“The birds that live around Tata Steel sing completely differently”

Dutch research is among the best in the world. Which is why KIJK Editor Laurien Onderwater introduces you to a world of our soils each month in this column. This time: Hans Slabbekoorn wants to know what noise pollution is doing to fishing.

Not only are you a seasoned scientist from nine to five during the week, but you work 24/7. Behavioral biologist Hans Slapikorn, who was born in Zeeland and worked at the University of Leiden, is such a researcher.

While he was on vacation with his family in the French Dordogne, he couldn’t resist driving to the Gironde, two hours away from his place of residence. There is an important spawning ground for European sturgeon, a species of fish that has become extinct almost everywhere in Europe. But in the Gironde, downstream (transitional zone) between the Atlantic Ocean and the confluence of the Garonne and Dordogne rivers, sturgeon females still lay eggs, after which the males pollinate them.

Read also from Underwater Investigations:

“I want to describe the possible last spawning grounds of European sturgeon in the Dordogne in order to see why the fish species continue to thrive there.” This information could help European countries reintroduce fish, says a behavioral biologist as we walk through the BioScience park in Leiden, where the university’s Institute of Biology is located. On the way we passed Martina Vijver, fellow Slabbekoorn at The Living Lab of Slabbekoorn. She’s investigating how invertebrates, including insects, react to light pollution.

Hans Slabikorn

air bubble curtains

On the other hand, Slabbekoorn is mainly concerned with what noise pollution does to animals. In 2003 it was published in the leading magazine temper nature Essay on “city birds” that are beginning to sing in a higher tone due to traffic noise than their rural counterparts. “It gave impetus to follow-up studies around the world.”

Over the past fifteen years, he has expanded his field of research to the underwater world. He is currently primarily concerned with the negative effects of man-made noise on fish in the sea, including herring and migratory fish that migrate from the sea into rivers, as European sturgeon has been doing with us.

Sound is very important to fish. Although they have no vocal cords, they make sound signals by moving their fins, clenching their teeth and mouthparts, or vibrating their swim bladder, explains Slappbikorn. Take the cod, which is the so-called benthic fish (which lives on the bottom of the sea). How do they react when the wind turbine core hits the sea floor? We figured this out by equipping the ancients with transmitters with which we could follow their movements. The type of movement says something about the behavior.”

For example, if a biologist saw animals meandering, he knew that they were looking for food. If they remain silent, this may indicate a fear response. “By placing the sensors in different places that read the transmitters, we were able to precisely locate the fish.”

This is also the case when a company began to accumulate at sea. It was surprising that the cod did not react sharply to this by swimming away. Then people were already shouting: “You see, this does not bother them at all.” But within two to two weeks after that, we suddenly saw that an astonishing number of fish had left the area. So the work definitely had an effect on the fish.”

Unfortunately, Slabbekoorn doesn’t know where they went next. At one point, the transmitters were too far from the location sensors. But with this kind of information, he hopes he will be able to encourage companies to find technical solutions that reduce noise pollution. For example, offshore companies in the Netherlands are already obligated to pull curtains of air bubbles around ships or piles to prevent the propagation of sound waves. The scientist is also working with boat builders to figure out how to make ships calmer.

Hans Slabikorn
Hans Slabbekoorn lowers an antenna (a type of underwater microphone) and echo sounder (by which water depth is determined) into the sea for acoustic research. © Hans Slapbekorn

Slabbekoorn also wants to check whether noise pollution in the sea – such as the construction of wind farms – is affecting the birds’ behaviour. “When a rider’s boat comes, cormorants fly a hundred metres.” Hence noise pollution is only one type of disturbance, because in crowded cities animals also have to deal with light pollution. Not to mention the emission of particulate matter, a form of pollution that can affect the behavior or well-being of a group of animals.

leaf blowers

For example, Slabbekoorn has been recording the song of birds for a few years that live around the Tata Steel production complex, where the air is polluted by particulates. “As verification, we recorded the same species in clean areas above and below IJmuiden. Then we found out that the birds in Tata Steel sing completely differently.”

An intense result, but Slappekorn talks about it calmly and objectively. That changes when he talks about his biggest annoyance: leaf blowers. “If there’s one thing that’s useless, it’s leaf blowers. You don’t have to remove leaf mounds at all; they actually preserve valuable ecosystems. Due to excessive use of leaf blowers, there are fewer leaves, fewer invertebrates, and therefore fewer Of birds. See, a city bustling with noise, but a lot of it has a purpose. Just think of an ambulance with the sirens going off,” he says as one passes by at that moment.

“I find leaf blowers to be an incredibly disproportionate and dysfunctional source. These things really have to go,” concludes Slapbekorn as we head back to the Institute of Biology where our career began.

In front of the property, the road is re-paved; Speaking of noise…

This episode of Underwater Interrogated is also in this very heavy summer issue of KIJK.

Photo: iStock / Getty Images

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