BIOACCUMULATION OF MANGANESE IN SELECTED TISSUES OF THE FRESH-WATER CRAB, POTAMONAUTES WARRENI (CALMAN), FROM INDUSTRIAL AND MINE-POLLUTED FRESH-WATER ECOSYSTEMS

Manganese concentrations in water and sediments of the Bronkhorstsprui t River, Nooitgedacht Dam and especially in the Natalspruit River, did not fall within stated limits for the protection of aquatic life. Tis sue manganese concentrations in Potamonautes warreni from the Natalspr uit River were generally higher than those in the tissues of crabs fro m the other two aquatic ecosystems. The highest mean manganese tissue concentration in crabs from the three systems was detected in the cara pace (587 +/- 445 mu g g(-1) wet weight). It appears that the carapace in these animals acts as a sink in which manganese can be deposited, thus also playing an important role in the detoxification of manganese in these crustaceans. No seasonal or sex-related variation was detect ed. Body size of the crabs, however, seems to be an important influenc ing factor in manganese bioaccumulation. A significant increase in car apace manganese concentrations was detected with an increase in body s ize. However, muscle manganese concentrations were higher in the small er groups. The concentration factors (BF) calculated for the different tissues with respect to the water were highest in the carapace and ra nged from 280.9 to 742.8. The BF with respect to the sediment was comp aratively low for all the tissues (0.1 to 0.7). As the manganese conce ntration in the tissues reflects to some extent the degree of manganes e contamination of the surrounding aquatic environment, it appears tha t P. warreni may be useful as a potential biomonitor of manganese poll ution.