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25-30 January 2009
Prepared by Denis Allemand, Centre Scientifique de Monaco, Avenue Saint- Martin, MC 98000 Monaco; email@example.com
Reprinted from L&O Bulletin 17.4.
The Centre Scientifique de Monaco (CSM) is a cutting-edge laboratory committed to fundamental research. It is a Monegasque government laboratory founded in 1960 by Prince Rainier III. Scientific research in Monaco has been a tradition for over a century. It began with Prince Albert I, born 161 years ago. He explained his commitment and passion for Sciences in these terms:
“I would very much have liked to be able, by broadening for you the horizon of oceanographic studies, to succeed in showing you that marine areas, far vaster than areas on land, comprise countless subjects for study from which biologists and after them, philosophers, would find material and intellectual riches for humanity” (Bulletin du Musée Océanographique, 1905, N° 56, page 13).
For 20 years the CSM has undertaken world renowned research in the biology of tropical and Mediterranean coral ecosystems in relation with global climate change. Its originality lies in the development of coral cultures in controlled conditions, and in the development of an integrated research program, spanning the molecular and cellular level to the scale of the organism and ecosystem by two complementary research teams; Physiology-Biochemistry (directed by Dr Sylvie Tambutté) and Ecophysiology-Ecology (directed by Dr Christine Ferrier-Pagès). The permanent staff numbers 15 scientists and technicians. Studies are conducted in the laboratory and in the field using ultramodern methods in ecology, biochemistry and molecular biology.
Coralligenous assemblages in the Mediterranean and coral reefs in tropical environments, both play a key role in the equilibrium of the planet and in the maintenance of marine biodiversity. Coral reefs can be considered as oases of diversity in the oceans: occupying less than 0.2% of the oceans’ surface area, they present more than 30% of the marine fauna known to date! They precipitate nearly half of the calcium carbonate on the surface of the Earth, thereby playing an essential role in the carbon dioxide cycle. They protect the coasts from erosion and provide an economic resource vital to human populations. Coralligenous assemblages are also home to a wide species diversity and attract divers, for their landscape and heritage value. Unfortunately, these ecosystems are under serious threat: massive mortality in the Mediterranean and bleaching in the tropics has lead to unparalleled reduction of these organisms on a global scale, which should alert us on the drastic effects of climate change on marine ecosystems.
It is with this perspective, that marine biomineralization and symbiosis, the key biological processes in these ecosystems, are particular foci at the CSM, approached with different complementary methods of study.
Biomineralization is the biological process through which living organisms transform ions in solution into highly organized mineral structures, biominerals. Corals are the major builders on Earth with 2000 km-long reef formations but current changes in ocean chemistry greatly affect this process. Biominerals are composite materials with both an inorganic and an organic fraction. The organic fraction, which is poorly known, is composed of a framework of organic macromolecules, called the organic matrix, which controls the shape and mineralogy of the inorganic fraction. We study Biomineralization using several approaches: i) physiological methods such as radiotracers for both ions and organic molecules, ii) histological methods using both light and electron microscopy, confocal microscopy and immunohistochemistry, iii) biochemical and immunological methods to characterize the organic fraction, and iv) molecular methods to identify genes involved in the biomineralization process.
Understanding biomineralization mechanisms is essential for several applications. Coral skeletons are indeed widely used as environmental archives for reconstruction of past climate (palaeoclimatology), but the “vital effect” imposed by biological activities of corals make the signal difficult to interpret. In order to improve the reading of skeletal paleomarkers, we are making “Experimental Paleoclimatology” by incubating corals growing on glass slides in controlled conditions. This allows accurate calibration of markers versus environmental parameters (temperature, CO2, light, nutritional status, seawater composition…) which will improve the use of coral skeletons in geochemistry and paleoclimatology. Coral skeletons are also used as bio-implants in bone surgery and dentistry. Our results show that coral may contain important macromolecules, which may act on osteoblasts after implantation. Finally, perhaps the most important aspect of our work is to further understanding of how changes in environmental parameters will affect coral growth and calcification. We were the first to demonstrate that increase in CO2 concentration and temperature may act synergistically, increasing effects and we recently proposed some physiological explanations of the sensitivity of calcification to CO2 increase and extended our studies to temperate corals.
Symbiosis is another key biological process underpinning the success of corals and their development in oligotrophic tropical waters. Indeed, corals, like many other Cnidarians, have the peculiarity of “culturing” unicellular algae inside their cells. These symbiotic algae, through photosynthesis, make corals potentially independent of heterotrophic nutrition. We have demonstrated that the coral host, unlike “standard” animals, absorbs and concentrates CO2 to allow photosynthesis of its symbionts, thus allowing the coral to regulate photosynthesis of its endosymbiotic partner. Corals are also able to absorb inorganic as well as organic nitrogen compounds. In order to ensure photosynthesis of their symbionts, corals are restricted to the upper level of the sea, thereby exposing them to the sun’s rays and oxygen radicals, which are potentially damaging to host cells. However, the algal symbionts protect corals from ‘sunburn’ and oxidative stress by producing substances of pharmaceutical value for humans. The coral host conserves its capacity to feed heterotrophically and we have found that coral feeding greatly enhances photosynthetic and calcification rates.
For further information and a complete bibliography of publications: http://www.centrescientifique.mc