English: As springtime brings lengthening hours of sunlight and increasing warmth, small plant-like organisms that live year-round in the surface waters of the North Sea begin to reproduce explosively to create huge “blooms” that color the waters in glorious jewel-toned colors. These tiny organisms float near the ocean surface and, much like plants found on land, turn sunlight and carbon dioxide chemical energy, and release oxygen.

Phytoplankton blooms may contain a single species, but it is more common for a very large bloom to be made up of several species. Each species contains chlorophyll as well as other pigments. It’s these pigments that turn the water various shades of blues and greens. While it’s not possible to determine species from satellite images, the presence of milky blue-green strongly suggests the presence of coccolithophores, a type of phytoplankton that possesses a skeleton of calcium carbonate. When present in large numbers, the chalky-white calcium carbonate creates milky shades, as seen in this image.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite acquired this true-color image of a large spring bloom of phytoplankton in the North Sea on June 16, 2019. The coast of Norway can be seen in the northeast section of the image.