Every summer, phytoplankton spread across the northern basins of the North Atlantic and Arctic Oceans, with blooms spanning hundreds and sometimes thousands of miles. Nutrient-rich, cooler waters tend to promote more growth among marine plants and phytoplankton than is found in tropical waters. Blooms in summer 2018 off Scandinavia seem to be particularly intense.

On July 18, 2018, the Operational Land Imager (OLI) on Landsat 8 acquired a natural-color image of a swirling green phytoplankton bloom in the Gulf of Finland, a section of the Baltic Sea. Note how the phytoplankton trace the edges of a vortex; it is possible that this ocean eddy is pumping up nutrients from the depths.