Algal bloom swirls in the north Adriatic Sea along the coast of Italy (Copernicus Sentinel-2 image).

Algal blooms show rapidly growing phytoplankton near the sea surface. The chlorophyll that phytoplankton use for photosynthesis tints the water green allowing  detection of ocean conditions from space with satellite sensors. With its 13 spectral channels, Copernicus Sentinel-2 detects the extent of blooms and in this example the bloom covers an area of 9000 sq km. Warm weather, with surface water temperatures reaching 29°C, and calm seas led to immense blooms in the Adriatic Sea. Satellite imaging from space provides important information about fluctuations in global climate.

https://astrobiology.com/2024/09/orbital-biosignature-survey-adriatic-bloom.html