Abstract
Recent climate warming has been shown to advance the seasonal timing of life cycle events, such as budding of trees and egg laying by birds. Species-specific differences in these changes in phenology may result in a decoupling of trophic relationships in food webs and subsequent cascading effects on community structure. For the timing of life cycle events, such as emergence, moulting and sexual reproduction, each species requires specific cues, which are used as proxies for the suitability of the environment for their reproduction and growth. Climate warming may change the validity of the proxies different species use. The fundamental questions underlying our proposed research are threefold: 1)What proxies do different species use to estimate the suitability of environmental conditions for successful reproduction and growth? 2) Could projected climate warming invalidate the use of these proxies and lead to a decoupling of trophic interactions? 3) Can adaptation to projected climate warming maintain or restore trophic interactions? The short generation time of the aquatic species and the availability of different types of models (e.g. a wide array of minimodels and the full ecosystem model PCLake) make the aquatic food web an ideal system to test the hypotheses generated from these fundamental questions using both experiments and model analyses. Analysis of an established mini-model on seasonal zooplankton-algae interactions indicate that under extreme climate warming the water flea Daphnia runs the risk of missing the peak in algal food. Given the key role the herbivore Daphnia plays in aquatic food webs, such decoupling of zooplankton-algae interactions may result in the absence of one of the most distinctive events in the seasonal cycle of lake plankton communities, the spring clear water phase. In our proposed research plan, we will focus on the impact of climate warming on two ?critical response windows? in the phenology of species in temperate pelagic food webs, i.e. spring and summer. We will use a tritrophic pelagic food web to test several hypotheses concerning the impact of climate warming on their phenological coupling. Our experimental model system will consist of highly and lowly nutritious algae as primary producers, the zooplankter Daphnia as a key-herbivore, and small planktivorous fish as predominant predators. Experiments will be carried out in laboratory systems of different scales, ranging from mesoscale laboratory ecosystems (1000-L Limnotrons), to microcosms and small-scale flow through systems. We will complement these experiments with model analyses of the full ecosystem model for shallow lakes- PCLake. In addition, the established mini-models on algae-zooplankton interactions will be extended to include planktivorous fish-zooplankton interactions. As we will be working with realistic climate scenarios of the KNMI, the outcome of our studies will be useful for decision makers, as it contributes to assessing the environmental impact of projected climate change in aquatic systems. The anticipated results of this study will be well-founded predictions on the risk of cascading effects due to climate change and the potential for adaptation to restore food web links.
Netherlands