Abstract

The effect of heavy metals (Pb, Ni and Zn) on the growth rate, number of generation, generation time and bioaccumulation potential of Saccharomyces-ESY₂ andCandida-ESY₁₃ isolated from the epipellic sediment of Qua Iboe mangrove ecosystem was evaluated. The investigation was conducted over a period of 90 days in laboratory microcosms bearing epipellic sediment simulated with 1642.00 mgkg^-1of Zn, 208.00 mgkg^-1 of Pb and 522.60 mgkg^-1 of Ni.  The growth attribute of yeasts were determined forth nightly, using the population dynamics of the inocula as an index of response to metal pollution and bioaccumulation capability.  Results revealed that Ni and Zn increased the generation time of Candida-ESY₁₃ andSaccharomyces-ESY₂ respectively, resulting in a reduced number of generations and decrease in growth rate. Both yeasts exhibited a high Pb accumulating capability.  However, Candida-ESY₁₃ with a bioconcentration factor (BCF) of 0.299 accumulated more Pb (41.87 mgg^-1) than Saccharomyces-ESY₂ with a BCF of 0.296.  These findings have demonstrated that yeasts could tolerate and detoxify metals especially Pb in mangrove ecosystem and could be adapted for the detoxification of metals-impacted environments. However, the ability of these isolates to bioaccumulate this metal raises the question of biomagnifications in the food chain within a tropical mangrove ecosystem.

Key words:     Heavy metals, bioaccumulation, growth rate, sediment.