The distribution and diversity of stygobites in Great Britain: an analysis to inform groundwater management

The invertebrate ecology of aquifers has received little attention. This paper presents an analysis of stygobite (obligate groundwater) fauna from Great Britain (England, Scotland and Wales). A review is presented of the ecosystem functions performed by these creatures, their potential vulnerability to anthropogenic stress including water pollution and abstraction, and research priorities that will allow current groundwater management challenges to be addressed. In Great Britain stygobites are largely restricted to England and Wales. The assemblage comprises crustacean invertebrates (nine species) and is very limited in comparison with continental Europe. There is only one known endemic species in Great Britain, Niphargus glenniei(a further two endemic crustaceans are also known from the Republic of Ireland). Additionally, a suite of water mites (18 species) is found in the interstitial habitats of running waters in Great Britain. Niphargus glenniei was recently added to the United Kingdom Biodiversity Action Plan priority species list. Stygobites, which are found only in subterranean environments such as aquifers, springs and the hyporheic zone of rivers, make a unique contribution to biodiversity. Our analysis suggests that both the glacial legacy and the nature of the (hydro)geology are major controls on the distribution of these assemblages. Most records were from locations to the south of the southern limit of the ice sheet during the Devensian glaciation. The majority of stygobites were also found in calcareous strata, although high calcium carbonate concentrations may not be important to all crustacean stygobites. Records were dominated by samples from the Chalk, the Carboniferous and Jurassic Limestone aquifers, and from other strongly fissured strata. Strata with extensive fissuring may provide the greatest availability of habitat for groundwater fauna. Our investigation revealed that there are relatively few sites from which stygobites have been recorded in Great Britain (513 sites at which records of stygobites have been confirmed). Research is needed to improve our understanding of the basic biology and ecology of groundwater-dwelling fauna and the range of ecosystem services that they provide. An understanding of the response of groundwater fauna to stress caused by pollution and abstraction pressures is also needed, together with the development of appropriate monitoring, assessment and protection criteria. The Water Framework Directive requires a more integrated assessment of the chemical, water resources and ecological conditions of water bodies. Stygobites have the potential to act as sentinels in the subterranean environment and help inform us about the condition and ecological health of this little-considered habitat.