2.2 Reef Structure

Types of Reefs

Global Distribution

Mesophotic Reefs

  • non-reef forming corals?

Tropical Reefs

  1. Below 30Ëš latitude around equator

  2. annual sea-surface temps average at least 20ËšC

  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.

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