NASA captured the Black Sea’s annual turquoise transformation as massive blooms of microscopic plankton turned the water into a dazzling spectacle visible from orbit.
The Black Sea lies between Europe and Asia and reaches the Mediterranean Sea through a series of connected waterways. Although its waters are often dark, the sea can undergo a dramatic color change during spring and summer, when broad swirls of turquoise spread across its surface.
NASA’s PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite observed this seasonal transformation on June 22, 2026. Its OCI (Ocean Color Instrument) captured the image above, revealing bright blue and turquoise patterns stretching across the Black Sea.
Tiny Plankton Turn the Black Sea Turquoise
The striking color was likely produced by coccolithophores, microscopic phytoplankton coated in small plates of calcium carbonate. When these organisms gather in enormous numbers, their reflective coverings can give the water a cloudy, milky blue appearance.
Coccolithophores are especially common in the Black Sea during late spring and early summer. At other points in the year, diatoms—a type of microscopic algae with silica shells—may become more abundant. Unlike coccolithophores, diatoms generally make the water appear darker rather than brighter.
A Colorful Bloom Reaches the Bosphorus
The turquoise waters were also visible in the Bosphorus, the narrow channel that passes through Istanbul and links the Black Sea with the Sea of Marmara.
On May 27, 2026, roughly one month before the PACE satellite observation, an astronaut aboard the International Space Station photographed the colorful strait below. The image shows blooming phytoplankton following the movement of currents on both sides of the waterway. (Note that north is oriented toward the bottom of the frame.)
A Massive Bloom Visible From Space
A single coccolithophore is far too small to see without magnification. During a major bloom, however, the organisms can multiply in such vast numbers that their collective presence becomes visible from orbit.
Satellite and astronaut observations allow scientists to follow how these blooms form, spread, and change over time. This type of remote sensing is particularly valuable in areas where researchers cannot easily collect samples directly from the water.
Black Sea Blooms and the Carbon Cycle
These blooms do more than create a spectacular view from space. Coccolithophores also participate in the ocean’s carbon cycle by absorbing carbon while they grow.
After the organisms die, some of that carbon can sink with their remains toward the seafloor. Once deposited there, it may stay out of the atmosphere for long periods of time.
NASA Earth Observatory image by Michala Garrison, using PACE data from NASA EOSDIS LANCE and GIBS/Worldview and the NASA Ocean Biology Distributed Active Archive Center OB.DAAC. Astronaut photograph ISS074-E-619520 was acquired on May 27, 2026, with a Nikon Z9 digital camera using a focal length of 50 millimeters. The photograph was supplied by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit at NASA Johnson Space Center.
A member of the Expedition 74 crew captured the image. It was cropped and adjusted to improve contrast, and lens artifacts were removed. Through the ISS National Lab, the International Space Station Program helps astronauts photograph parts of Earth that are especially valuable to researchers and the public. The program also makes those images freely available online.
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