Evidence for intraspecific variation of salinity tolerance in zooplankton collected from lakes of differing salinities on the Great Plains

The Great Plains are expected to become drier over the coming decades as
droughts caused by natural variation in precipitation are exacerbated by
climate change. The resulting increases in lake salinity may impact
biodiversity, including zooplankton. To better understand how salinity
changes will affect zooplankton, our study evaluated intraspecific
differences in salinity tolerance of zooplankton originating from lakes
with differing salinity levels. Three species, including Ceriodaphnia
laticaudata, Daphnia magna and Daphnia schodleri were collected from lakes
near Saskatoon, Saskatchewan and were subjected to acute salinity
tolerance tests. The 24-h and 48-h half-effective concentration (EC50)
results for all three species were estimated using three replicate
cultures established for each species. Calculations for EC50 values were
conducted using the drc library in the R programming language. Comparisons
of the EC50 values for individual species among lakes were made using
ANOVAs. The EC50 values for all three species were significantly lower for
cultures originating from lower salinity lakes, providing evidence that
the osmoregulatory capacity of some zooplankton species may change through
evolution or acclimation.