1. Coral Reefs & Lagoons Part 3
AICE Marine Science
Unit 5

2. Artificial Reefs (Made From):
Airplanes
Obsolete oil rigs
Bridges
Tyres
Junked appliances
Ballistic missiles
Subway cars
Ships
Boats
Concrete
Reef Balls
Steel boxes
Military equipment (incl. tanks)
Docks

3. Impact of Artificial Reefs
Local economies/tourism
Habitat for other organisms (& growth site of new coral polyps)
Food/fisheries
Coastline protection

4. Disadvantages to Artificial Reefs
Expensive / cost (to produce)
Difficult to install
Navigation hazard
Negative impact of tourism / unattractive

5. Reconstructing the History of Coral Reefs
Drilling: core samples; visible layers help to determine age (think of rings in a tree)
Geomorphologic analysis: studying the shape; fringing, barrier, or atoll
Carbon dating: comparing the proportions of carbon isotopes: 12C & 14C (14C taken up by corals decays to 12C) helps determine the age (14C half-life is 5,730 years)

6. Drilling
Drilling: core samples (drill down past limestone of reef); visible layers help to determine age (think of rings in a tree)
Interpretation of the bands provide evidence for changes in the growth rate of corals, in response to changes in environmental conditions, such as temperature or nutrient availability.

7. Geomorphologic analysis
Geomorphologic analysis: studying the shape; fringing, barrier, or atoll
study of landforms & the processes involved in shaping them. EX: Reefs forming on the drowned edge of continents during melted glaciers
Changes in structure over time

8. Carbon Dating
Carbon dating: used to find the age of a sample of coral.
As corals grow, carbon, originating from carbon dioxide, is deposited in their skeleton in the form of calcium carbonate. Some of the carbon taken up by corals, in the form of 14C, slowly decays to 12C. The proportion of 14C to 12C in a sample of material is used to estimate the age of the corals.
Carbon dating is used on organic remains up to about 50,000 years old.
Ratio of 14C : 12C used to estimate age