The occurrence of species of semi-aquatic Enchytraeidae (Oligochaeta) in Ireland

The Enchytraeidae are essentially terrestrial oligochaetes but many species have marked aquatic tendencies. Over two thirds of recorded Irish species were found in soils which were submerged or frequently flooded and 35% showed a distinct preference for these conditions. Relatively few species were living in soils subject to drought. Red blood was present in 28 species, all but one from soils with more than 55% water. Cognettia sphagnetorum and C. glandulosa developed red blood in very wet conditions. In a survey of Irish wetlands, samples were taken from bog, heath, marsh, fen, margins of lakes and rivers, and saltmarsh. The influence of various environmental parameters was determined using ordination techniques. Magnesium and pH were found to be the most important factors. A high level of magnesium distinguished coastal sites and pH 5.2 separated two clusters representing acid peat and marsh-fen-aquatic sites. Groups of indicator species characterized each of the three clusters. The ecological distribution of the indicator species is described, and their usefulness in classifying enchytraeid communities is discussed.