Field application of metallothionein and stress protein biomarkers in the shore crab ( Carcinus maenas) exposed to trace metals

Abstract

A field study was conducted to assess the potential use of metallothionein (MT) and stress proteins (stress-70) as biomarkers of trace metal exposure and adverse effects. Shore crabs ( Carcinus maenas) were collected from five sites: three located in the metal-contaminated Fal Estuary and two control sites located in estuaries along the Devon coast (Southwest England). MT concentrations were determined using either a direct method in which MT was quantified by spectrophotometric measurement of SH content, or an indirect method in which MT concentrations were estimated by measuring copper and zinc bound to partially purified MT. The two techniques yielded similar results. Stress protein levels (stress-70) were determined in crab gills using an improved western blotting procedure. Midgut gland copper concentrations were elevated (compared to values in controls) in crabs from the Fal Estuary. No differences in midgut gland zinc concentrations were evident in crabs collected from the five sites. Copper MT concentrations in midgut gland were elevated in crabs from the metal-contaminated Fal Estuary (compared to concentrations in crabs from other sites). However, differences in metal contamination among sites within the Fal Estuary were revealed only when the ratio of cytosolic zinc to copper was examined. Both copper and zinc concentrations in gill tissue reflected the trends in metal contamination in the underlying sediment. Similarly, both copper and zinc MT concentrations measured in gills reflected the copper and zinc exposure gradients. In contrast, stress-70 levels in gills did not appear to correlate with the degree of trace metal exposure. The findings are discussed with regard to the interpretation and potential use of biomarker responses as tools for use in ecological impact assessments.