Inside coral skeletons they have found techniques of interpreting the patterns of wet-dry seasons for many centuries past. This new knowledge is already providing climate researchers from all over the world with a way of extending their understanding of the Earth's weather history before it was measured with man-made instruments. These massive coral domes of Porites are the most widespread reef building corals on the planet and they contain their own regular and consistent calendar which extends back over centuries in many cases and, in rare examples, perhaps as long as a thousand years.
Scientists can thus work the age of sections of skeleton.
In the mid 1980's Dr Peter Isdale and his colleagues at the Australian Institute of Marine Science discovered a remarkable way that corals incorporate special substances from the water surrounding them as they grow. These substances, which are complex chemicals dissolved in the seawater, are laid down with the skeleton material as it deposits its layers, week by week, year by year, and century by century. Annual runoff reconstruction from the early 1600's to the present time. Of particular interest to hydrologists, climatologists and meteorologists is the way in which corals growing within about 20 kilometres of the coastline can trap river-borne organic compounds. Most of these are humic compounds derived from the decayed remains of land plants.