Download Coral Reefs and Lagoons

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
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What is a coral?
Healthy corals accumulate CaCO3 at
rate of 3-15 meters in 1000 years
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Predation
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Crown-of-thorns starfish (Acanthaster planci): coral
predator in Indo-Pacific Reefs
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Time lag = cause/effect (max. # of predators as coral level falls)
Removal of the starfish
Click video
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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
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Exposure to air
◦ Corals dry out
◦ Overheat
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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
Click
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Prevents erosion of land
Anchorage/protection for harbors
New habitats
Increase fishing areas
Tourism – snorkeling/diving
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USS Oriskany (2006)
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Geomorphology – study of landforms and
processes involved in shaping them
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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
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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
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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
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Fossil corals found above sea level
◦ Evidence of changes in sea level
Human impacts on coral
includes:
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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
Dynamiting Reef
Destructive Resource
Extraction Practices
Toxic Chemical Spills
Sediment Plume Entering the Ocean
Corals Smothered in Sediment
Dredging
Coastal Development
Anchor Damage
Diver Damage
Ecotourism
Pennekamp Reef, Key Largo, FL
Net Damage
Net Entanglement
Overfishing and Bycatch
Ornamental Trade:
Fan worm
Threadfin Butterfly fish
Introduced Species
Acanthophora, Eucheuma, & Gracillaria
Feeding Fish
Nutrients and Algae Growth
Dictyosphaeria cavernosa
Bleaching
Global Bleaching (2002)
none
low
moderate
severe
severity
unknown
Acid Rain in Marine Environment
• reduces ability of marine
organisms to utilize calcium
carbonate
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Coral calcification
rate reduced
15-20%
Skeletal density
decreased,
branches thinner
Sea Level Rise
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Climate Close-up (paleoclimatology)
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Coral Reefs