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Heat-tolerant Corals Discovered
Context:
Recent research has revealed surprising evidence of variable heat tolerance in corals, a critical finding as the Great Barrier Reef has experienced five mass bleaching events since 2016, including one during the world’s warmest year recorded this summer.
Key Findings on Heat-Tolerant Corals
- Variable Heat Tolerance: Coral colonies show different levels of heat tolerance, comparable to human stress responses.
- Recent Events: The Great Barrier Reef has suffered five mass bleaching events since 2016, with the latest in 2024, during the warmest year on record.
- Need for Action: Reducing global carbon emissions is critical to slowing ocean warming and preserving coral reefs.
Research Methodology
- Species Studied: Acropora hyacinthus, a common but vulnerable coral species.
- Experiment Setup:
- Over 500 coral colonies from 17 reefs were studied using a portable system with 12 tanks at varying temperatures to measure coral responses.
- Bleaching Thresholds: The temperature at which coral pigmentation drops to 50% of its healthy level was used to measure bleaching.
Key Results
- Bleaching Variation: Coral pigmentation retention varied from 3% to 95% under heat stress.
- Heat-Tolerant Colonies: 12 of the 17 reefs had colonies in the top 25% of heat tolerance, indicating widespread resilience.
Nature vs. Nurture
- Genetic Factors: Coral heat tolerance is influenced by unique genetic traits, suggesting potential for adaptation across the Great Barrier Reef.
- Environmental Influences: Water temperature and nutrient levels are crucial to coral stress responses.
- Geographical Differences:
- Northern corals tolerate higher temperatures but are near their limits.
- Southern corals withstand less heat but are more adaptable to local warming.
Implications for Coral Conservation
- Adaptation Potential: Corals may adapt to warmer waters, increasing their chances of survival amid climate change.
- Restoration Efforts: Selective breeding of heat-tolerant corals is underway to enhance offspring resilience.
Formation of Coral Reefs
- Coral Polyps: Secrete calcium carbonate skeletons, forming limestone structures through biomineralisation.
- Symbiotic Algae: Zooxanthellae provide nutrients through photosynthesis, supporting coral growth.
- Growth: Coral reefs grow in warm, shallow, nutrient-poor waters with stable salinity and low sedimentation.
Types and Locations of Coral Reefs
- Fringing Reefs: Found near shores, common in the Gulf of Mannar and Andaman Islands.
- Barrier Reefs: Separated from the shore by a lagoon, farther from the coast.
- Atolls: Ring-shaped reefs with a central lagoon, common in Lakshadweep.
- Indian Locations: Reefs are located in the Gulf of Kutch, Gulf of Mannar, Andaman, Nicobar, and Lakshadweep Islands.
Importance of Coral Reefs
- Biodiversity: Host 25% of marine species, supporting fisheries and food security.
- Coastal Protection: Act as barriers, preventing erosion and storm damage.
- Tourism and Recreation: Significant source of income for coastal communities.
- Medicinal Value: Potential sources for new medicinal compounds.
- Climate Regulation: Play a role in carbon and nitrogen cycles.
- Cultural Value: Integral to the livelihoods of coastal communities.
- Scientific Research: Crucial for studying marine ecosystems and climate change.
Threats to Coral Reefs
- Coral Bleaching: Rising sea temperatures lead to the expulsion of zooxanthellae, causing bleaching and coral death.
- Ocean Acidification: Increased CO₂ absorption hinders coral skeleton formation.
- Pollution: Agricultural runoff and sewage introduce harmful nutrients to reefs.
- Overfishing and Destructive Fishing: Disrupt reef ecosystems and damage coral structures.
- Coastal Development and Tourism: Leads to habitat destruction and reef damage.
- Invasive Species: Species like crown-of-thorns starfish prey on coral polyps.
- Natural Disasters and Diseases: Hurricanes, tsunamis, and coral diseases cause physical damage and stress to reefs.
International Regulations and India’s Efforts
- Global Efforts:
- Convention on Biological Diversity (CBD)
- UNFCCC for climate change mitigation
- CITES regulates trade in endangered coral species
- SDG 14 emphasises marine ecosystem conservation.
- India’s Measures:
- Marine Protected Areas (MPAs) in regions like the Gulf of Mannar and Andaman Islands
- Coral reef monitoring, conservation awareness, and tourism regulation
- Coral restoration programs and participation in global agreements.
Way Forward:
- Sustainable Management: More MPAs and better enforcement of reef protection measures.
- Climate Action: Reduction in global greenhouse gas emissions.
- Community Engagement: Involve local communities in reef conservation efforts.
- Scientific Research and Coral Restoration: Continue research on coral resilience and invest in coral farming.
- International Cooperation: Share resources and strategies for global reef conservation.