Abstract: Ocean acidification, the increase in seawater CO₂ with all its associated consequences, is relatively well understood in open oceans. In shelf seas such as the Great Barrier Reef, processes are much less understood, due to complex interactions with water quality and biological processes. I will show new data how ocean acidification has been progressing in the Great Barrier Reef, and its direct and indirect effects on coral reefs of the GBR, including shifts from corals to seaweed, impaired coral recruitment, and increasing bioerosion. Our new data from the Great Barrier Reef suggest that functional changes are already occurring, measurably affecting coralline algae, and coral recruitment and promoting macroalgae. Although most reefs are still net accreting, some reefs in marginal locations and high latitudes have started to dissolve in winter. The future integrity of GBR reefs under increasing ocean acidification will depend on their specific biophysical properties, and effective mitigation of the cumulative stressors from nutrient pollution. Unlike a clean-up of water quality, OA is irreversible on time scales of thousands of years, and there is no latitudinal escape, re-emphasising the imperative for rapid action on atmospheric CO₂ pollution.

Biography: Dr Katharina Fabricius is a Senior Principal Research Scientist, and leader of the Team ‘Cumulative Impacts’ at the Australian Institute of Marine Science. She has spent over 30 years actively researching coral reefs, and has received her PhD from the University of Munich in 1995 for her work on soft corals the Great Barrier Reef, the Red Sea and reefs in Florida. A major focus of her research is to understand the effects of anthropogenic disturbances on ecological processes in coral reefs. She has spent ten years investigating the effects of ocean acidification on reefs using volcanic CO2 seeps in Papua New Guinea as a natural laboratory. Her present focus is now on understanding the consequences of ocean acidification and poor water on the capacity of GBR reefs to recover. Katharina has published >165 journal articles and book chapters, and holds advisory roles as coral reef expert on ocean acidification, water quality and climate change issues, and is still fascinated by soft corals.