Understanding the genomics responses of freshwater zooplanktons to salinization: a research hotspot in a saltier world.

The worldwide salinization of freshwater ecosystems poses a major threat to the biodiversity, functioning and services that these essential ecosystems provide. We are far from fully understanding the ecological and evolutionary consequences of salinization for freshwater organisms. Here we review current research on the genomic responses to salinity in freshwater zooplankton. Surveying transcriptomic studies, we identify many key ion transport genes critical for osmoregulation of ions in multiple zooplankton species in response to salinity stress. Laboratory investigations of natural zooplankton populations inhabiting gradients of salinity often reveal additional candidate genes that are not identified in gene expression experiments (e.g., trehalose). We suggest that future studies should focus on genomic approaches to explore the molecular mechanisms of adaptation to freshwater salinization in zooplanktons, and to predict the eco-evolutionary consequences of freshwater salinization.