimnion, but trapping 299 mg m P-SRP, 7877 mg m N-NH4 and 36 mg m N-NO3 in the bottom waters. Nutrients supplied by snow melt runoff (138 mg m P-SRP, 430 mg m N-NH4 , 596 mg m N-NO3 ) were an order of magnitude greater than rain event loads (0.13 mg m P-SRP, 0.17 mg m N-NH4 , and 1.05 mg m N-NO3 ) during the transition time from ice cover to open water. Reduced spring mixing did not have a large impact on N:P molar ratios, because external N:P ratios were low (7.5) compensating for reduced supply of P from the bottom waters. Bacterial production was greater in the hypolimnion than in the epilimnion, and mesocosm experiments showed that bacteria were P limited in the epilimnion but not in the hypolimnion. Total algal and zooplankton densities increased after ice-out, while Daphnia and Bosmina densities decreased. Increases in zooplankton grazing rates after ice-off were most dramatic in small-bodied zooplankton. Sediment core analysis showed that Asterionella relative abundance continues to increase, suggesting that the lake has become more brackish and oligotrophic. Our findings suggest that TSL has undergone a transition from dimictic to meromictic conditions, and that continued salt inputs have altered the structure and function of this ecosystem.
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Cladocerans of the genus Daphnia are keystone pelagic filter feeders in many temperate ponds and lakes. They have also become popular model organisms in various biological disciplines, from aquatic ecology to biomedical sciences. The crucial features that make these organisms excellent experimental models are their cyclical parthenogenetic life cycle together with easy culturing and handling. Thanks to these characteristics, the number of publications dealing with Daphnia is rapidly growing. The special insert to the Journal of Limnology on Daphnia biology contains contributions that deal directly or indirectly with the reproduction and development of these water fleas, in relation to various ecological factors. These include predator-prey interactions and their impact on morphology, population dynamics, or senescence-related traits, growth of daphnids on a diet consisting of invasively spreading cyanobacteria, and also the impact of extreme floods on a Daphnia population (and particularly on its dormant ephippial egg bank) in a reservoir. Here, we discuss these presented works, and point out the potential lines of research that may improve the generalisation of their findings.
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Using several clonal lineages of Simocephalus vetulus (Cladocera, Daphniidae) as a random sample, we investigated the genetic component of the halotolerance of one brackish and two freshwater populations of this littoral filter feeder. We hypothesized that genotypes from the brackish population were more tolerant than freshwater ones, via adaptation to local environmental conditions. Clonal identity was established by a cost-effective molecular fingerprinting technique (microsatellite-primed polymerase chain reaction (MSP-PCR)). Two distinct methodologies were used to assess cladoceran sensitivity to synthetic-grade sodium chloride (NaCl): (i) standard 48-h acute assays and (ii) 12-h survival time (ST) trials. No correlation was found between acute EC50 and ST values. The sensitivity of brackish and freshwater clones was comparable in terms of acute EC50 (varied from 2.28 to 3.83 g.L-1). On the contrary, genetically determined differential tolerance to NaCl among populations was found for ST: all brackish genotypes, except one, were more resilient (ST > 120 min) than freshwater clones (ST < 120 min). Bearing in mind that these results were obtained with isolates from the extant population, it is surprising that the range of acute sensitivity of the freshwater and brackish genotypes was similar, and that the only difference between them was the ability of brackish clones to survive longer under high salinity stress (6 g.L-1 in ST trials). We must conclude that the effect of salinity (original environment context) on the selection of genotypes was weaker than we had expected and than other authors have shown for other stressors.