Reefs are defined structures in the marine environment that arise from the seabed and cover an extensive area
. Or as 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 can be both natural and artificial in origin.
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