Patches of the Singapore River turned a
startling shade of green yesterday morning because of an algal
overgrowth.
People working in the area said they noticed a greenish
tint on the water's surface two days earlier. Some detected a
pungent smell too.
"I was quite shocked. I was wondering if it was because
the water was polluted," said Ms Tina Teng, 29, a service staff
member at a seafood restaurant on Boat Quay.
Others were less alarmed as they had seen it happen
before.
Said Ms Asha Azizan, 45, a ticket sales agent: "I
usually notice it after heavy rain. I don't think much of it
because I figured it is probably a natural thing."
National water agency PUB confirmed that the
greener-than-usual waters were caused by algae - microscopic
organisms naturally present in reservoirs and waterways. It added
that algae in waters here are removed effectively during the water
treatment process for drinking water.
By 3pm yesterday, the river looked normal after routine
clean-up operations by the PUB.
Environmental experts said recent weather - rain
followed by strong sun, typical just after monsoon season - creates
a conducive environment for algal blooms.
"Rain will wash off nutrients from land into the water
bodies, and the sun allows photosynthesis, which helps green algae
multiply faster," said Mr Chan Wei Loong, programme chair of the
diploma in marine science and aquaculture at Republic
Polytechnic.
An algal bloom usually lasts up to a week and
disappears after that because the nutrients within the water body
would have been used up.
Said Associate Professor Federico Lauro of the Asian
School of the Environment at Nanyang Technological University: "I
don't think people should be alarmed unnecessarily.
"We should, however, put things in place to prevent
their recurrence because they can be harmful to aquaculture."
Most algae are not toxic, but an algal bloom can kill
fishes by starving them of oxygen and clogging up their gills. In
2015, fish farmers were hit by a bloom that wiped out more than 500
tonnes of fish stocks, causing them to lose millions of
dollars.
Algal blooms have also turned other water bodies here
green, including the waters of Marina Bay outside the Fullerton Bay
Hotel in 2015 and Kranji Reservoir last year.
Said Prof Lauro: "It will happen and will keep on
happening until we correct the underlying causes behind the
introduction of nutrients into the water."
TNP