CHENNAI: Tamil Nadu’s coral reefs are being placed under heightened surveillance as scientists warn that a projected ‘Super’ El Niño in 2026-27 could trigger another episode of widespread bleaching. The state forest department is preparing measures to detect thermal anomalies early and respond to reef damage.
Historically, major global coral bleaching events have coincided with El Niño years. The latest event was in 2023-24, when there was an 8.9% decline in hard coral cover globally. A recent assessment by world meteorologists has warned of the risk posed by the projected super El Niño, while the National Oceanic and Atmospheric Administration’s Climate Prediction Center has forecast an over 90% probability of a very strong El Niño event during 2026-27.
Tamil Nadu is particularly significant in India’s coral reef conservation efforts, with reefs distributed across the Gulf of Mannar and Palk Bay. The state has maintained systematic coral monitoring for more than two decades through the Gulf of Mannar Marine National Park (GOMMNP), in association with the Suganthi Devadason Marine Research Institute (SDMRI).
Tamil Nadu’s reefs have experienced severe bleaching and mortality during previous El Niño years of 1998, 2010, 2016 and 2024. Annual summer bleaching has also been observed since 2005 when temperatures rise above 30°C, although reefs generally recover after temperature declines. Prolonged elevated temperatures associated with El Niño, however, have resulted in significant mortality.
“The advantage Tamil Nadu has is that we already have a long-term baseline and regular monitoring programme. This allows us to identify anomalies at an early stage rather than waiting for large-scale mortality to occur,” said Akhil Tambi, Wildlife Warden, Gulf of Mannar Marine Biosphere Reserve.
A rapid underwater survey conducted jointly by GOMMNP and SDMRI between May 7 and 12 this year covered 12 islands in the Gulf of Mannar and reef areas of northern Palk Bay. Water temperatures had crossed the bleaching threshold and touched 31.2°C. Yet, bleaching was relatively mild and did not result in mortality as temperatures subsequently fell below 30°C in June. “The average bleaching cover was 3.69% in the Gulf of Mannar, compared with 13.9% in Palk Bay. In Palk Bay, 10.8% was fully bleached and 3.1% was partially bleached,” Tambi said.
The current concern is compounded by unusually high temperatures during the September-October period. While bleaching has not yet been recorded during the current period, daily temperature monitoring is continuing.
Edward JK Patterson, director, SDMRI and a member of Tamil Nadu’s El Niño Expert Advisory Committee, said the monitoring programme is crucial in distinguishing short-term thermal stress from a sustained bleaching event. He said, “The objective is to detect changes early and enable the forest department to respond quickly.”
Long-term plans
The forest department is also preparing longer-term management measures. Rakesh Kumar Dogra, Chief Wildlife Warden, Tamil Nadu, said the experience of previous bleaching events and other climate-related disturbances would be incorporated into the next 10-year management plan for the Gulf of Mannar Marine National Park and Biosphere Reserve.
“Climate-related events such as El Niño require a dedicated protocol covering the pre-event, event and post-event phases. We are looking at appropriate guidelines, management interventions and restoration measures so that the response is not limited to dealing with mortality after it occurs,” Dogra said.
A detailed underwater survey is also under way as part of a three-phase assessment covering the period before, during and after the projected El Niño event. The exercise is expected to create a comprehensive baseline for the Gulf of Mannar and Palk Bay.
The state has also standardised coral restoration protocols for enhancing coral biomass if substantial damage occurs. Guidelines for practitioners on coral reef restoration are expected to help researchers and forest department personnel undertake restoration and subsequent monitoring.
The forest department is considering the impact of multiple stressors. Extreme freshwater inflows during the 2023 floods, for instance, severely affected extensive seagrass beds along the Thoothukudi coast. Such cumulative pressures, officials said, highlight the need to prepare the reef ecosystem not only for El Niño but for a combination of climate and local anthropogenic stresses.