TACLOBAN CITY — Red tide has spread to Biliran province, the Bureau of Fisheries and Aquatic Resources (BFAR) said Wednesday, adding to the seven bays in Samar province already contaminated by the toxic algae.

A report by the Philippine News Agency quoting a BFAR advisory said water samples collected this week detected red tide in Biliran’s coastal waters.

In Samar, Villareal Bay, Daram Island, Zumarraga Island and Maqueda Bay — which includes parts of Jiabong, Motiong, Paranas, San Sebastian, Calbiga, Pinabacdao and Hinabangan — remain affected.

Also on the list are Cambatutay Bay in Tarangnan, Irongirong Bay in Catbalogan City, and the coastal waters of Calbayog City.

BFAR has declared the coastal waters of Guiuan and Matarinao Bay — covering General MacArthur, Quinapondan, Hernani, and Salcedo — free of red tide as of 23 July.

The agency blamed the expansion of the red tide bloom on the interplay of weather patterns, including El Niño and occasional heavy rains.

These conditions can stir up sediments containing red tide microorganism cysts, which then multiply rapidly.

The bureau warned of a red discoloration in parts of the Samar Sea, where tests found Pyrodinium bahamense, a toxic organism that causes paralytic shellfish poisoning.

Red tide is an overgrowth of algae that can discolor water, often to a reddish hue. It produces toxins harmful to humans and marine life.

The public is strictly prohibited from gathering, selling, or consuming any shellfish, including small shrimp, from the Samar Sea, BFAR said.