bio

Biogenic reef

A geological structure built entirely by living organisms rather than by tectonics or sedimentation. Reef-building corals draw calcium and carbonate ions from seawater to precipitate limestone skeletons; over millennia, living tissue, skeletal framework, biological cements and bound sediment accumulate into a three-dimensional, wave-resistant landform. The remarkable part is that the habitat *is* an animal's body: the ground that everything else settles on, bores into and hides within is something another animal grew by farming algae inside its own cells.