The large volume of freshwater flowing into the Black Sea from large European rivers, including the Danube and Dnieper Rivers, makes the sea much less salty than open oceans. The freshwater flow also delivers many nutrients, which are washed into the sea from land. These nutrients support large blooms of phytoplankton: microscopic photosynthetic organisms (algae and bacteria). This image of the Black Sea on May 30, 2006, shows swirling blooms of phytoplankton coloring the surface waters blue and green. The chlorophyll and other pigments the organisms use for photosynthesis change the way light reflects off the surface, and these changes are visible in satellite imagery. This image was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite.
This image shows a colorful bloom of phytoplankton in the Black Sea on June 4, 2008, along the southern coast near the Turkish cities of Sinop and Samsun. The natural-color image was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite. Loops and swirls of blooming phytoplankton follow the coastline, while farther out in the open waters (upper right), the blooms become more spread out. The greenish plumes hugging the coast from Sinop westward to just beyond Samsun may be river plumes. River plumes can contain nutrients that stimulate phytoplankton blooms, but they may also contain sediment and organic matter that can color the water.