The effect of temperature on Daphnia?s stoichiometric knife edge

CECILIA LASPOUMADERES; ESTEBAN BALSEIRO; BEATRIZ MODENUTTI; JAMES ELSER

Toronto

Congreso; Conference on Biological Stoichiometry; 2015

Stoichiometric food quality in terms of carbon:phosphorus (C:P) ratios affects the growth rate of consumers whether the imbalance involves a deficit or an excess of nutrients; hence, organisms exist on a ?stoichiometric knife edge?. Temperature is also a key modulator of growth rate, although the interactions between temperature and nutrient, excess and deficit, is scarcely known. In this work we evaluate if the knife edge hypothesis is valid at different temperatures. We analysed the knife edge of Daphnia in a temperature gradient. We fed Daphnia with algae with different elemental composition in order to encompass the complete knife edge, in a temperature range of 15-28°C. Our results reveal a complex interaction among temperature and nutrient excess and deficit. We found that the knife edge of Daphnia is modified and less evident at extreme temperatures, while the knife edge is clear around the temperature for optimal development. A better understanding of the interactions among temperature and nutrients is clearly needed for developing realistic predictions about ecological responses to drivers of global change that include climate warming and elevated nutrient supply to ecosystems.