West Coast hit by Velella mass stranding

Millions of Velella velella, a hydrozoan with a cosmopolitan distribution hits the US West Coast

by Lorenzo Ciotti
West Coast hit by Velella mass stranding
© @OlympicCoast

Many beaches along the West Coast of the United States have been invaded by millions of Velella velella, a hydrozoan with a cosmopolitan distribution.

There are years in which concentrations of animals are particularly abundant, even on the West Coast, as in 2024.

The study Long-term patterns of mass stranding of the colonial cnidarian Velella velella: influence of environmental forcing, published by Julia Parrish of the University of Washington and two other marine biologists in Inter-Research Science Publisher, said more massive strandings would appear take place after particularly warm winters, like the current one, obviously caused by the serious climate crisis affecting our planet.

What is Velella

Velella velella is a colony of siphonophores of the Porpitidae family. It is often found in all oceans, on the shores or at most 1-2 cm deep in the water, with a preference for warm or temperate waters.

Velella velella is a carnivorous animal. It captures its prey, generally plankton, using its tentacles which contain toxins. These toxins, although effective against prey, are harmless to humans, as they cannot penetrate the skin and do not cause any reaction to human skin. That said, it is still preferable to avoid touching your eyes after picking up a Velella velella.

However, mass strandings of these organisms can occur, especially in spring, which change from blue to pink as they die.

Shaped like an oval disk, 4-7 cm in diameter, surmounted by a vertical crest that looks like the sail of a tiny hull, hence the name velella. Below the vertical sail, composed of a medusoid shape, there are various zoids that perform different functions.