Wadden Sea Study: Porpoises, Underwater Noise Unveiled

Thanks to a €1.5 million grant from the Wadden Fund and the Dutch Ministry of Agriculture, Fisheries, Food Security and Nature, researcher Annebelle Kok from the Institute of Biology will be mapping both the natural sounds made by porpoises and the human-generated underwater noise in the Wadden Sea.

Experts in bioacoustics

'This project fits really well with the work we do,' says Kok. 'We'll be using sound to study the behaviour of harbour porpoises. At Leiden, we specialise in bioacoustics, which is a key part of this research.'

Shipping activity is increasing, dredging operations are ongoing, work is being done on dykes and dams, and military jets frequently fly overhead. All of these activities contribute to noise levels in and around the Wadden Sea. That noise travels underwater and can affect marine animals. The harbour porpoise, a protected species that lives in the area, is especially vulnerable. These animals rely on sound to navigate and hunt, making them particularly sensitive to disturbances.

Mapping the soundscape

For the next three years, underwater microphones - known as hydrophones - will continuously record sound at twelve locations throughout the Wadden Sea. These recordings will capture both human-made noise and the clicking sounds that harbour porpoises use to 'see' underwater. This will give researchers a detailed picture of the Wadden Sea's soundscape and show where and when porpoises are present throughout the year.

'Harbour porpoises are very vocal animals. By picking up their clicks, we can track their movements and see how they hunt for fish in the Wadden Sea,' Kok explains. Together with Klemens Eriksson from the University of Groningen, she is responsible for the scientific side of the research.

Better understanding for better protection

'To manage nature well, we need a clear understanding of what's happening,' says Belinda Burtonshaw from the Waddenvereniging. 'We know that noise is disrupting the peace in the Wadden Sea, but we don't yet know how serious the problem is or what its exact effects are. This project is a first step towards better insight and will allow us to make recommendations for protecting areas that are particularly sensitive to noise.'

Alongside the scientific work, the project also invites people who live in or visit the Wadden Sea area to take part. Activities will include expeditions where participants can listen for porpoises, and a special reporting point will be set up where people can share their porpoise sightings. This citizen involvement helps raise awareness and also provides valuable extra data for the research.