D.8. Coral Reefs
- Corals are, in fact, living animals.
- They form a remarkable symbiotic partnership with tiny algae called zooxanthellae. In this mutually beneficial relationship, the algae reside within the coral’s tissues rather than on the seafloor. This elevated position near the ocean surface ensures that the algae receive ample sunlight for photosynthesis. In return, the corals benefit from the nutrients the algae produce.
- Interestingly, the vibrant hues seen in coral reefs don’t come from the corals themselves—their tissues are actually transparent or white. The dazzling colors are thanks to the zooxanthellae living inside them.
- There are two types of corals:
(i) Hard corals
(ii) Soft corals
Such as sea fans and gorgonians, only the builders of coral reefs are tiny animals called polyps. - As these polyps thrive, grow, then found in tropical and sub-tropical water, there are also deep water corals in colder hard corals build reefs, die, they leave their limestone (calcium carbonate) skeletons behind. The limestone is colonized by new polyps.
- Regions The United Nations Environment Programme reports that there are more cold-water coral reefs worldwide than tropical reefs. There are only about 6 different coral species associated with these reefs.
- The largest cold-water coral reef is the ‘Rost Reef’ off Norway Occur in shallow tropical areas where the sea water is clean, clear and warm, one of the most productive and complex coastal ecosystems with high biological diversity.
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Classified depending on their locations |
(i) Fringing (ii) Patch (iii) Barrier (iv) Atoll |
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Details of above four types Coral reefs |
Among the four major reef areas of India, Andaman and Nicobar Islands are found to be very rice in species diversity followed by the Lakshadweep Islands, the Gulf of Mannar and finally the Gulf of Kachchh. (i) The fringing reefs are contiguous with the shore and they are the most common – by occurring reef form, found in Andamans. (ii) Patch reefs are isolated and discontinuous patches, lying shoreward of offshore reef structures as seen in the Palk bay, Gulf of Mannar and Gulf of Kachchh. (iii) Barrier reefs are linear offshore reef structures that run parallel to coastlines and arise from submerged shelf platforms.
(iv) Atolls are circular or semi – circular reefs that arise from subsiding sea floor platforms as coral reef building keeps ahead of subsidence. The examples are the atolls of Lakshadweep and Nicobar. |