The Bering Sea is no stranger to phytoplankton blooms, such as this late-summer event off the coast of Alaska.

On September 4, 2014, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a natural-color image (top) of a bloom southwest of Nunivak Island and the coast of Alaska. The bloom was still visible a day later when astronauts aboard the International Space Station took photographs (below).

Blooms in the Bering Sea typically increase in spring, when nutrients and freshened water (from melting ice) are more abundant near the ocean surface. Then phytoplankton populations usually plummet in summertime after exhausting the nutrients in surface waters or falling prey to ocean grazers. By autumn, however, storms and cooler water allow nutrients to mix back to the surface, fueling more blooms.

“Phytoplankton blooms in the Bering Sea are very common,” said Kevin Arrigo, a biological oceanographer at Stanford University. “It is one of the most productive places in the world ’s oceans.”

The chlorophyll contained in these tiny plant-like organisms often shows up in natural-color images as a green hue. However, the phytoplankton in this image are very reflective, which suggests they are a type of algae called coccolithophores, according to Arrigo.

“These algae cover themselves with little calcium carbonate discs, and if they are concentrated enough, they can make the water milky in appearance,” he said. “These kinds of blooms used to be rare in the Bering Sea but are becoming more common.”

NASA MODIS image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Astronaut photographs ISS040-E-12807 and ISS040-E-12808 were acquired on September 5, 2014, with a Nikon D3S digital camera, and are provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by the Expedition 40 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by Kathryn Hansen.