1.   The coral skeleton is ground into small particles, but can not be digested.

2.   In its advanced stages, the living tissue of the coral becomes flimsy and falls away from the coral skeleton.

3.   The researchers found that coral skeletons and clam shells did not even contain elevated levels of arsenic.

4.   They gradually build coral skeletons that form the elaborate reefs that then become home to thousands of fish, lobsters, sea turtles and other species.