Coral calcification from skeletal records revisited

Skeletal growth records in annually banded massive coral skeletons are an under-exploited archive of coral responses to environmental changes. Average linear extension and calcification rates in Indo-Pacific Porites are linearly related to average water temperatures through 23 to 30¯C. Assessing long-term trends in Porites extension and density requires caution as there is evidence of an age effect whereby in earlier growth years corals will tend to extend less and form a higher density skeleton than in later years. This does not appear to affect calcification rates. Coral growth characteristics at 2 of 3 reefs in the central Great Barrier Reef provide evidence of a recent decline. This is of concern, although the exact causes cannot be identified. International efforts are required to make full use of both coral growth histories and geochemical tracers contained in massive coral skeletons to understand the nature and significance of recent trends and their possible links with environmental changes such as ocean chemistry, warming tropical oceans and increased frequency of coral bleaching events.