Geochemical Consequences of Increased Atmospheric Carbon Dioxide on Coral Reefs

TLDR

Coral reefs grow by accumulating calcium carbonate, a process that relies on the saturation state of aragonite in surface waters, so a decline in calcification would reduce reef‑building capacity. Elevated CO₂ is projected to lower tropical aragonite saturation by 30 % and reduce biogenic aragonite precipitation by 14–30 %, threatening reef‑building organisms that produce metastable CaCO₃ and potentially impacting other calcifying ecosystems.

Abstract

A coral reef represents the net accumulation of calcium carbonate (CaCO 3 ) produced by corals and other calcifying organisms. If calcification declines, then reef-building capacity also declines. Coral reef calcification depends on the saturation state of the carbonate mineral aragonite of surface waters. By the middle of the next century, an increased concentration of carbon dioxide will decrease the aragonite saturation state in the tropics by 30 percent and biogenic aragonite precipitation by 14 to 30 percent. Coral reefs are particularly threatened, because reef-building organisms secrete metastable forms of CaCO 3 , but the biogeochemical consequences on other calcifying marine ecosystems may be equally severe.