During the spring and summer of 2026, the waters of the Black Sea and adjacent waterways displayed a milky blue hue, attributed to a phytoplankton bloom. This phenomenon, visible from space, is a seasonal manifestation of biological activity in the marine ecosystem, where these photosynthetic microorganisms reproduce massively, altering the water's surface reflectance.

Phytoplankton, by absorbing sunlight and reflecting certain wavelengths, imparts a distinct turquoise or blue-green tone to the waters. Although a natural event, the intensity and extent of these blooms can vary annually, influenced by factors such as water temperature, nutrient availability, and salinity. Observing these chromatic changes is relevant for monitoring the health of marine ecosystems and understanding biogeochemical cycles in large bodies of water.