Metallothionein and stress protein levels in shore crabs (Carcinus maenas) along a trace metal gradient in the Fal estuary (UK)

A field study was conducted to assess the potential use of metallothionein (MT) and stress proteins as biomarkers of trace metal exposure. Shore crabs (Carcinus maenas) were collected from five sites: three located in the metal-contaminated Fal estuary (Southwest England) and two control sites located on the south coast of England. Two methods for determining MT levels in crab midgut gland were compared. A direct method in which MT was quantified by spectrophotometric measurement of SH content, and an indirect method in which the metal content (Cu and Zn) of partially purified MT was measured. Stress protein levels (stress-70) were quantified in crab gills using an improved western blotting technique. Elevated Cu and Cd concentrations compared to values in control crabs were found in the midgut glands of crabs from the Fal estuary. No significant variation was seen in Zn concentrations among the five sites. The two techniques used for MT analysis yielded similar results. Metallothionein concentrations were slightly higher in crabs from Restronguet Creek (the most metal-contaminated site) than in crabs from the other four sites, however this difference was not significant (p > 0.05). Stress protein levels did not reflect the metal gradient.