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Coral Reefs Damages and Threats

Context: Coral Reefs are getting damaged due to bleaching and overfishing.

What are Coral Reefs?

  • Definition: Corals are marine invertebrates or animals not possessing a spine.


    • 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.
    • Coral Reefs are largest living structures on the planet.
  • Zooxanthellae: Corals share a symbiotic relationship with single-celled algae called zooxanthellae.
    • The algae provides the coral with food and nutrients, which they make through photosynthesis, using the sun’s light.
    •  In turn, the corals give the algae a home and key nutrients. The zooxanthellae also give corals their bright colour.
  • Hard and Soft Coral:
    • Hard corals, also called hermatypic or ‘reef building’ corals extract calcium carbonate (also found in limestone) from the seawater to build hard, white coral exoskeletons.
    • Soft coral polyp borrow their appearance from plants, attach themselves to such skeletons and older skeletons built by their ancestors.
      • Soft corals also add their own skeletons to the hard structure over the years and these growing multiplying structures gradually form coral reefs.
  • Classification of Corals:
    • Fringing reefs: Fringing reefs evolve and develop near the continent and remain close to the coastline.
      • These reefs are separated from the coastline by small, shallow lagoons. They are the most commonly found reefs in the world.
    •  Barrier reefs: Barrier reefs are found offshore on the continental shelf.
      • They usually run parallel to the coastline at some distance..
    •  Atolls: Atolls are formed on mid-oceanic ridges.
      • They are shaped circularly or elliptically and are surrounded by seas on all four sides and have shallow waters in the center called a lagoon.
  • Largest Coral Reef: Australia’s Great Barrier Reef is the world’s largest reef system stretching across 2,300 km.
    • The most biologically diverse reefs in the world can be found in a region known as the Coral Triangle in Southeast Asia.
    • India has four coral reef areas: Gulf of Mannar, Andaman and Nicobar Islands, Lakshadweep islands and the Gulf of Kutch.

What is Coral Bleaching?

  • Process: When corals are under stress, they expel the microscopic algae that live in their tissues. Without these algae, corals’ tissues become transparent, exposing their white skeleton. This is called coral bleaching.
    • Bleached corals are not dead, but are more at risk of starvation and disease.
  • Cause: The leading cause of coral bleaching is climate change. A warming planet means a warming ocean, and a change in water temperature can cause coral to drive out algae.
    • Coral may bleach for other reasons, like extremely low tides, pollution, or too much sunlight.
  • Impact: Coral bleaching matters because once these corals die, reefs rarely come back.
    • A 2021 study by the Global Coral Reef Monitoring Network (GCRMN showed that 14% of the world’s coral on reefs had been lost between 2009 and 2018, with most of the loss attributed to coral bleaching.
What is Coral Bleaching
What is Coral Bleaching

Why are Coral Reefs Important?

  • Medicinal Value: Many drugs are now being developed from coral reef animals and plants as possible cures for cancer, arthritis, human bacterial infections, viruses, and other diseases.
    • The anticancer agent Ara-C, included on the World Health Organization’s List of Essential Medicines, is found in sea sponges on a Caribbean reef.
  •  Ocean Habitat: Coral reefs cover less than 0.5% of the earth’s surface, but they are home to about 25% of all marine species.
    • Reefs provide a large fraction of Earth’s biodiversity so they have been called “the rain forests of the seas.”
  • Economic Benefit: Healthy coral reefs support commercial and subsistence fisheries as well as jobs and businesses through tourism and recreation.
    • Coral reef systems generate $2.7 trillion in annual economic value through goods and service trade and tourism.
  • Act as Buffer: Coral reef structures also buffer shorelines against 97% of the energy from waves, storms, and floods, helping to prevent loss of life, property damage, and erosion.
    • When reefs are damaged or destroyed, the absence of this natural barrier can increase the damage to coastal communities from normal wave action and violent storms.
  • Source of Food: About one billion people source their food or income directly from reefs.
    •  In countries like the Maldives, it provides people with 77% of their dietary animal protein. If managed well, reefs can continue providing this important source of food.

What Endangers Coral Reef?

  • Climate Change:  Climate change affects coral reef ecosystems by increasing sea surface temperatures and leads to coral bleaching, disease, sea level rise and storm activity.
  • Coral Harvesting: Coral Harvesting for the aquarium trade, jewelry, and curios can lead to over-harvesting of specific species, destruction of reef habitat, and reduced biodiversity.
  • Ocean Acidification: Ocean acidification occurs because of rising carbon dioxide (CO2) levels.
    • The ocean absorbs carbon dioxide released into the atmosphere. Carbon dioxide alters the chemistry of seawater by reducing pH, a measure of acidity. Water that has a lower pH is more acidic.
      • Consequently, the availability of carbonate ions, one of the main building blocks in their calcium-carbonate skeletons is reduced, and corals have a tougher time building up, or even maintaining, their skeleton.
  • Unsustainable Fishing Practices: These practices  in coral reef areas can lead to the loss of ecologically and economically important fish species.
    •  Such losses often have a ripple effect not just on the coral reef ecosystems themselves, but also on the local economies that depend on them.
  • Marine Pollution: The effects of land-based sources of pollution, such as coastal development and agricultural runoff, can impede coral growth and reproduction, disturb ecological function and cause disease.
  • Ozone Depletion: Coral polyps have in-built UV rays protection. However, now that the radiation is increasing, the corals in shallow waters can get damaged and destroyed.

Global Efforts to Protect Coral Reefs

  • International Coral Reef Initiative:  It is a global partnership for the preservation of the world’s coral reefs and associated ecosystems.
  •  Global Coral Reef Monitoring Network:  It is an operational network of ICRI (International Coral Reef Initiative) with the primary task of reporting on the condition of the world’s coral reefs.
  • Global Coral Reef Alliance: It is a worldwide coalition of volunteer scientists, divers, environmentalists and other individuals and organizations, committed to coral reef preservation.
  • Global Coral Reef Research and Development Accelerator Platform: It is an innovative action-oriented initiative aimed at creating a global research and development programme to advance research, innovation and capacity building in all facets of coral reef conservation, restoration and adaptation.

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What are Coral Reefs?

Definition: Corals are marine invertebrates or animals not possessing a spine.

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