Taking streams to extremes: the effects of intensifying drought on running water ecosystems

Aspin, Thomas William Hallamore (2018). Taking streams to extremes: the effects of intensifying drought on running water ecosystems. University of Birmingham. Ph.D.

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Abstract

Climate change is subjecting many ecosystems to novel environmental conditions, including unprecedented extremes of drought that may push communities beyond critical ecological thresholds. Stream ecosystems may be particularly prone to catastrophic responses, due to a dependence on flowing water and continued exposure to other major threats to their ecological integrity. However, a lack of gradient-based approaches that explore beyond the limits of current disturbance regimes constrains our ability to predict the impacts of future droughts. This study used artificial channels (mesocosms) as perennial headwater stream analogues to simulate a broad gradient of drought intensity, ranging from flowing controls through fragmented pools to dewatered streambeds. Drought intensification pushed macroinvertebrate communities over structural and functional thresholds, and eroded complex food webs from the top down and the bottom up. Moreover, important exceptions to some established ‘rules’ in disturbance ecology emerged, with population collapses not biased to larger body sizes or higher trophic levels, and community responses not buffered by high functional redundancy. Benthic algae, macroinvertebrates and fish were all sensitive to relatively low intensity drought, suggesting that pool fragmentation, and not streambed drying, may be the most crucial stage of habitat loss for many running water ecosystems.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):