It is still too early to tell whether the recent reports of algal bloom in Laguna de Bay could turn into a major fish kill.
That was the contention of the Laguna Lake Development Authority (LLDA) following reports of algal blooms, known as "liya," as well as "abnormal behavior" of fish and other marine creatures near Talim Island in Rizal.
In a statement, LLDA officials said that while it handles the issue with high priority, a comprehensive scientific evaluation is needed before reaching any conclusions.
It also asserted that the presence of algal bloom as reported in Talim Island is a natural phenomenon that occured due to a backflow of water from Pasig River.
"In May 2026, an increase in phytoplankton concentrations was observed following the intrusion of saltwater from Manila Bay through the Pasig River and into Laguna de Bay, a phenomenon commonly referred to as 'Pasig River backflow.' During this period, the highest chloride concentrations were recorded in the municipalities of Angono and Taytay, Rizal. By June 2026, the peak concentrations shifted, with the highest levels observed along Diablo Pass near Talim Island in Binangonan, Rizal," the LLDA said in its statement.
"As these accumulated algae reach the end of their life cycle and begin to die off, their decomposition leads to a significant drop in dissolved oxygen levels within the water. This sudden oxygen depletion is a well-documented factor that places immense stress on aquatic life," it added.
In addition, the current shift from hot summer months to the rainy season has brought abrupt fluctuations in temperature and weather patterns, which naturally destabilize and affect the overall water quality of the lake.
Initial monitoring also noted that most of the affected fish are those reared within commercial fishpens and fishcages, rather than the open-water wild fish populations, which points toward localized environmental stress within the aquaculture structures.
On the other hand, the LLDA also addressed the issue of a video circulating in social media of an alleged water pipe of the Manila Water Company, Inc. (MWCI) discharging foul-smelling water into Laguna de Bay.
"While the LLDA cannot dismiss the potential environmental impact of the recent water flushing activities conducted by Manila Water Company Inc. (MWCI), a fair assessment requires exact data. The LLDA needs to ascertain the actual volume of water released and evaluate the specific quality of the discharged water to determine the true extent and scope of its impact on the lake's ecology," it said.
In a message to OpinYon Laguna, MWCI officials claimed that all flushing operations have been halted, while they have also coordinated with LLDA officials on how to safely handle the process.
"Just to briefly explain, this is part of the energization process of our East Bay phase 2 treatment plant to prepare for full operation. This part of the flushing still includes the stagnant lake water that accumulated in our submarine pipe," officials said.
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