Reef

Definition of Reef: . Reefs are hard mineral substrates such as rocks, till, or stones, primarily moraine ridges with block and stone cover in gravel/sandy surroundings, which rise mildly to prominently above the seafloor; biogenic hard substrates such as honeycomb (Sabellaria) reefs and mussel banks are present; they are permanently submerged; often they are overgrown with mussels and a characteristic macrofauna. Reefs have a number of ecological functions: feeding grounds for birds and marine mammals; habitat and retreat; habitat and nursery area with high species diversity; spawning grounds and feeding ground for fish; stepping-stone and regeneration reservoir for the expansion of benthic organisms. This is the common definition for Reef, other definitions can be discussed in the article