The woodlouse Porcellio scaber as a ‘biological indicator’ of zinc, cadmium, lead and copper pollution

Abstract

The amounts of zinc, cadmium, lead and copper were determined in the hepatopancreas and whole body of the woodlouse Porcellio scaber (Crustacea, Isopoda) and soil and leaf litter collected from 89 sites in the counties of Avon and Somerset, south-west England. Maps were drawn to compare the regional distribution of concentrations of metals in the samples. The main source of zinc, cadmium, lead and copper pollution was centred on Avonmouth to the north-west of Bristol, the site of a primary zinc, lead and cadmium smelting works. Concentrations of all four metals in the hepatopancreas, whole woodlice, soil and leaf litter were above background levels over a large area on all maps which, in the case of cadmium in the hepatopancreas, extended for 25 km to the east of the smelting works. The correlation coefficients between the concentrations of each metal in woodlice and soil, and between woodlice and leaf litter, were positive and statistically significant ( P < 0·001) in all cases. At individual sites, however, particularly those associated with disused mining areas, rubbish tips or busy roads, the concentrations of zinc, cadmium, lead and copper in woodlice could not have been predicted accurately from the levels of metals in leaf litter or soil due to the large scatter of data points along the lines of ‘best fit’. Future exercises in pollution monitoring should include analysis of at least one representative of the primary consumers of vegetation to enable the ‘availability’ of metals to the fauna to be reliably assessed. Porcellio scaber is probably the ideal ‘indicator species’ in the UK because it has a strong affinity for zinc, cadmium, lead and copper, is large enough to provide sufficient tissue for analysis, and is common in a wide range of rural and urban habitats.