• The apparent physical stability of reefs belies an underlying natural turmoil of growth, death and destruction of calcareous organisms. Much like a modern city, reefs are constantly being rebuilt and torn down at the same time. Corals are the bricks, broken pieces of plant and animal skeletons the sand, and algal crusts and chemical cements the mortar. Reef growth is determined by the production, accumulation, and cementation of all this calcareous stuff into solid limestone.