On July 18, NASA's 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. /VCG Photo

The tiny white specks are ships in the region. Note how the phytoplankton trace the edges of a vortex; it is possible that this ocean eddy is pumping up nutrients from the depths. /VCG Photo

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