Assessment of Shellfish Contamination by Coliform Bacteria in Tidal Creeks of Delta State

Shellfish harvested from tidal creeks in Delta State, South South Nigeria, are widely consumed raw or lightly cooked, creating significant public health risks if harvesting areas are microbiologically contaminated. This study assesses faecal coliform contamination in water, sediment, and shellfish tissue from oyster (Crassostrea gasar) and periwinkle (Tympanotonus fuscatus) harvesting sites in three tidal creeks in Warri South and Burutu Local Government Areas of Delta State. Samples were collected bimonthly over six months and analysed for total coliform, faecal coliform, and Escherichia coli using the most probable number method and membrane filtration. Results showed that faecal coliform counts in shellfish tissue exceeded the USEPA guideline threshold of 14 MPN/100g in 68% of oyster samples and 54% of periwinkle samples. Water and sediment coliform counts were positively correlated with shellfish tissue contamination at all sites. Highest contamination levels were recorded at sites closest to residential wastewater discharges. Seasonal analysis revealed elevated contamination during the wet season, attributed to surface runoff from surrounding communities. The study provides evidence of significant microbiological contamination in shellfish harvesting areas of Delta State tidal creeks and recommends the designation of classified shellfish harvesting areas with defined water quality standards, regular monitoring by the Delta State Government, and public health education campaigns targeting shellfish consumers in the affected communities.

Keywords: shellfish contamination, faecal coliforms, oyster, tidal creek, Delta State