Whole lake responses to species invasion mediated by climate change
Lakes face multiple stresses including nutrient enrichment, climate change and invasion of non-indigenous species. This latter stress can have a major impact on biodiversity and the functioning of ecosystems worldwide and its effects are increasing as human activity enhances rates of dispersal and climate change opens new niches at higher latitudes.
Windermere is England's largest natural lake and one of the best studied in the world with detailed records extending back over 70 years. A marked deterioration in water quality has been observed in the last 10 to 15 years despite continued removal of a key nutrient, phosphorus, at the two adjacent wastewater treatment works. For example in recent years, summer algal blooms have increased, concentrations of oxygen at depth have decreased and the numbers of the rare and protected fish, the Arctic charr, have declined dramatically. These changes have coincided with the population expansion of a lower-latitude, non-indigenous species, the roach.
In this project we will use a range of methods to test the hypotheses that the roach expansion is a result of the documented warmer waters in Windermere and that the expansion has triggered a 'trophic cascade' leading to greater predation on the zooplankton, which in turn has reduced the control on algal abundance by their grazer. We will also test whether the decline in Arctic charr numbers results from competition with roach, since both feed on the zooplankton and will also consider trophic-interactions with the top-predator in the lake, the pike.
The results will be highly relevant to the management of lakes since, if our hypotheses are correct, nutrient removal will need to be even more stringent in the face of climate change and disruption of food-chains caused by invasion of non-indigenous species.
The project is funded by the Natural Environment Research Council’s Ecology & Hydrology Funding Initiative and the work will be carried out by staff at the Centre for Ecology & Hydrology’s Lake Ecosystem Group (http://www.ceh.ac.uk/sci_programmes/Water/Lake%20Ecosystems/LakeEcosystems.html) and the School of Biological & Chemical Sciences (http://www.sbcs.qmul.ac.uk/) at Queen Mary University of London. Two project partners, the Freshwater Biological Association (http://www.fba.org.uk/) who instigated the long-term monitoring and hold some of the archived samples, and Dr Chris Harrod at Queen’s University Belfast (http://www.qub.ac.uk/schools/SchoolofBiologicalSciences/Staff/DrCHarrod/), will assist with the project.
