MANILA, Philippines – Heavy rains caused the fishkill at the Las Piñas-Parañaque Wetland Park (LPPWP) in Manila Bay last Oct. 10, the Department of Environment and Natural Resources (DENR) said yesterday.
The initial water quality test results showed that the fishkill resulted from low concentrations of dissolved oxygen (DO) in the water, DENR Secretary Roy Cimatu said.
“Fish, like all other complex life forms, need oxygen to survive. They get theirs in the form of oxygen gas dissolved in water,” Cimatu said.
According to Domingo Clemente, who heads the DENR’s Environmental Management Bureau-National Capital Region, the low DO levels “may have resulted from the recent heavy rains that caused the flushing of decomposed organic matter from the surface run-offs and inland water tributaries, eventually polluting the open seas.”
Cimatu said the DO for three of four monitoring stations at the LPPWP on Oct. 10 was too low for Class SB waters, which is six milligrams per liter.
The Class SB water classification means that the water is “suitable for commercial propagation of shellfish and intended as spawning areas for milkfish.”
All four stations exceeded the water quality guideline (WQG) for fecal coliform bacteria, which is 100 most probable number per 100 milliliters (MPN/100 ml). Station 2 recorded the highest concentration of fecal coliform at 350,000 MPN/100 ml, while the levels in the three other stations ranged from 23,000 to 24,000 MPN/100 ml.
Traces of cyanide were found at all four stations, exceeding the WQG of .02 mg/l for Class SB waters.
Cimatu said DO concentrations increased and fecal coliform levels went down to 540 to 1,600 MPN/100 ml during follow-up tests conducted on Oct. 14, four days after the fishkill.
The DENR will continue to monitor water quality in the LPPWP to ensure it would not affect efforts to rehabilitate Manila Bay.
Last Oct. 11, more than 5,000 kilos of dead fish, shrimp and crabs were found floating in the LPPWP’s waters.