Velella velella, because Italian beaches are tinged with blue. The expert: “No danger to health”
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Once again the beaches of Italy are tinged with blue. From the Liguria – where the phenomenon has been extremely significant in recent days – at Sardiniafrom the Campania at the Sicilythousand of Velella Velella they run aground along the coasts, frequented by the first smartphone-equipped bathers. To whom what is technically a does not go unnoticed blooma seasonal phenomenon linked to the explosion of some populations, in this case of a colonial animal of hydrozoan group: what you see on the beach are not jellyfish, but associations of individuals physically joined together, as happens in corals, to form a single body.
And it is therefore the aggregation between different units, each of which a few centimeters, to form the large bluish patches which, dragged by the currents, extend over the sea surface even for several tens of meters and end up along the beaches, punctually photographed for social use. But that’s no surprise, apparently.
“That’s right. – he nods Ferdinand Boer, former professor of zoology at the Federico II University of Naples, today president of the Dohrn Foundation – The Velellas are a bit like swallows: in spring they arrive from the deep sea, where they return like jellyfish at the beginning of summer. And it is something that happens every year in this period, with the ascent from the deep waters”. Curious species, therefore, and largely still mysterious in its ethology to the general public, although in fact Linnaeus has already described its characteristics over two centuries and a half ago.”Velella is a floating colony of polyps that produce small jellyfish. – explains Boero again – These go deep, reproduce sexually and produce the new Velellas, which date back and appear by the millions this season. And it surprises me, indeed, how people forget it from one year to the next”.
Health
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The stranding has no consequences for humans (Velella velellas are in fact harmless) except for any unpleasant odor associated with their decomposition. The frequent sightings of these hours in Liguria have induced Arpalthe regional agency for environmental protection, to issue a note specifying the active role in monitoring Velella, “together with other species that are part of the gelatinous macrozooplankton, within the Marine strategya Community directive which is based on an integrated approach and aims to become the environmental pillar of the future maritime policy of the European Union”. It is a bimonthly monitoring along four transects located between 3 and 12 nautical miles from the coast in front of Vado Ligure, Genova Voltri, Portofino and Punta Mesco. In the event of a sighting, Arpal operators have the task of noting coordinates, date and time, weather and sea conditions, observed species, abundance, density and type of aggregation: the data collected is sent to the Ministry of the Environment.
But could monitoring show a growth in the population of Velella velella? “We know that in general, intensive fishing benefits the gelatinous plankton. – underlines Boero – The presence in our seas of a smaller number of fish configures a lower competition for plankton, which feeds on the same things as the larvae and juveniles of fish and which therefore enjoys a competitor less in the search for food”.
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A discourse analogous to the one concerning theexpansion of jellyfish in the Mediterranean, which however have one more ally: global climate change. That’s right: the progressive and apparently inexorable water heating it favors their proliferation and lengthens their reproductive season. and theacidification progressing of the waters does not seem to have deleterious effects on their presence, being animals that also show an excellent adaptation in acidified waters, with low quantities of oxygen or very polluted.
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