The dinoflagellate Akashiwo sanguinea will benefit from future climate change: The interactive effects of ocean acidification, warming and high irradiance on photophysiology and hemolytic activity.

Due to global climate change, marine phytoplankton will likely experience low pH (ocean acidification), high temperatures and high irradiance in the future. Here, this work report the results of a batch culture experiment conducted to study the interactive effects of elevated CO, increased temperature and high irradiance on the harmful dinoflagellate Akashiwo sanguinea, isolated at Dongtou Island, Eastern China Sea. The A. sanguinea cells were acclimated in high CO condition for about three months before testing the responses of cells to a full factorial matrix experimentation during a 7-day period. This study measured the variation in physiological parameters and hemolytic activity in 8 treatments, representing full factorial combinations of 2 levels each of exposure to CO (400 and 1000μatm), temperature (20 and 28°C) and irradiance (50 and 200μmol photons ms). Sustained growth of A. sanguinea occurred in all treatments, but high CO (HC) stimulated faster growth than low CO (LC). The pigments (chlorophyll a and carotenoid) decreased in all HC treatments. The quantum yield (F/F) declined slightly in all high-temperature (HT) treatments. High irradiance (HL) induced the accumulation of ultraviolet-absorbing compounds (UV) irrespective of temperature and CO. The hemolytic activity in the LC treatments, however, declined when exposed to HT and HL, but HC alleviated the adverse effects of HT and HL on hemolytic activity. All HC and HL conditions and the combinations of high temperaturehigh light (HTHL) and high COhigh temperaturehigh light (HCHTHL) positively affected the growth in comparison to the low COlow temperaturelow light (LCLTLL) treatment. High temperature (HT), high light (HL) and a combination of HTHL, however, negatively impacted hemolytic activity. CO was the main factor that affected the growth and hemolytic activity. There were no significant interactive effects of COtemperatureirradiance on growth, pigment, F/F or hemolytic activity, but there were effects on P, α, and E. If these results are extrapolated to the natural environment, it can be hypothesized that A. sanguinea cells will benefit from the combination of ocean acidification, warming, and high irradiance that are likely to occur under future climate change. It is assumed that faster growth and higher hemolytic activity and UV of this species will occur under future conditions compared with those the current CO (400μatm) and temperature (20°C) conditions.