Scientists are collecting the sounds of the sea to help get a picture of the biodiversity challenges marine life in New Zealand faces
The ocean is louder than you think.
Maybe its because of Jacques Cousteau’s famous film The Silent World – when people think of the alternate reality that exists beneath sea level, the image of a soundless and tranquil world comes to mind, full of shapes gliding inaudibly through still reefs and kelp beds.
The reality is quite different.
According to Dr Craig Radford, Associate Professor of marine science at the University of Auckland, the ocean has a lot to say.
“You might just hear the bubbles if you go scuba diving,” he said. “But if you go out to Goat Island Marine Reserve and sink to the bottom and just stay still and listen, it’s actually very noisy.”
Now with a group of scientists from around the world, Radford is putting together a library of the myriad noises you might hear under the sea if you stop and listen.
The Global Library of Underwater Biological Sounds, or GLUBS – fitting name for a catalogue of submarine sounds – has been proposed by a group of 17 international experts, led by Miles Parson of the Australian Institute for Marine Science.
The project aims to collect the sounds of sea life using specially developed hydrophones, and then use this data to get a handle on the biodiversity of different regions.
Radford hopes it will give marine scientists a leg-up when it comes to monitoring the populations of species around New Zealand.
“At the moment, we survey biodiversity with survey dives,” he said. “So this makes our lives easier.”
More than just that, it allows them to leave sensors in the water, even after the researchers have taken off their scuba gear and gone back to dry land. The hydrophones also allow data to be collected from places difficult to access.
Researchers from the University of Auckland currently have hydrophones 1000km northeast of Auckland in the Kermadec Islands. It’s a place they may only have been able to visit and conduct survey dives in once a year or so, but now they listen in and record the noises of the sea life.
But for this to work, the library needs a wide database of sea creature sounds.
Radford said the project hopes to make hydrophones easy to access or even free for the public, so recreational fishers and divers can drop one in the water and then upload their findings.
An AI program will then take a look at the audio and automatically categorise it after cross-referencing it with the rest of the library.
“We’re hoping to get people using it off their own bat,” said Radford.
Audio metrics may be the future of marine science, partially due to the nature of water itself. Water’s density means sound travels more than four times faster under the sea than it does in the air – around 1.5 kilometres per second, as opposed to 340 metres per second on dry land.
Hence humpback whale song being heard across a distance of thousands of miles.
But while the performative talents of cetaceans are well-known, there are some undersea chatterboxes that get less credit.
Radford said GLUBS will be used to determine the whereabouts of fish species by listening out for the range of sounds they make.
These range from the bark and growl of a John Dory, made by rapidly flexing the muscles alongside its swim bladder to produce drum-like sounds, or bone attachments on their pectoral fins that can be clicked in and out of joint – like a human cracking their knuckles.
“They can do all of it,” Radford said. “They can click, they can moan – it just depends on what mechanism they have for making sound.”
The purposes also run the gamut, from attracting potential mates to males intimidating rivals who stray too close to the unfertilised eggs in their nest.
But there are gaps of knowledge in New Zealand waters, which Radford hopes GLUBS will help to fill.
“Compared to the tropics we know very little about fish that produce sound in temperate waters,” he said.
And if we start putting our ears to the water, we may be surprised by how much noise there is under the surface of human origin, Radford said.
He described the noise of boats and busy harbours as creating a cocktail party atmosphere for sea life.
“It’s like at a busy party where everybody needs to get close to hear one another,” he said. “Noise pollution can mask important sounds.”
Another aspect the project can help explore is the regional dialects of different species.
It was already known that whales from different parts of the world have their own unique way of singing – a humpback from Sydney will sound different to one in Tonga. But more recently, scientists have discovered that even fish from different parts of the world may have an ‘accent’.
Between fish up in the Kermadecs and those in the Hauraki Gulf, there are a range of different sounds.
“I guess it might be like Southlanders rolling their r’s,” Radford said.
The research platform is next in the tradition of similar ideas such as BirdNET, a bird-identifying project from Cornell University, which allows for biometric data collection at a massive scale and encourages weekend birders to get involved in a bit of citizen science by sending in their recordings.
Radford would like to see the same thing in New Zealand once GLUBS is up and running.
“I’d like to see people take the time to listen underwater,” he said.