Coral bleaching

Context: Across the globe, unprecedented heatwaves have plunged both animals and humans into challenging circumstances. Among the affected creatures, corals stand out as exceptionally vulnerable.

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Corals Reefs:

  • They are most biologically diverse ecosystems of the planet. They are formed when Coral Polyps, the animals primarily responsible for building reefs, develop a symbiotic relationship with photosynthetic algae called zooxanthellae, which live in its tissues.
  • Coral reefs are critically important ecosystems that underpin ocean sustainability and the economic, social and cultural security of hundreds of millions of people around the world. Despite their immense value, they are uniquely vulnerable to the increasing global threat of climate change, as well as other anthropogenic impacts.
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Symbiotic Relationship:

It is defined as a close, prolonged association between two or more different biological species, where both parties involved benefit from the interaction.

Favourable Conditions for the formation of Corals:

  • Optimal Sunlight Exposure: Corals thrive in shallow water where ample sunlight penetrates to support their symbiotic relationship with zooxanthellae (algae). These microscopic algae residing within the coral provide vital oxygen and other essential nutrients, relying on sunlight for their survival. Consequently, corals, too, depend on sunlight to flourish. 
  • Translucent Water Conditions: Clear and unpolluted water is crucial for corals as it allows sunlight to permeate through the depths. The clarity of water determines the amount of sunlight that reaches the corals, thereby ensuring their sustenance and vitality. 
  • Optimal Water Temperature: Corals exhibit a remarkable adaptability to a narrow temperature range, typically thriving in water temperatures between 20–32°C. The temperature within this specific range is essential for their growth and survival. 
  • Salinity Requirements: Corals necessitate a specific balance in the salt-to-water ratio to thrive. As a consequence, they cannot survive in areas where freshwater from rivers flows into the ocean, as the altered salinity in these estuaries is unsuitable for coral growth. Instead, corals are restricted to habitats with the appropriate saltwater conditions.

Distribution of Corals in the world:

Distribution of Corals in the world

Ecosystem services provided by Corals:

  • Human health and wellbeing: 70% of the protein in the diets of Pacific Islanders comes from reef-associated fisheries (SDGs 2, 3, 6, 9 & 14; Aichi Biodiversity Targets 13, 14, 16).
  • Shoreline protection: A healthy coral reef can reduce coastal wave energy by up to 97%. Globally, USD6 billions of built capital is protected from flooding by coral reefs (SDGs 1, 8, 11, 13, 14).
  • Food security and livelihoods: Coral reef fisheries support as many as six million people and are worth USD6.8 billion per year, providing an average annual seafood yield of 1.42 million tonnes (SDGs 2, 4, 5, 8, 12, 13, 14, 16).
  • Tourism: Coral reef tourism contributes USD36 billion to the global tourism industry annually (SDGs 2, 4, 5, 6, 8, 9, 12, 14).
  • Biodiversity: Coral reefs support approximately 4,000 species of fish and 800 species of hard corals, Globally, about 830,000 species of multicellular plants and animals are estimated to occur on coral reefs, of which an estimated 13% are unnamed and 74% are yet to be discovered. Most of these species are cryptic, small and relatively rare.
  • Medicines: Coral reefs are the medicine chests of the 21st century, with more than half of all new cancer drug research focusing on marine organisms.

What is Coral Bleaching?

When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white.

Coral Bleaching flowchart

Ocean acidification which is caused by CO2 absorption in oceans, lowers pH levels of ocean water and affects calcium carbonate minerals. The combination of acidification and ocean warming poses a significant threat to coral reefs’ ability to form skeletons. 

Status of Corals in the world at present:

The 2019 global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Service (IPBES), and the Intergovernmental Panel on Climate Change (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate, warn that:

  • Over half of the world’s coral reefs have been lost;
  • At warming of 1.5oC, 70-90% of the world’s coral reefs are expected to be lost. At 2oC degrees, this increases to >99% loss of coral reefs.

Global Initiatives for protection of Coral reefs:

The International Coral Reef Initiative (ICRI) is the only international partnership, between nations and organizations, focussing solely on the protection of coral reefs and related ecosystems worldwide. The Initiative was founded in 1994 by Australia, France, Japan, Jamaica, the Philippines, Sweden, the United Kingdom, and the United States of America. It was announced at the First Conference of the Parties of the Convention on Biological Diversity (CBD) in December 1994.

India’s efforts for Coral Restoration:

The Zoological Survey of India (ZSI), with help from Gujarat’s forest department, is attempting for the first time a process to restore coral reefs using biorock or mineral accretion technology. Biorock is the name given to the substance formed by electro accumulation of minerals dissolved in seawater on steel structures that are lowered onto the sea bed and are connected to a power source, in this case solar panels that float on the surface. The technology works by passing a small amount of electrical current through electrodes in the water. When a positively charged anode and negatively charged cathode are placed on the sea floor, with an electric current flowing between them, calcium ions combine with carbonate ions and adhere to the structure (cathode). This results in calcium carbonate formation. Coral larvae adhere to the CaCO3 and grow quickly.

Steps need to be taken for protection of corals:

  • Safeguarding Coral Reefs: Government should regulate nearshore fishing to ensure sustainable practices that do not harm the reef. This involves managing fishing activities around coral reefs and prohibiting harmful practices such as dynamite and cyanide fishing, as well as the harvesting of live coral. 
  • Marine Protected Areas(MPAs): MPAs define specific rules and guidelines to protect reef life while also allowing sustainable human use. By designating specific zones for protection and regulated use, MPAs offer a practical approach to safeguarding coral reefs and their invaluable ecosystems. 
  • Combating Land-based pollution: To protect coral reefs from land-based pollution and runoff, it is imperative to implement measures that reduce pollution sources and preserve critical coastal ecosystems. This includes sustainable land-use practices, responsible waste management, and protecting and restoring vital coastal habitats. 
  • Effective Monitoring and Enforcement: Engaging stakeholders in monitoring and enforcing regulations empowers communities to take ownership of their coral reef resources, fostering a sense of responsibility and stewardship. However, in areas with limited resources, community-based management efforts can play a crucial role.
  • Education and Outreach: It should target stakeholders, community members, and even school children, enlightening them about the importance of coral reefs and their interconnectedness with human well-being. By empowering people with knowledge, communities can foster a deeper sense of appreciation and encourage positive actions to safeguard coral reefs. Education can also prompt individuals to adopt sustainable practices in their daily lives, further contributing to the conservation efforts for these invaluable ecosystems.

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