Species-specific heavy metal accumulation patterns of earthworms on a floodplain in Japan

We identified all earthworm species found on a floodplain contaminated by heavy metals (Cu, Zn, Cd, and Pb) from an old mine in central Japan and compared their abundance, biomass, and heavy metal concentrations in tissue. There were six species belonging to three families: Megascolecidae, Moniligastridae, and Lumbricidae. Earthworm community structure seemed to be influenced mostly by soil properties, especially pH and clay fraction. Despite the same endogeic characteristics, species-specific patterns of heavy metal accumulation were observed: species in Megascolecidae and Lumbricidae had relatively lower concentrations compared to those in Moniligastridae. Within Moniligastridae, Drawida sp. accumulated Cu and Pb markedly higher than Drawida japonica. Based on heavy metal concentrations in extracts of CaCl2 and diethylenetriaminepentaacetic acid, the aging caused remarkably low concentrations in pore water, indicating low availability by dermal uptake. Therefore the different patterns of heavy metal accumulation among species would partly result from species-specific gut process.