The study looked at how different groups of a harmful algae called Cochlodinium polykrikoides affected blooms in Korean coastal waters. They found that in 2009, two genetically distinct groups of the algae took turns blooming, leading to a longer bloom period. In contrast, in 2010, only one group was responsible for the bloom, resulting in a shorter bloom period. The two groups of algae responded differently to environmental conditions like water temperature, pH, and phosphate concentration. The researchers also observed that one group of algae was transported by a warm ocean current, which influenced its bloom dynamics. These findings suggest that genetic differences within the algae population can impact the duration and intensity of harmful algal blooms in coastal waters.