Fourth mass coral bleaching

Fourth mass coral bleaching

Subject: Geography

Section: Oceanography

Context : According to the U.S. NOAA, the world is on the verge of a fourth mass coral bleaching event which could see wide swathes of tropical reefs die, including parts of Australia’s Great Barrier Reef.

Coral reef

• But corals are quite sensitive to warming water. They host a microscopic symbiotic alga called zooxanthella that photosynthesizes just like plants, providing food to the coral. When the surrounding waters get too warm for too long, the zooxanthellae leave the coral, and the coral can turn pale or white – a process known as bleaching.
• If corals stay bleached, they can become energetically compromised and ultimately die.
• When corals die or their growth slows, these beautiful, complex reef habitats start disappearing and can eventually erode to sand.

Importance of coral reefs:

• Coral reefs are hot spots of biodiversity. They are often referred to as the rainforests of the sea because they are home to the highest concentrations of species in the ocean.
• Healthy reefs are vibrant ecosystems that support fish and fisheries, which in turn support economies and food for millions of people.
• Additionally, they provide billions of dollars in economic activity every year through tourism, particularly in places like the Florida Keys, where people go to scuba dive, snorkel, fish and experience the natural beauty of coral reefs.
• If that isn’t enough, reefs also protect shorelines, beaches and billions of dollars in coastal infrastructure by buffering wave energy, particularly during storms and hurricanes.

What is Coral Bleaching?

• When corals face stress by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae zooxanthellae living in their tissues, causing them to turn completely white. This phenomenon is called coral bleaching.
• The pale white colour is of the translucent tissues of calcium carbonate which are visible due to the loss of pigment producing zooxanthellae.
• Bleached corals can survive depending on the levels of bleaching and the recovery of sea temperatures to normal levels.
• If heat-pollutions subside in time, over a few weeks, the zooxanthellae can come back to the corals and restart the partnership but severe bleaching and prolonged stress in the external environment can lead to coral death.
• Over the last couple of decades, climate change and increased global warming owing to rising carbon emissions and other greenhouse gases have made seas warmer than usual.
• Coral bleaching has occurred in the Caribbean, Indian, and Pacific oceans on a regular basis.

Mass Coral Bleaching:

To officially declare a global mass bleaching event, widespread bleaching must be observed in three major ocean basins: the Atlantic, Pacific, and Indian Oceans. According to Manzello, “technically we’re already there” in 2024, pending final confirmation from Indian Ocean scientists.

Previous Mass Coral Bleaching

• 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 caused 8% of the world’s coral to die.
• Second Mass Bleaching: This event took place in 2002. In the past decade, however, mass bleaching occurrences have become more closely spaced in time, with the longest and most damaging bleaching event taking place from 2014 to 2017.
• Third Mass Bleaching: The event that took place between 2014-17 affected reefs in Guam in the Western Pacific region, the North, South-Pacific, and the Indian Ocean.

What are the Findings of the National Oceanic and Atmospheric Administration (NOAA)?

• The world is on the verge of a fourth mass coral bleaching event (after 1998, 2010 and 2014).
• Preliminary results suggest that about 15% of the world’s reefs saw large coral die-offs in this event.
• This year is turning out to be even worse. For example, following the Northern Hemisphere summer last year, the Caribbean registered its worst coral bleaching on record.
• Coral bleaching is often tied to the naturally occurring El Nino climate phenomenon which leads to warmer ocean waters.
• The world also just registered (as a result of climate change) its first 12-month period with an average temperature over 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre industrial levels.
• A rise of 1.5C is believed to be the tipping point for mass coral die-offs, with scientists estimating that 90% of the world’s corals could be lost.

Initiatives to Protect Corals

• International Coral Reef Initiative
• Global Coral Reef Monitoring Network (GCRMN)
• Global Coral Reef Alliance (GCRA)
• The Global Coral Reef R&D Accelerator Platform
• Similarly, the Ministry of Environment and Forests and Climate Change (MoEF&CC), India has included the studies on coral reefs under the Coastal Zone Studies (CZS).
• In India, the Zoological Survey of India (ZSI), with help from Gujarat’s Forest department, is attempting a process to restore coral reefs using “biorock” or mineral accretion technology.
• National Coastal Mission Programme, to protect and sustain coral reefs in the country.