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Reefs Biology 4701 Global

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Reefs Biology 4701 Global Powered By Docstoc
					       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

				
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posted:11/26/2011
language:English
pages:32