Fourth global mass coral bleaching event

22 Apr Fourth global mass coral bleaching event

THIS ARTICLE COVERS ‘DAILY CURRENT AFFAIRS’ AND THE TOPIC DETAILS “CORAL BLEACHING”. THIS TOPIC IS RELEVANT IN THE “Environment” SECTION OF GS3 IN THE UPSC CSE EXAM.

Why in the news?

The US National Oceanic and Atmospheric Administration(NOAA) has noted that the fourth global mass coral bleaching event has been triggered by extraordinary ocean temperatures.

The great barrier reef in Australia, the largest in the world is most affected by severe bleaching.

About coral reefs

• Coral reefs are underwater structures formed by  calcium carbonate secreted by corals. Corals are tiny, soft-bodied organisms related to sea anemones and jellyfish. They live in colonies and form hard exoskeletons as they grow. These exoskeletons accumulate over time, creating the complex structures we know as coral reefs.
• Coral reefs are referred to as the “rainforests of the sea” due to their high biodiversity and the crucial role they play in supporting marine ecosystems. They provide habitats for a vast array of marine life, including fish, crustaceans, mollusks, and many other organisms. Additionally, coral reefs protect coastlines from erosion by acting as natural barriers against waves and storms.
• However, coral reefs are highly sensitive to environmental changes, such as rising sea temperatures, pollution, and ocean acidification. These factors often lead to coral bleaching, a phenomenon where corals expel the algae living in their tissues, causing them to turn white and potentially die. Protecting coral reefs is essential for maintaining marine biodiversity and the health of our oceans.

What is coral bleaching?

Coral bleaching is a phenomenon in which corals lose their vibrant colors due to the expulsion of symbiotic algae living within their tissues. These algae, called zooxanthellae, provide corals with energy through photosynthesis and contribute to their vibrant colors. When corals are stressed by environmental factors such as high water temperatures, pollution, or changes in water chemistry, they expel the algae, causing them to turn white or pale.

Several factors can trigger coral bleaching:

1. High Water Temperatures: Elevated sea temperatures, particularly during periods of prolonged heat stress, can cause corals to bleach. Warmer temperatures stress the corals, leading them to expel the zooxanthellae.
2. Pollution: Pollution from sources such as agricultural runoff, sewage, and coastal development can degrade water quality and stress corals, making them more susceptible to bleaching.
3. Ocean Acidification: Increasing levels of carbon dioxide in the atmosphere can lead to ocean acidification, which can weaken coral skeletons and make corals more vulnerable to bleaching.
4. Physical Damage: Physical damage from factors such as boat anchors, fishing gear, and coastal construction can stress corals and increase their susceptibility to bleaching.

When corals bleach, they are not necessarily dead, but they are under increased stress and more vulnerable to mortality. If the stressful conditions persist, bleached corals may eventually die. Mass bleaching events, where large numbers of corals bleach simultaneously across extensive reef systems, can have devastating consequences for coral reef ecosystems, leading to widespread coral mortality and ecosystem decline.

Coral bleaching is a significant concern for coral reef conservation, as it is increasingly occurring at higher frequencies and severities due to climate change and human activities. Mitigating climate change, reducing pollution, and implementing sustainable management practices are essential for protecting coral reefs and preventing further bleaching events.

Other challenges posed to corals

• Ocean Acidification: Increasing levels of carbon dioxide in the atmosphere lead to ocean acidification, which can weaken coral skeletons and hinder coral growth and reproduction.

• Overfishing: Overfishing of key reef species, such as herbivorous fish and invertebrates, can disrupt ecological balance and degrade coral reef health. Removing herbivores can lead to overgrowth of algae, which can smother corals and inhibit their growth.

• Invasive Species: Invasive species, such as crown-of-thorns starfish, can prey on corals and contribute to reef degradation by causing outbreaks that lead to widespread coral mortality.

• Sedimentation: Excessive sediment runoff from coastal development, deforestation, and erosion can smother corals, reduce light penetration, and hinder coral growth and reproduction.

• Climate Change: Climate change exacerbates many of the threats facing coral reefs, including coral bleaching, ocean acidification, and more frequent and severe storms. Rising sea temperatures disrupt the symbiotic relationship between corals and zooxanthellae, leading to bleaching events.

• Illegal Trade: Illegal collection of coral for the aquarium trade and for use in jewelry and decorative items can deplete coral populations and disrupt reef ecosystems.

Way forward

The way forward to protect and conserve coral reefs involves a multi-faceted approach that addresses the various threats facing these ecosystems. Here are some key strategies:

1. Mitigating Climate Change: Addressing the root cause of coral bleaching and ocean acidification requires global efforts to reduce greenhouse gas emissions. This includes transitioning to renewable energy sources, improving energy efficiency, and implementing policies to limit carbon emissions.
2. Marine Protected Areas (MPAs): Establishing and effectively managing marine protected areas can help conserve coral reef ecosystems by reducing fishing pressure, protecting critical habitats, and enhancing ecosystem resilience. MPAs should be designed based on scientific evidence and involve stakeholders in their management.
3. Sustainable Fisheries Management: Implementing sustainable fishing practices, such as regulating fishing quotas, protecting spawning grounds, and promoting selective fishing methods, can help maintain fish populations and preserve the ecological balance of coral reef ecosystems.
4. Pollution Reduction: Implementing measures to reduce pollution from land-based sources, such as improving sewage treatment, regulating agricultural runoff, and reducing plastic pollution, can improve water quality and reduce stress on coral reefs.
5. Integrated Coastal Zone Management: Adopting integrated coastal zone management approaches that consider the interactions between land and sea can help minimize coastal development impacts, reduce sedimentation, and protect coral reef habitats.
6. Community Engagement and Education: Engaging local communities in coral reef conservation efforts through education, awareness campaigns, and participatory management approaches can foster stewardship and support sustainable resource use practices.
7. Research and Monitoring: Continued research and monitoring of coral reef ecosystems are essential for understanding the drivers of coral reef decline, identifying priority conservation areas, and evaluating the effectiveness of conservation measures.
8. International Cooperation: Collaboration among governments, non-governmental organizations, researchers, and local communities is crucial for addressing transboundary issues, sharing knowledge and best practices, and mobilizing resources for coral reef conservation.

By implementing these strategies in a coordinated and holistic manner, we can work towards safeguarding coral reef ecosystems for future generations and ensuring their ecological, economic, and cultural value persists.

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Ankit Kumar

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