Red Tide warning up in Surigao del Sur’s Lianga Bay

WHAT LIES BENEATH The pristine islets that dot Lianga Bay in Surigao del Sur, shown here in 2021, are a major tourist draw for the province. The bay is also rich in marine life. On Saturday, however, shellfish gathering at the bay is prohibited by the Bureau of Fisheries and Aquatic Resources because of the presence of red tide toxins. Fish, shrimps and other marine products are safe provided they are thoroughly cleaned. —PHOTO FROM THE SAN AGUSTIN TOURISM FACEBOOK PAGE

SAN FRANCISCO, AGUSAN DEL SUR—The Bureau of Fisheries and Aquatic Resources in Caraga region (BFAR 13) has again declared Lianga Bay in Surigao del Sur positive for toxic red tide after laboratory tests confirmed the presence of paralytic shellfish toxins (PST) beyond safe levels.

The PST levels at the bay ranged from 113 to 286.714 micrograms per 100 grams of shellfish meat collected from the coastal waters of Barobo town in the province, the BFAR said in a report released on Saturday.

The PST levels were way beyond the 40 micrograms per 100 grams of shellfish meat set by BFAR as deemed safe from paralytic shellfish poisoning (PSP).

The agency warned the public against harvesting, selling or eating any shellfish and Acetes species locally known as “alamang” from Lianga Bay until further notice.

According to BFAR 13, fish, squid, shrimp and crabs caught in the area are considered safe for consumption, as long as they are fresh and thoroughly cleaned.

BFAR also advised consumers to remove the gills and internal organs of fish and other seafood before cooking.

Recurring

Lianga Bay, which covers the waters of Barobo, San Agustin and Tagbina towns in Surigao del Sur, has been placed under repeated red tide warnings in recent years. BFAR records show the bay was also found positive for PSP in 2022 and 2024.

The ban was briefly lifted when the bay tested negative for PSP on April 16 this year, but the toxins have reappeared, BFAR said.

Marine scientists attribute the recurring outbreaks to nutrient buildup and poor water circulation in semi-enclosed bays like Lianga.

Runoff from agricultural lands and nearby communities is also believed to have contributed to the algal blooms that generate the toxic organisms responsible for PSP.

According to Dr. Rhodora Azanza of the University of the Philippines Marine Science Institute and Dr. Aletta Yñiguez, an expert in Pyrodinium dynamics and ecological modeling, the recurrence of toxic red tide events in Lianga Bay reflects the same environmental patterns observed across Philippine coastal waters.

Their research points to nutrient enrichment, weak flushing and the life cycle of Pyrodinium bahamense—which forms resting cysts in sediments that can germinate under favorable conditions—as the main causes of repeated PSP events.

BFAR and local authorities continue to monitor toxin levels in Lianga Bay to determine when it will be safe to lift the ban. Residents and fishers have been urged to comply with advisories to prevent paralytic shellfish poisoning cases.

Local fishermen and shellfish gatherers in Barobo and nearby towns continue to suffer losses each time a red tide warning is raised. Authorities said continuous monitoring is being done until toxin levels drop to safe limits.

BFAR and local government units have reminded residents to stay alert and follow advisories to prevent poisoning incidents.