ഇന്ത്യയിലെ പവിഴപ്പുറ്റുകളിൽ ആഗോളതാപനം വരുത്തുന്ന മാറ്റങ്ങൾ: പുതിയ പഠനം പുറത്തുവന്നു

A new study examining the effects of the fourth global coral bleaching event on India’s coral reefs in 2024 shows how reefs in different parts of India are responding to warming in different ways. The study also highlights the shortage of data on coral reefs in South Asia compared with the rest of the world.

While Lakshadweep was found to be the most affected, with up to 37% of the coral cover bleached or dead at intermediate levels of accumulated heat stress, Mahatma Gandhi Marine National Park (MGMNP) in Andaman Islands faced only 11.5% bleaching or mortality.

Pointing to these differences, the paper titled Regional and genus‑specific factors underpin bleaching variation across India’s coral reefs during the fourth global coral bleaching event, published in the journal Coral Reefs by Springer Nature, emphasises the need to integrate local geographical context into the understanding of bleaching impact on tropical reefs.

Information asymmetry

More than 80% of the world’s coral reefs were affected in the fourth global coral bleaching event between 2023 and 2025 due to extreme levels of heat stress. Long-term ocean warming, marine heatwaves, and a strong El Niño in 2023 contributed to this.

However, despite having multiple reef regions, data on the impacts of mass bleaching events on coral reefs across South Asia is sparse, the researchers point out.

As part of the study, rapid bleaching assessment was conducted across five reef regions in the Indian sub-continent, including the Lakshadweep archipelago, Goa, Palk Bay, MGMNP, and Ritchie’s Archipelago. All surveys were conducted between April 20 and June 7, 2024.

“We looked at the impact of the current heat stress event on coral cover – whether the coral cover was healthy, bleached, slightly pale, or recently dead,” explains Wenzel Pinto, lead author of the paper.

Regional and taxonomic variations

Lakshadweep exhibited significantly higher bleaching intensity, while Goa and MGMNP showed comparatively lower bleaching. Across regions, Acropora, Pocillopora, Galaxea, and Montipora corals were found to be the most affected, while Pavona, Platygyra, Goniastrea, and Favites were among the least affected.

Palk Bay showed an unusual pattern in coral damage. The Acropora corals, which are usually vulnerable, showed only a modest bleaching or mortality of 13.6%. On the other hand, Porites colonies, which are generally considered more resistant, displayed 61.8% mortality.

“These contrasting regional and taxonomic responses indicate how context-specific resistance patterns, and local oceanography may mediate thermal stress and underscore the need to integrate these local geographical contexts in our understanding of bleaching impacts on tropical reefs,” the study notes.

Understanding local contexts

Pinto stresses the importance of understanding regional differences and the local threats individual reefs face, alongside broader global threats.

“There might be reefs that are facing problems with nutrient input from, say, agriculture, or sewage input. Some reefs may be facing overfishing, which can also affect reef health. These effects compound the effects of climate change. Addressing these local threats would help give reefs a slightly longer life,” according to Mr. Pinto

While the coral reefs in India fare better than most reefs in the Pacific, Mr. Pinto points out that there are reefs in Southeast Asia, like those in Indonesia, that are doing even better.

Relevance amid super El Niño

Mr. Pinto acknowledges the limitations that arise from the one-time nature of the survey.

“Since it was only a one-time survey, the places we surveyed were at slightly different levels of heat stress. Some were slightly hotter, some were slightly cooler. That limits our inferences a little bit. But even among sites experiencing similar heat stress, we found differences in impacts,” he says.

With El Niño expected to reach very strong intensity towards the end of 2026 and continue into 2027, he believes such studies assume greater importance.

“We are trying to get together multiple organisations again to do another coordinated assessment across the region so that we can understand what the baseline levels are before heat stress begins, how it progresses over time in each place and what the mortality or recovery trajectories of each place are.”