macroalgae, responses are highly species specific and often indicate synergistic interactions between warming and acidification . Ocean acidification poses a large risk for coralline algae that is further amplified by warming  . However, temperatures up to 5℃ above ambient do not decrease calcification , and there is limited evidence that some species have the physiological capacity to resist acidification via pH upregulation at the calcification site . For seagrass, warming beyond a species' thermal tolerance will limit growth and impact germination, but ocean acidification appears to increase thermal tolerance of some eelgrass species by increasing the photosynthesis-to-respiration ratio  .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report