Hong Kong can attribute a large part of its success to its deepwater port, but it is often accused of taking little care of the aquatic resources that have helped it generate vast riches. Hong Kong has one of the busiest harbours in the world and more than 1,600km of coastal waters, but fish stocks in many areas have been depleted and the water polluted with human and industrial waste. Even pockets of unspoiled clean water in remote areas that support a diversity of marine life are under pressure from increasing recreational activities and illegal fishing. Water pollution can be invisible to the naked eye, but the impact can be wide-ranging. Ecoli bacteria and other pollutants can make swimmers sick and contaminate or kill marine life. Around Lau Fau Shan in Hong Kong's far north, home to what remains of the oyster farming industry, discarded plastic bottles, bags, styrofoam boxes and fast-food wrappers litter the shoreline. 'Pollution is a huge problem,' said a spokesman from the WWF, which studies water and air quality. 'Visit Lau Fau Shan and you will certainly be wary of buying oysters in Hong Kong. But it is the rubbish you can't see that's causing the real problems.' According to the United Nations, there are more than 100 million tonnes of plastic floating in the world's seas and oceans. The UN estimates that about 50 per cent of plastic waste comes from Asia. In the Aberdeen typhoon shelter, more than 300 tonnes of floating refuse are collected every year, most of which is household rubbish including bottles, cans, bags and packaging. Floating refuse collected along Hong Kong's coastline is also on the increase. Adding to the waste washed and blown into the sea from factories in the Pearl River Delta is the debris left behind by swimmers, beachgoers and litter from streets and storm drains. There is also rubbish dumped from fishing boats and vessel operations that adds to debris from landfill sites, household and construction. According to the Environmental Protection Department (EPD), the number of beaches meeting the Water Quality Objective for bathing water increased to 34 in 2006 from 26 in 1997. The number of river monitoring stations with bad or very bad water quality dropped from 52 per cent in 1988 to less than 15 per cent in recent years. Programmes such as the Harbour Area Treatment Scheme - a strategy for collecting and treating sewage - have been credited with helping to reduce pollution loads. Realising that Hong Kong's marine pollution problems are not entirely of its own making, the Hong Kong-Guangdong Joint Working Group on Sustainable Development and Environmental Protection has devised measures to reduce water pollution. An EPD spokesman said: 'Hong Kong shares its waters with Guangdong. It makes sense, therefore, that pollution control efforts be matched by both sides.' The sides set up a joint working group and in 2000 agreed on a 15-year plan to clean up Deep Bay and reduce pollution from existing sources and control future pollution. The two sides also initiated the first review of the regional water quality control strategy for Mirs Bay at the end of last year. The EPD conducts monthly marine water quality monitoring at 76 sampling stations. It monitors water and sediment quality of 17 typhoon shelters, marinas and dockyards. The EPD carries out monthly sampling of phytoplankton in the water at 25 monitoring stations. Three main areas the EPD monitors are dissolved oxygen - needed to support marine life; ammonia - harmful to water quality; and bacteria - linked to raw sewage. Water quality in Hong Kong harbour is expected to improve with the addition of the Stonecutters Island centralised sewage treatment plant. The new plant, capable of handling 1.7 million cubic metres of sewage each day has been built as part of the harbour treatment scheme. Discarded plastic bottles, supermarket bags and other plastic items that end up in the sea might look unsightly, but they could also pose an even bigger problem for humans. Studies show that tidal movement and erosion grinds plastic waste into tiny non-degradable particles. Doug Woodring, an environmental consultant for small businesses and founder of Project Kaisei, a global initiative which he started in Hong Kong, which aims to clean up the plastic vortex in the Pacific Ocean, said because these particles were petroleum based they attracted harmful chemicals such as DDT, PCBs and heavy metals dumped in the world's oceans. These are eaten by small fish as indigestible food and passed along the food chain until they are consumed by humans. Mr Woodring said: 'As large consumers of seafood, Hongkongers are quite likely eating toxic time bombs, particularly when they eat bigger and older fish, which tend to have larger concentrations of toxic particles. 'We have all seen plastic in our rivers and oceans and we can all do something about it,' said Mr Woodring, who is organising a water clean-up project as part of the World Ocean Day with Hong Kong's surfing, diving, sailing and paddling community next weekend.