Further doubts have been raised over the water quality near a proposed artificial beach in Tai Po after an environmental group found sea snails with defective sex organs - signalling the presence of a toxic chemical.
The Eco-Education and Resources Centre said the chemical caused all 30 to 40 of the dog whelks it took from the sea near the proposed beach site to develop sexual deformities.
The chemical and other substances that would lead to a harmful red tide and a bloom of poisonous jellyfish could also not be easily cleared by the government's attempts to improve water quality. A red tide is a discoloration of sea water caused by an algal bloom of toxic dinoflagellates.
Dr Michelle Cheung Ma-shan, the centre's science manager, said the chemical responsible for the phenomenon in sea snails was tributyltin, used as an anti-fouling paint for fishing boats to prevent barnacles adhering to the hulls.
It could cause irritation of the skin and harms the immune system if ingested. Although its concentration had yet to reach a harmful level for people, Cheung said it was a clear sign the site was heavily contaminated.
Another problem was the high concentration of nitrate at site, the eco centre said. Cheung said underground water in the area had a high level of nitrate because of its history of industrial development and pig farming. This water flowed into the sea, which could cause red tides and attract jellyfish to breed, she said.
Ken Ching See-ho, director of the centre, said a common jellyfish found in Tolo Harbour was the poisonous lion's mane, with tentacles as long as five metres.
A government report found that among 823 cases of red tide in 2010, 39 per cent occurred in Tolo Harbour. Ching said the figure was probably an underestimation. "The government's attempt to improve the water quality only addresses issues about E coli," he said. "The pollutants had accumulated in the soil for a long time and there's no way they can be cleared."
Meanwhile, the Tai Po District Council passed a motion yesterday in support of the government's Lung Mei and Ting Kok development and conservation proposal, after a two-hour discussion. Twenty out of 23 council members, half of them affiliated to Beijing loyalist parties, supported the motion. Many said they had been fighting for the plan on behalf of the district's residents for the past decade.
The council's three pan-democratic members abstained from the vote. They supported building the beach but asked for more time to discuss the recent concerns raised, including the ecological impact and the safety of swimmers if an artificial beach was built at Lung Mei.
Kwan Wing-yip, a NeoDemocrat who abstained, tabled an amendment to the motion for three months be given for further discussion of the proposal. It was voted down by 19 members.
Leisure and Cultural Services Department assistant director Donald Choy Chi-mun said after the meeting that it had addressed concerns by providing water quality improvement records and proper handling procedures for tidal animals during the proposed beach's construction. Its opponents said they had doubts about the records' reliability.
During the meeting, councillor Eric Tam Wing-fun, of the Democratic Alliance for the Betterment and Progress of Hong Kong, compared the controversy over Lung Mei to a pregnant woman being told she was not suited to giving birth just when she was about to do so.
Kwan disagreed. "Putting the beach plan on hold won't kill."
"Locals fear loss of Lung Mei beach" Video by Hedy Bok