Abstract
The accumulation of cadmium, copper and zinc and the induction of metallothioneins (MT) in liver of three freshwater fish species was studied. Gudgeon (Gobio gobio), roach (Rutilus rutilus) and perch (Perca fluviatilis) were captured at 6 sampling sites along a cadmium and zinc gradient and one reference site in a tributary of the Scheldt River in Flanders (Belgium).At each site up to 10 individuals per species were collected and analyzed on their general condition factor (K), hepatosomatic index (HSI) and gonadosomatic index (GSI). From each individual fish the liver was dissected and analyzed on Cd, Cu and Zn and MT-content. Although not all species were present at each site, hepatic Cd and Zn levels generally followed the pollution gradient and highest levels were measured in perch, followed by roach and gudgeon. Nevertheless also an effect of site was observed on this order. MT-levels appeared to be the highest in gudgeon although differences with the other species were not very pronounced and depended on the site. Significant relationships were found between hepatic zinc accumulation and MT levels. For each species the ratio MTtheoretical/ MTmeasured was calculated, which gives an indication of the relative capacity to induce MTs and thus immobilize the metals. Perch had the lowest capacity in inducing MTs (highest ratio). Relationships between hepatic metal levels and fish condition indices were absent or very weak.
Highlights
Despite a decrease in discharges of metals in most WestEuropean countries, including Belgium, several water courses are still historically contaminated with metals [1,2,3], potentially affecting different stages of the aquatic food chain
Total Cd and Zn levels clearly followed a gradient between site 2 and site 7
Cd and Zn levels exceeded quality standards at all sites, including site 1 upstream of the pollution source but except the reference site, Table 2 gives the results of the sediment and pore water analysis
Summary
Despite a decrease in discharges of metals in most WestEuropean countries, including Belgium, several water courses are still historically contaminated with metals [1,2,3], potentially affecting different stages of the aquatic food chain. Fish are interesting species for the evaluation of biological effects of metal pollution under natural circumstances because they might accumulate metals from water, sediment as well as food [4,5,6]. Fish species that differ in their feeding strategies and/or detoxification capacities might accumulate metals to a different extent [21,22,23,24]. Bottom dwelling species such as the gudgeon (Gobio gobio) will be exposed to water, sediment and food whereas pelagic species are mainly exposed via water and food
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