Recognizing Salinity Threats in the Climate Crisis

Abstract

Climate change is causing habitat salinity to transform at unprecedented rates across the globe. While much of the research on climate change has focused on rapid shifts in temperature, far less attention has focused on the effects of changes in environmental salinity. Consequently, predictive studies on the physiological, evolutionary, and migratory responses of organisms and populations to the threats of salinity change are relatively lacking. This omission represents a major oversight, given that salinity is among the most important factors that define biogeographic boundaries in aquatic habitats. In this perspective, we briefly touch on responses of organisms and populations to rapid changes in salinity occurring on contemporary time scales. We then discuss factors that might confer resilience to certain taxa, enabling them to survive rapid salinity shifts. Next, we consider approaches for predicting how geographic distributions will shift in response to salinity change. Finally, we identify additional data that are needed to make better predictions in the future. Future studies on climate change should account for the multiple environmental factors that are rapidly changing, especially habitat salinity.

The dynamic response to hypo‐osmotic stress reveals distinct stages of freshwater acclimation by a euryhaline diatom

“…The effects on the transcriptome were rapid and dramatic—more than 21% of the genes in the genome were differentially expressed within 60 min, and more than half of the genes were differentially expressed for at least one time point, substantially more than the 39% observed when a freshwater strain from the diatom genus Nitzschia was exposed to high salinity (Cheng et al, 2014). The types of genes most impacted by hypo‐osmotic stress provide new insights into how diatoms maintain homeostasis during an abrupt salinity shift, which has implications for understanding how diatoms have repeatedly diversified into freshwaters and, more pressingly, how they will respond to changes in ocean salinity that are predicted to occur in response to climate change (Lee et al, 2022).…”

“…Climate change is expected to increase the frequency and magnitude of these fluctuations. For example, the prevalence of large storms that inundate coastal habitats with freshwater from both precipitation and increased river flow is expected to increase in the future (Pörtner et al, 2019;Shu et al, 2018), and many marine and brackish environments will likely experience "freshening" due to melting ice caps and altered precipitation patterns (Lee et al, 2022). However, the specific mechanisms by which marine microbes mitigate the effects of short and long-term salinity changes remains poorly understood.…”

The ecosystem implications of road salt as a pollutant of freshwaters

“…Lastly, most research has focused on the impact of increased salinity on freshwater organisms, and usually has ignored the role evolution might play in enabling organisms to adapt to rising salinity in freshwater environments. Will species evolve osmoregulatory strategies, such as decreasing the permeability of membranes to water, changing the expression and activity of ion transporters, or synthesizing osmolytes to maintain osmotic pressures (Lee et al, 2022)? History of exposure is a factor that may contribute to variation in salt toxicity.…”

Assessing the Toxicity of Sea Salt to Early Life Stages of Freshwater Mussels: Implications for Sea Level Rise in Coastal Rivers

“…Although seawater is rich in Na + and Cl − , it also contains other major ions such as Mg 2+ , Ca 2+ , K + , Sr 2+ , and SO 4 − , among others. The toxicity of the mixture of these ions on freshwater mussels has not been widely explored (Lee et al, 2022).…”