Algal bloom in the Black Sea, satellite image. Algal blooms are formed by the rapid multiplying of phytoplankton, microscopic marine plants that drift on or near the surface of the sea, sustained by sunlight. Here, nutrients are provided by flow from waters entering the Black Sea. One type of phytoplankton commonly found in the Black Sea are coccolithophores, microscopic plankton that are plated with white calcium carbonate. When aggregated in large numbers, these reflective plates are easily visible from space as bright, milky water. Diatoms, which also bloom in the Black Sea, tend to darken water more than they brighten it. Image obtained on 29 May 2017, by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's Aqua satellite |