Biology 4701
Global Distribution of Reefs
What Factors are
Responsible?
Controls on Reef Growth and Distribution
1. Macro-scale controls - global
2. Meso-scale controls - within same basin
3. Micro-scale controls - effects on a single reef
Macro-Scale Controls
a) Tectonic
Macro-Scale Controls
b) Sea level
Macro-Scale Controls
Darwin Point
Interaction between plate movement/sea level and growth
Grigg (1882) & Flood (2001)
Darwin Point
Erosion Fringing Reef Reef is
& reefs coral drowned and
fringing begin to growth becomes
reefs form ceases platform or
atolls basement
Time
Macro-Scale Controls
b) Sea level
Meso-Scale Controls
1) Temperature
Meso-Scale Controls - Temperature
Astrangia - coral but no reef
Meso-Scale - Wave Energy
Meso-Scale - Wave Energy
Type III
Type II
Type I
Wave energy and the types of coral
Micro-scale controls - Salinity
Micro-scale controls - Salinity
Below 32‰
Serpulid worms Vermetid worms
Micro-scale controls - Antecedent Topography
Micro-scale controls - Light
Micro-scale controls - Light
Micro-scale controls - Light
-at depth - corals
change their
growth form to
compensate for
decrease in light
-e.g. Montastrea
Micro-scale controls - Light n.s
Light also controls settlement of larvae
Mundy et al (1998)
Goniastrea flavulus
High Medium Medium Low Low
neutral blue neutral neutral blue
Acropora tenuis
High Medium Medium Low Low
neutral blue neutral neutral blue
Oxypora lacera
High Medium Medium Low Low
neutral blue neutral neutral blue
Micro-scale controls - Sedimentation
Sources of Sediment
1) Rivers
Micro-scale controls - Sedimentation
Sources of Sediment
2) Dust
Effects of Sedimentation - Shading
1) Turbidity and reduction of light level
Effects of Sedimentation
-realized through:
1) Turbidity and reduction of light level
Effects of Sedimentation
2) Smothering
Effects of Sedimentation
3) Abrasion
Effects of Sedimentation
4) Inhibition of recruitment
Micro-scale controls - Nutrients
Algal Turf
Micro-scale controls - Nutrients
Other effects:
1) Phosphate poisoning - high phosphate levels stop calcification
2) Higher nutrient levels - favour sponges/algae
Micro-scale controls - Nutrients
Effects of removing nutrient sources
Kaneohe Bay, Hawaii
Micro-scale Factors
Effects of Sediment and Nutrients
Negative effects shown on:
-calcification -fertilization -coralline algae
-tissue thickness -settlement -bioeroders
-zooxanthellae density -metamorphosis -macroalgae
-photosynthesis -recruit survival
-adult colony survival -juvenile growth
Direct effects on Effects on Organisms
growth and reproduction and affecting coral
survival recruitment cover
Global distribution of coral reefs
Global distribution of coral reefs and diversity