HKU Bulletin October 2003 (Vol. 5 No. 1)

8 RESEARCH T he fishermen who dangle lines from the piers around Victoria Harbour should think twice before they bring their catch home for supper. For not only is the environment the fish swim in of questionable quality, the fish themselves may also be unwell. Fish can swim away from pollution, but long-term exposure means contaminants can build up in their flesh. And while the water is cleaner now that better sewage treatment is being introduced in Hong Kong, the sediment is still highly polluted. To better understand the impact of pol lution on marine organisms, the gover nment ’s Env i ronmental Protect ion Department (EPD) commissioned a consultancy study led by Dr Kenneth Leung of the Swire Institute of Marine Science within the Department of Ecology and Biodiversity. The study investigated the use of biological indicators in Hong Kong to assess the health of fish and marine organisms in local polluted waters. The current marine water quality monitoring programme mainly focuses on physico-chemical parameters of water and sediments, which do not reliably reflect the stress on marine organisms. “Just like a medical doctor who checks their patient’s health once in a while, we are trying to use diagnostic tools to say whether an animal is healthy or not in a given body of water. If not, then you can investigate the reason why,” Dr Leung said. The $1.3 million study focused on fish and mussels in open waters around Hong Kong, including Victoria Harbour, Port Shelter, Tolo Harbour and wester n waters. Dr Leung and his team measured a special enzyme in fish – EROD – which indicates if a fish has been exposed to harmful organic compounds such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). They also looked at the lysosome function in mussel cells, to see if they had been weakened or stressed by pollution. The findings showed that fish with elevated levels of EROD and mussels with weakened lysosome either had higher levels of PAHs or PCBs in their flesh, or were caught in areas where the sediment had high levels of these compounds. Pony fish were an especially good indicator and those caught in Victoria Harbour and Deep Bay had the highest EROD levels. Both bodies of water have been heavily polluted in the past with industrial and organic pollution. “We hope the Hong Kong gover nment wi l l fol low the European and US governments and incorporate more bio- and eco-moni tor ing methods, as these are a more di rect measurement of the health status of marine organisms,” Dr Leung said. The EPD is now explor ing how to implement the recommendations from the study. In the meantime, Dr Leung and his team have demonstrated bio-testing techniques to EPD officers and provided them with protocols for carrying out their own tests. As for those pier-based fishermen, or anyone who eats fish from polluted waters, Dr Leung has this warning. “I wouldn’t recommend anyone to eat mussels or fish from Victor ia Harbour and Deep Bay as these organisms have accumulated high levels of PAHs and PCBs, plus other things like heavy metals and faecal contaminants. If people eat them very occasionally, they may be fine. But if they do it more often, chronic toxicity can occur in their body, causing such problems as liver damage and gastrointestinal problems,” he said. Sick Fish Blamed on Pollution Kenneth Leung with a poster of diseased fish. 9