Biodiversity and ecosystem multifunctioning in rivers with modified flow regimes

"The regulation of river flows is one of the biggest stressors affecting river ecosystems across the world. In many westernised countries, major legislative efforts are therefore underpinning the development of new approaches to mitigate the impacts of river flow regulation. These approaches are based on optimising the management of river flows to maintain services to humans (e.g. water supply, hydropower) whilst protecting and/or rejuvenating the aquatic environment with water of adequate quantity and quality in space and time (i.e. environmental flows). In this context, a field of applied aquatic science has developed to generate the evidence base for identifying the best ways to manage the quantity, quality and patterns of environmental flows to sustain river ecosystems. The importance of the field is best exemplified by environmental flows being the number 1 option put forward recently as a way to halt and reverse global freshwater biodiversity declines.

Despite numerous recent research advances, there are still significant knowledge gaps that prevent a full understanding of how river flow dynamics drive ecological processes. For example, many studies have focused on individual groups of organisms (e.g. fish, invertebrates) but relatively few have factored in the important role of species interactions within and between these groups. Other biotic groups such as microbes and primary producers have received comparatively less attention. Similarly, less research has been undertaken on ecosystem functional processes such as organic matter and nutrient cycling. These research gaps offer the potential for multiple lines of enquiry, with the specific focus of the study being tailored to suit the skills and interests of the successful candidate.

The main aim of the PhD will be to increase understanding of how river management by regulation of flow regimes influence the structure (e.g. algae/macroinvertebrate biodiversity) and/or multifunctioning (e.g. production, decomposition, carbon cycling) of river ecosystems. The paucity of knowledge in this field is creating problems for river managers who are under pressure to identify and implement management measures (including environmental flows) as a way of improving river quality and in reaching biodiversity goals. Therefore, findings will have the potential to inform conservation targets for rivers through collaboration with businesses such as water companies and hydropower, and regulators such as environmental protection agencies. Specifically, the project will examine the extent to which environmental flows can be used to enhance river ecosystems, for example comparing 'control' sites (with either no regulation or sites with reservoirs but no variable environmental flows) against rivers in which reservoir operators are undertaking experiments through approaches such as reinstating seasonal flood flows, and/or introducing seasonally variable compensation releases.
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