Predicting of HABs by phytoplankton type and abundance in northern Bone Bay, South Sulawesi, Indonesia

Introduction: Harmful Algal Blooms (HAB) are the rapid growth of algae or cyanobacteria in water that can cause negative impacts on people, animals, or the environment by production of natural toxins. Information about HABs in the bays in Indonesia is limited. Objective: To predict HABs based on the type and abundance of phytoplankton in the northern part of Bone Bay, South Sulawesi, Indonesia. Methods: The study was conducted in four locations, namely Tj Ringgit (TR), Passampa (PS), Siwa (SW), and Barangmamase (BM) between May and July 2024. Various environmental parameters, including nutrients, were measured. Phytoplankton samples were collected by filtering seawater using a 25 μm plankton net and analyzed in the laboratory. Results: The dominant types of phytoplankton were found to be Bacteriastrum, Chaetoceros, Leptocylindrus, Rhizosolenia, Thalassionema, and Ceratium. All of them are classified as Non-HABs. The identified types of HABs include Pseudo-nitzschia, Dinophysis, Prorocentrum, Protoperidinium, and Oscillatoria. Orthophosphate and salinity are two environmental parameters that affect the occurrence of HABs. The proportion of HABs abundance was lower than that of non-HABs in all locations. An increase in the abundance of HABs was detected in two locations: SW and BM. Conclusion: Although the proportion of HABs is lower than that of Non-HABs, the increased abundance of HABs in some locations, such as SW and BM, indicates the potential for future blooms. Monitoring environmental parameters, especially orthophosphate and salinity, is critical to mitigating the impact of the development of HABs, which ultimately affects the ecosystem and human health in Bone Bay. This study emphasizes the importance of sustainable water management to maintain the balance of the ecosystem in the bay.