CHENNAI: The evolving El Niño conditions appear to be leaving a signature on the Indian Ocean, with ISRO's EOS-06 (Oceansat-3) satellite detecting a reduction in ocean Chlorophyll-a levels in June 2026, along with changes in surface winds, providing satellite-based evidence of changes in ocean conditions.
ISRO's EOS-06, also known as Oceansat-3, has detected changes in ocean Chlorophyll-a levels during June 2026, indicating changes in phytoplankton activity in the Indian Ocean. The satellite observations also show a shift in surface wind patterns, offering an indication of how changing climate and ocean conditions are influencing the region.
EOS-06 is the third-generation Oceansat mission developed by the Indian Space Research Organisation (ISRO) and was launched on November 26, 2022. The satellite is designed to provide ocean-related data and strengthen remote sensing capabilities for oceanography, meteorology and climate monitoring.
Chlorophyll-a is a natural green pigment found in plants, algae and cyanobacteria. It plays a crucial role in photosynthesis by absorbing sunlight and helping convert water and carbon dioxide into energy, while releasing oxygen.
In the oceans, microscopic plants known as phytoplankton contain Chlorophyll-a and form the foundation of the marine food chain. Changes in Chlorophyll-a concentrations can therefore provide valuable information about variations in phytoplankton abundance and ocean productivity.
Warming of the ocean surface associated with El Niño conditions could reduce the upwelling phenomenon in the ocean-- VS Chandrasekaran, former principal scientist at CIBA
Areas with higher concentrations of phytoplankton often support greater numbers of small marine organisms and fish, which subsequently support larger fish through the food chain.
Satellite-based monitoring of Chlorophyll-a is consequently useful for identifying potential productive fishing zones and understanding changes that could affect fisheries.
Phytoplankton also play a major role in the global carbon cycle by absorbing carbon dioxide from the atmosphere through photosynthesis. Monitoring ocean Chlorophyll-a levels from space can therefore help scientists study changes in ocean productivity and the role of the oceans in absorbing atmospheric carbon.
The latest Oceansat-3 observations for June 2026 show a reduction in Chlorophyll-a compared with earlier observations, alongside a shift in surface winds. The changes are being viewed in the context of the evolving El Niño conditions and can be compared with ocean signatures observed during 2024 and 2025.
VS Chandrasekaran, former principal scientist at the Central Institute of Brackishwater Aquaculture (CIBA), told DT Next that the warming of the ocean surface associated with El Niño conditions could reduce the upwelling phenomenon in the ocean.
"Upwelling is the process by which cold, nutrient-rich water from the deeper parts of the ocean rises to the surface. When this nutrient-rich water is reduced, the population of phytoplankton can also decline, " he said.
He explained that Chlorophyll-a is a colour-based index used in satellite observations to estimate the abundance of phytoplankton.
"A reduction in Chlorophyll-a indicates a reduction in phytoplankton. Phytoplankton are the primary food producers in the ocean, just as trees and plants are primary food producers on land. A reduction in phytoplankton can affect fishery production through a chain reaction, " he said.
According to the scientist, a decline in phytoplankton could affect organisms at the lower levels of the marine food chain, eventually influencing fish populations.