Rapid climate-driven changes in marine environments are expected to significantly alter the dynamics of harmful algal blooms (HABs). Anticipating these shifts requires understanding the distribution of sediment resting cysts, which serve as the seeds for future blooms. However, traditional morphological identification of these cysts is notoriously time-consuming and technically challenging. To overcome these limitations, this study applied a metagenomic approach to accurately profile the resting cyst community in the southern coastal waters of Korea. The metagenomic results revealed that Alexandrium was the dominant genus, accounting for 11.5–47.5% of the sediment community. Additionally, other harmful algal genera such as Gymnodinium, Heterosigma, and Fibrocapsa were identified. Notably, our analysis also detected Azadinium, a genus not previously recorded in Korean waters. The dominant genus, Alexandrium, also exhibited high genetic diversity, highlighting the need for further research to investigate its adaptability to climate change and its cyst germination characteristics.

Harmful Algal Bloom,Resting Cyst,Metagenomic Profiling