El Niño disrupts Pacific marine food web
Satellite data shows a major drop in Pacific Ocean chlorophyll due to the 2026 El Niño, indicating a decline in foundational phytoplankton.
Satellite observations from NASA's Earth Observatory show a substantial drop in chlorophyll concentrations across the Central Pacific Ocean in June 2025 compared to neutral conditions. This decline signals a reduction in phytoplankton, the base of the marine food web, triggered by the strengthening 2026 El Niño climate pattern.
According to the NASA Earth Observatory, the ecological consequences of this nutrient decline mean less food for zooplankton, fish, seabirds, and marine mammals. This directly affects fisheries; Peru's anchovy fisheries, for example, saw significant catch declines during previous El Niño events. This year, Peru has repeatedly suspended its vital anchovy fishery to protect stocks, while starving pelicans have invaded urban ports searching for food.
Mechanism of Disruption
Hyung-Gyu Lim, an associate professor of oceanography at Chonnam National University in South Korea, told Mongabay that a developing El Niño can slow the process of nutrient-rich upwelling from the ocean depths. Matthew Kehrli and Graham Trolley, oceanographers at NASA’s Goddard Space Flight Center, explained that El Niño suppresses upwelling because easterly equatorial trade winds weaken, causing the warm surface layer of the ocean to extend deeper. They added that as El Niño progresses, chlorophyll concentrations will likely decrease further over a broader region.
Duration and Recovery
The National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center estimates a greater than 90 percent chance the current El Niño will persist into early 2027. Despite severe immediate disruptions, the NASA Earth Observatory said oceans often undergo a "chlorophyll rebound" once the event subsides.
Research led by Hyung-Gyu Lim suggests higher iron concentrations from ocean currents and iron dust blown from dry land in parts of Central and South America help fuel this resurgence. "Recent Earth System Model studies suggest that oceanic drivers facilitate a post-El Niño chlorophyll rebound fueled by subsurface iron supply," Lim said. He added that atmospheric drivers like dust-iron deposition can significantly modulate marine productivity.
Lim noted that surface satellite maps only show part of the ecological picture. To truly capture the dynamics, he said advanced observation systems must integrate both surface and subsurface ocean observations.
