Sentinel-2 (MSI) provides global, regular and repeated coverage of inland, coastal and open sea waters under cloud-free sky. One of the many applications of Sentinel-2 data is for marine ecosystem monitoring in shallow coastal waters.

In particular, Quasar can provide customized Sentinel image services specifically designed to map the meadows of Posidonia oceanica in the Mediterranean Sea. Posidonia oceanica is a seagrass species that is endemic to the Mediterranean Sea, and it constitutes one of the most important ecosystems of the sea. Posidonia is one of the main sources of oxygen in the sea and it is considered to be a good bioindicator of the quality of the water.

S2 routinely collects large amounts of images which are made freely available. The vast amounts of data produced by the constellation of satellites are a great opportunity to develop systems for marine ecosystem monitoring in shallow coastal waters. To become fully operational, these processing systems must be entirely automatic with a controlled level of reliability and robustness.

Quasar’s system provides Posidonia oceanica maps with a 10 m spatial resolution and at different temporal scales, being the recommended one, but not limited to, yearly cartography. A seasonal and yearly scale cartography should be enough for decision-making on conservation measures. Our classification technique is able to recover from S2 images the detailed spatial shape of the seagrass meadows with a correct recall rate of 84% for Posidonia pixels. These results prove accurate up to depths close to 30 meters in depth. Our classification method can provide an extremely cost-effective way to monitor variations of Posidonia oceanica meadows using the S2 archive (2015-present). Another advantage of the system designed is the ability to replicate results.