Glowing Phytoplankton Turn the Black Sea Bright Blue

An unusually large bloom of phytoplankton has transformed the Black Sea -- so named for its dark color -- into a turquoise so bright it can be seen from space.

Phytoplankton are microscopic organisms that live in both salt and fresh water. Like land plants, they use chlorophyll to capture light and photosynthesis to convert it to energy. And sometimes the show is downright stunning.

The Black Sea bloom this year is the brightest since 2012, according to Norman Kuring, a NASA ocean scientist. The colorful composite images that NASA created have been circulating on social media since May 29, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured the data.

The kind of phytoplankton found in the Black Sea, called coccolithophores, are quite common, thriving in warm, stratified waters with only a few nutrients needed to survive. They also multiply asexually, which is how they can proliferate so well. Although they only live a few days, their white calcium carbonate shells scatter sunlight, which creates their signature luminous turquoise effect.

"The optical effect is striking," researcher William M. Balch at the Bigelow Laboratory for Ocean Sciences in Maine told The New York Times.

Although the phytoplankton blooms are common in the Black Sea, scientists don't know why they are unusually bright this year. It may be due to increased light availability, warmer, more stratified water, or an absence of the nutrients their competitors eat.

Similar phytoplankton blooms are also found in Iceland, Chile, and New Zealand.