Predictable feedbacks between warming, community structure and ecosystem functioning: a combined experimental and theoretical approach

Global warming is creating an extensively modified world. An ever increasing number of animals and plants are having to migrate to keep up with changes to their habitats, alterations in the timing of key seasonal events e.g., breeding season and local extinction. New evidence suggests that the underlying structure of marine and freshwater ecosystems is changing, and potentially most alarmingly, key global cycles which control climate have been altered. However, how the processes that sustain life in these ecosystems will respond to future global warming are unknown. An understanding of these processes is crucial if we are to be able to predict how ecosystems will respond to warming in the future and furthermore implement management strategies to protect the fundamentals of these ecosystems. This represents a significant challenge for scientists because ecosystems are inherently complex and their response to environmental change can often be idiosyncratic. We will adopt a powerful, multi-disciplined approach to this challenge. We will develop mathematical models that capture the structure of aquatic communities and the cycling of key elements and their relationships with temperature. At the same time we will continue a large scale experiment which has been running since 2006 which involves the warming of a series of replicated artificial ponds to simulate the effects of future global warming. The combination of these approaches will allow us to determine the biological mechanisms that will govern the response of aquatic ecosystems to the elevated temperatures predicted for the end of the century. The general mathematical models that will come from this research will provide scientists will crucial predictive tools for the study of global warming on ecosystems. While our experimental manipulation will allow us to test or model predictions and provide direct evidence of the effects of warming on whole aquatic ecosystems. Ecologists typically break ecosystems down into structural (animals and plants) and functional (photosynthesis, decomposition) components. The structural component generally focuses on the numbers, diversity and interactions between plants and animals. While the functional component typically analyses the cycling of key biological elements. The study of these components in isolation has hindered progress in understanding how ecosystems will respond to environmental change e.g. warming. Using the described experimental system we have already shown that warming changes the size structure of aquatic ecosystems, reduces their ability to absorb carbon dioxide, and increases the amount of methane they release. Furthermore, our results have hinted towards the possible interactions between structural and functional components. Determining the 'links' between the structure and function of aquatic ecosystems and how they will respond to warming will represent a significant advance in the science of ecology and understanding the effects of future global warming. We will combine two theories in ecology that are both well established but not yet fully integrated: the Metabolic Theory of Ecology (MTE), which looks at the changes in energy within an ecosystem; and the Ecological Stoichiometric Theory (EST), which looks at the balance or 'harmony' of nutrients within an ecosystem. Using these theories, we hypothesise that warming will alter the balance of essential elements in plants which will go onto to affect the structure of the reliant animal food web. Further, we predict imbalances in the nutrient cycles (nitrogen and phosphorous) which maintain the integrity of these ecosystems. We will test our ideas by making high resolution seasonal measurements of nutrients and the size distribution of plants and animals, along with rates of photosynthesis and decomposition in our experimental systems.