Plenary 2: impacts of ocean acidification on coralline algae (text & video)

OA Week 2021, Plenary Session 2 GOA-ON Goal #2 – Improve our understanding of ecosystem response to OA

Dr. Chris Cornwall Research Fellow & Lecturer, Victoria University of Wellington, New Zealand


Ocean acidification (OA) is a major threat to the persistence of biogenic reefs throughout the world’s ocean. Coralline algae are comprised of high magnesium calcite and have long been considered one of the most susceptible taxa to the negative impacts of OA. In a recent meta-analysis/systematic review, we uncover some consistent and some inconsistent impacts of ocean acidification: most coralline algae experienced reduced abundance, calcification rates, recruitment rates, and declines in pH within the site of calcification in laboratory experiments simulating ocean acidification or at naturally elevated CO2 sites. There were no other consistent physiological responses of coralline algae to simulated OA (e.g. photo-physiology, mineralogy and survival). OA is the dominant driver in the majority of laboratory experiments where other local or global drivers were assessed. The interaction between OA and any other single driver was often additive, though factors that changed pH at the surface of coralline algae (light, water motion, epiphytes) acted antagonistically or synergistically with OA more than any other drivers. Coral reefs will be severely impacted by ocean warming and associated marine heatwaves. Reefs that could fair well under marine heatwaves currently have high contributions of coralline algae. However, the ability of these reefs to continue to calcify will be threatening by intensifying ocean acidification.

Ocean Acidification Week 2021 was sponsored by the following organizations:

(1) GOA-ON, the Global Ocean Acidification Observing Network,

(2) NOAA, the United States National Oceanic & Atmospheric Administration,

(3) IAEA OA-ICC, the International Atomic Energy Agency – Ocean Acidification International Coordination Centre, and

(4) IOC-UNESCO – the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization

For more information, please visit

GOA-ON, YouTube, 24 September 2021. Text and video.

  • Reset


OA-ICC Highlights

%d bloggers like this: