SEMINAR: Predicting the effects of ocean acidification on macroalgae

Ocean acidification is the sustained absorption of anthropogenically derived carbon dioxide (CO2) by surface seawater. Increasing CO2 concentrations shift the carbonate chemistry of seawater by reducing pH and carbonate, and by increasing dissolved inorganic carbon and bicarbonate. Macroalgae are important components in coastal reef ecosystems, but our ability to predict their future responses to ocean acidification is limited. The primary obstacles are that macroalgae utilise inorganic carbon via multiple understudied physiological mechanisms, and that their responses to ocean acidification can be extremely variable. The effects of ocean acidification on calcareous macroalgae (i.e. those that precipitate calcium carbonate material) are the clearest; declines in overall growth/calcification rates are associated with increasing CO2 concentrations, though great variability even in their responses exist. The responses of non-calcareous macroalgae to ocean acidification are the hardest to discern; positive, neutral and negative responses are all possible.

A picture has been painted that reefs dominated by calcareous macroalgae will be overcome by non-calcareous macroalgae in the future; however Chris Cornwall will demonstrate why the effects of ocean acidification will likely be subtle, species-specific, and environment-dependent.