El NiƱoĀ Alters Marine Life in the Pacific
As of June 2026, El NiƱo has officially arrived. This naturally recurring phenomenon is characterized by warmer-than-normal water temperatures in parts of the equatorial Pacific along with changes to atmospheric and oceanic circulation patterns. Its regional effects range from desert floods to delayed monsoons to shifts in where tropical cyclones are more likely to form.
NOAAās Climate Prediction Center expects the current El NiƱo to continue to strengthen through the end of 2026, with a 97 percent chance of lasting through early Northern Hemisphere spring 2027. Even during El NiƱo's early stages, satellites have observed characteristic changes along the equatorial Pacific, such as warmer-than-normal sea surface temperatures and higher-than-normal sea surface height.
Among the first ecological downstream effects are changes to the marine food web. The maps above show chlorophyll-a concentrationsāthe pigment present in most phytoplanktonāas observed by the OCI (Ocean Color Instrument) on NASAās PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite. In June 2025 (left), conditions were neutral, while in June 2026 (right), El NiƱo was strengthening.
The most noticeable difference appears in the central Pacific, around the equator due north of New Zealand: chlorophyll concentrations, an indication of phytoplankton abundance, are substantially lower in 2026. This change is expected, said Matthew Kehrli and Graham Trolley, oceanographers in the Ocean Ecology Laboratory at NASA's Goddard Space Flight Center. Thatās because during an El NiƱo, easterly equatorial trade winds weaken, the warm surface layer of the ocean extends deeper, and the upwelling of cool, nutrient-rich water that typically fuels phytoplankton growth is suppressed.
As the El NiƱo progresses, the scientists anticipate the differences in the central Pacific will become more pronounced. āThis may manifest as a greater difference in values across the current region, as a broadening region of reduced surface chlorophyll-a concentration, or both, depending on the behavior of the equatorial trade winds,ā they said.
Reductions in phytoplankton have ripple effects through the marine food web, including in coastal regions. Less food is available for zooplankton, as well as for fish, seabirds, and marine mammals. Peruās anchovy fisheries have seen profound declines in catch during past El NiƱos, driven similarly by warmer surface waters, reduced upwelling, and lower phytoplankton abundance. In 2026, Peruās Ministry of Production repeatedly suspended the fishery to safeguard the country's main fishing resource. Pelicans have been seen venturing into Peruvian ports and urban areas in search of food.
Although the disruptions to marine life can be severe, a post-El NiƱo āchlorophyll rebound,ā with higher-than-normal concentrations in the equatorial Pacific, can occur. Research suggests that higher iron concentrations delivered in ocean currents, as well as dust arriving from drier land in parts of Central and South America, help fuel the resurgenceāa rebound that doesnāt require a follow-on La NiƱa. La NiƱa, which often follows El NiƱo events, can also produce elevated chlorophyll concentrations. A strong La NiƱa in 1998ā1999 set off a large phytoplankton bloom in the eastern Pacific and a dramatic increase in fish populations.
Scientists have new tools available for studying this sort of variability. The PACE mission launched in February 2024, making this the first complete El NiƱo event for which the satellite will gather global, near-daily hyperspectral measurements. āThe scientific community will be able to observe the 2026 El NiƱo with data across more wavelengths of light than ever before,ā Kehrli and Trolley said.
To better understand effects on life in the ocean, researchers hope to use PACE data to gauge the responses of specific phytoplankton communities to El NiƱo. And the possibilities extend beyond the marine realm, the scientists note. PACEās sensors can measure plant pigment composition on land and clouds and aerosols in the atmosphere, all of which are influenced by El NiƱo.
NASA Earth Observatory images by Michala Garrison, using PACE data from the NASA Ocean Biology Distributed Active Archive Center OB.DAAC and processed by Matthew Kehrli. Story by Lindsey Doermann.
JPEG (1.40 MB)
JPEG (1.37 MB)
JPEG (2.85 MB)
Full text from nasa.gov (public domain).