Transgenerational plasticity to warming decreases nutrient release by a keystone grazer

Increasing temperatures as a result of global climate change can alter the physiology of organisms via selection for tolerant genotypes and individual-level plasticity. Organisms experiencing thermal stress can not only modify their own physiological expression, but also those of future generations; i.e. transgenerational plasticity (TGP). While warming triggered TGP is well documented, its effects on key physiological rates and subsequent ecosystem functioning is poorly understood. In this study, we used reciprocal transplant experiments to examine if warming triggers TGP impacts on grazing, uptake and release of nitrogen (N) and phosphorus (P), in the keystone aquatic herbivore Daphnia magna. Individuals were reared for two generations at either 18°C or 24°C. Offspring from the second generation were exposed to either 18°C or 24°C for a period of 12 hours and an assay was conducted to measure rates of algal clearance, N-P uptake and release. Our results show that while differences in maternal temperature exposure did not lead to differences in grazing rates, warmer maternal exposure increased N release rates, increased proportion of body P content, and reduced P release. These results suggest that transgenerational plasticity can alter physiological responses to warming in Daphnia with potentially major consequences for N and P cycling in lake ecosystems.