2.2 Reef Structure

Types of Reefs

Also Patch reefs

Global Distribution

Mesophotic Reefs

• non-reef forming corals?

Tropical Reefs

1. Below 30˚ latitude around equator

2. annual sea-surface temps average at least 20˚C

3. eastern margins of continents where shallow shelfs provide suitable habitat

4. thrive on normal-salinity seawater

5. usually found within 50 m of the surface in clear waters

• tropical regions with warm water and no upwelling needed for CaCO3 deposition

• macroalgal competition is high in higher latitudes

• Patterns in diversity

  • higher diversity in the indo-pacific (700 species) than Atlantic (175)

  • high diversity created by uniform and predictable conditions on tropical reefs promoted fast specialization (contradicts intermediate disturbance hypothesis)

Temperate corals

Zonation

• spurs & buttresses - form from low tide - 20m, dissipate energy from waves

• associated with changes in macromorphology - branching & complex structures in shallow to massive/platelike structures in deep

Environmental Factors Affecting Structure

• Light

• Wave action - large amounts of wave action restructure the reef completely. These are the most common type of disturbance and cause fragmentation and removal of species for new succession to

• Sedimentation

• Oxygen

• Temperature

Biological Factors Affecting Structure

• Oligotrophic waters - tropical seas are very depleted in dissolved nutrients and therefore plankton. Corals rely on their symbiosis to be the primary producers in this ecosystem.

• Competition

References

Goreau 1959

Describes reef zonation, primarily by genus. Discusses reef formation and requirements for maintaining structure.