This part of the fore reef zone begins immediately seaward of the reef crest. It is characterized by a comparatively gentle downward slope and the frequent presence of branching corals.
The upper fore reef has the most coral species within the coral reef ecosystem.
Wave energy is high at the base of the reef crest, so the uppermost portion of the fore reef is dominated by massive or encrusting corals that are more resistant to the destructive forces of wave impact.
As depth increases and wave energy abates, the frequency of branching corals (e.g., Acropora spp.) rapidly increases. This deeper part of the upper fore reef sub-zone contains the highest coral species diversity and greatest variety of hard coral colony forms to be found in the entire coral reef ecosystem. Most typically, this “upper” portion of the fore reef extends from about 3-15 meters in depth, but it is not uncommon for the upper section to reach depths of 20 meters.