Zooplankton Morphology, Abundance, and their Relationship with Physicochemical Parameters in Coastal Waters of Fuerte, Caoayan, Ilocos Sur

Zooplankton, which graze on the water column, play a crucial role in maintaining the balance of phytoplankton communities and reducing the frequency of blooms. Despite their substantial contributions to the marine ecosystem, their value to coastal communities was frequently overlooked because of their microscopic nature. The lack of data on marine zooplankton in the Ilocos Sur Region motivated this study conducted in Brgy. Fuerte, Caoayan, Ilocos Sur, to generate new insights into the zooplankton community. It aims to analyze zooplankton morphology, abundance, and physicochemical parameters. Sample collection was conducted during the evening (7 pm to 10 pm). Surface water samples were collected using a handheld fine mesh plankton net (50 m) and preserved with formaldehyde and Lugol’s solution. Thirteen groups of zooplankton populations were recorded in Brgy. Fuerte, Caoayan, Ilocos Sur. They were categorized into two kingdoms: Animalia and Chromista. Common zooplankton included Nauplius larvae, Calanus sp. (Calanoid), and Dioithona sp. (Cyclopoid). The overall density of zooplankton recorded was 192,050 cells/L, which comprises four stations. Regarding species density, the top five dominant species were Favella sp. (Tintinnids) with 163,689 cells/L, Nauplius larvae with 13,478 cells/L, Calanus sp. (Calanoid) with 9,300 cells/L, Sabellaria sp. (Middle trochophore larvae) with 1,283 cells/L, and Dioithona sp. (Cyclopoid) with 1,211 cells/. Future studies should investigate the complex relationships between physicochemical factors and zooplankton abundance and diversity while extending the sampling period to include additional zooplankton species. Understanding these relationships will enhance the comprehension of ecosystem dynamics and develop more effective coastal water management strategies.