In the depths of the Antarctic, microphones are used to understand sea life (Le Progrès – AFP, 02/18/2024)
A scientific team listens to the white continent’s sea wildlife by immersing microphones in its depths. This is a fascinating journey.
In the depths of the Antarctic Ocean, immersed microphones record sounds of “spaceshifts” and a range of “impressive” buzzing. This is what the Colombian scientist Andrea Bonilla explains, while she monitors sea life during an expedition to the edges of the white continent.
500 meters below surface
This biologist from the New York Cornell University immerses hydrophones 500 meters deep. They are wrapped with titanium and will register these depths’ soundwaves during one whole year.
Once the soundwaves are deciphered, they will help to understand the sea mammals’ behavior and their movements during austral winter, when the Antarctic becomes almost uninhabitable.
“Here, you can find species whose sound is impressive, literally like in Star Wars, they sound like spaceships. Very few ears have the privilege to hear them.” the 32-year-old scientist reports aboard the ARC Simon Bolivar, a Colombian navy’s ship.
Tension and excitement
Andrea Bonilla – who holds a PhD in marine acoustics – and the other scientists aboard the tenth Colombian expedition in the Antarctic also gather the microphones that were left the year before during a mission operated by the Turkish Navy.
Guided by the GPS, the boat is entering the meeting zone. In order to make the hydrophone come back to the surface, Andrea Bonilla is releasing the anchor that keeps it immerged. The whole team is now peering into the quiet waters during eight long minutes until a little flag unfurls at the surface, welcomed by joy.
She’s warmly congratulated by her co-workers and expresses relief. “I’m really excited because it was the first time we did this operation in those waters. Everything turned out great.” the Colombian scientist says delightedly.
Assessing the impact of human activity
Once back onto dry land, she will analyze one year of recording. “In a marine environment, sound is one of the core elements.” she says. It is, because noise or auditory disturbances can affect intraspecies communication or hinder the normal continuity of natural activities such as hunting.
These investigations also intend to assess the impact of human activity and of the pollution to which mammals are exposed in one of the most preserved spots on earth.
“Protected marine area »
Another purpose is to support the proposal, which has been promoted by Chili and Argentina since 2012, to make the Antarctic peninsula “a protected marine area”. Andrea Bonilla works with spectrographs who visually represent the sound frequencies. Medium and high frequencies arise from animals of different sizes.
Her discoveries won’t just be used to monitor the sea mammals, they will help as well geophysical research: the microphones capture low frequencies that are emitted by Earth movements and melting ice.
Penguins and whale
Not far from the ship, a penguin colony is walking on a giant toboggan-shaped ice block while on the surface, the scientists are watching a humpback whale take a last breath before winter makes it leave towards Pacific’s warmer waters.
“My first encounter with a whale happened with a singing whale, and I think it changed my life”, the scientist remembers.
After having eaten for months in the Antarctic peninsula and the Strait of Magellan in Chile, thousands of these large mammals meet between June and October in order to breed, in a sea corridor which stretches from South Costa Rica to North Peru.
Melodious animal songs
But “there are also species which live only here”, she stresses, such as Weddell seals and leopard seals, which make high-pitched songs of various tones and melodious compositions which provide information about their behavior.
Andrea Bonilla is getting ready to drop new hydrophones and is tying on top of the titanium tank a red flag which will be used to detect it in the midst of the waters when she comes back next year. During the expedition, three microphones have been immersed, two in the Strait of Bransfield and one in the Drake Passage.
Source: https://www.leprogres.fr/environnement/2024/02/18/des-micros-dans-les-fonds-de-l-antarctique-pour-comprendre-la-vie-marine#Echobox=1708238993 (translated from French by the Karukinka association)