Prolonged El Nino may hurt marine ecosystem: INCOIS

The current El Niño conditions are likely to remain dominant until at least April 2027, with probabilities ranging between 80% and 100% and could adversely affect the marine ecosystem, according to scientists at the Indian National Centre for Ocean Information Services (INCOIS) on Monday.

El Niño refers to the warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean and represents the warm phase of the El Niño-Southern Oscillation (ENSO). Such conditions are known to weaken the Indian summer monsoon, often affecting rainfall patterns and, in turn, the country’s agriculture and economy.

Beyond its influence on rainfall, El Niño can trigger stronger and longer-lasting marine heatwaves across the northern Indian Ocean that can disrupt marine ecosystems, damage coral reefs and impact fisheries. In contrast, La Niña, characterised by unusually cool waters in the equatorial Pacific, generally supports stronger monsoon conditions over India.

Scientists say El Niño has strengthened and is expected to remain strong through the August 2026-March 2027 period. Its persistence is likely to influence ocean conditions across the North Indian Ocean, leading to higher sea surface temperatures, increased upper-ocean heat content, stronger water-column stratification and widespread marine heatwaves.

Marine heatwave conditions are already widespread across the northern Indian Ocean, with moderate to extreme events affecting large parts of the Arabian Sea and Bay of Bengal. The area impacted by marine heatwaves has expanded in 2026 compared with 2025, they attest.

The ongoing El Niño has also resulted in a significant reduction in coastal upwelling along India’s west coast — a process that brings nutrient-rich waters to the surface and is crucial for sustaining marine productivity. Reduced upwelling, coupled with marine heatwaves, may adversely affect fish habitats and productivity.

Senior scientist and head of the Ocean Modelling & Data Assimilation Centre (OMDA), P.A. Francis, said historical analyses of fishery landings since 1950 show that marine fish catches across the Indian Ocean region generally tend to decline during El Niño phases, although the impact varies by region.

Studies using data from the Central Marine Fisheries Research Institute (CMFRI) for 1985-2023 indicate that El Niño-induced warming has negatively affected the maturation and recruitment success of key small pelagic species, such as the Indian oil sardine and Indian mackerel, in Kerala and Karnataka.

Climate variability can also push fish populations towards their physiological limits, forcing them into deeper waters or higher latitudes. Mr. Francis said El Niño also influences extreme wave conditions, leading to higher significant wave heights in the Bay of Bengal and reduced wave activity in the Arabian Sea, largely because the South Asian monsoon weakens.