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Questions and Answers
What is the primary source of energy for corals?
What is the process by which corals expel their zooxanthellae and turn white?
What is the main component of coral reefs?
What is the role of zooxanthellae in coral-algal symbiosis?
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What happens to the coral when it loses its zooxanthellae?
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What is the term for the process by which corals secrete calcium carbonate?
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Which of the following organisms is a producer of CaCO3?
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What is the reason why corals require transparent waters?
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What is the typical shape of platform reefs?
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In which location can platform reefs be found?
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What can form around the edges of platform reefs?
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What is the ideal temperature range for coral reefs?
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What is the estimated net reef carbonate budget in kg CaCO3 m-2 year-1 in coral-rich forereef zones?
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What is a factor that can affect the existence of coral reefs?
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What percentage of the Earth's surface is covered by coral reefs?
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How fast can some coral colonies grow per year?
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What can be found in the middle of a platform reef?
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Which type of coral reef grows parallel to the coastline and is separated from it by a lagoon?
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What type of reef can form within an atoll?
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What is the main difference between aragonite and calcite?
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Which region has the largest percentage of coral reefs?
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What is the estimated area of the Great Barrier Reef in km2?
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How far is the Great Barrier Reef from the main continent?
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What is the rate of carbonate production in kg/m2/yr in lagoons and rubble substrates?
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Study Notes
Marine Organisms
- Pteropods, macroalgae, and mollusks also deposit aragonite, while other organisms like calcareous algae, echinoderms, crustaceans, and forams deposit CaCO3 as calcite.
- Aragonite has a stronger and more resistant structure.
Carbonate Production
- Typical rates of carbonate production: 10 kg/m2/yr on productive coral-rich forereef zones, 4 kg/m2/yr on reef flats, and 0.8 kg/m2/yr in lagoons and rubble substrates.
- Global map of coral reef carbonate budgets: values indicate estimated net reef carbonate budgets, in kg CaCO3 m-2 year-1.
Coral Reefs Around the World
- Coral reefs cover approximately 300,000 km2 of the Earth's surface, less than 0.1% of the ocean's surface.
- The Indo-Pacific region (including the Red Sea, the Indian Ocean, Southeast Asia, and the Pacific) represents 91.9% of the world's coral reefs.
- The Southeast Asian region represents 32.3%, while the Pacific, including Australia, represents 40.8%.
- The Atlantic and Caribbean regions represent 7.6% of the world's coral reefs.
Classification
- Atolls: a type of coral reef structure.
- Barrier reef: a coral reef growing parallel to the coastline, separated from it by a lagoon, characterized by a shallow seabed and coral growth.
- Fringing reef: a type of coral reef structure.
The Animal
- Coral is a carnivorous animal that feeds on microscopic animals that fall from above, filtering the water at night.
- Coral has a white, calcium carbonate structure, and the different colors it presents are due to microalgae called zooxanthellae that live in symbiosis with the coral polyps.
- Coral needs transparent waters to develop, as the zooxanthellae perform photosynthesis.
- Coral polyps are a few millimeters in diameter and have the ability to fix dissolved calcium in the water, forming rigid structures.
Zooxanthellae
- Zooxanthellae are microalgae that live in symbiosis with coral polyps and provide them with energy in the form of carbon compounds.
- They can provide more than 90% of the coral's energy requirements.
- Zooxanthellae live in other protozoa and invertebrates and are mostly autotrophic.
Coral Bleaching
- When coral is under stress, it loses its zooxanthellae and turns white, leading to coral bleaching and eventually death.
CaCO3 Producers
- Coral
- Calcareous algae
- Mollusks/gastropods
Reef Types
- Platform reefs: form on the continental shelf or in the open ocean, variable in size, and can grow in all directions.
- Fringing reefs: extend only seaward.
- Barrier reefs: grow parallel to the coastline, separated from it by a lagoon.
Elements of a Reef
- Coral polyps
- Zooxanthellae
- CaCO3 structures
- Other organisms
Factors Conditioning the Existence of Reefs
- Temperature: 18°C – 20°C
- Oxygen levels
- Salinity
- Turbidity
- Dissolved carbonate
- Nutrients
- Hydrodynamic conditions
- Light
Origin and Evolution
- Modes of reef growth in response to sea-level changes: reef growth oscillates between 1 cm/year for slow-growing massive corals and 30 cm/year for fast-growing, branching forms.
Impacts
- Human activities affecting coral reefs: e.g., climate change, pollution, overfishing.
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Description
This quiz is about the different marine organisms that deposit calcium carbonate, including pteropods, macroalgae, and molluscs, and their roles in coral reef ecosystems.
