Uptake and distribution of copper in the freshwater crab Potamonautes perlatus (Crustacea) in the Eerste River, South Africa

Abstract

The uptake and distribution of copper in the freshwater crab Potamonautes perlatus in the Eerste River, South Africa, were studied seasonally by comparing copper concentrations in crabs, water and sediment at two localities, one upstream and one downstream from the town of Stellenbosch. Copper concentrations were determined by atomic absorption spectrophotometry in whole crabs of different size classes as well as in various organs and tissues. The digestive gland contained the highest concentration of copper (mean 29.9, range 1.9–74.1 µg/g wet mass) irrespective of season, when compared to other tissues. No differences in total sediment (range 1.2–13.5 µg/g) or water (range 0.01–0.2 µg/g) copper concentrations were found between the two localities. An influence of anthropogenic activities between the localities on the sediment and water levels of copper could not be detected. Smaller crabs accumulated more copper per unit mass than larger crabs with all crabs having significantly higher concentrations than both water and sediment. Higher copper concentrations per unit mass in whole crabs from the downstream locality indicated that environmental conditions at this locality may have favoured uptake since total copper concentrations both in water and sediments did not differ significantly between the two localities. P. perlatus may therefore still be utilized in biomonitoring studies, not necessarily to reflect prevailing environmental concentrations, since copper can also be regulated, but to assess exposure to and bioavailibility of copper.