MANILA – Far from being clean, Manila Bay’s change of color from gray to turquoise that was observed last week may actually indicate that its waters have been contaminated with chemicals that kill marine life, a scientist said on Monday.
Last March 25, netizens shared photos and videos showing how Manila Bay’s waters near Roxas Boulevard had changed color and now looked clean and “Boracay-like.”
This was after photos of much clearer skies over a locked-down Metro Manila spread on social media.
Some speculated that the enhanced community quarantine imposed over Metro Manila, which suspended the operations of many industries and establishments, had also lessened pollution and allowed Manila Bay’s water to “heal.”
But a marine biologist from UP Diliman’s Marine Science Institute said a 2- to 3-week pause in pollution was not enough for Manila Bay's water quality to improve.
“Hindi dahil ganun ang kulay, malinis na sya (Having that color doesn’t mean it’s clean),” Dr. Deo Florence Onda said referring to the turquoise patch of water that was observed in Manila Bay starting March 11.
Instead, the change in color was most likely due to chemical pollution, said Onda.
“It could actually be a dead zone,” said Onda, who heads the Microbial Oceanography Laboratory of the UP Diliman College of Science.
Onda said scientists at the laboratory are looking at two possibilities for the water’s change in color.
First, it could be the result of microorganisms blooming in Manila Bay’s waters. A bloom of phytoplankton called coccolithopores has been known to result in turquoise waters.
But these microorganisms bloom only in waters that are free from man-made pollution, and have never been observed in Manila Bay.
“Mukhang yung experience natin at yung kaalaman natin, sinasabi na mukhang hindi yun yung possibility,” said Onda.
(Our experience and knowledge do not point to this possibility.)
The second and more likely possibility is that the change in color was due to chlorine pollution, Onda said.
Large establishments in Manila Bay like malls, restaurants and hotels with pools may be discharging chlorinated water into the sewerage system, which drains into Manila Bay, Onda said.
The constant disinfection of many parts of Metro Manila using chlorine solutions may have also led to this, Onda said.
Chlorine contamination may explain why patches of the turquoise water looked clear, Onda said, because chlorine kills microorganisms whose bodies then settle at the bottom of the Bay.
Besides microorganisms, chlorine also kills fish and other marine life.
Manila Bay’s discoloration was also reported in 2014. That incident coincided with a fish kill, which prompted the Department of Environment and Natural Resources to investigate the incident.
Apparently, the discoloration happened again in the succeeding years, though the turquoise patch was not as large and as prominent in 2014.
It was seen again in 2017, based on satellite photos shared by Google Earth. Netizens also posted photos showing that it recurred in October 2018
“So mukhang nangyayari sya nang mas madalas. Di lang napapansin kasi mas maliit, mas patchy.”
(So it seems that this happens often. It just doesn’t get noticed as often because its smaller, patchier.)
Onda said scientists from the Microbial Oceanography Laboratory would have wanted to analyze samples from Manila Bay, but are constrained by the enhanced community quarantine in effect over Metro Manila and Luzon.
Last Monday, Environment Secretary Roy Cimatu ordered the discoloration of Manila Bay to be investigated.
Before Metro Manila went into lockdown, the DENR closed several establishments in Pasay City that were found to be discharging untreated wastewater into Manila Bay.