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This text was initially featured on Hakai Journal, a web-based publication about science and society in coastal ecosystems. Learn extra tales like this at hakaimagazine.com.
Within the North Sea, almost 100 meters underwater, the seafloor is plagued by greater than 40,000 shallow pits within the sand. The pockmarks, typically spanning greater than 10 meters, are available in quite a lot of sizes and odd shapes. Whereas some appear to be lengthy furrows, half-moons, or concentric circles of sand, others are ringed by mounds of sediment.
When he first noticed the pockmarks, Jens Schneider von Deimling, a marine geophysicist on the College of Kiel in Germany, puzzled whether or not they had been proof of methane seeping from the sediment. Methane seeps are sometimes websites of distinctive seafloor communities that stay off the fuel the best way vegetation stay off daylight. Methane can be a short-lived however potent, local weather change–inducing molecule: over simply 20 years, the greenhouse fuel can entice 84 instances extra warmth than carbon dioxide. So if a variety of methane had been effervescent out of the North Sea, scientists would wish to find out about it.
However the bodily look of those seafloor marks weren’t like these seen at typical methane seeps. Gasoline burping out of the seafloor and into the water tends to go away a distinctly round pit with a conical backside. Schneider von Deimling was puzzled. “The [pockmarks] appeared actually peculiar,” he says. It appeared as if somebody had disturbed the sand from above.
Schneider von Deimling’s crew investigated by analyzing tens of millions of preexisting scans of the realm made with a multibeam echo sounder, a bit of apparatus that shoots out sound waves and measures how they bounce again—very similar to how sonar works. The strategy gave the scientists extremely detailed photos of the curious cavities, confirming the pits’ uncommon shapes. And when the researchers filmed the seafloor, they couldn’t discover any methane-reliant organisms residing close by. The crew additionally made new scans to see how the realm modified over a 12 months: not solely did new pits seem, however previous ones widened or merged with neighbors, a change not normally seen with fuel seeps.
Schneider von Deimling was stumped. However his colleagues who research marine mammals supplied what’s now the scientists’ most certainly clarification for the seafloor pits: hungry harbor porpoises.
In earlier analysis, scientists have discovered grains of sand within the stomachs of stranded harbor porpoises. They’ve additionally discovered the stays of sand eels, small fish that bury themselves within the seafloor. Maybe porpoises are grubbing within the sand to scare sand eels out of hiding, creating these unusual pits as they vacuum up their quarry?
Thus far, it’s simply an concept. Researchers know harbor porpoises feed throughout their lengthy dives, they usually’ve seen captive porpoises digging within the sand. However nobody has truly caught a wild harbor porpoise within the act of disturbing the seafloor.
Magnus Wahlberg, who research cetacean biology on the College of Southern Denmark and wasn’t concerned within the analysis, says harbor porpoises are skittish, onerous to establish, and tough to observe. However Wahlberg has seen harbor porpoises poking into stones and algae, prone to reveal small fish, and says the cetaceans change their foraging strategies relying on the accessible meals.
The North Sea is dwelling to many porpoises and lots of sand eels. “If I had been a porpoise, I’d undoubtedly spend my time poking round within the sand for them,” says Wahlberg.
Schneider von Deimling says researchers have discovered related pits round Eire’s Aran Islands and within the English Channel, different locations with harbor porpoises and sand eels however no underwater fuel seeps. He’s now persevering with his analysis finding out the seafloor off Canada and New Zealand.
If this foraging habits is as frequent as harbor porpoises—there are roughly 700,000 unfold across the planet—then figuring out porpoise habitat could possibly be so simple as searching for the holes they dig.
This text first appeared in Hakai Journal and is republished right here with permission.
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