Life history responses to covariance between temperature and food availability in Daphnia magna

Abstract

Freshwater systems are important for a wide variety of organisms. With the addition of increased mean temperatures, increased frequency of extreme weather events and changes in precipitation patterns brought upon by climate change, organisms in freshwater systems face many perils. Ecological systems at all levels can be resistant to change and adverse conditions, but one should not underestimate the risk of synergistically damaging effects of multiple stressors. Daphnia magna is a filter feeding freshwater zooplankton. The perform diel vertical migration (DVM) as a predatory defence mechanism. Daphnia mexperience fluctuations in food an temperature during DVM and this study explores the effect of negative and postitive covaience between food an temperature in relation to a constant mean level. The results show a strong negative effect of negatove covariance and a smaller negative effect of positive covariance. The results shows that DVM during a deep chlorophyll maximum is detrimental to Daphnia magna.