According to the US National Oceanic and Atmospheric Administration (NOAA), the fourth global mass coral bleaching event has been triggered by extraordinary ocean temperatures. According to the EU Copernicus Climate Change Service (C3S), the average sea surface temperature (SST) has been increasing and it has reached a record monthly high of 21.07 degree Celsius.
ABOUT CORAL REEFS
Corals are small (0.25-12 inches), soft-bodied marine invertebrates (not possessing a spine) which belong to the group cnidaria. These are sessile animals which permanently attach themselves to the ocean floor.
Each individual coral animal is known as a polyp and it lives in groups of hundreds to thousands of genetically identical polyps that form a ‘colony’. They use their tiny tentacle-like hands to catch food from the water and sweep into their mouth.
These coral polyps have microscopic algae called zooxanthellae living within their tissues. The corals and algae have a mutualistic relationship.
The coral provides the zooxanthellae with the compounds necessary for photosynthesis. In return, the zooxanthellae supply the coral with organic products of photosynthesis, like carbohydrates, which are utilized by the coral polyps for synthesis of their calcium carbonate skeletons.
In addition to providing corals with essential nutrients, zooxanthellae are responsible for the unique and beautiful colors of corals.
Coral Reefs in India- Coral reefs in India are located in seven regions namely Goa coast, Kerala coast, Palk Bay, Gulf of Kutch, Gulf of Mannar, Lakshadweep islands and Andaman and Nicobar islands.
SIGNIFICANCE OF CORAL REEFS
CORAL BLEACHING
MASS CORAL BLEACHING EVENTS
First Mass Bleaching : It occurred in 1998 when the El Niño weather pattern caused sea surfaces in the Pacific Ocean to heat up. This event led to the death of 8% of the world’s coral.
Second Mass Bleaching :This event took place in 2010. It led to increased destruction of 35% coral reefs.
Third Mass Bleaching :The event that took place between 2014-17 and affected reefs in Guam in the Western Pacific region, the North, South-Pacific, and the Indian Ocean. It affected 56% of coral reefs around the world.
Fourth global bleaching event is currently underway. Nearly 54 countries, territories and local economies- from Florida, the US, Saudi Arabia to Fiji- have confirmed bleaching. Bleaching has been confirmed in the Western Indian Ocean, including Tanzania, Kenya, Mauritius, Seychelles, and off the western coast of Indonesia.
CAUSES RESPONSIBLE FOR CORAL BLEACHING:
Rise in Sea Temperature: As global warming continues, sea temperatures rise, causing stress to coral reefs. Elevated temperatures lead to a phenomenon known as thermal stress, where corals expel the symbiotic algae living in their tissues, resulting in bleaching.
Ocean Acidification: Increased levels of carbon dioxide in the atmosphere are absorbed by the oceans, leading to higher acidity levels. This acidification inhibits the ability of corals to form their calcium carbonate skeletons, essential for their growth and structural integrity.
Solar and Ultraviolet Radiation: Changes in weather patterns, often associated with climate change, result in decreased cloud cover and increased exposure to solar radiation. Additionally, ultraviolet radiation can directly stress corals, contributing to bleaching events.
Infectious Diseases: Bacteria such as Vibrio shiloi can proliferate in warmer waters and infect coral tissues, disrupting their normal functions, including photosynthesis. Elevated sea temperatures can exacerbate the virulence of these pathogens, leading to more severe coral bleaching.
Chemical Pollution: Runoff from agricultural and industrial activities introduces excess nutrients into coastal waters, promoting the growth of algae that compete with corals for space and resources. This heightened competition can weaken corals and make them more susceptible to bleaching events.
Human Induced Threats: Activities such as overfishing, coastal development, and coral mining directly damage coral ecosystems. Additionally, pollution from sources like oil spills and plastic waste further stress corals, compounding the effects of other environmental stressors.
CONSEQUENCES OF CORAL BLEACHING:
Food Chain disruption : Coral reefs provide crucial habitat and food resources for a diverse array of marine species. When corals bleach and die, this disrupts the delicate balance of the marine food web, affecting species that rely on corals for shelter and sustenance.
Loss of Biodiversity: Coral reefs are among the most biodiverse ecosystems on the planet, supporting a myriad of species. When corals bleach and perish, this results in a decline in genetic diversity and species richness, impacting the overall health and resilience of coral reef ecosystems.
Economic Decline: Coral reefs are major tourist attractions, drawing visitors for diving, snorkeling, and recreational fishing. Bleached and degraded reefs deter tourists, leading to loss of revenue for coastal communities reliant on tourism income.
Affects Food Availability: Changes in fish communities due to coral bleaching can reduce fishery yields, affecting the availability of seafood for both local consumption and commercial markets. This, in turn, can impact food security and livelihoods dependent on fishing.
Impact on Coastal Protection: Healthy coral reefs act as natural barriers, dissipating wave energy and protecting coastlines from erosion, storm surges, and flooding. When corals bleach and die, this protective function is compromised, leaving coastal communities more vulnerable to the impacts of climate-related hazards.
INITIATIVES TO PROTECT CORALS
Initiatives by GoI: Marine Protected Areas (MPAs), Wildlife Protection Act, Gulf of Kutch Marine Park, Coral Reef Recovery Project, National Coastal Mission Programme
International initiatives- International Coral Reef Initiative, Global Coral Reef Monitoring Network (GCRMN), Global Coral Reef Alliance (GCRA) and The Global Coral Reef R&D Accelerator Platform have been established to deal with the issue.
Biological restoration- It uses methods for coral growth and transplanting to assist the restoration of a coral reef. It includes Asexual propagation and Coral Gardening.
Structural restoration- It involves the construction of artificial reefs, or relocation of rocks/dead coral heads. The goal is to increase the amount of reef structure and habitat available for the corals and other reef organisms to grow on. For ex- Bio rock technology
Physical restoration- It addresses the conditions in which the corals are growing to improve their health, growth rates, or reproductive ability.
WAY FORWARD
Regulate Coastal Development: Enforce zoning regulations and ecosystem-based management to control unplanned development, preventing habitat destruction and pollution.
Promote Sustainable Practices: Encourage sustainable fishing methods and responsible ecotourism to maintain fish populations, support local economies, and minimize environmental impact.
Reduce Chemical Pollution: Promote organic farming, implement runoff controls, and raise awareness to minimize the use of harmful chemicals, protecting coral reef health from nutrient enrichment and degradation.
Address Climate Change: Transition to renewable energy, enhance energy efficiency, and support international agreements to reduce greenhouse gas emissions and mitigate the impacts of climate change on coral reefs.
PRACTICE QUESTION
Q. Highlight the significant role played by coral reefs in maintaining ocean ecosystems. Discuss the impact of climate change on corals. (10M, 150W)
