Posidonia oceanica is not an algae but a flowering plant. It grows in vast meadows and hosts 25% of Mediterranean marine species. Seagrass meadows are considered the lungs of marine ecosystems. On average, a seagrass meadow produces 14 L of O2/day/m2.

The P. oceanica meadow is one of the most important ecosystems in Kuriat. Its monitoring and conservation are a priority due to its fragility. Posidonia poorly withstands pollution, and its slow growth (1 cm/year) cannot compensate for the damage caused by anchors. It has been classified as a protected species since 1988. Preserving Posidonia also means preserving all the species that live in it and depend on it for survival.