Effects of road salt on larval amphibian susceptibility to parasitism through behavior and immunocompetence

Milotic, Dino; Milotic, Marin; Koprivnikar, Janet

doi:10.1016/j.aquatox.2017.05.015

Cited by 38 publications

(43 citation statements)

References 57 publications

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“…Stockwell, Clulow, and Mahony (2015) actually found that NaCl concentrations >1,213 mg Cl − /L reduced host infection loads of chytrid fungus (Batrachochytrium dendrobatidis) in the eastern dwarf tree frog (Litoria fallax). However, in a recent study, Milotic, Milotic, and Koprivnikar (2017) found that wood frogs exposed to road salt concentrations >360 mg Cl − /L had more helminth parasite cysts and exhibited reduced anti-parasite behaviour compared to concentrations <100 mg Cl − /L. Road salt concentrations >600 mg Cl − /L also increase parasite infections in wood frog tadpoles (Lithobates sylvaticus) (Buss & Hua, 2018).…”

Section: Wetland Communitiesmentioning

confidence: 95%

A review of the species, community, and ecosystem impacts of road salt salinisation in fresh waters

2019

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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.

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Section: Wetland Communitiesmentioning

confidence: 95%

A review of the species, community, and ecosystem impacts of road salt salinisation in fresh waters

2019

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“…In a third sample of larvae from this cohort, we tested whether salinity affects contact rates to increase direct transmission [50], because elevated salinity reduces larval activity [26,28]. We counted the number of contacts between group-housed larvae (16 replicates of 10 l aquaria, 6 larvae each) that were either In (a-e), black and grey points indicate ponds where die-offs were and were not observed, respectively.…”

Section: (B) the Progression Of Naturally Acquired Ranavirus Infectionsmentioning

confidence: 99%

Salinity stress increases the severity of ranavirus epidemics in amphibian populations

et al. 2020

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The stress-induced susceptibility hypothesis, which predicts chronic stress weakens immune defences, was proposed to explain increasing infectious disease-related mass mortality and population declines. Previous work characterized wetland salinization as a chronic stressor to larval amphibian populations. Thus, we combined field observations with experimental exposures quantifying epidemiological parameters to test the role of salinity stress in the occurrence of ranavirus-associated mass mortality events. Despite ubiquitous pathogen presence (94%), populations exposed to salt runoff had slightly more frequent ranavirus related mass mortality events, more lethal infections, and 117-times greater pathogen environmental DNA. Experimental exposure to chronic elevated salinity (0.8–1.6 g l −1 Cl − ) reduced tolerance to infection, causing greater mortality at lower doses. We found a strong negative relationship between splenocyte proliferation and corticosterone in ranavirus-infected larvae at a moderate elevation of salinity, supporting glucocorticoid-medicated immunosuppression, but not at high salinity. Salinity alone reduced proliferation further at similar corticosterone levels and infection intensities. Finally, larvae raised in elevated salinity had 10 times more intense infections and shed five times as much virus with similar viral decay rates, suggesting increased transmission. Our findings illustrate how a small change in habitat quality leads to more lethal infections and potentially greater transmission efficiency, increasing the severity of ranavirus epidemics.

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“…As road salt is applied to hard surfaces, water bodies in urbanized environments are more likely to display elevated salinity (reviewed by Tiwari & Rachlin, 2018), and electric conductivity can be 20 times higher in water bodies near roads compared to forests (Karraker et al ., 2008; Dananay et al ., 2015). Conductivity reflects total dissolved solids, and is often used as a surrogate measure for dissolved salts (Milotic et al ., 2017). The ratio of salinity to conductivity for use in conversion between these measures varies among freshwater bodies (Pawlowicz, 2008), but conductivity values (in micromhos) were approximately double those of NaCl (in mg/l) in a field study of ponds in Ontario (Milotic et al ., 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Conductivity reflects total dissolved solids, and is often used as a surrogate measure for dissolved salts (Milotic et al ., 2017). The ratio of salinity to conductivity for use in conversion between these measures varies among freshwater bodies (Pawlowicz, 2008), but conductivity values (in micromhos) were approximately double those of NaCl (in mg/l) in a field study of ponds in Ontario (Milotic et al ., 2017). Thus, salinity levels in freshwater habitats vary spatially and temporally, and measured in different ways.…”

Section: Introductionmentioning

confidence: 99%

Effects of road salt on a free-living trematode infectious stage

Milotic

Koprivnikar

2020

J. Helminthol.

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Many temperate freshwater habitats are at risk for contamination by run-off associated with the application of road de-icing salts. Elevated salinity can have various detrimental effects on freshwater organisms, including greater susceptibility to infection by parasites and pathogens. However, to better understand the net effects of road salt exposure on host–parasite dynamics, it is necessary to consider the impacts on free-living parasite infectious stages, such as the motile aquatic cercariae of trematodes. Here, we examined the longevity and activity of cercariae from four different freshwater trematodes (Ribeiroia ondatrae, Echinostoma sp., Cephalogonimus sp. and an unidentified strigeid-type) that were exposed to road salt at five different environmentally relevant concentrations (160, 360, 560, 760 and 960 mg/ml of sodium chloride). Exposure to road salt had minimal detrimental effects, with cercariae activity and survival often greatest at intermediate concentrations. Only the cercariae of Cephalogonimus sp. showed reduced longevity at the highest salt concentration, with those of both R. ondatrae and the unidentified strigeid-type exhibiting diminished activity, indicating interspecific variation in response. Importantly, cercariae seem to be relatively unaffected by salt concentrations known to increase infection susceptibility in some of their hosts. More studies will be needed to examine this potential dichotomy in road salt effects between hosts and trematodes, including influences on parasite infectivity.

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Effects of road salt on larval amphibian susceptibility to parasitism through behavior and immunocompetence

Cited by 38 publications

References 57 publications

A review of the species, community, and ecosystem impacts of road salt salinisation in fresh waters

A review of the species, community, and ecosystem impacts of road salt salinisation in fresh waters

Salinity stress increases the severity of ranavirus epidemics in amphibian populations

Effects of road salt on a free-living trematode infectious stage

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