Impacts of multiple environmental stressors on coral reef erosion and secondary accretion

Ocean acidification threatens to shift coral reefs from net accreting to net eroding. While corals build reefs through accretion of calcium carbonate (CaCO3) skeletons, net reef growth depends on bioerosion by grazers and borers and on secondary calcification by crustose coralline algae and other calcifying invertebrates. Primary calcification, secondary calcification, and erosion processes respond differently to climate change stressors; therefore, the combined accretion-erosion response is uncertain. Using a new micro-computed tomography (CT) method, we measured the simultaneous response of secondary accretion and bioerosion along an environmental gradient: bioerosion rates ranged from 0.02 to 0.91 kg m􀀀2 yr􀀀1 and secondary accretion rates ranged from 0.01 to 0.4 mm yr􀀀1 across a 32m transect. Co-located measures of secondary accretion and bioerosion had different environmental drivers: bioerosion rates were highly sensitive to ocean
30 acidity while secondary accretion rates were most sensitive to physical drivers. These results suggest that bioerosion plays a significant role in the shift from net accretion to net erosion on coral reefs.

Silbiger N. J., Guadayol O., Thomas F. I. M. & Donahue M. J., 2015. Impacts of multiple environmental stressors on coral reef erosion and secondary accretion. PeerJ PrePrints 3:e1451. Article.


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