Prolonged El Nino can damage the marine ecosystem: INCOIS

In addition to affecting rainfall, El Niño can trigger stronger and longer-lasting marine heat waves that can disrupt marine ecosystems. | Photo credit: File photo

The current El Niño conditions are likely to remain dominant until at least April 2027, with probabilities ranging from 80% to 100% and could adversely affect the marine ecosystem, scientists at the Indian National Center for Ocean Information Services (INCOIS) said 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 India’s summer monsoon, often affecting rainfall patterns and subsequently the country’s agriculture and economy.

In addition to affecting rainfall, El Niño can trigger stronger and longer-lasting marine heat waves in the northern Indian Ocean that can disrupt marine ecosystems, damage coral reefs and affect fisheries. In contrast, La Niña, characterized by unusually cold waters in the equatorial Pacific, generally promotes stronger monsoon conditions over India.

Scientists say El Niño has strengthened and is expected to remain strong from August 2026 to March 2027. Its persistence is likely to affect ocean conditions in the northern Indian Ocean, leading to higher sea surface temperatures, increased heat content in the upper oceans, stronger stratification of the water column and large-scale marine heat waves.

Marine heat wave conditions are already widespread in the northern Indian Ocean, with moderate to extreme events affecting large parts of the Arabian Sea and Bay of Bengal. The area affected by marine heat waves expanded in 2026 compared to 2025, they confirm.

The ongoing El Niño is also resulting in a significant reduction in tidal waves along India’s west coast—a process that brings nutrient-rich waters to the surface and is critical to maintaining marine productivity. Reduced upwelling associated with marine heat waves can adversely affect fish habitat and productivity.

Senior scientist and head of the Ocean Modeling & Data Assimilation Center (OMDA), PA Francis, said historical analyzes of fish landings since 1950 show that marine fish catches in 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 the period 1985-2023 indicate that El Niño-induced warming has negatively affected the maturation and recruitment success of key small pelagic species such as Indian oil sardine and Indian mackerel in Kerala and Karnataka.

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

Published – 28 Sep 2026 18:43 IST