Swirls of intense green covered the Baltic Sea in late July, 2014, marking an explosive start to the late summer phytoplankton bloom. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image on July 22 as it passed over the Baltic Sea.
The color of the green in the bloom matches the green vegetation on shore, although the color lightens and becomes infused with milky white in the southern Baltic Sea. The bloom stretches from Sweden (west) to Estonia (east) and from Finland (north) to Poland (south).
Phytoplankton are plant-like organisms which form the base of the marine food chain. They live in the Baltic Sea year-round, but when temperature, nutrients and light are balanced favorably, phytoplankton can experience explosive reproduction and create massive blooms which can be seen from space. Such blooms in the Baltic Sea typically occur twice a year – once in spring, and once in late summer.