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Scientists have a new ally to help them explore the ocean’s seabed: sea lions. A team recruited in Australia is in danger Australian sea lions (Neophoca cinerea) to bring video cameras to this little-explored part of the ocean. The videos helped the team identify a number of previously unmapped sea lion habitats in the benthic zone lowest ecological zone in a body of water. The pinniped-supported findings are described in a study published Aug. 7 in the journal Frontiers in marine sciences.
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Deep dives
Our knowledge of the sandy and rocky bottoms of the seas is rather fragmentary. Dives with remotely operated underwater vehicles (ROVs). Alvin or Jason Jr. from Woods Hole Oceanographic Institution can be expensive and logistically prohibitive. The vehicles are expensive and require certain weather conditions for diving. It is also simply difficult for humans to reach deep and remote offshore habitats, even with high-tech submarines.
“Using animal-borne video and movement data from a benthic predator is a highly effective way to map diverse benthic habitats across large areas of the seafloor,” said Nathan Angelakis, co-author of the study and PhD candidate at the University of Adelaide and the South. Australian Research and Development Institute, said in a statement. “These data are useful for mapping critical habitats for an endangered species such as the Australian sea lion, and more broadly, for mapping unexplored areas of the seabed.”
In the studyeight adult female Australian sea lions from the Olive Island And Seal Bay Colonies were equipped with small and lightweight cameras. The team glued the cameras and tracking instruments to small pieces of neoprene – the material most wetsuits are made of – which were then attached to the sea lions’ fur. In total, the filming and tracking equipment weighed less than 1 percent of the sea lions’ body weight. This prevented additional resistance and ensured that they could move without restrictions. The sea lions recorded for two to three days.
“We deployed the instruments on adult females so that we could retrieve the equipment a few days later when they returned to the country to nurse their pups,” Angelakis said. “We used satellite-linked GPS loggers on the sea lions, which meant we could track their position in real time and know when they had returned to the colony.”
How to predict a habitat
In total, the team rallied 89 hours of animal-borne video. The researchers identified six benthic habitats: macroalgal reef, macroalgal meadow, bare sand, sponge/sand, invertebrate reefs and invertebrate boulders.
Back on dry land, the team used machine learning models to predict the large habitats on the continental shelf of southern Australia. They did this by recording data on oceanographic and environmental factors collected over 21 years in the models. These factors may be important factors in the structure and distribution of these habitats.
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“The sea lions from both locations covered quite large areas around the colonies. In our calculations, we kept the area in which we predicted habitats small to maximize the accuracy of our predictions,” Angelakis said. “This allowed us to model benthic habitats over more than 5,000 square kilometers [1,930 square miles] of the continental shelf.”
Vision of a sea lion
The Sea Lion Cams also filmed habitats different from some of the previously mapped regions of South Australia. The pinnipeds may not use or swim through certain habitats or may prefer some areas over others. The researchers also point out that some regions may have been missed.
However, the images still fill some gaps in knowledge about the seabed while providing critical information endangered marine species. Marine populations has decreased by more than 60 percent over the past forty years. This method can also be used to investigate and assess other interesting marine species that the sea lions have captured on camera.
According to the teamAssessing a marine environment from a predator’s rather than human’s perspective can improve our understanding of the benthic environment and develop a more complete map of the seafloor.