Climate change scenarios predict increased seawater intrusion resulting in salinization of low-lying coastal freshwater ecosystems. Largely, ecological risk assessment of this intrusion has used standard organism toxicity tests, in which lethal or sublethal effects are assessed following forced stress exposure. For mobile organisms, however, stress avoidance is common, suggesting that emigration may result in local population losses at much lower saline concentrations.
Cátia Venâncio from the University of Coimbra, Portugal, and co-authors used a lab-based avoidance system to observe the emigration of four diverse aquatic species in response to a saline gradient. Planktonic crustacean (Daphnia magna), epibenthic ostracod (Heterocypris incongruens), frog (Xenopus laevis) and zebrafish (Danio rerio) exposed to species-specific salt concentrations associated with 50% population lethality (LC50) all showed avoidance of well above that 50%. Including avoidance, LC50 concentrations resulted in 85–97% decrease in local population.
To assess the full risk of local losses due to salinization, avoidance emigration must be considered.
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Armarego-Marriott, T. Freshwater fauna flee. Nat. Clim. Chang. 10, 100 (2020). https://doi.org/10.1038/s41558-020-0702-7
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DOI: https://doi.org/10.1038/s41558-020-0702-7
