The footage captured by sea lions using lightweight video cameras gives researchers a glimpse into previously unexplored areas of the seafloor off Australia's southern coast.

The one on August 7th inFrontiers in Marine Science 1The published results include detailed maps of the seafloor created by combining videos captured by the animals with a machine learning model. The camera footage also shows details about the distribution of different habitats and species.

“These are particularly deep and remote offshore habitats that cannot be reached with the usual surveys you would do from a boat,” says co-author Nathan Angelakis, who researches ecology and evolutionary biology at the South Australian Research and Development Institute in West Beach. “With the data we collect, we are essentially exploring new parts of the ocean that have not yet been mapped.”

Unknown waters

Knowledge of the seafloor is important for several reasons, including marine conservation, navigation, and predicting hazards such as tsunamis. “You can’t manage what you haven’t measured,” says Steve Hall, director of partnerships at ocean mapping organization Seabed2030, based in Liverpool, UK.

Globally, only 26% of the seafloor has been mapped at high resolution. This is partly due to the challenges of exploring the deep sea, where pressure is extremely high and light levels are low. Researchers typically map the seafloor using remotely operated underwater vehicles or by dropping cameras from surface ships - but both methods are time-consuming and costly.

Angelakis and his colleagues tried a comparatively simpler approach by enlisting the help of wild Australian sea lions (Neophoca cinerea). These animals spend most of their time on the ocean floor, searching for food along the continental shelf, the area of ​​the ocean that extends from the coast. The researchers suspected that by tracking the sea lions' movements, they could gather information about the shape of the seafloor and the distribution of different habitats.

The authors attached sensors to neoprene patches that they stuck to the backs of eight adult females from two of Australia's largest sea lion colonies. The equipment, which included GPS trackers, cameras and motion sensors, was designed to be small and non-obstructive, weighing less than 1% of the sea lions' body weight, so as not to impact the animals or influence their behavior. Once the project was completed, team members were able to remove the sensors from the patches without damaging the sea lions' fur.

Together, the sea lions captured 89 hours of video footage spanning six different seafloor habitats, from bare sand to algae meadows.

The researchers used the footage to assess the biodiversity in these areas and compare the locations visited by the two colonies. They also used the videos to check the accuracy of a machine learning model designed to predict seafloor habitat based on variables such as ocean temperature and distance from shore. They found that the model was more than 98% accurate, so they then used it to map seafloor habitats in surrounding areas. “One of the great strengths of the study is to use the data collected to predict other unknown areas,” says Angelakis.

The team also wants to use the sensor data to explore how factors such as depth and nutrient supply influence habitat distribution and species diversity on the seafloor. This could help researchers “further explore the ecological value of different habitats and marine areas for sea lions,” says Angelakis, which could strengthen conservation efforts.

Using sea lion mounting sensors is a “very good way to get high-resolution data from a hard-to-reach area,” Hall says. He suggests that in future studies, researchers could equip the sea lions with additional sensors to collect data on the physical and chemical properties of seabeds.