LLDA probes Laguna de Bay fish kill

LUCENA CITY – The Laguna Lake Development Authority (LLDA) is conducting a comprehensive investigation into the reported fish kill in the Rizal portion of Laguna de Bay, but stressed that it is still too early to determine the exact cause of the incident.

In a statement issued on Monday, the agency said a thorough “evaluation is necessary” before drawing any conclusions, in reaction to a July 10 report about the fish kill incidents from the fisherfolk group Pambansang Lakas ng Kilusang Mamamalakaya ng Pilipinas (Pamalakaya).

While the investigation is ongoing, the LLDA said Laguna de Bay is currently experiencing a widespread algal bloom, a natural phenomenon that alters water conditions.

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The agency also noted that phytoplankton concentrations increased in May following the intrusion of saltwater from Manila Bay through the Pasig River into Laguna de Bay, a phenomenon commonly known as the “Pasig River backflow.”

According to the LLDA, the highest chloride concentrations during that period were recorded in the municipalities of Angono and Taytay in Rizal. By June, the peak concentrations had shifted to the waters near Diablo Pass off Talim Island in Binangonan town.

As algae die and decompose, dissolved oxygen levels in the water can decline significantly, placing aquatic life under severe stress, the agency explained.

“This sudden oxygen depletion is a well-documented factor that places immense stress on aquatic life,” the LLDA said.

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Initial monitoring also indicated that most of the affected fish came from commercial fish pens and fish cages rather than wild fish populations in open waters, suggesting that the environmental stress may be localized within aquaculture areas.

The LLDA added that the transition from the dry season to the rainy season has brought abrupt changes in temperature and weather conditions, which can further affect water quality.

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The agency said it has not ruled out the possible environmental effects of recent water-flushing activities conducted by Manila Water Company Inc. (MWCI). However, it emphasized that determining any connection would require additional scientific data.

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According to the LLDA, investigators are gathering information on the volume of water released and the quality of the discharged water while conducting water sampling and other field assessments./coa