Blue, mysterious and arriving by the millions: the alien-like creatures blanketing US beaches

[cbabe]

https://www.theguardian.com/environment/2024/apr/05/blue-tide-west-coast-beaches

Blue, mysterious and arriving by the millions: the alien-like creatures blanketing US beaches

Masses of ephemeral organisms known as ‘by-the-wind sailors’ wash up in a ‘blue tide’ on the west coast most years but warmer winter seas could be increasingly their numbers

Katharine Gammon
Fri 5 Apr 2024 07.00 EDT

From Oregon to California, blankets of alien-like blue creatures are washing up on rocky beaches. They are Velella velella, tiny colonies of organisms with a sombrero-esque fin sticking out the top and tentacles dangling down.

Millions have been spotted along the US west coast this spring, much to the surprise and delight of beachgoers who have gleefully posted footage on social media. Some call it a “blue tide” and it happens most springs – but not always to the same degree of abundance.

Though they look like one organism, velella – also known as by-the-wind sailors – are actually colonies of creatures from a class called hydrozoa that use the wind to speed along. They spend most of their lives out in the open ocean, searching the water column below them with tentacles that sting fish larvae or zooplankton, but are harmless to humans. One part of the colony is responsible for eating, another for reproduction. Coral is another colonial organism – but it’s uncommon to encounter such colonies on land, says Anya Stajner, a doctoral student at the Scripps Institution of Oceanography.

There are a few theories about how the animals got their brilliant blue color. Living at the interface of the air and ocean doesn’t offer them many places to hide from predators such as the huge mola mola ocean sunfish, which sucks up velella like candy. Their color might help them disguise themselves by blending in with waves, Stajner says. Another theory is that the color protects them from harsh UV rays – a sort of built-in sunscreen.

…more…

(Maybe someone can post a photo?)