Phytoplankton Functional Types in Tropical Hypertrophic Waters: A Case Study of the Coastal Waters of Jakarta Bay, Indonesia

ABSTRACT Grouping phytoplankton into functional groups can simplify the structure of their communities, making it easier to analyze phytoplankton dynamics within ecosystems, especially in waters with hypertrophic conditions. This study aims to examine the composition of phytoplankton functional types in the hypertrophic waters of Jakarta Bay. Phytoplankton samples and environmental parameters were collected from 16 research stations along the coastal waters of Jakarta Bay. Environmental parameters include temperature, pH, salinity, total dissolved solids, and nutrients (phosphate, nitrate, and silicate). Based on the analysis, four main phytoplankton functional types were identified in the coastal waters of Jakarta Bay: silicifiers (diatoms), mixotrophs (dinoflagellates), DMS producers (dinoflagellates), and nitrogen fixers (cyanobacteria). The proportion of silicifiers ranged from 95.79% to 99.54%, mixotroph‐DMS producers from 0.42% to 4.19%, and nitrogen fixers from 0.03% to 0.04%. The PCA analysis underscores the significance of salinity, TDS, turbidity, and nutrient levels in shaping PFT distribution. These findings provide a foundation for future studies examining long‐term ecological trends and potential shifts in phytoplankton community dynamics in response to environmental changes in Jakarta Bay.