Seasonal variation in the abundance, biomass and biodiversity of earthworms in soils contaminated with metal emissions from a primary smelting works

Abstract

Summary 0[ Earthworms "Annelida] Oligochaeta# were sampled on four occasions "spring\ summer\ autumn and winter# at 03 sites along two transects from a primary lead: zinc:cadmium smelting works at Avonmouth\ UK[ 1[ Total abundance and biomass of earthworms decreased with proximity to the smelter[ No worms were collected from the two sites closest to the factory "³9=5 km# and catches were signi_cantly lower than controls at a further _ve sites "³2 km#[ 2[ Seasonal composition of sampled communities di}ered only for summer with lower numbers of individuals and species collected at all sites[ Reduced catches in the summer sample is a response to drought[ 3[ Species richness was lowest at sites close to the factory[ For example\ worms such as Aporrectodea caliginosa "Savigny# and Allolobophora chlorotica "Savigny# that were dominant at relatively clean sites further from the smelter are absent from the most contaminated soils[ 4[ Reduced species richness resulted in lower ShannonÐWeiner diversity and higher BergerÐParker dominance[ Multivariate cluster analysis for spring\ summer and win! ter indicated that sites could be split into three groups based upon relative species composition[ In autumn\ two clusters were identi_ed[ 5[ The absence of sensitive species from sites close to the smelting works supports the inclusion of earthworms as a key group in a terrestrial prediction and classi_cation scheme for quantifying the e}ects of pollutants on soil biodiversity[ However\ sam! pling should be carried out in spring or autumn to obtain an accurate picture of community structure[ Key!words] community monitoring\ metal pollution\ size classes\ species richness\ zinc[ Journal of Applied Ecology "0888# 25\ 062Ð072

Living in highly dynamic polluted river floodplains, do contaminants contribute to population and community effects?

“…In a study with a higher number of replicates (including other floodplains), however, the number of earthworm species significantly decreased with increasing copper and zinc levels, with only L. rubellus present at the highest contaminated floodplain sites . A similar finding was reported by Spurgeon and Hopkin (1999) in the surroundings of a smelter. Aquatic community effects have been assessed both in the field and in microcosms and experimental ponds.…”

“…Also effects on the composition of the population, segregated in cocoons, juveniles, subadults and adults, have not been reported in studies on floodplains, whereas in other environments populations consisted of more individuals in the younger development classes at sites with high levels of heavy metals compared to those with background levels (Spurgeon and Hopkin, 1999;Klok et al, 2006a). At these sites the average individual weight was also lower, and maturation delayed (Klok et al, 2006a).…”

“…Therefore Ma et al (2004) concluded that the negative correlation between metals and earthworms may equally well be explained by flooding. In less dynamic environments effects on biomass and density have been reported at lower heavy metal levels (cadmium 13.2 mg/kg; copper 74.8 mg/kg; zinc 710 mg/kg; pH 7.25) by Spurgeon and Hopkin (1999), see also (Bisessar, 1982;Bengtsson et al, 1983;Hunter et al, 1987).…”

High mitochondrial DNA sequence diversity in the parthenogenetic earthworm Dendrobaena octaedra

“…These results are somewhat surprising as metal contamination is known to have detrimental effects on earthworm population densities and biodiversity (Bengtsson et al, 1992;Spurgeon and Hopkin, 1999). However, due to decreasing emissions at least in our study localities, metal concentrations are lower in the litter layer, where D. octaedra is found, than deeper in the soil (Lukkari et al, 2004).…”

Heavy Metal Pollution as a Biodiversity Threat

“…These differences were attributed to differences in calcium metabolism between earthworm species. Also, earthworm communities (L. terrestres, L. rubellus, L. castaneus, A. chlorotica, A. rosea, A. caliginosa, A. longa, E. tetraedra, M. minúscula, O. cyaneum) in a polluted site (Pb, Cd, Zn and Cu) were studied [25]. They found that the relative abundance and the Shannon-Weiner diversity index were lower on the nearest sites to the pollution source and higher in the farthest sites from the pollution source.…”