The Great Barrier Reef-The Hindu-08-08-2022
CONTEXT: The highest levels of coral cover, within the past 36 years, have been recorded in the northern and central parts of Australia’s Great Barrier Reef (GBR), according to the annual long-term monitoring report by the Australian Institute of Marine Science (AIMS).
WHAT IS COREL REEF?
Corals are marine invertebrates or animals which do not possess a spine. They are the most significant living structures on the planet. Each coral is called a polyp and thousands of such polyps live together to form a colony, which grows when polyps multiply to make copies of themselves.
Corals are of two types — hard corals and soft corals.
Hard corals extract calcium carbonate from seawater to build hard, white coral exoskeletons. Hard corals are in a way the engineers of reef ecosystems and measuring the extent of hard coral is a widely accepted metric for measuring the condition of coral reefs.
Soft corals attach themselves to such older skeletons built by their ancestors. Soft corals also add their own skeletons to the complex structure over the years. These growing multiplying structures gradually form coral reefs.
How do they cook food?
Corals share a symbiotic relationship with single-celled algae called zooxanthellae. The algae prepare food for corals through photosynthesis and also give them their vibrant colouration.
Ideal conditions for coral growth
Corals thrive in tropical waters-between 30°N and 30°S latitudes.
The ideal depths for coral growth are 45 m to 55 m below the sea surface, where there is abundant sunlight available.
The temperature of water generally is around 20°C.
Clear salt water is suitable for coral growth, while both fresh water and highly saline water are harmful to polyp growth.
An adequate supply of oxygen and microscopic marine food, called plankton, is essential for growth and existence. As the food supply is more abundant on the seaward side, corals grow more rapidly on the seaward side.
Significance of coral growth :
Protect coastlines from the damaging effects of wave action and tropical storms
Provide habitats and shelter for many marine organisms
Coral growth is the source of nitrogen and other essential nutrients for marine food chains
Coral Growth assist in carbon and nitrogen fixing
Coral growth help in nutrient recycling.
The fishing industry depends on coral reefs because many fish spawn there and juvenile fish spend time there before making their way to the open sea.