When consumers and their resources respond differently to warming, this can lead to seasonal mismatches between consumer demands and resource availability. A less acknowledged threat to the coherence of consumer-resource dynamics is mismatch in food quality. Many plant and algal communities respond to warming with shifts towards more carbon-rich species and growth forms, thus diluting essential elements in their biomass and enhancing the mismatch with herbivore nutrient requirements. We report on a mesocosm experiment with a spring plankton community where warming caused a dramatic regime shift that coincided with extreme stoichiometric mismatch. At ambient temperatures, a typical spring succession developed, where a moderate bloom of nutritionally adequate phytoplankton was grazed down to a clear-water phase by a developing Daphnia population. While warming accelerated initial Daphnia population growth, it speeded up algal growth rates even more, triggering a massive phytoplankton bloom of poor food quality. Consistent with a stoichiometric producer-grazer model, accelerated phytoplankton growth promoted the emergence of an alternative system attractor, where extremely low phosphorus content of abundant algal food drove Daphnia to extinction. The experiment is a demonstration of the ‘paradox of energy enrichment’ (= grazer starvation in abundant but nutritionally imbalanced food). It supports the notion that warming can exacerbate the stoichiometric mismatch at the plant-herbivore interface and limit energy transfer to higher trophic levels.

Primary Presenter: Sebastian Diehl, Umea University (sebastian.diehl@umu.se)

Authors:

Sebastian Diehl, Umeå University  (sebastian.diehl@umu.se)

Stella Berger, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (berger@igb-berlin.de)

Wojciech Uszko, Umeå University  (wojciech.uszko@umu.se)

Herwig Stibor, Ludwig-Maximilians University Munich  (stibor@zi.biologie.uni-muenchen.de)