Fireworms with toxin-loaded bristles found on Hong Kong beaches as breeding season intensifies
But ecologists urge calm, saying large number is natural during the species’ breeding season
Fireworms covered with toxin-loaded bristles have been wading into Hong Kong’s beaches in recent weeks, triggering concern among local lifeguards.
But marine ecologists urged calm, shrugging the phenomenon off as a natural occurrence, especially during the worms’ breeding season.
Commonly found in local waters, beachgoers and lifeguards have reported seeing large groups of the gangly polychaetes – bristled marine worms – near city shorelines over the past week, sending swimmers bolting back to shore.
Their sharp bristles contain toxins that can cause a burning pain when in contact with bare skin, often followed by itching, inflammation and numbness that can last days and even weeks.
No injuries have been reported so far.
The tiny, flat worms typically measure about 10cm in length and usually hide beneath rocks in the water. They can sometimes be spotted swimming with the currents.
“On your average day, it’s rare to even see one or two and we usually just ignore them but we’ve never seen anything quite like this,” Government Lifeguards General Union chairman Anson Tang Tsz-on said. “Never have they appeared in a large swarm or caused a nuisance.”
Lifeguards at Tsuen Wan’s Lido Beach reportedly had to scoop up about 100 of the worms from the water over the Dragon Boat festival holiday on Monday alone, Tang noted, and a similar number the day after.
The worms were also spotted at beaches on Tuen Mun’s Gold Coast and some outlying islands.
On Wednesday, the Leisure and Cultural Services Department put up a sign at Lido Beach warning swimmers about the marine worms discovered in the water.
A department spokeswoman said the worms were part of natural marine life, but conceded that its staffers had indeed noticed a greater number “than usual” recently at beaches near Tsuen Wan district.
“The department has put up notices, and if necessary, will make the broadcasts,” she said.
A small number of worms was also found on both Golden Beach and Cafeteria Old Beach in Tuen Mun and on Stanley Main Beach.
“If a person is accidentally wounded by marine life on a public beach, they can seek assistance from the first aid posts, where lifeguards will immediately help clean the wound,” the spokeswoman added.
“If necessary, the department’s staff will help call an ambulance to take the victim to a hospital for further treatment.”
Tang slammed the department – which the union has already been at loggerheads with recently, over manpower shortage issues – for in its words ignoring the problem and failing to issue guidelines on what to do if a swimmer is injured by a fireworm.
Kenneth Leung Mei-yee, professor of aquatic ecology and toxicology at the University of Hong Kong, believed the polychaetes were likely of the genus Chloeia and were common in marine environments with sea beds of soft soil sediment such as Hong Kong’s.
“Completely normal,” he said of their appearance. “Most people were just never aware of them until the recent [media coverage]. They’ve likely been in the vicinity for months since April, but as the weather got warmer, more people swim at beaches and come across them.”
Marine worms typically appear in shallow waters near the coast during the breeding season and may swarm to the surface then.
“Reports of hundreds or thousands being pulled out are probably not accurate,” Leung said.
If caught, the worms can be deposited outside the shark nets, where they would make their own way back down to the seabed, Leung added.
Hong Kong is home to two-thirds of all the polychaetes and marine worm species ever recorded in the South China Sea.
They are vital to coral reef ecosystems as they help filter organic matter for decomposition, and are an important source of food for other marine life.