Baltic Swirls

Captured by Sentinel-3A on 23 June 2016, this image shows an algae bloom in the Baltic Sea. Sentinel-3A carries a suite of instruments to monitor our changing world. This image was captured with its ocean and land colour instrument, OLCI, which provides biogeochemical measurements to monitor, for example, concentrations of algae, suspended matter and chlorophyll in seawater. This information can be used to predict harmful algal blooms, which is particularly relevant in the Baltic Sea where extreme blooms are a significant problem. The health and vulnerability of marine ecosystems is fundamental to our knowledge of ocean productivity and, in turn, fish stocks.