BLOWING BUBBLES
Uncover the origins of the mysterious spongy white balls tumbling around our shorelines
They catch a diver’s eye in the same way a discarded plastic bag or yogurt pot might. An unexpected glimmer in the gloom of a typical offshore winter dive. But on closer inspection, the object is moving. It’s white with black speckles, like a melted Friesian cow, and turns out to be dragging a familiar item around on its ‘back’.
A common whelk or ‘buckie’, Buccinum undatum, this sea snail, or at least its shell, is a common sight on almost any shoreline at this time of the year. In fact, it’s our largest gastropod, whose dull creamy shell can grow to be 10-11cm long. But it’s not the adult snail that fascinates as much as another related item you can find on the beach this winter.
The sea wash ball, also known as ‘fisherman’s soap’ or an ‘egg cloud’, is a strange, off-white cluster of flattish capsules – imagine a bundled-up sheet of bubble wrap. They’re the egg clusters of the common whelk and while they’re a constituent part of almost any strandline at any time of the year, right now there are fresh ones to be found: November to January is the whelk’s breeding season.
Somewhere below the low tideline they amass. Quite how this frenzy of egglaying starts is a mystery, but once they get going, other whelks quickly join in, perhaps sniffing out tell-tale odours in the water. The whelks are hermaphrodite, so this clustered spawning makes sense, because each snail can release both eggs and sperm, and they can all fertilise each other.
With each snail engaged in a slowmotion production line of egg capsules, each clump or cloud takes anything up to a week or so to complete. Sometimes they’re produced by a solitary animal but sometimes several contribute to form a single mass – a behaviour that explains the size differences you see in the egg clusters that wash up on the shore.
When you next find a sea wash ball, have a close look. Each of the ‘bubbles’ is