Ries placed his artificial seawaters in 10-gallon glass tanks, then added fragments of the three species of Caribbean reef-building corals. These were replete with colonies of polyps, which had spent the previous month in "equilibration tanks." Ries adjusted the chemistry of those tanks over 30 days, until their magnesium-to-calcium ratios were in line with the prescribed "ancient seawater" chemistries.
Two months later, Ries removed the coral skeletons and used X-ray diffraction to analyze their mineral composition. He was surprised to find that corals grown in the artificial seawater with a magnesium-to-calcium ratio less than 2-to-1 began producing a large portion of their skeleton with the calcite mineral, while those grown in unmodified modern seawater produced exclusively the aragonite mineral.
Though most scientists believed that corals were programmed to produce only the aragonitic form of calcium carbonate, he said, the team's work reveals that corals are far more flexible and able to vary at least a portion of their skeleton to growth favored by seawater chemistry. He postulates that this "mineralogical flexibility" provides corals with an "evolutionary advantage," as it would take more energy for corals to produce skeletons that are not favored by the chemistry of the seawater surrounding them.
The calcite-producing corals grown in artificial ancient water grew significantly slower than did the aragonite-producing corals grown in modern water.
"The reduction in the corals' rate of growth that accompanied their exposure to the chemically mod
Source:Johns Hopkins University