NASA recently captured a summertime spectacle in orbital imagery of the Black Sea, as eerie-looking swirls of turquoise could be seen swarming in its waters.
The curious curling features were observed by astronauts aboard the International Space Station in May, and more recently by the Ocean Color Instrument (OCI) on NASA’s Plankton, Aerosol, Cloud, Ocean Ecosystem (PACE) satellite on June 22, 2026, as it passed over the body of water that marks the boundary between Europe and Asia.
The vibrant oceanic display is believed to be the result of summertime blooms of coccolithophores, which begin surging in ocean waters near the shoreline in warmer weather months.
These phytoplankton are armored in plates composed of calcium carbonate, which can often cause discoloration in ocean waters as the blooms occur, which are driven by nutrients entering ocean waters that are often carried from inland sources.
Earlier this year, a similar turquoise spectacle occurred in Atlantic waters along the eastern United States, as coccolithophores surged in numbers as temperatures rose, and meltwater in mountainous regions made its way downstream, carrying vital nutrients which were deposited in coastal waters after they made their way downstream.
Unlike coccolithophores, which generally brighten the color of ocean water in the spring and early summer, later in the year another kind of microscopic organism, known as diatoms, can darken the water due to the silica shells that encase their microscopic bodies.
Similar orbital color shows were observed in recent weeks within the narrow waters of the Bosporus Strait, which separates Turkey as it parts Asia Minor and Thrace. In the recent photos obtained from the ISS, the entire Bosporus can be seen illuminated in turquoise as its waters have been flooded with coccolithophores.
Apart from the odd but beautiful swirling patterns they produce as these phytoplankton are carried by ocean currents, these colorful creatures also provide a more practical benefit, since they can be leveraged by remote sensing technologies to help study the dynamics of these blooms when they occur.
Additionally, these microscopic creatures can also make significant contributions to oceanic carbon cycles, since the creatures sink to the seafloor at the end of their life cycles, carrying carbon they’ve absorbed with them. Once deposited on the ocean floor, this carbon can be maintained at such depths for long periods.
Additional information about the recent coccolithophore blooms in the Black Sea, along with other imagery of our planet as seen from space, can be found at NASA’s Earth Observatory page.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.