aragonite

So will corals, especially those whose skeletons are composed of aragonite, a particularly unstable form of calcium carbonate.

珊瑚礁对此也受到同样的危险，对于骨骼由霰石（极不稳定的碳酸钙）构成的珊瑚来说，情况更是如此。

One indicator is the levels of calcium and aragonite.

其中一个就是水体中的钙和霰石的水平。