Zostera marina
There are about 60 species of fully marine seagrasses belonging to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the order Alismatales (in the class of monocotyledons). Seagrasses beds or meadows can be either made up of a single species (monospecific) or mixed. In temperate areas one or a few species usually dominate (like the eelgrass "Zostera marina" in the North Atlantic), whereas tropical beds are usually more diverse, with up to thirteen species recorded in the Philippines. Like all autotrophic plants, seagrasses photosynthesize, in the submerged photic zone. Most species undergo submarine pollination and complete their life cycle underwater.