How common road salts and organic additives alter freshwater food webs: in search of safer alternatives

Schuler, Matthew S.; Hintz, William D.; Jones, Devin K.; Lind, Lovisa; Mattes, Brian M.; Stoler, Aaron B.; Sudol, Kelsey; Relyea, Rick A.

doi:10.1111/1365-2664.12877

Cited by 60 publications

(50 citation statements)

References 38 publications

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“…However, zooplankton group responses to elevated salt concentrations tend to vary across studies. Experiments using NaCl concentrations more similar to ours have found declines in calanoid copepods around 125 mg Cl/L (Thompson & Shurin, ), or no effect on any zooplankton up to 200 mg Cl/L (Schuler et al., ), both of which contrast to the changes in cladocerans that we observed at 250 mg Cl/L. Even in experiments that use much higher chloride concentrations, which are often well above suggested chronic and even acute chloride thresholds, there is a great deal of variability in the response of particular zooplankton groups.…”

Section: Discussionsupporting

confidence: 60%

Local context and connectivity determine the response of zooplankton communities to salt contamination

Sinclair

Arnott

2018

Freshwater Biology

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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.

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Section: Discussionsupporting

confidence: 60%

Local context and connectivity determine the response of zooplankton communities to salt contamination

Sinclair

Arnott

2018

Freshwater Biology

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“…There has also been growing interest in using other road salts (or mixtures of salts) for deicing roads including MgCl 2 and CaCl 2 . Little research has examined the ecological impacts of these alternative salts and organic salt additives (but see Schuler et al 2017b, Schuler andRelyea 2018). As we move forward on these frontiers, we will have a much more holistic idea of how anthropogenic impacts are altering aquatic ecosystems and develop management strategies for their mitigation.…”

Section: Discussionmentioning

confidence: 99%

Salty fertile lakes: how salinization and eutrophication alter the structure of freshwater communities

et al. 2018

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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.

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“…Although most alternative salts share a common anion (i.e. Cl − ), recent work suggests that they can have very different effects on aquatic organisms due to difference in cations (Schuler et al., ). 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, ; Daley, Potter, & McDowell, ; James, Cant, & Ryan ).…”

Section: Discussionmentioning

confidence: 99%

Interactive effects of road salt and sediment disturbance on the productivity of seven common aquatic macrophytes

et al. 2018

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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.

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How common road salts and organic additives alter freshwater food webs: in search of safer alternatives

Cited by 60 publications

References 38 publications

Local context and connectivity determine the response of zooplankton communities to salt contamination

Local context and connectivity determine the response of zooplankton communities to salt contamination

Salty fertile lakes: how salinization and eutrophication alter the structure of freshwater communities

Interactive effects of road salt and sediment disturbance on the productivity of seven common aquatic macrophytes

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