Aquatic and terrestrial invertebrate community responses to drying in chalk streams

Tim Sykes,Judy England,Kieran Gething,George Bunting,Jon Webb,Rachel Stubbington

doi:10.1111/wej.12621

Tim Sykes, Judy England + Show 4 more

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https://doi.org/10.1111/wej.12621

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Abstract

AbstractTemporary streams are dynamic ecosystems that shift between wet and dry states and include the ‘winterbourne’ chalk streams of south England. Our understanding of temporary stream biodiversity is biased, with most research to date exploring aquatic invertebrate communities in benthic sediments during flowing phases. We surveyed the invertebrate communities of the Candover Brook chalk stream, comparing aquatic (benthic, hyporheic) and terrestrial communities in reaches with different flow permanence regimes. We used kick and Bou–Rouch sampling methods to collect aquatic invertebrates, and compared the terrestrial communities characterised by pitfall traps and ground searches and in different seasons. Although aquatic taxa richness was lower in temporary compared to perennial reaches, the total biodiversity of temporary stream channels was enhanced by contributions from both aquatic and terrestrial species, including several of conservation interest. We recommend that both aquatic and terrestrial communities should be considered in research and monitoring to characterise the biodiversity and ecological quality of temporary streams.

Highlights

Temporary rivers are those in which flow sometimes ceases, and many lose most or all surface water (Leigh et al, 2016)
Regulatory monitoring done to assess Water Framework Directive (WFD) status at the downstream perennial site (Fig. 1) indicates that physico-chemical and hydromorphological quality are good to high, whereas the WFD macrophyte and phytobenthos quality element is of moderate quality, which is attributed to groundwater abstraction and drought (Environment Agency, 2019)
Many sites were typical of chalk streams in south England: wide, shallow channels with substrates dominated by gravel to cobble-sized clasts, superficial bed siltation affected three aquatic sampling sites (Fig. S1c–e)

Summary

Introduction

Temporary rivers are those in which flow sometimes ceases, and many lose most or all surface water (Leigh et al, 2016). Temporary streams are aquatic–terrestrial ecosystems in which profound differences in habitat availability during wet and dry phases influence biodiversity (Stubbington et al, 2017). The total biodiversity of temporary stream channels reflects contributions from both terrestrial and aquatic communities (Corti and Datry, 2016), and ecological assessments of temporary streams should characterise both communities. Such assessments are needed in temporary streams protected by legislation, including the ‘winterbourne’ reaches of chalk streams in south England, United Kingdom (JNCC, 2019). Methods enabling effective temporary stream assessments still require development (Stubbington et al, 2018)

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