Investigation and evaluation of risk of pathogen transfer by ballast water in Shahid Rajaee Port, Hormozgan Province, Iran

Abstract

Ballast water is essential for ship operations, but can also transport harmful organisms between ports, threatening local environments. The Ballast Water Management (BWM) Convention, established by the International Maritime Organization (IMO), requires ships to implement ballast water management measures to address this issue. In this study, ballast water samples were collected from ships entering Shahid Rajaee Port in Iran before and after the Ballast Water Management Convention came into force in 2017. The sampling was conducted in coordination with Iranian authorities, following IMO guidelines. Vibrio cholerae, Escherichia coli, and Enterococci were identified in 97 ships, and physical parameters such as temperature, salinity, and pH were measured in 15 ships. To prevent sample contamination, rigorous protocols were followed, including using sterile equipment, appropriate storage, and immediate transfer to the lab. The results showed that before the BWM Convention, V. cholerae was found in 6 out of 14 ships (42%), with ballast water retention times of 2–58 days. After the convention, V. cholerae was found in only 2 out of 83 ships (2.4%), with ballast water retention of 2–3 days. This indicates a significant reduction in the risk of pathogen transfer through ballast water. Further analysis after the Convention showed that V. cholerae was initially detected in 4 out of 15 ships, but only 1 ship (6.6%) had levels above the standard. E. coli and Enterococci were also detected in multiple ships, but their levels were below the standard. The study investigated the relationship between the bacterial levels and the physical parameters. While some correlations were found between E. coli/Enterococci and parameters like pH, temperature, salinity, and water retention time, no significant impact of physical parameters on V. cholerae levels was observed. T-tests revealed significant relationships between the bacterial levels and the physical parameters, as well as the ballast water retention time. Ships were found to have followed the ballast water exchange guidelines of exchanging at least 200 or 50 nautical miles from shore and at depths over 200 m, as mapped out for the Persian Gulf region. The results indicate that the implementation of the BWM Convention has been effective in reducing the risk of pathogen transfer through ballast water. However, the study emphasizes the importance of ongoing monitoring and enforcement to ensure continued compliance with the convention’s requirements.