Two centuries of variation in coral growth in a massive Porites colony from Moorea (French Polynesia): a response of ocean-atmosphere variability from south central Pacific

Long-lived massive corals can contribute to the monitoring of coral reef environments through measurable growth records in the annual density patterns; these can provide an historical perspective against which to assess environmental changes, and can help to establish limits of coral growth. Furthermore, proxy records from corals may provide information about long-term variability in the performance of coral reefs, allowing unnatural changes to be distinguished from natural variability. A measurement of two centuries (1800–1990) coral growth, using computerized tomography, has led to a refined record of skeletal extension, density and calcification rates in a massive coral head from Moorea Island (French Polynesia). Correlation analysis of coral-growth characteristics with climatic instrumental data indicates a link between variations in average annual calcification and variations in annual air temperature. Linear regression of temperature versus calcification shows a trend in which a rise of 1°C in temperature would increase the calcification rate by about 4.5%. Moreover, these data suggest that calcification has increased over recent decades, which differs notable from the 6–14% decline in calcification over the past 100 yr predicted by certain researchers. Spectral analysis of annual calcification record indicates a strong concentration of variance at the quasi-biennial (∼2.5 yr), El Nino/Southern Oscillation (∼4–7 yr) and decadal-scale variability (∼21.9 yr) frequency bands.