The effect of the heavy metals lead (Pb2+) and zinc (Zn2+) on

Abstract

This investigation explored the effect of the heavy metals Pb (Pb²⁺) and Zn (Zn²⁺) individually and in combination (i.e. three metal solutions) on both the brood and larval development of the burrowing crustacean, Callianassa kraussi. Egg and larval mortalities at factorial (4x7) combinations of salinity (20, 24, 30, 35 mg/l) and seven respective metal concentrations were examined. The results provided various statistically significant trends. Individual concentrations of Pb and Zn at various salinities impacted negatively upon the brood and larval development of Callianassa kraussi. Increasing the specific concentrations of both metals further demonstrated a negative influence, especially on brood development and to a lesser extent on larval development of Callianassa kraussi. Comparing the toxicity of the three concentrations of metals to Callianassa kraussi brood and larval development, it was found that individual Pb concentrations exhibited the least mortality (LC_{50 Pb-eggs-35ppm} = 1.580 mg/l ^-1 whilst individual Zn concentrations displayed considerably higher mortality (LC50 Zn-eggs-35ppm =0.066 mg/l) but that the combination of Zn and Pb concentrations produced the highest mortality (LC_{50 Pb&Zn-eggs-35ppm} =0.036 mg•l ^-1). Varying salinities in permutation with varying metal concentrations exhibited a significant detrimental influence on the brood and larval development of Callianassa kraussi, notably at the lowest salinities in combination with the highest metal concentrations.

Key words: heavy metals, Pb, Zn, mortality, toxicity, brood and egg development, estuarine environment, Callianassa kraussi, sediment, sand prawn

Water SA Vol.31(1) 2005: 107-116