Warming and rising CO2 concentrations enhance growth and/or photosynthetic rates in many species of cyanobacteria, picoeukaryotes, coccolithophores, dinoflagellates and diatoms  , and the optimum pCO2 for growth and/or primary production shifts upward under warming  . Warming and ocean acidification appear to jointly favour the proliferation and toxicity of harmful algal bloom  species  , but a 2021 analysis found no uniform global trend in HABs or their distribution over 1985-2018 once field data were adjusted for regional variations in monitoring effort . The predominantly detrimental impacts of ocean acidification on coccolithophores can partly be offset by warming  but also be exacerbated, depending on the magnitudes of drivers . For non-calcifying
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report