Coral Bleaching

Subject : Environment

Section: Ecosystem

Concept :

The water off South Florida is over 90 degrees Fahrenheit (32 Celsius) in mid-July, and scientists are already seeing signs of coral bleaching off Central and South America.
If the extreme heat persists, it could have dire consequences for coral reefs.
Just like humans, corals can handle some degree of stress, but the longer it lasts, the more harm it can do.
Corals can’t move to cooler areas when water temperatures rise to dangerous levels. They are stuck in it.
For those that are particularly sensitive to temperature stress, that can be devastating.

Why coral reefs matter to everyone ?

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 goes into a coral reef?

But corals are quite sensitive to warming water. They host a microscopic symbiotic algae 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.

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:

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.

Initiatives to Protect Corals

A number of global initiatives are being taken to address the issues, like:
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.