Agriculture, Aquatic, and Natural Resources

Monsoonal Variation in Phytoplankton Assemblages and Selected Water Physicochemical Parameters in Shark Fin Bay, Taytay, Palawan

Noe D. Reyes, Marlgaux Kaye R. Castro, Edgar P. Paalan, Jhonamie A. Mabuhay-Omar

Abstract

Phytoplankton serve as important indicators of water quality and ecosystem condition. This study examined the seasonal variation of phytoplankton communities in Shark Fin Bay, Taytay, Palawan, Philippines, in relation to monsoonal changes. Monthly sampling was conducted from July to December 2025 at six sites within the Shark Fin Bay Marine Protected Area. Phytoplankton composition, abundance, diversity, and harmful genera were assessed together with selected physicochemical parameters, including temperature, salinity, dissolved oxygen, pH, total suspended solids, water transparency, depth, and nutrients. Results showed clear differences between the Southwest and Northeast Monsoons. The Northeast Monsoon recorded higher phytoplankton abundance but lower diversity, indicating dominance by fewer taxa. In contrast, the Southwest Monsoon supported a more diverse community, although overall abundance was lower. Harmful genera, including Alexandrium and Prorocentrum, were also observed. These findings provide baseline information for phytoplankton monitoring and harmful algal bloom management in Shark Fin Bay, with relevance to fisheries sustainability and coastal conservation.