气候变化领域集成服务门户

Although reef coral skeletal carbon isotopes (delta C-13) are routinely measured, interpretation remains controversial. Here we show results of a consistent inverse relationship between coral delta C-13 and skeletal extension rate over the last several centuries in Porites corals at Fiji, Tonga, Rarotonga and American Samoa in the southwest Pacific. Beginning in the 1950s, this relationship breaks down as the atmospheric C-13 Suess effect shifts skeletal delta C-13 > 1.0% lower. We also compiled coral delta C-13 from a global array of sites and find that mean coral delta C-13 decreases by -1.4% for every 5m increase in water depth (R = 0.68, p < 0.01). This highlights the fundamental sensitivity of coral delta C-13 to endosymbiotic photosynthesis. Collectively, these results suggest that photosynthetic rate largely determines mean coral delta C-13 while changes in extension rate and metabolic effects over time modulate skeletal delta C-13 around this mean value. The newly quantified coral delta C-13-water depth relationship may be an effective tool for improving the precision of paleo-sea level reconstruction using corals.