Effect of depuration on microbial load of mangrove oyster (Crassostrea gasar) from a polluted creek in Rivers State, Nigeria

Abstract

The efficiency of depuration in the removal of microbial load in mangrove oyster (Crassostrea gasar) from a polluted creek in Rivers State, Nigeria using a flow-through method with high loading density was evaluated in this study. Depuration experiments were conducted with cartridge-filtered and UV-light using seawater in segregated plastic tanks at a salinity of 30 ‰, pH of 8.0 and temperature of 29.0 °C. The oysters in segregated tanks were taken at intervals of 24, 48, 72 and 96 hours of depuration and analyzed for microbial load (total hetrotrophic bacteria, total fungi counts, hydrocarbon utilizing bacteria and fungi and feacal coliform counts). Results from the two-way ANOVA showed that time, method and season had significant effect on the microbial counts. At different locations, there was significant difference (P<0.05) at different time intervals of depuration for both seasons. The control for all the locations had the highest counts for depuration at both seasons. Notably between 24 and 48 hours of depuration for both seasons, no significant difference (P>0.05) on total fungi counts, feacal coliforms and hetrotrophic bacteria was recorded. This study depuration method at the different time interval is recommended.

Keywords: Cleansing, contaminants, poisoning, food safety, Crassostrea gasar