For instance, some parts of the bay are no longer safe from mercury, a toxic element, according to a team of researchers from the Batangas State University (BSU) in Batangas City.
This is particularly true in the Taal-San Juan-Bauan area and in Mabini town, according to the researchers, who conducted a study titled "Assessment of Coastal Water Quality of Balayan Bay."
The researchers — Jocelyn Castillo, Bessielyn Aldedo, Jommelson Castillo and Allan Talain — also noted that the waters of Balayan Bay in the Taal-San Luis-Bauan area and in Lemery and Mabini towns are now unsafe due to chromium, another harmful metal.
But they added that the coastal waters of Balayan Bay are still generally safe and of good quality in terms of cadmium and lead levels.
"Based on these findings, it is recommended that coastal resource management be strengthened and mandatory actions be undertaken by various agencies to sustain the intended use of Balayan Bay," they said.
They added: "Activities that are contributory to metal contamination of some parts of the bay should be checked and monitored."
The BSU researchers presented their report at the recent 16th STARRDEC Regional Symposium on R&D Highlights held here.
STARRDEC stands for Southern Tagalog Agriculture and Resources Research and Development Consortium, one of the 14 regional government research and development consortia being coordinated by the Los Baños-based Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD).
Located in the western part of Batangas, Balayan Bay serves as a source of livelihood for many local residents.
Over the years, a number of establishments and industries have spawned on the bay’s coastal areas. These industries, in addition to households and agricultural activities, discharge effluents that considerably damage marine life.
To date, the Department of Environment and Natural Resources (DENR) has not classified Balayan Bay. Hence, the BSU study attempted to determine the present water quality of the bay.
A total of 138 seawater samples were collected at quarterly intervals from 47 sampling points in six sampling sites throughout the entire bay from December 2000 to January 2002.
Results showed that Balayan Bay can be classified as "Class SC" based on pH level (acidity or alkalinity), temperature, oil and grease, dissolved oxygen, biochemical oxygen demand, and total suspended solids during the first (December 2000-January 2001) and second (April-May 2001) samplings.
The researchers said the bay is suited for boating and can be utilized for commercial and sustenance fishing. Marshy and mangrove areas declared as fish and wildlife sanctuaries can still thrive.
Likewise, they classified as "Class SC" based on pH level, temperature, oil and grease, dissolved oxygen and biochemical oxygen demand during the third sampling (October 2001-January 2002).
However, the bay can be categorized as "Class SD" based on total suspended solids, and as such, its water can be recommended as cooling water for industrial purposes.