Beaches along the west coast of America have been swamped with transparent blue creatures resembling jellyfish, known as “purple sails” or “by the wind sailors.” The phenomenon is a result of the wind's direction and probably not an indicator of environmental destruction. The sheer scale of this event is breathtaking, with estimates of a billion specimens washed ashore.
Credit: Jennifer Nicole Buchanan via Shutterstock. Individual Velella colonies are small, but in their millions they can dominate a beach.
Velella float in the open ocean and use poisonous tentacles to catch prey such as plankton. Balloon-like bubbles stick above the water's surface and catch the wind in such a way that they sail at an angle to it. Every few years, however, prevailing winds in the wrong direction wash large quantities onto beaches where they die. This spring has proven particularly disastrous for the northern Pacific population as winds were sustained long enough to wash huge numbers onto the coast.
As usual, the beaches are not hit at the same time, with the wave of blue starting in Washington and sweeping south over a period of several weeks. Coincidentally, there have also been major strandings in Italy at the same time.
Despite their numbers, permits are required to collect them. Kevin Raskoff of Monterey Peninsula College told National Geographic that touching them is unwise. Unlike both the man-of-war and many true jellyfish, their toxins will do little damage to the skin, but can rub off. If you rub your eyes after receiving some of the venom on your fingers, “you're going to feel it,” Raskoff said.
Last year's American Velella stranding was unusually late, leading to reports such as this one.
It is also rare to have such large strandings on the same coastline in successive years.
Credit: Bettina Walter, "Velella velella," via Flickr. CC BY-NC-SA 2.0