environmental factors affecting corals water motion depth: photic vs aphotic zone & water motion...
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Coral Reefs and Lagoons
Environmental Factors Affecting Corals
Environmental Factors Affecting Corals
• Water Motion• Depth: photic vs aphotic zone & water
motion• Sedimentation• Salinity: 32-35o/oo
• Temperature: 18-32 oC• Tidal fluctuations• Nutrients: Eutrophic vs oligotrophic
• Water Motion• Depth: photic vs aphotic zone & water
motion• Sedimentation• Salinity: 32-35o/oo
• Temperature: 18-32 oC• Tidal fluctuations• Nutrients: Eutrophic vs oligotrophic
What is a coral? Healthy corals accumulate CaCO3 at
rate of 3-15 meters in 1000 years
Reef Growth to Erosion
Predation Crown-of-thorns starfish (Acanthaster planci): coral
predator in Indo-Pacific Reefs Time lag = cause/effect (max. # of predators as coral level
falls) Removal of the starfish
3 parts of erosion (1st)
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Storm Damage◦ Hurricanes or tropical storms◦ Physical breakage of corals◦ Abrasive sediments
Hurricane Hattie (1961 – Cat 5) destroyed 43 km of the British Honduras barrier reef◦ Recovery – 25 to 100 years
3 parts of erosion (2nd)
Exposure to air◦ Corals dry out◦ Overheat
3 parts of erosion (3rd)
Reef erosion = shores/coastal properties are exposed to damages from waves
Artificial reefs: human-made structures = concrete/stone blocks, sacks filled with sand or shipwrecks (sunken ships)◦ Colonized by algae, corals and fish◦ Used as submerged breakwater
Dissipate wave energy
Impact of Erosion
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Prevents erosion of land Anchorage/protection for harbors New habitats Increase fishing areas Tourism – snorkeling/diving
Artificial Reefs
USS Oriskany (2006)
Shipwrecks (Artificial Reef)
Geomorphology – study of landforms and processes involved in shaping them
History of Reefs
Shows growth and geological history of reef Carbon Dating – age of coral sample
◦ As corals grow, carbon (from carbon dioxide) is deposited in their skeleton as CaCO3
◦ 14C carbon slowly decays to 12C Proportion of 14C to 12C estimates age of coral Can estimate age up to 50,000 years old
History: Drilling and Carbon Dating
Deep drilling – cores of material to identify corals and estimate growth rate◦ Have ‘bands’ just like tree rings (give age)
Evidence of growth rate due to environmental conditions like temperature or nutrient availability
History: Drilling and Carbon Dating
Growth up to 20m deep Fossil corals found at 1200 m is evidence of
subsidence (caving in and sinking of land area)◦ New coral grow on top of old as reef gradually
sinks Fossil corals found above sea level
◦ Evidence of changes in sea level Mexico – sea level changes between ice ages
Growth of coral
Human impacts on coral includes:
• Aquarium/Souvenir Trade• Overfishing• Pollution• Dredging• Coastal Development• Tourism• Global Climate Change• Ozone Depletion
Coral Reefs: Human Impact
Worldwide disappearance
Fishing with explosives
Waste oil dumping
Sediments
Philippines: 75% of the reefs damaged
Destructive Resource Extraction Practices
Destructive Resource Extraction Practices
Toxic Chemical SpillsToxic Chemical Spills
Sediment Plume Entering the OceanSediment Plume Entering the Ocean
Corals Smothered in SedimentCorals Smothered in Sediment
DredgingDredging
Coastal DevelopmentCoastal Development
Anchor DamageAnchor Damage
Diver DamageDiver Damage
Ecotourism
Pennekamp Reef, Key Largo, FL
Net DamageNet Damage
Net Entanglement
Ornamental Trade:
Fan worm
Threadfin Butterfly fish
Introduced SpeciesIntroduced SpeciesAcanthophora, Eucheuma, & Gracillaria
Feeding Fish
Nutrients and Algae Growth
Dictyosphaeria cavernosa
Global Bleaching (2002)Global Bleaching (2002)
none
low
moderate
severe
severity unknown
Acid Rain in Marine Environment
• reduces ability of marine organisms to utilize calcium carbonate
• Coral calcification rate reduced 15-20%
• Skeletal density decreased, branches thinner
Sea Level RiseSea Level Rise
Climate Close-up (paleoclimatology)
Coral Reefs
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