Environmental Futures

Climate change is occurring. All evidence to date suggests a rise in global temperature and elevated levels of atmospheric CO2. Therefore it is important to understand how the relationship between biodiversity and ecosystem process may change under different temperature-CO2 ranges (present and future scenarios). Recent research has focussed on finding out how ecosystem processes alter with decreasing biodiversity. Experiments have been performed in the laboratory which mimic biodiversity loss by assembling different numbers of species in aquaria and measuring the effect each species mixture has on ecosystem processes under controlled environmental conditions. By comparing aquaria with many species to those containing fewer species, the impact of species loss from a system can be determined. This project will adopt the same approach for different environmental regimes (CO2 and temperature) using small animals that live in the sediments of estuaries. These organisms are particularly important because they churn up sediments from the bottom of the ocean – a process referred to as bioturbation - which results in nutrients being returned to the water column where they are vital for the growth of phytoplankton and other species in the food web. We will record the levels of nutrients that are released into the water from the sediment as a result of bioturbation. We will measure the extent of bioturbation using brightly coloured sediment particles called luminophores. As the animals bioturbate they will move some of these particles deeper into the sediment. These can be recovered at the end of the experiment by taking sediment from different depths of the aquarium and counting the number of luminophores. From these data we can define the rate, magnitude and way in which different species mixtures move sediments and what impact this has on nutrient cycling.

Collection of the animals	The Environment Chamber
Prepared Mesocosms (lights off)	Prepared Mesocosms (lights on) Yellow luminophores visible

By matching the nutrient and bioturbation data with the number of species and environmental conditions, we can predict the likely consequences of biodiversity loss for future climate scenarios. A problem with adopting this approach is that there is an error associated with the values obtained, which means there is a level of uncertainty. When we make predictions from these results it is important to take this uncertainty into account. This project will use the uncertainty of the results to predict which temperature-CO2 regime has the greatest confidence. Thus this project will establish the relationship between biodiversity and ecosystem processes in estuarine sediment fauna under a range of different future environmental scenarios. It will also establish those combinations of temperature-CO2 for which we are most uncertain about the predictions, highlighting where our knowledge is weakest and for which scenarios we are most unlikely to be able to predict what is going to happen. The outcomes of such research will therefore have immediate relevance for assessing and managing change in marine systems, and provide important information for policy makers.