FIELD APPLICATION OF METALLOTHIONEIN AND STRESS PROTEIN BIOMARKERS INTHE SHORE CRAB (CARCINUS-MAENAS) EXPOSED TO TRACE-METALS

A field study was conducted to assess the potential use of metallothio nein (MT) and stress proteins (stress-70) as biomarkers of trace metal exposure and adverse effects. Shore crabs (Carcinus maenas) were coll ected from five sites: three located in the metal-contaminated Fal Est uary 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 measure ment of SH content, or an indirect method in which MT concentrations w ere 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 b lotting procedure. Midgut gland copper concentrations were elevated (c ompared to values in controls) in crabs from the Fal Estuary. No diffe rences in midgut gland zinc concentrations were evident in crabs colle cted from the five sites. Copper MT concentrations in midgut gland wer e 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 o nly when the ratio of cytosolic zinc to copper was examined. Both copp er and zinc concentrations in gill tissue reflected the trends in meta l contamination in the underlying sediment. Similarly, both copper and zinc MT concentrations measured in gills reflected the copper and zin c exposure gradients. In contrast, stress-70 levels in gills did not a ppear to correlate with the degree of trace metal exposure. The findin gs are discussed with regard to the interpretation and potential use o f biomarker responses as tools for use in ecological impact assessment s.