Based on the latest water quality monitoring conducted by the Laguna Lake Development Authority in Laguna de Bay on June 14, 2021, bits of algae were observed in all of its 15 established water quality stations which is an indication of a recurrence of algal bloom in the lake. Microcystis aeruginosa, a bloom forming blue-green alga, was noted to have occurred in the lake in large numbers from the water samples collected and analyzed.



Map showing the locations of LLDA’s Water Quality Monitoring Stations in Laguna de Bay and the actual pictures taken during the sampling activities.

The observed formation of algal bloom in the lake could have been triggered by the combination of various factors such as the prolonged hot weather and calm lake condition this summer followed by the heavy influx of nutrients into the lake particularly nitrate and phosphate from the tributaries after the rainy season started this June. In this regard, intense algal bloom may occur in sheltered or cove areas of the lake and that the places where the algal bloom usually accumulates will depend on the prevailing wind direction. The problem associated with algal bloom is that it uses much of the oxygen in the water column at nighttime for their respiration which could lead to shortage of oxygen available for the fish stocks in aquaculture structures, particularly in fishpens and fishcages. Fishkills or death of the fish stocks may happen if they failed to recover from stress due to insufficient supply of oxygen in the water.

Massive algal bloom collapse or die-off also usually happens when there will be a sudden drop in the water temperature of the lake from very high after a heavy rainfall or the supply of nutrients becomes exhausted. This can also result to oxygen depletion in the water and may lead to fishkills due to massive decomposition of the dead algae.

Operators of aquaculture structures in the lake are therefore advised not to overstock their fishcages and fishpens and to always keep closed watch of their fish stocks whenever there is an algal bloom. The unusual behavior of the fish stocks swimming at the lake surface could be an indication of the shortage of oxygen in the water. Once this is observed, operators must immediately undertake aeration of the water either by running a motorized boat in the affected area or by using paddle wheels or gas-powered aerators. For those fish stocks affected by the fishkills because of the algal bloom, the aquaculture operators are advised to remove them immediately and disposed properly outside the lake. The support of various LGUs around the lake are also needed to intensify the implementation of their environmental programs, projects, activities and other interventions towards reduction of nutrient loadings into the lake.

To report any incident or request for other information, you may contact the Environmental Laboratory and Research Division (ELRD) at 83764044 local 106, 140, 141 and 142 or at elrd@llda.gov.ph.