Earthworms from a Sand Dune Ecosystem

Emma Chamberlain and Kevin R. Butt 

School of Natural Resources, University of Central Lancashire, Preston, PR1 2HE, UK

An investigation of the spatial distribution of earthworms across a dune ecotone along the Sefton Coast, Lancashire, NW England, was undertaken to examine species distribution and abundance with respect to coastal accretion, soil physico-chemical conditions and management. Replicated 0.1 m² quadrats were taken every 50 m along two transects crossing successional areas from beach strand line to established soils (700 m). In addition, more detailed samples were taken every 10 m where earthworms were first encountered on one transect. A translocation of Aporrectodea longa was undertaken in the field to assess the ability of this species to live in soils with a high sand content. In addition a laboratory experiment was set up to test the growth, maturation and survival of this species in soils with a range of sand contents. Treatments used juvenile A. longa kept in soils produced by mixing collected sand from the Sefton coast with commercially available loam in combinations of 100, 75, 50, 25 and 0 percent sand.

Within the system examined, a total of 9 earthworm species were encountered. As expected, no earthworms were found within the yellow dunes near the shore, where organic matter (OM) content was negligible (<1%). Earthworms, represented by Dendrobaena octaedra and Lumbricus rubellus, were first located 300 m from the strand line in grey dunes with an OM content of 3.9 %. Within a dune slack (OM content 11 %) at 350 m, the green morph of Allolobophora chlorotica was found as was Lumbricus castaneus. Anthropic influences (car park construction) along one transect revealed Aporrectodea longa, A. caliginosa and Lumbricus terrestris at 400 m. Within pine trees planted as a shelter belt (700 m), both L. castaneus and L. rubellus were present. Neither translocated A. longa nor any signs of them were found after 6 months (autumn), but casts of A. longa did extend into the dunes from the parking area half way (25 m) towards the translocation point. Laboratory growth of A. longa demonstrated no significant increases in growth (2g to 2.75g) in 0, 25 and 50 % sand, to 16 weeks, but higher sand content produced significantly lower biomasses (p<0.05), less maturation and zero cocoon production.

Earthworm distribution was influenced by dune successional stage. Soil OM content, moisture content and human activity also had a bearing on earthworm number and species present. Laboratory findings of A. longa tolerance to sand content of soil were not supported by field observations and experiments.