Biology 4701

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Biology 4701 Global Distribution of Reefs What
Factors are Responsible?
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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
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• Macro-Scale Controls
• Tectonic

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Macro-Scale Controls
b) Sea level
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Macro-Scale Controls
Darwin Point
Interaction between plate movement/sea level and
growth
Grigg (1882) Flood (2001)
Darwin Point
Fringing reefs begin to form atolls
Erosion fringing reefs
Reef coral growth ceases
Reef is drowned and becomes platform or basement
Time
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Macro-Scale Controls
b) Sea level
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Meso-Scale Controls 1) Temperature
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Meso-Scale Controls - Temperature
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Astrangia - coral but no reef
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Meso-Scale - Wave Energy
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Wave energy and the types of coral
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Micro-scale controls - Salinity
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Micro-scale controls - Salinity
Below 32
Vermetid worms
Serpulid worms
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Micro-scale controls - Antecedent Topography
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Micro-scale controls - Light
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Micro-scale controls - Light
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Micro-scale controls - Light
-at depth - corals change their growth form to
compensate for decrease in light -e.g. Montastrea
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Micro-scale controls - Light
n.s
Light also controls settlement of larvae
Mundy et al (1998)
Goniastrea flavulus
High neutral
Medium neutral
Low blue
Medium blue
Low neutral
Acropora tenuis
High neutral
Medium neutral
Low blue
Medium blue
Low neutral
Oxypora lacera
High neutral
Medium neutral
Low blue
Medium blue
Low neutral
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Micro-scale controls - Sedimentation
Sources of Sediment 1) Rivers
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Micro-scale controls - Sedimentation
Sources of Sediment 2) Dust
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Effects of Sedimentation - Shading 1) Turbidity
and reduction of light level
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Effects of Sedimentation -realized through 1)
Turbidity and reduction of light level
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Effects of Sedimentation 2) Smothering
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Effects of Sedimentation 3) Abrasion
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Effects of Sedimentation 4) Inhibition of
recruitment
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Micro-scale controls - Nutrients
Algal Turf
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Micro-scale controls - Nutrients
Other effects
1) Phosphate poisoning - high phosphate levels
stop calcification
2) Higher nutrient levels - favour sponges/algae
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Micro-scale controls - Nutrients
Effects of removing nutrient sources
Kaneohe Bay, Hawaii
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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
Organisms affecting coral cover
Effects on reproduction and recruitment
Direct effects on growth and survival
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Global distribution of coral reefs
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Global distribution of coral reefs and diversity