Despite people thinking that there is only seaweed in the sea, the Posidonia oceanica Is a real sea plant!
This species is in fact a plant for all intents and purposes. Its component parts are the same as those of terrestrial plants, such as roots, leaves, flowers e fruits (also called sea olives), which have adapted perfectly to aquatic life, thus enabling the Posidonia oceanica To survive in the waters of the Mediterranean Sea!
Traces of these structures can be found not only underwater, but also on our beaches.
Parts of Posidonia Oceanica - Source Ragonese and Norrito 2019
The most famous of all is surely theegagropil! These are those brown "balls" that are deposited on beaches throughout the year. They are nothing but residues from the woody vessels of the leaves of Posidonia oceanica And sediment twisted together by wave motion.
Egragopilo - Source: Ragonese and Norrito 2019
Two other features often found along our beaches are banquettes, which are clusters of Posidonia oceanica leaves after several cycles of beaching. These structures are very important for the protection of coastlines from erosion due to the action of the sea, which is why cleaning beaches of these biomasses is not always a positive action!
Banquette (Source: Ispra)
But this is not the only reason why this species to date is considered critical to the preservation of an entire marine ecosystem.
The grasslands of Posidonia oceanica, in fact, constitute the habitat of various animal species, thus representing an important source of biodiversity. Already found at a depth of a few meters, this plant is also visible through snorkeling trips, during which one can see on the leaves both traces of epiphytes (i.e., microorganisms living above their surface) both of predation. Among the fish that most commonly can find a perfect habitat in the prairies of Posidonia oceanica there is certainly Sarpa salpa (the Salpa), whose bites can be recognized on the leaves of this plant by their rounded shape; but also Paracentrosus lividus (the sea urchin) is common to feed on, however, leaving much more jagged marks than those of the Salps.
Salpa bites on Posidonia Oceanica leaves - Source: The Outdoor Gulf
Given the importance of the Posidonia oceanica, posidoniae were classified as. priority habitat in Annex 1 by the Habitats Directive, that is, whose conservation requires the designation of special areas of conservation. The presence of several marine protected areas in Italy allows the protection of this important species, especially from activities that cause the most damage to Posidonia oceanica seagrass beds, such as anchoring and fishing. L'Marine Protected Area Island Bergeggi is an example of this!
Curiosities: did you know that other plants belonging to the genus Posidonia Are they found only in one other place in the world? It is Australia! Which makes it even more interesting to be able to see grasslands of Posidonia oceanica, since its presence is not so common outside the Mediterranean Sea!
