Marked shifts of harmful algal blooms in the Bohai Sea linked with combined impacts of environmental changes

•A large dataset of harmful algal blooms in the Bohai Sea (1952–2017) is compiled.•HABs in the Bohai Sea exhibit marked changes, with three distinct periods.•HABs have increased in frequency, seasonal window and species number over time.•Typical HAB-forming algae shifted from dinoflagellates, haptophytes to pelagophytes.•Warming, mariculture and eutrophication are correlated with HAB changes.