Elevated pCO2 effects on the macroalgal genus Halimeda: Potential roles of photophysiology and morphology

While ocean acidification (OA) is predicted to inhibit calcification in marine
macroalgae, species whose photosynthesis is limited by current dissolved inorganic
carbon (DIC) levels may benefit. Furthermore, variations in macroalgal morphology will
likely give rise to a range of OA tolerance in calcifying macroalgae. One genus of
calcifying macroalgae that has shown varying species’ tolerance to OA is Halimeda, a
major carbonate sediment producer on tropical reefs. Species within this genus occupy a
range of habitats within tropical environments (reefs and lagoons), illustrating their
ability to adapt to diverse environmental conditions (e.g. carbonate chemistry,
irradiance). To date it is not clear if morphological and photophysiological diversity in
Halimeda will translate to different tolerances to OA conditions (elevated pCO2 and
lower pH).