The Applied Phycology and Biochemistry of Managed Reservoirs in the East of England

Climate Change is one of the greatest threats to drinking water supplies around the world. Managing these vulnerable systems is complex, requiring mitigation and adaptation strategies that can combat multiple stressors (i.e. drought and eutrophication). This is especially true for reservoirs in the East of England, which are facing climate extremes such as heat and drought to a greater extent than other parts of the UK. To understand how these and other climate stressors are currently affecting drinking water reservoirs and their vulnerability under future climate change, this thesis performs whole-system ecological studies that investigate biodiversity, eutrophication, and internal sediment dynamics driving the succession of harmful algal blooms. These studies were designed to provide a baseline assessment of climate stressors in the East of England, identify potential risk, and address management strategies and challenges faced by the UK water industry. The outcome of these investigations identified toxin-producing cyanobacteria dominated throughout the year resulting in lower biodiversity and increased risk to recreational users and treatment practices. Furthermore, it was found internal loading is feeding these blooms providing a steady supply of the limiting nutrient, phosphorus. While a management bund wall is currently in place to trap phosphorus in the reservoir inlet, it was found to be inefficient, in turn allowing nutrients to flow down the reservoir gradient. In order to address these management concerns and prepare UK reservoirs for the threats of climate change, a multi-disciplinary approach that address multiple stressors will be necessary to allow drinking water reservoirs to remain thriving ecosystems under a changing climate.