Identification of Harmful Algal Bloom-Causing Phytoplankton and Water Quality Status in Hurun Bay, Lampung, Indonesia

Abstrak

Harmful algal blooms (HABs) are increasingly reported in coastal waters influenced by anthropogenic nutrient enrichment. This study aimed to identify phytoplankton genera potentially causing HABs in Hurun Bay, Lampung, and to evaluate the supporting physical-chemical water parameters. Sampling was conducted at three sites representing areas with intensive human activities: fish cage culture waters, coastal tourism zone, and harbor area. Phytoplankton samples were collected using vertical towing methods and identified microscopically, while water quality parameters included temperature, salinity, pH, dissolved oxygen, nitrate, and phosphate. Nine phytoplankton genera associated with HABs were identified, dominated by Chaetoceros, Bacteriastrum, and Nitzschia. Nutrient concentrations indicated eutrophic conditions, while physical parameters remained within tolerance ranges for phytoplankton growth. The combination of elevated nutrients and suitable environmental conditions suggests that Hurun Bay has a high vulnerability to HAB events. Nutrient management and monitoring are therefore required to mitigate ecological and aquaculture risks in this coastal system.