File:Bloom in the Black Sea (MODIS 2024-05-10).jpg

English: Bright colors continued to mark the progress of an expanding spring phytoplankton bloom in the Black Sea in early May 2024. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this true-color image on May 7.

The Black Sea is a large inland body of water bordered by Bulgaria, Romania, Ukraine, Russia, Georgia, and Turkey. It receives fresh water—and nutrient rich runoff— from several major rivers such as the Danube, Dnieper, Rioni, and Dniester. Nutrients also spill into the sea from human activity, such as agriculture and industry, and drop into it in the form of mineral-rich dust from frequent dust storms that cloud the skies across the region. All of these sources help to feed the growth of tiny floating organisms known as phytoplankton.

Phytoplankton are the “primary producers” of the seas and oceans. These plant-like, microscopic algae, bacteria, and protists use chlorophyll to make food from sunlight and dissolved nutrients. More than 150 different types of phytoplankton have been observed in the Black Sea, supporting a rich bounty of fish and other marine life.

While phytoplankton live in relatively small numbers in the Black Sea year-round, the combination of plentiful nutrients, warm sea temperatures, and lengthening sunlight often spur explosive reproduction that results in massive blooms that can be seen from space. The swirls and patterns are created from currents and eddies in the water.