NASA's PACE Satellite Watches Phytoplankton Thin Out in the Central Pacific

NASA Earth Observatory has published satellite maps showing that phytoplankton abundance across part of the central equatorial Pacific was substantially lower in June 2026, as El Niño strengthened, than in June 2025 under neutral conditions. The comparison, released as the agency's Image of the Day for August 10, 2026, draws on chlorophyll-a measurements from the Ocean Color Instrument (OCI) aboard NASA's PACE — Plankton, Aerosol, Cloud, ocean Ecosystem — satellite.

According to NASA Earth Observatory, El Niño officially arrived as of June 2026, bringing warmer-than-normal water temperatures in parts of the equatorial Pacific along with changes to atmospheric and oceanic circulation. The agency notes that NOAA's Climate Prediction Center expects the event to continue strengthening through the end of 2026, with a 97 percent chance of lasting through early Northern Hemisphere spring 2027. Even in the event's early stages, NASA Earth Observatory says, satellites have picked up characteristic signals including warmer-than-normal sea surface temperatures and higher-than-normal sea surface height.

What the chlorophyll maps show

Chlorophyll-a is the pigment found in most phytoplankton, so its concentration at the sea surface serves as a proxy for how much plant life the ocean is supporting. The OCI derives those concentrations from green and blue light reflected back to the sensor. NASA Earth Observatory reports that the most noticeable contrast between the two months appears in the central Pacific, around the equator due north of New Zealand, where 2026 values were substantially lower.

Matthew Kehrli and Graham Trolley, oceanographers in the Ocean Ecology Laboratory at NASA's Goddard Space Flight Center, said the drop was expected. During El Niño, they explain, easterly equatorial trade winds weaken, the warm surface layer of the ocean deepens, and the upwelling of cool, nutrient-rich water that normally feeds phytoplankton growth is suppressed.

The two scientists anticipate the difference will grow as the event progresses. "This 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," they said.

Up the food web, and toward the coast

NASA Earth Observatory notes that less phytoplankton means less food for zooplankton and, in turn, for fish, seabirds and marine mammals, including in coastal regions. The agency points to Peru's anchovy fisheries, which it says have seen profound declines in catch during past El Niños, driven by warmer surface waters, reduced upwelling and lower phytoplankton abundance. In 2026, according to NASA Earth Observatory, Peru's Ministry of Production repeatedly suspended the fishery to safeguard the country's main fishing resource, and pelicans have been observed moving into Peruvian ports and urban areas in search of food.

The agency also stresses that the picture does not end with depletion. A post-El Niño "chlorophyll rebound," with higher-than-normal concentrations in the equatorial Pacific, can occur. NASA Earth Observatory says research points to higher iron concentrations delivered by ocean currents, plus dust from drier land in parts of Central and South America, as contributors to that resurgence — and notes the rebound does not require a follow-on La Niña. La Niña, which the agency says often follows El Niño events, can also lift chlorophyll: NASA Earth Observatory cites a strong La Niña in 1998–1999 that set off a large phytoplankton bloom in the eastern Pacific and a dramatic increase in fish populations.

A first for PACE

PACE launched in February 2024, which NASA Earth Observatory says makes 2026 the first complete El Niño event for which the satellite will collect global, near-daily hyperspectral measurements. "The scientific community will be able to observe the 2026 El Niño with data across more wavelengths of light than ever before," Kehrli and Trolley said.

Researchers hope to use PACE data to measure how specific phytoplankton communities respond to the event, according to the agency. The scientists add that the mission's reach extends past the ocean: PACE's sensors can measure plant pigment composition on land and clouds and aerosols in the atmosphere, all of which are influenced by El Niño.

The maps were produced by NASA Earth Observatory's Michala Garrison using PACE data from the NASA Ocean Biology Distributed Active Archive Center, processed by Matthew Kehrli, with the accompanying story by Lindsey Doermann.