He is hatched something in the Australian reefs
By Denis Delbecq • January 2nd, 2009 in 13:25 · Category: Actuality
Say that the coral reefs of the planet are not undamaged am not a novelty. However observations for several decades begin being supported with solid studies. As jobs published in the magazine Science today by an Australian team. Four researchers notice a net reduction of the calcification of the reef of the Big coral reef, off Australia. A fall which would not have had antecedent in the course of 500 last years.
Suffering inflicted by the man on the reefs of the planet is numerous. For a long time, fishermen used the dynamite for example to pick up the gold mine. The increasing pollution of oceanic waters unsettles however the development of these fragile animals corals are. And undoubtedly also an increasing acidification of the water, linked to the dissolution augmented by some atmospheric carbon dioxide, amplified by the intense programme of this gas by human activities and increase in the temperature of the water. Other reasons, biological (parasites, etc.), those can also threaten corals.
The growth of exoskeletons (1) is the result of a competition between the good health of the animal, which takes a sample of the calcium in the water to form its skeleton, and the erosion caused by the movements of the water, notably qu passage of cyclones. Luckily, some huge corals, as porites, deposit successive layers of limestone which it is possible to differentiate, year per year, by making cuts. A bit as trees are studied by noticing the rings of growth in trunks.
From cuts of corals taken from 1983 till 1992 and from 2002 till 2005, the Australian researchers could measure, for every year, the annual rate of calcification. Result is peremptory. While the rate of calcification increased of 5,4 % between 1900 and 1970, it fell of 14,2 % between 1990 and 2005. A result got on the study of 189 samples of 13 reefs of the Big barrier.
The reason of this deterioration of the state of health of corals remains to know. The Australian team reminds of the long-term correlations which exist between the climatic swing of the Pacific and the growth of corals. But they also remind that since the beginning of industrial epoch, the acidity of the oceans augmented — as predict it the climatic models. And many models of laboratories point out that corals develop less quickly in a more sour water. Without having unanimous support, reminds the magazine Science in a comment of Australian jobs.
Would the man be the culprit? Difficult to cut. Because if the increase in programmes gas with greenhouse effect linked to human activities began well at the end of the XIXth century, the decline of corals would have begun only a century later. But the official report remains worrying. While the half of the reefs of the planet seems not to carry the stigmata of warming (the laundering), Australian jobs reveal that he is even hatched something indoors of reefs.
(1) the skeleton of the coral is external to the animal. Of Greek exo, which means outdoors.
Picture: © Jurgen Freund - Freund Factory / Science
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