Metallothionein concentrations in natural populations of gudgeon (Gobio gobio): relationship with metal concentrations in tissues and environment.

A field monitoring campaign investigating the suitability of (Cd, Zn)-metallothionein concentrations (MTs) in different tissues of the gudgeon as a biomarker for metal contamination in the aquatic environment was conducted. Gudgeons were captured at 10 sampling sites on a river system in Flanders (Belgium). Nine sampling sites were situated along a Cd and Zn gradient with a nearby tributary as the reference site. Cadmium, Cu, and Zn concentrations were measured in the water and sediments. Concentrations of (Cd, Zn)-MT were measured in different organs (gill, liver, kidney) of gudgeon (Gobio gobio). The hepatic and gill Cd and Zn concentrations, as well as the hepatic (Cd, Zn)-MT concentrations, reflected the polymetallic contamination gradient. Moreover, the hepatic Cd and Zn concentrations could describe 72% of the variance in the (Cd, Zn)-MT concentrations in the liver, illustrating the possible use of hepatic MT concentrations as a biomarker for environmental metal contamination. In this way a dose-response relationship could be established under natural conditions. However, a poor negative relation between the Cd and Zn concentrations in the gills and the corresponding (Cd, Zn)-MT concentrations was found. No relation between the Cd and Zn concentrations in the kidney tissue and the corresponding (Cd, Zn)-MT concentrations could be established. These results clearly illustrate the tissue-specificity of the MT concentrations, thus for monitoring purposes MT concentrations should be measured in liver tissues, rather than in kidney or gill tissues.