Every spring, some Italian beaches are tinged with blue. A phenomenon, sometimes misunderstood, which features the sailssmall marine creatures that come to the shore driven by currents. Contrary to what many think, it is not about jellyfishbut of colonial hydrozoacomplex and fascinating organisms that tell us a lot about the health of our sea.
What are sails?
The sails, whose scientific name is Velella Velellathey are colonies of floating polyps. Their triangular “sail” characteristic, which makes them similar to small boats, allows them to move to the surface of the water pushed by the wind. The intense blue color protects them from ultraviolet rays. Although they own Cnidocists, stinging organs, they are harmless to man.
A natural and recurring phenomenon
The massiveness of the sails is an event that occurs every year, especially in spring and autumn, when the storms push them to the coast. In recent years, however, it seems that the frequency of these phenomena has increased. Some experts hypothesize that this may be due to decrease in sea turtlesone of the main predators of the sails.
An indicator of the health of the sea
The massive presence of Velelle is, in reality, a good sign. These organisms feed on plankton and their abundance indicates that the marine ecosystem is in balance. In addition, the presence of Velelle is often associated with that of a mollusk, the Janthina palewho lives in symbiosis with them and then feeds on them.
The role of monitoring
The sails are monitored byArpal (Regional Agency for the protection of the Ligurian environment) as part of the Marine strategya European directive that aims to maintain the good environmental state of marine waters. The monitoring takes place through visual census of the gelatinous macrozooplacton, of which the sails are part. The data collected are essential to understand the dynamics of these organisms and their impact on the marine ecosystem.
