December 2, 2023


Seals as research assistants –

Research ships cannot penetrate many marine areas on the Antarctic continental shelf because of the ice clinging to the coast. Thanks to animal helpers, researchers have now been able to gather valuable data on ocean circulation in these areas: Eight seals carried sensors with them over several months to measure salinity, temperature and water depth. The results show: in the Antarctic autumn, warm surface waters pass under the ice shelf due to easterly winds. This affects the ecosystem, but also the ice.

The Antarctic continental shelves are one of the most biologically productive regions in the world’s oceans. Interactions between the ocean, sea ice, and ice shelf produce large amounts of nutrients near the surface that nourish many organisms – from microorganisms to mammals and birds. In order to better understand the physical and biological processes, researchers need more data about the ocean currents involved. However, many of the Antarctic shelf areas are covered with mainland ice, which makes research with the help of research vessels almost impossible – especially in the Antarctic winter from March to September.

seals with gauges

A team led by Nobu Kokubun of the National Polar Research Institute in Tokyo used another method to collect data: To explore the particularly inaccessible regions of East Antarctica, they outfitted eight Weddell seals native to this region with small gauges. The researchers explained that “the devices collected hydrographic data and the behavior of seals in diving.” “They sent this data back to us via satellite when the seals surfaced.”

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Seven out of eight transmitters provided data for more than a month and showed that the seals first migrated east – up to 633 kilometers from their original position – and then approached June when coastal ice shut down in hibernation in the designated areas. These ice areas were previously unknown to researchers. “Previous studies with tools associated with the migration of southern elephant seals and resident Weddell seals have shown some interesting physical processes in Antarctica, but even here there has been little study of coastal areas covered by ice shelves,” says Kokubun.

Ocean currents affect food availability

Based on data on salinity, temperature and water depth, the researchers were able to differentiate between different types of water and determine their source – for example from shelves of melting ice, and from the surface of the water in other parts of the water. The sea, from large, cold bodies of water known as winter waters, or from depths where the water is relatively warmer. They combined measurement data with meteorological and oceanographic models.

The result: Especially in the Antarctic autumn, easterly winds push surface waters with lower salt content from outside the shelf area into coastal areas. These warmer bodies of water bring more nutrients and prey with them, and the researchers used the data to note that seals in these waters hunted more intensively. “Previous studies have emphasized the importance of warm, deep waters, which bring with them high concentrations of nutrients,” the authors wrote. “Our study shows that warm Antarctic surface waters also play an important role and have a positive impact on food availability for predators such as Weddell seals.”

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Animal-assisted data collection also for future projects

According to the researchers, their method with animal assistants may also be useful for future studies. “Our study shows that Weddell seals equipped with gauges are well suited to research oceanographic conditions and their biological impacts on the Antarctic continental shelf,” the researchers said. In further studies, the team wants to shed more light on the physical and environmental processes in the area. They hope this will also provide insight into how the Antarctic ecosystem is reacting to rapid changes in sea ice.

Quelle: Nobuo Kokubun (National Arctic Research Institute, Tokyo, Japan) et al., Lakes and Oceanography, doi: 10.1002/number 111914