Can zooplankton on the North American Great Plains ‘keep up’ with climate-driven salinity change?

Abstract

The Great Plains of North America are projected to become more arid over the next century. Paleolimnological studies show that lake salinity levels in this region are tightly linked with climate, and that lakes will become more saline as the climate becomes drier. One group of organisms that might be affected by increased salinity levels are the zooplankton. Although recent studies suggest that zooplankton can evolve to tolerate small increases in salinity over short time periods, few studies have examined how they respond when experiencing large increases over longer time frames. For this study, we used resurrection ecology to examine how a common zooplankter, Ceriodaphnia dubia, has responded to long‐term salinity change in Moon Lake, North Dakota over the last 150 yrs. We ran experiments to determine the salinity levels that induced C. dubia eggs to hatch and we ran toxicity experiments to determine the salinity tolerance of adults. These experiments showed that C. dubia eggs hatched in saltier water during periods of drought and in fresher water during wet periods. Similarly, our toxicity experiments showed that EC50 values for C. dubia were higher during episodes of drought. The presence of C. dubia eggs throughout the sediment core during the last 150 yrs combined with their ability to adapt to changing salinity levels, suggests that they will likely be able to persist through coming droughts. Further studies will be needed to determine if other common zooplankton species in Great Plains’ lakes are similarly adaptable.