Ashwell Springs

Also within

Hertfordshire County

Condition (Natural England)

Habitats

Fast flowing river and stream

Geology & landscape

Rock Type: Chalk, Flint

Landscape processes: Glacial

Description

Area,0.3 hectares 0.6 ac Description Ashwell Springs are a series of freshwater springs arising from the foot of the Hertfordshire chalk and forming a source of the River Cam. The springs maintain an almost constant low water temperature throughout the year and flow into small pools with a chalk and flint gravel substratum. The springs and pools provide a habitat for a specialised cold water invertebrate community, with species of limited distribution in southern England and rare elsewhere in the county. The site is important for flatworms Platyhelminthes and amongst a range of more common species are found Crenobia alpina and Polycelis felina which represent "glacial relict" populations. Apart from the flatworms the most abundant invertebrate species are the shrimp Gammarus pulex, the small snail Potamopyrgus antipodarum, larvae of the caddis fly Trichoptera Drusus annulatus and chironomid midge larvae. The scarce caddis fly Apatania muliebris and Plectrocnemia geniculata occur, the latter usually a species of more north western distribution. The stonefly Plecoptera Nemurella pictetii is also present, a species typically found at stream sources. The pools are surrounded by species poor semi improved neutral grassland with mature ash Fraxinus excelsior, sycamore Acer pseudoplatanus and crack willow Salix fragilis, which are important in providing some shade for the pools. The site has educational value for the study of freshwater invertebrate communities.

Species mentioned

Plant communities