environmental factors affecting corals water motion depth: photic vs aphotic zone & water motion...

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)

Click video

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

Click

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

Dynamiting Reef

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

Overfishing and Bycatch

Ornamental Trade:

Fan worm

Threadfin Butterfly fish

Introduced SpeciesIntroduced SpeciesAcanthophora, Eucheuma, & Gracillaria

Feeding Fish

Nutrients and Algae Growth

Dictyosphaeria cavernosa

BleachingBleaching

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

Additional Helpful Links