Eutrophication of heathland ponds at a site in Southern England: Causes and effects, with particular reference to the Amphibia

Abstract

Chemical and biological features of bog pools at a heathland site in south-east England were investigated. The heath is one of the largest remaining in Britain, and the only locality where all 12 species of native herpetofauna coexist. The ponds showed considerable variation with respect to water chemistry, and several ion sources causing eutrophication of some of the pools were identified. Species richness and abundance were greater in the eutrophicated ponds, which generally had pHs of 5·0–6·5 and calcium concentrations of 4–10 mg litre −1, than in the purely rain-fed bog pools with pHs of 3·8–4·3 and calcium concentrations of 1–5 mg litre −1. Palmate newts Triturus helveticus occurred in all pond types, but were rarest in the purely rain-fed ones; the other five amphibians were confined to eutrophicated pools, with the rare natterjack Bufo calamita breeding only in ponds enriched by calcium-rich solid debris (limestone or concrete fragments). The significance of these findings with regard to recent natterjack declines on heathland is discussed.