Why is Lakshadweep facing widespread coral bleaching?

Coral reefs in Lakshadweep are suffering from widespread bleaching.

That’s what a new survey by the ICAR-Central Marine Fisheries Research Institute (CMFRI) revealed.

But did the survey show? How bad is it? And why is this happening?

Let’s take a closer look:

What happened?

First, let’s take a brief look at coral reefs.

According to the National Oceanic and Atmospheric Administration, coral reefs are the “rainforests of the sea.”

Around 25 per cent of the ocean’s fish depend on healthy coral reefs.

Fish and other life forms take refuge, look for sustenance, mate and raise their young in the corals.

Corals also help keep the coastlines safe from storms and erosion around the world.

Unfortunately, climate change, overfishing and pollution are putting coral reefs at risk.

So, what happened?

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The survey of various Lakshadweep Islands by CMFRI researchers showed that a substantial percentage of the hard coral species experienced severe bleaching.

This came after a protracted period of marine heat waves impacted the region since late October 2023.

Marine heatwaves are rare extreme weather events that involve prolonged periods of abnormally high ocean temperatures, according to the CMFRI.

These temperatures often exceed the 90th percentile of typical regional ocean temperatures based on historical data.

In Lakshadweep, the Degree Heating Week (DHW) indicator, which measures accumulated heat stress, has surged above four degrees Celsius-weeks.

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Dr Shelton Padua, senior scientist at CMFRI, identified the primary causes of these marine heatwaves as excessive heat atmospheric transfer coupled with shifts in ocean currents, leading to unusually high-water temperatures.

The Lakshadweep Sea has been experiencing these conditions since 27 October 2023.

Temperatures have consistently been over one degree Celsius above the norm, researchers said.

As per Indian Express, corals react to the heat by ejecting their microscopic algae that live in their tissues.

Sans the algae, the tissues lose all their colours and become transparent.

These corals are now in danger and barely last for two weeks, experts say.

“Such heat stress levels signify a severe threat to coral health, leading to extensive bleaching where corals lose the symbiotic algae (zooxanthellae), compromising their survival by depriving them of essential nutrients," said Dr KR Sreenath, senior scientist of CMFRI explained.

“Over a large part of 2023 and 2024, the temperatures have been pretty high in this region. While the corals are not dead, about 80 per cent are showing bleaching signs,” Nature Conservation Foundation (NCF) researcher Wenzel Pinto told the newspaper.

“Some corals have turned completely white, others are dying, and some exhibit a fluorescent colour as an adaptation to reflect sunlight and reduce temperature-induced stress.”

“Losing coral on reefs is akin to losing trees in a rainforest,” Mayukh Dey of NCF told The Times of India.

How bad is it?

Quite bad.

According to Indian Express, though the Lakshadweep has witnessed coral bleaching events in 1998, 2010 and 2015, the size and scope of this one is extraordinary.

Sreenath said multiple species could die off and create an ‘unprecedented biodiversity crisis’ if the DHW continues to rise and touches over 12 degrees Celsius-weeks.

Noting that the health of marine ecosystems is integral to the livelihoods of coastal communities, influencing tourism and fisheries sectors, Sreenath said that the ongoing marine heatwaves are likely to cause significant economic losses by disrupting their vital ecosystem services.

Further, the death and disintegration of coral reefs can threaten coastal communities, leaving them vulnerable to the impacts of sea level aggressions, Padua added.

The ongoing heat waves also threaten other critical marine habitats, including seagrass meadows, the expert said, adding that similar to corals, seagrass meadows are experiencing detrimental impacts due to the heatwaves, such as impaired photosynthesis, reduced growth, and hindered reproductive functions.

“The degradation of these ecosystems can lead to the collapse of local marine food webs, affecting a wide range of marine species, from fish communities to marine mammals like dugongs and dolphins,” Sreenath added.

The CMFRI has been actively undertaking studies to better understand ecological changes affecting coral reefs, the statement said.

The agency has initiated a comprehensive national project aimed at investigating the resilience potential of various coral reefs in India.

By integrating advanced climatic modelling, deep-learning, and ecological research, CMFRI aims to enhance survey efficiency and develop resilience-based management actions ensuring the long-term sustainability of coral reef ecosystems, the statement added.

Worldwide phenomenon

Lakshadweep isn’t alone.

K Diraviya Raj, associate professor, Suganthi Devadason Marine Research Institute, Chennai, said researchers have been keeping an eye on the four coral regions of the country including the Gulf of Mannar.

Those corals are also giving off signs of bleaching, Raj added.

This phenomenon isn’t limited to India either.

According to New Indian Express, the NCF has recorded a 25 per cent decline in coral cover since the first global bleaching event.

The NOAA, which issued a coral reef watch (CRF) alert in December 2023, last month announced that the world is witnessing its fourth global mass coral bleaching event since the late 1990s.

At least 53 countries are facing coral bleaching.

“I am becoming increasingly concerned about the 2024 summer for the wider Caribbean and Florida,” Derek Manzello, the coordinator for NOAA’s Coral Reef Watch program told Interesting Engineering.

Arguably the most high-profile example of coral bleaching has occurred in Australia’s Great Barrier Reef – which just had its worst ever summer on record, as per CNN.

According to The Guardian, the Australian Institute of Marine Science and the Great Barrier Reef Marine Park Authority in April released a report warning that the reef is experiencing “the highest levels of thermal stress on record.”

“What is happening now in our oceans is like wildfires underwater,” Kate Quigley, principal research scientist at Australia’s Minderoo Foundation told CNN. “We’re going to have so much warming that we’re going to get to a tipping point, and we won’t be able to come back from that.”

“It’s a die-off,” added professor Ove Hoegh-Guldberg, a climate scientist at the University of Queensland in Australia and chief scientist at The Great Barrier Reef Foundation. “The temperatures got so warm, they’re off the charts … they never occurred before at this sort of level.”

Scientists say that if nothing changes by 2050 when it comes to global temperatures, 99 per cent of coral reefs will go extinct.

“Humanity is being threatened at a rate by which I’m not sure we really understand,” Hoegh-Guldberg said.

David Wachenfeld, research program director at AIMS told CNN, “Coral reefs are at least a canary in the coal mine for climate change."

“The trajectory that we’re on now is really quite scary.”

Peter Harrison, a researcher at Southern Cross University, described the scene.

“If you swim over a reef system that a few months before was vibrant, colourful — the sounds of the reef were incredible,” he said.

“And you swim back over it, and the whole thing is like a graveyard. It’s as silent as a graveyard.”

With inputs from agencies