Sentosa waterway turns pinkish-purple, dead fish found near the banks
Dead fish found near the banks; algae bloom to blame for coloured water, say experts
The waterway running through Sentosa South Cove has turned an unnatural pinkish-purple since Tuesday afternoon, alarming residents.
Warning signs emerged on Jan 5 when a foul, sewage-like smell came from the waterway.
As the odour became stronger over the next few days, dead fish were found near the banks from last Wednesday to Sunday.
Saturday saw the "largest clean up and haul of dead fish," said Knight Frank Property Asset Management on behalf of Sentosa Cove Resort Management (SCRM), in a letter sent to residents on Monday, which was seen by The Straits Times.
Marine experts identified rabbitfish, moonyfish, batfish and leatherjacket fish among the dead fishes.
In response to queries from ST, an SCRM spokesman said the dead fish were observed in the waterway of South Cove between Jan 6 and 9, and subsequently a change in colour in the waters on Jan 12.
The North Cove waterway has not been affected.
The resort management is working with the National Environment Agency (NEA) on investigations.
"As a precautionary measure, SCRM has advised residents to refrain from water sport activities in the waterway. SCRM will continue to monitor the waters," added the spokesman.
Dr Sandric Leong, senior research fellow at the National University of Singapore's Tropical Marine Science Institute, said the coloured water was caused by picocyanobacteria bloom - a form of algae bloom.
A bloom is caused when a large amount of algae or cyanobacteria accumulates in the water, resulting from high amounts of nutrients such as phosphorus and nitrogen.
He added that the heavy and persistent rain over the past couple of weeks may have contributed to the bloom.
The NEA said there is no indication of any industrial or marine pollution that could have impacted the waters in the surrounding area.
Algae blooms can remove dissolved oxygen from the water, causing marine life to suffer. But it is unclear if the fish deaths and coloured water are linked, the experts emphasised.
Common causes of fish deaths include oxygen deprivation, toxins produced by algae blooms and high concentrations of algae species that can damage the gills of fishes, said Associate Professor Federico Lauro from Nanyang Technological University's Asian School of the Environment.
Mr Dan Paris, 54, a resident of South Cove's Turquoise condominium, bemoaned how lifeless the waterway has become this past week.
"In Sentosa Cove, you have this marine life around you - fish, heron, otters. I didn't see any otters last weekend," said Mr Paris, who works in marketing.
"And the herons, eagles and kingfishers were picking up the dead fish floating in the waters. Those fish might be contaminated."