Instability and breakdown of the coral-algae symbiosis upon exceedence of the interglacial pCO(2) threshold (> 260 ppmv): the 'missing' Earth-System feedback mechanism

摘要

Changes in the atmospheric partial pressure of CO2 (pCO(2)) leads to predictable impacts on the surface ocean carbonate system. Here, the importance of atmospheric pCO(2) < 260 ppmv is established for the optimum performance (and stability) of the algal endosymbiosis employed by a key suite of tropical reef-building coral species. Violation of this symbiotic threshold is revealed as a prerequisite for major historical reef extinction events, glacial-interglacial feedback climate cycles, and the modern decline of coral reef ecosystems. Indeed, it is concluded that this symbiotic threshold enacts a fundamental feedback mechanism needed to explain the characteristic dynamics (and drivers) of the coupled land-ocean-atmosphere carbon cycle of the Earth System since the mid-Miocene, some 25 million yr ago.