A map of ocean colour can be a map of life

Sunlight reflected from the sea carries clues about material near its surface. Satellite instruments measure bands of colour that researchers use, with models and field observations, to estimate chlorophyll and study phytoplankton. These microscopic organisms form the base of marine food webs and participate in the carbon cycle.

Colour is an indirect signal, not a census. Sediment, dissolved matter, clouds and different plankton communities complicate interpretation, especially near coasts. The observational lesson is therefore double: remote sensing can make tiny drifting life visible at planetary scale, but the image is a measured proxy whose translation requires continual checking.