Tolerance to high irradiance levels as a determinant of the bloom-forming Heterosigma akashiwo success in estuarine waters in summer

► Heterosigma akashiwo growth is not photoinhibited in summer. ► Heterosigma akashiwo adjusted photoprotective pigments at > 350 μE m−2 s−1. ► Culture results and field distribution are positively correlated with irradiance. ► Salinity is a growing determinant at suboptimum levels. ► 20-2 5°C temperatures affected positively cell survival at low salinities.