Glob. Change Biol. (2012)


Macroalgae (seaweed) form an important component of rocky shore ecosystems, so an understanding of their sensitivity to ocean acidification is important for understanding the wider ocean acidification impacts on coastal ecosystems.

To investigate the long-term impact of acidification on macroalgae and their sea-urchin grazers, Vivienne Johnson, from the Marine Biology and Ecology Research Centre, University of Plymouth, UK, and co-workers compared ecological assemblages in subtidal rocky shore systems along carbon dioxide gradients created by volcanic seeps in the Mediterranean and off the coast of Papua New Guinea.

Results were consistent across the temperate and tropical systems with species of the calcifying macroalgal genus Padina showing reductions in calcium carbonate content with carbon dioxide enrichment. Nevertheless, an increase in the abundance of Padina spp. in acidified conditions was observed. Reduced sea-urchin grazing pressure and significant increases in photosynthetic rates are thought to explain the unexpected success of decalcified Padina spp. at increased levels of carbon dioxide. Similarities in the responses of Padina spp. and sea-urchin abundance across carbon dioxide vent systems increases confidence in the generality of these observations for large geographical areas.