Fragility of stream ecosystem functioning in response to drought: an experimental test

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Climate change and human activities are expected to change the quantity of water entering rivers and streams, with potentially dramatic impacts on animals and plants resident in these ecosystems. In many regions, climate change is expected to reduce rainfall and bring about drought conditions, and water abstraction and river diversions may also reduce flows in rivers and streams. To date, relatively little work has been done to determine the effect of hydrologic droughts on aquatic biodiversity, and less is known about impacts on important processes, such as decomposition and nutrient cycling, that affect water quality and productivity of aquatic life.Our study will use novel experiments to understand the ecological effects of hydrologic droughts in streams, with a view to predicting future change. We will use a series of artificial stream channels to directly manipulate flows, thereby simulating drought episodes, and measure the responses of flora and fauna, and a series of processes that reflect the ecological health of the ecosystem. We will establish a series of experimental drought treatments which differ in the extent of flow reduction, from unaltered reference conditions to extreme low flows that cause habitat loss. We will also examine how the physical nature of the stream bed affects the extent to which animals and plants can withstand periods of drought, and how quickly these communities recover from these events. With a project student, we will investigate how water abstraction, a leading anthropogenic cause of stream drought, affects biodiversity and functioning across a suite of lowland streams in south west England. Together, the results will give valuable insights into the ways in which the environment responds to change brought about through human activities and the likely effects of climate change.