Coral reefs will transition to net dissolving before end of century.

Ocean acidification refers to the lowering of the ocean's pH due to the uptake of anthropogenic CO ₂ from the atmosphere. Coral reef calcification is expected to decrease as the oceans become more acidic. Dissolving calcium carbonate (CaCO ₃ ) sands could greatly exacerbate reef loss associated with reduced calcification but is presently poorly constrained. Here we show that CaCO ₃ dissolution in reef sediments across five globally distributed sites is negatively correlated with the aragonite saturation state (Ω _ar ) of overlying seawater and that CaCO ₃ sediment dissolution is 10-fold more sensitive to ocean acidification than coral calcification. Consequently, reef sediments globally will transition from net precipitation to net dissolution when seawater Ω _ar reaches 2.92 ± 0.16 (expected circa 2050 CE). Notably, some reefs are already experiencing net sediment dissolution.
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