For years scientist have been puzzled by a humming sound thousands of feet below the surface of the Pacific Ocean. The humming was first noticed when scientists dropped hydrophones in the Ocean to study the songs of migrating humpback whales, clicking signals of dolphins and other marine mammals.
The puzzling sounds could be heard just a few decibels above the background level of noise from the hydrophones, definitely unique from the normal sounds of the ocean. For several years scientist have wondered what was causing the deep sea buzz, however a team of marine biologist from the Scripps Institution of Oceanography think they have may have cracked the code.
According to Simone Baumann-Pickering, the sound was “more as if you’re sitting on an airplane and it’s humming, buzzing.” The sound starts after the sun sets, she says, and goes on for a couple of hours, then stops. The same thing happens at dawn. Biologist have already known that small fish, crustaceans and squid like to hide out in the deep, dark water during the day, and migrate up to the mesopelagic (twilight) zone at night to feed
Upon closer investigation scientist have now been able to link the humming with the daily rise and fall of the fish migration. Why the noise? Scientists can only speculate. It could be, says Baumann-Pickering, that the creatures “are truly, actively communicating — potentially to initiate migration.” In other words, maybe the buzz is just a signal that “it’s time to go,” she says.
Although their is another possibility, could the humming actually be fish farts? “It’s known that some fish are considered to be farting,” says Baumann-Pickering, “that they emit gas as they change depths in the water column.” This happens when gas is released from the swim bladder as it moves up to the surface.
Wether it is fish communicating to their friends that it is time for dinner, or just simply fish farts, billions of fish are swimming up and down in the ocean everyday, and making it hum. [NPR]