Coral Reefs and Lagoons

Part IISection 5

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

Access this link:◦ http://oceanservice.noaa.gov/education/tutorial_c

orals/◦ Answer Questions passed out to you.◦ Due Monday, April 8th

Read Marine Biology book pages 10-11◦ Answer question 1 AND write bolded words with

definitions!

Homework!

Climate Close-up (paleoclimatology)

Coral Reefs

Additional Helpful Links