Lakshadweep worst-affected by coral bleaching on India’s coastline, scientists tell DTE

Lakshadweep, an archipelago of 36 islands that is a Union Territory (UT) of the Republic of India, has suffered the most in terms of coral bleaching, scientists have confirmed.

The world is undergoing its fourth global coral bleaching event (GCBE4) on record, the most severe by far according to US-based National Oceanic and Atmospheric Administration (NOAA) Satellite and Information Services.

At least 67 countries and territories across Atlantic, Pacific and Indian Oceans have reported bleaching due to severe heat stress since early 2023, according to NOAA.

Mass coral bleaching events across the world were recorded in 1998, 2010 and 2014-2017. GCBE3, experienced in 2014-17, was the most severe on record with 65.7 per cent of the world’s coral reefs experiencing bleaching.

“On May 23, 2024, GCBE4 surpassed GCBE3 in terms of extent of bleaching. As the time of this writing, more than 70.7 per cent of coral reefs worldwide have been impacted by bleaching-level heat stress since January 1, 2023,” NOAA has noted.

Kavaratti-based Idrees Babu KK, scientist at the Department of Science & Technology, UT of Lakshadweep, told Down To Earth (DTE) that the extent of coral bleaching in Lakshadweep’s waters is severe, as per the Department’s last survey conducted at Kavaratti atoll. The extent of bleaching is 84.6 per cent, with mass bleaching observed.

“This recent event is noted to be one of the worst compared to previous years (1998: 81 per cent, 2010: 65 per cent, 2020: 41.9 per cent),” he said.

Babu explained that the increase in sea surface temperatures, attributed to global warming, has exacerbated the frequency and intensity of bleaching events in this region. “The most affected areas are in the coral reef of atolls and lagoons, followed by outer reef flats and outer reef slope respectively,” he added.

As per the observations, sea surface temperatures between April 1 and May 2 this year hovered between a minimum of 29.6 degree Celsius (°C) to a maximum of 32.8°C. “The long duration temperature stayed more than 29.5°C,” Babu said.

He noted that species most impacted included Porites cylindrical, Porites lobata, Porites lutea, Acropora muricata, Montipora foliosa, etc. Resilient species like Acropora digitifera and Pocillopora grandis have also shown signs of bleaching, indicating the severity of this year’s event. However species such as Isopora palifera, Pavona venosa and Hydnophora microconos appeared to be more resilient, Babu told DTE.

Coral reefs in Lakshadweep are crucial for several reasons. They support a diverse range of marine life, including fish, invertebrates, algae, etc. Reefs act as natural barriers, protecting shorelines from erosion and storm surges. Local communities rely on reef-associated fish for sustenance and livelihood. The reefs also attract tourists, contributing to the local economy.

B M Praveen Kumar, a marine biologist working for non-profit Wildlife Trust of India (WTI), works at the Mithapur reef off the Gujarat coast. He said it would be too soon to determine the extent of damage caused by coral bleaching this year.

“Usually, coral bleaching is witnessed post-summer in several parts of the Indian coastline. On average, we observe about 30-40 per cent of coral bleaching annually. But the majority of corals recover,” he said.

However, anticipating that coral bleaching may peak and cause severe damage, Kumar said monitoring this year had begun mid-summer. Corals were being closely inspected for any signs of bleaching every week. “Our data would be better placed in the coming weeks,” he added.

Tamil Nadu’s Principal Conservator of Forests and Chief Wildlife Warden, Srinivas Reddy, said the extent of coral bleaching in the Gulf of Mannar and other regions is not severe, compared to other coral reefs in India.

“The impact reported is lesser than Lakshadweep. The reason being that the bleaching started late and the monsoon arrived sooner, helping bring seawater temperatures down and preventing further spread of damage,” he told DTE.

Venkatesh Charloo, founder trustee of Coastal Impact, an organisation involved in marine conservation, education and research in Goa, said the diving in Goa waters will resume post- monsoon and only then will the status of coral bleaching be known.

Back in Lakshadweep, Babu said there has been a slight reduction in water temperatures, with the onset of the monsoon. This has offered some relief. “However, the recovery status remains uncertain. While lower temperatures can help reduce immediate stress, the long-term health of the corals depends on continued cooler conditions and the absence of further stressors,” he added.