In News:

A recent 24-year study (1998–2022) of coral reefs in the Lakshadweep Archipelago revealed that live coral cover has declined by nearly 50%, from about 37.2% to 19.1%. The research, conducted across three atolls—Agatti, Kadmat, and Kavaratti—highlights the severe impact of repeated marine heatwaves linked to climate change.

What are Corals?

Corals are small, soft-bodied marine invertebrates belonging to the Cnidaria group. Individual corals, called polyps, secrete a calcium carbonate exoskeleton, forming vast reef structures. Coral reefs provide crucial habitats for about 25% of marine life and support over 1 billion people worldwide with food, livelihoods, and coastal protection.

Types and Distribution:

India’s coral reefs are mainly found in the Gulf of Kutch, Gulf of Mannar, Andaman & Nicobar Islands, Lakshadweep Islands, and Malvan.

Causes of Coral Decline:

• Marine Heatwaves & Climate Change: Rising sea surface temperatures disrupt the symbiotic relationship between corals and their algae (zooxanthellae), causing bleaching and mortality.
• Ocean Acidification: Increased CO? lowers ocean pH, hampering coral skeleton formation.
• Pollution: Land runoff with fertilizers, pesticides, and heavy metals harms coral health.
• Physical Damage: Coastal development, sedimentation, and unsustainable fishing.
• Overfishing: Imbalance in reef ecosystems due to loss of algae-eating fish.

Key Findings from the Lakshadweep Study:

• Coral mortality from bleaching has decreased over time but so has the reefs’ recovery rate.
• Heat-sensitive coral species have largely disappeared, leaving more stress-tolerant species like Porites dominant.
• Recovery accelerates only if reefs are given at least a six-year gap between bleaching events.
• The 2010 marine heatwave was the most severe, with a Degree Heating Week (DHW) value of 6.7, indicating significant heat stress.
• The study emphasizes the need for longer recovery periods between bleaching for coral regeneration.

Implications for Conservation:

• The study provides a predictive framework to identify reefs vulnerable to bleaching and prioritize restoration.
• Local conservation must be combined with urgent global climate action to reduce the frequency of heatwaves.
• Without global intervention, even resilient coral species may not survive repeated disturbances.

This study underscores the vulnerability of India’s coral reefs, especially in Lakshadweep, to climate change and highlights the urgent need for integrated local and global conservation efforts.

In News:

In a paper published in the Cell Press journal Trends in Biotechnology, researchers demonstrate that the ink could boost coral settlement by more than 20 times, which they hope could contribute to rebuilding coral reefs around the world.

Recent Development in Coral Restoration

• Institution: University of California, San Diego
• Innovation: Development of SNAP-X, a specialized bio-ink.
• Significance: SNAP-X boosts coral larvae settlement by 20 times, marking a major advancement in coral reef restoration, especially vital in the context of climate change-induced reef degradation.

What are Coral Reefs?

• Coral reefs are diverse marine ecosystems formed by colonies of coral polyps, which secrete calcium carbonate to create hard exoskeletons.
• These ecosystems thrive in warm, shallow, and clear tropical waters and are among the most productive on Earth.

Examples of Coral Reefs

• Global: Great Barrier Reef (Australia)
• India: Gulf of Mannar, Lakshadweep Islands

Importance of Coral Reefs

• Biodiversity Hotspots: Support thousands of marine species.
• Coastal Protection: Act as natural barriers against storms and erosion.
• Livelihoods: Sustain tourism and fisheries industries.
• Food Security: Provide fish and other resources to coastal communities.

Types of Coral Reefs

• Fringing Reefs
  • Found close to coastlines
  • Separated from land by shallow lagoons
  • Most widespread type
• Barrier Reefs
  • Located farther from shore
  • Separated by deeper, wider lagoons
  • Example: Great Barrier Reef
• Atolls
  • Ring-shaped reefs surrounding a central lagoon
  • Often form around subsiding volcanic islands
  • Found in the Indian and Pacific Oceans

Favorable Conditions for Coral Reef Growth

Factor                                                 Requirement

Water Temperature                 Around 20°C; typically in tropical zones (30°N to 30°S)

Sunlight                                            Shallow depths (up to ~55 meters) allow photosynthesis

Water Clarity                                 Low nutrient and sediment levels for light penetration

Salinity                                              Stable marine salinity levels

Pollution                                           Minimal; corals are sensitive to chemical/sediment pollutants

Food Supply                                   Plankton-rich water sustains coral polyp

Why is it in the News?

The world stands on the brink of witnessing its fourth mass coral bleaching event, a phenomenon that threatens to hit vast expanses of tropical reefs, including significant portions of Australia's iconic Great Barrier Reef.

Key Findings from the National Oceanic and Atmospheric Administration (NOAA):

• Impending Fourth Mass Coral Bleaching Event: The world is on the brink of a fourth mass coral bleaching event, following those in 1998, 2010, and 2014.
  • To classify as global, widespread bleaching must occur across three ocean basins: the Atlantic, Pacific, and Indian.
• Impact of Previous Events: The last global mass coral bleaching event occurred from 2014 to 2017, resulting in the loss of nearly a third of the Great Barrier Reef's corals.
  • Preliminary data indicates that approximately 15% of the world's reefs experienced significant coral die-offs during this event.
• Current Situation: This year is witnessing even more severe bleaching events, with the Caribbean experiencing its worst coral bleaching on record following the Northern Hemisphere summer last year.
• Link to Climate Phenomena: Coral bleaching is often associated with the naturally occurring El Niño climate phenomenon, which leads to warmer ocean waters.
• Climate Change Impact: The world recently experienced its first 12-month period with an average temperature exceeding 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels.
  • A temperature rise of 1.5°C is considered the tipping point for mass coral die-offs, with scientists estimating that 90% of the world's corals could be lost as a result.

About the Corals and Coral Reefs:

• Corals: Corals are animals known as polyps, which engage in a symbiotic relationship with tiny algae called zooxanthellae.
  • These algae provide corals with food and oxygen, while corals offer them a safe habitat.
•  Coral Reefs: Coral reefs are limestone structures formed by thousands of tiny coral animals and are predominantly found in tropical climates.

Coral Bleaching and Its Concerns:

• Coral bleaching occurs when corals are exposed to stressful conditions like high temperatures, pollution, or changes in water chemistry, leading them to expel the zooxanthellae.
  • Without these algae, corals lose their color and turn white, hence the term 'bleaching,' and cannot survive for long in this state.
• Recovery Potential: Despite its severity, coral bleaching doesn't necessarily mean the end of the reef; timely removal of stressors can facilitate the return of zooxanthellae and coral recovery.
• Ecological Importance: Coral reefs serve as habitats and food sources for numerous fish and marine species.
  • They also offer coastal protection from erosion and storms and play a critical role in regulating the Earth's climate by absorbing and storing carbon dioxide.
• Cultural and Aesthetic Value: Beyond their ecological functions, coral reefs represent stunning biodiversity and natural beauty, making their loss a tragic prospect for future generations.
• Impacts: When coral reefs suffer, so do the ecosystems and communities reliant on them, underscoring the far-reaching consequences of coral degradation.