A report from the IPCC in 2018 stated that corals would decline by 70-90% with global warming of 1.5°C, but virtually all (> 99%) would be lost with 2°C. if we continue with business as usual, severe bleaching events, currently about a decade apart, will become much more frequent—happening yearly by 2049. This is alarming because it doesn't give corals the time they need to recover.
Coral reefs are often called the "rainforests of the sea" because they host around 25% of all marine biodiversity. Beyond that, they provide coastal protection from storms, and support the livelihood of hundreds of millions of people through tourism and fisheries. They're vital ecosystems.
Coral reefs are formed by the hard skeletons of coral polyps, which are tiny animals that live in colonies. The polyps get their food from the algae that live in their tissues. These algae, called zooxanthellae, are tiny single-celled organisms that photosynthesize. They provide the coral with food and oxygen, and the coral provides them with a protected environment.
The relationship between coral polyps and zooxanthellae is called symbiosis, which means that both organisms benefit from each other. This relationship is essential for the survival of coral reefs. Without the zooxanthellae, the coral would not be able to get enough food to survive. And without the coral, the zooxanthellae would not have a protected environment to live in. Coral reefs are incredibly important ecosystems. They provide food and shelter for a wide variety of marine life, including fish, turtles, and dolphins.
What is Coral Bleaching?
Coral bleaching is essentially a stress response. When water temperatures rise, corals expel the algae living in their tissues. The algae give the corals their color and help them to survive. When the corals expel the algae, they become white and may eventually die. While this isn't immediately fatal, it puts the coral under significant stress, and if the algae don't return, the coral will eventually die. These algae provide the coral with 90% of its energy. Bleached corals can survive but are under more stress and are more susceptible to disease. One of the main reasons for coral bleaching is temperature stress, which can be exacerbated by weather events like El Niño.
The El Niño weather pattern in 2016 had devastating effects on coral reefs, especially the Great Barrier Reef, one of the most biodiverse ecosystems in the world. There have been five mass bleaching events recorded since 1998, with the most recent one occurring in 2022-2023. The 2023 bleaching event is the first to occur during a La Niña, which is a climate pattern that typically brings cooler water temperatures. This suggests that climate change is making coral reefs more vulnerable to bleaching, even during events that would normally be beneficial.
The ideal environmental conditions for corals to grow are:
* Shallow water
* Semi-hard or hard surface
* Clear water
* Warm water
* Saline-filled waters
* Rich supply of nutrients
These conditions are met in the Andaman and Nicobar Islands, which is why they have the largest area under coral reefs in India, the others being Lakshadweep Islands, the Gulf of Mannar, and the Gulf of Kachchh. Each of these areas has its unique ecosystem, but they're all feeling the heat, literally and figuratively.
The Indian government has taken some steps to address the threats to coral reefs:
* The Indian government has established a number of MPAs to protect coral reefs.
* The Reef Watch India program is a citizen science initiative that monitors coral reefs and raises awareness about the threats they face.
* The National Centre for Sustainable Coastal Management (NCSCM) is conducting research on coral reef ecology and management.
* The International Union for Conservation of Nature (IUCN) is working with the Indian government to develop a plan for the conservation of coral reefs.
However, more needs to be done to protect these important ecosystems.
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neeraj@unown.org
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