Adaptation to Pollution by Mine Site Worms

Mechanistic bases of metal and metalloid tolerance of the soil fauna inhabiting metalliferous soils: linking phenotypic characteristics to the genome (and epigenome)

The soil ecotoxicology group at CEH at Wallingford is involved in collaborative studies (with Cardiff and Edinburgh Universities and Imperial College) to establish the mechanisms by which invertebrate (earthworm) populations adapt to the presence of high concentrations of trace metals at polluted sites. It is already well known that in temperate soils, annelids are one of the key groups involved in maintaining soil function. This is because of their roles in soil mixing and organic fragmentation, which makes them vital contributors to carbon, nutrient and trace element cycling (n.b. a popular science book has recently listed earthworms as the most important taxa of all in the development of our biosphere: see What on Earth Evolved, by Christopher Lloyd).

The Draft EU Soil Framework Directive explicitly considers potential threats to soil sustainability, with key biodiversity seen as an important focus for protection and climate influences and pollution seen as major threats. Because of importance and vulnerability of soil fauna to environmental threats, policy-makers are becoming increasingly aware of the need to understand the tolerance limits of soil fauna and their ability to adapt to change.

By studying sensitivity to trace metal stress and adaptive responses at long-term polluted sites, the project team are providing key data in this area. To link phenotype to genotype, detailed approach to both phenotypic characterisation (e.g. using 1H-NMR and high resolution mass spectrometry base metabolomics and high throughput transcriptomics) and genotyping (e.g. using COII based “bar coding” and restriction-site associated DNA analysis) are being applied. Applying these methods to both field-collected individuals and F0, F1 and F2 worms from designed pedigree study is allowing the team robustly to link tolerant traits to underlying changes in the genome.

Distribution of main COII haplotype lineages of field-collected earthworms collected from a range of metalliferous (and industrial organic chemical) polluted sites, matching control sites and Environmental Change Network reference sites.