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Abstract Development can play a critical role in how organisms respond to changes in the environment. Tolerance to environmental challenges can vary during ontogeny, with individual- and population-level impacts that are associated with the timing of exposure relative to the timing of vulnerability. In addition, the life history consequences of different stressors can vary with the timing of exposure to stress. Salinization of freshwater ecosystems is an emerging environmental concern, and habitat salinity can change rapidly due, for example, to storm surge, runoff of road deicing salts, and rainfall. Elevated salinity can increase the demands of osmoregulation in freshwater organisms, and amphibians are particularly at risk due to their permeable skin and, in many species, semi-aquatic life cycle. In three experiments, we manipulated timing and duration of exposure to elevated salinity during larval development of southern toad (Anaxyrus terrestris) tadpoles and examined effects on survival, larval growth, and timing of and size at metamorphosis. Survival was reduced only for tadpoles exposed to elevated salinity early in development, suggesting an increase in tolerance as development proceeds; however, we found no evidence of acclimation to elevated salinity. Two forms of developmental plasticity may help to ameliorate costs of transient salinity exposure. With early salinity exposure, the return to freshwater was accompanied by a period of rapid compensatory growth, and metamorphosis ultimately occurred at a similar age and size as freshwater controls. By contrast, salinity exposure later in development led to earlier metamorphosis at reduced size, indicating an acceleration of metamorphosis as a mechanism to escape salinity stress. Thus, the consequences of transient salinity exposure were complex and were mediated by developmental state. Salinity stress experienced early in development resulted in acute costs but little long-lasting effect on survivors, while exposures later in development resulted in sublethal effects that could influence success in subsequent life stages. Overall, our results suggest that elevated salinity is more likely to affect southern toad larvae when experienced early during larval development, but even brief sublethal exposure later in development can alter life history in ways that may impact fitness.
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The effects of parasite exposure on mortality from aquatic contaminants, carbaryl and elevated salinity, in a freshwater crustacean
Abstract Freshwater pollution is a major global concern. Common methods for determining the effects of contaminants on freshwater organisms involve short-term laboratory experiments with otherwise healthy organisms. However, in natural systems, organisms are commonly exposed to parasites, which could alter their ability to survive exposure to aquatic contamination. We used a freshwater crustacean (Daphnia dentifera) to quantify the effects of parasite exposure on mortality from two common freshwater contaminants (elevated salinity [NaCl] and carbaryl). In our salinity trial, both parasite exposure and elevated salinity reduced survival in an additive manner. In our carbaryl trial, exposure to carbaryl reduced survival and we found a less-than-additive (i.e. antagonistic) interaction between carbaryl and the parasite; the parasite only reduced survival in the control (no carbaryl) treatments. Our results demonstrate that parasites and contaminants can jointly affect mortality in aquatic organisms in an additive or less-than-additive manner.
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- Award ID(s):
- 1856710
- PAR ID:
- 10224419
- Date Published:
- Journal Name:
- Journal of Plankton Research
- Volume:
- 42
- Issue:
- 3
- ISSN:
- 0142-7873
- Page Range / eLocation ID:
- 394 to 397
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/plankt/fbaa023
