B.J.O. Efiuvwevwere^1,, L.O. Amadi²

Changes in the physico-chemical and bacteriological attributes of mangrove oysters subjected to depuration process on daily basis for 4days in brackish and tap water microcosms were determined. There were progressive decreases in the brackish water (BW) salinity (20.3-11.5ppt), dissolved oxygen (DO) (7.0-6.0mg/l) and conductivity (32.1-19.4x10³µS/cm) and increases in BOD (2.1-4.0mg/l) and turbidity (1.0-5.5NTU) whereas pH and temperature fluctuated between 6.6 and 7.2 and 26.5°C and 30.0°C respectively. In contrast, there were marked increases in the salinity (0.1-1.0ppt) and turbidity (0.5-1.5NTU) with decreases in DO (7.0-4.9mg/l) and BOD (3.8-1.0mg/l) whereas conductivity, pH and temperature were relatively constant in the tap water (TW) microcosm. The microorganisms isolated from the samples varied with the most heterogeneous genera; Bacillus, Pseudomonas, Vibrio, Enterobacter, Staphylococcus, Escherichia, Proteus, Lactobacillus, Acinetobacter and Micrococcus occurring in the BW and the least (7 genera) in the TW microcosm. The results indicate that changes in the physico-chemical parameters of the microcosms impacted adversely on the bacterial quality of mangrove oysters during depuration. The bacterial population dynamics and profiles obtained using the two microcosms have demonstrated the benefits of depuration on the potential health risk/safety of oysters prior to consumption.

Gbolokiri, depuration, microcosms, estuary, bacterial profliles