A Plankton Bloom Turns the Bosphorus Strait Turquoise

The word turquoise comes from the French for “Turkish stone.” But right now, the term describes nothing better than it does Turkey's most famous body of water, the Bosphorus Strait, where microbes have sent clouds of aquamarine waters swirling into the flowing waters all the way down to Istanbul—as you can see in the image above—and out to the Sea of Marmara.

In May, NASA’s Aqua satellite first spotted the vivid swirls in the Black Sea, where the Bosphorus originates.

From there, the bright bloom drifted all the way down to Istanbul, transforming the strait—which divides Turkey into its Asian and European sides—from royal to electric blue.

This is far from the first time these bright colors have appeared; images from space have spotted them year after year in early summer. This is last year's bloom.

These grand, painterly sights are made possible by a type of phytoplankton called coccolithophores. These single-celled, plant-like, disk-shaped organisms live near the water’s surface.

Like full-size plants, coccolithophores take in sunlight and other organisms’ discarded nutrients and turn them into food. They’re an essential part of both the food chain and the carbon cycle, helping collect and sink excess carbon to the sea floor.

Each soft coccolithophore is armored in a limestone shell, or coccolith. The shells reflect the sunlight back up through the water, producing a milky turquoise visible from space.

Experts say that while larger and more frequent plankton blooms can block sunlight at the water’s surface and harm other organisms, a modest annual color change is no cause for concern. And this year's show is especially brilliant.