A research team from the IRD "Tropical Palaeo-environments and climatic variability" research unit and their American co-workers (1) have succeeded in retracing over a 23 000 year period the history of a coral reef of the Island of Urelapa, in Vanuatu. This fossil reef bears the record of the longest continuous growth – 17 000 years – ever studied by scientists (2). For the first time, researchers have at their disposal uninterrupted records of environmental data on the whole of the deglaciation period, which began around 20 000 years ago (3). A major finding is that the Urelapa reef changed growth strategy, in response to environmental changes which occurred during the post-glacial sea-level rise. More broadly, this research has brought new key information which contributes to a better understanding of the influence of climatic change on the coral reefs of the Pacific, which are the most complex ecosystems of the marine environment.
In the course of the last glacial maximum, around 20 000 years B.P., sea levels reached their lowest point, at 120 to 130 metres below the present level. The subsequent ice-cap melting induced a gradual rise of the oceans up to current levels. In the tropical regions, these large-amplitude fluctuations have contributed to the formation and growth of coral reefs.
IRD researchers at Noumea, in conjunction with scientists from three American universities (1), have just reconstructed the history of the oldest post-glacial reef ever studied in the Pacific which has grown under the influence of sea-level oscillations. This reef is situated at Urelapa, off the island of Espiritu Santo in the Vanuatu group in the South-West Pacific. It shows the longest recorded continuous growth, at 17 000 years, between 23 000 and 6 000 years B.P.. (2). The scientists thus have at their disposal environmental data (sea-levels, quantity of nutrients, temperatures, and so on) covering the entire period of deglaciation (3).
Bénédicte Robert | EurekAlert!
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