The secondary salinization of freshwater habitats is a widespread issue caused by a diversity of activities (i.e. agricultural irrigation, sea water intrusion, road salts). Understanding how increased salt concentrations influence freshwater organisms has broad ecological and conservation implications. Traditional approaches focus on evaluating the direct consequences of salt in laboratory settings (i.e. LC-50). However, it is well-recognized that the effects of contaminants in nature can be more complex than predicted by laboratory approaches. For example, at the ecosystem level, abiotic changes caused by other anthropogenic activities (i.e. invasive species, global climate change) may modify the susceptibility of aquatic organisms to salt. At the community level, salts may modify ecological interaction (i.e. host-parasite interactions). Finally, at the population level, different exposure regimes may lead to different adaptive responses to salt (i.e. evolution of tolerance via different mechanisms). Therefore, to understand the myriad ways increased salinity influences freshwater aquatic ecosystems, integrating ecological and evolutionary perspectives is paramount.
Results/Conclusions
This talk will provide a broad overview of how incorporating ecological and evolutionary complexity can alter the way we understand the effect of increased salinity on wetland organisms. First, we demonstrate that shifts in abiotic conditions caused by other human activities (invasive species and global climate change) can interact with salt to affect amphibians. Specifically, we found that embryonic exposure to leaf litter from invasive plants increased the susceptibility of a native amphibian to salt but decreased the susceptibility of an invasive amphibian to salt. We also found that exposure to prolonged (press) but not intermittent (pulse) cold conditions during embryonic stages increased tadpole susceptibility to salt. Second, we demonstrate that exposure to salt can modify ecological interactions. Specifically, exposure to low environmentally-relevant concentrations of salt increased amphibian susceptibility to parasites. Third, we found that some amphibian populations have increased tolerance to salt. Tolerance occurred via multiple mechanism (i.e. constitutive expression and via phenotypic plasticity) but patterns of tolerance across populations was not consistent with predictions of evolved tolerance. Collectively, these results underscore the diverse consequences of increased salinity on freshwater aquatic ecosystems and highlights the potential utility of hierarchical approaches to evaluating the effects of salt across multiple organization levels.