Biosphere 2 studies reflect real world changes — страница 2

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of the atmosphere in the ocean biome of the Biosphere 2 Center. By taking water chemistry measurements, he could detect a correlating drop in the saturation state of aragonite in the water. He found this drop had a significant effect on decreasing the amount of calcium carbonate in the water, thereby also decreasing the growth rate of the coral reef. Said Kleypas, "The fact that the Biosphere 2 mesocosm illustrated the same response to changes in saturation state as that of individual coral and marine alga in aquaria increases our confidence that the system responses at aquarium, or mesocosm, scales can be extrapolated to the field." These findings have important global implications, since measurements of the saturation state of aragonite in surface ocean water show

that it has been decreasing. In the past 100 years, for example, the average aragonite saturation state in the tropics has dropped about 10 percent. It is predicted this tend will continue, amounting to an average decrease of about 40 percent by the year 2100 from preindustrial levels. Precipitation, the process by which aragonite and other calcium carbonate minerals produced by corals solidify into reefs, also is expected to decrease, by 17 to 35 percent from preindustrial times to 2100. Reefs that may be the most vulnerable to these changes are those with balanced calcium carbonate budgets, characterized by rates of growth that equal their rates of erosion. Any decrease in the calcium carbonate produced by these reefs, located primarily in high-latitude areas like Bermuda and

deep-water upwelling regions like the Galpagos Islands, could corrupt this balance, leading to reef-building rates that could not compete with higher rates of erosion. Though it has been evidenced that productive reef ecosystems do emit some carbon dioxide into the atmosphere, and that a decrease in the total surface area of reefs globally would decrease this level of emission, research has not indicated this decrease will have a significant effect on lowering atmospheric levels of carbon dioxide. Currently, scientific estimates state reef-to-atmosphere emissions of carbon dioxide only amount to one percent of human-to-atmosphere emissions of this gas due to fossil fuel combustion. This research study indicates this discrepancy will become even wider, as reef emissions of

atmospheric carbon dioxide are expected to decrease while anthropologic emissions are expected only to increase. By Robert J. Nelson