Scientists have a new ally to help them the ocean seabeds – sea lions. A team in Australia recruited endangered Australian sea lions (Neophoca cinerea) to take video cameras into this little-explored area of the ocean. The videos helped the team to discover some previously uncharted sea lion habitats in the benthic zone-or the lowest ecological zone in a body of water. The findings using seals are described in a study published August 7 in the journal Frontiers in Marine Science.
(Related: How animals see the world, according to a new camera system.)
Deep dives
Our knowledge of the sandy and rocky seabed is rather fragmentary. Diving with remotely operated underwater vehicles (ROVs) such as Alvin or Jason Jr. from Woods Hole Oceanographic Institution can be costly and logistically prohibitive. The vehicles are expensive and require certain weather conditions to dive. It is also simply difficult for humans to reach deep and remote offshore habitats, even with high-tech submarines.
“Using animal-borne video and motion data from a benthic predator is a very effective way to map diverse benthic habitats across large areas of the seafloor,” said Nathan Angelakis, co-author of the study and a 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 like the Australian sea lion, and more broadly for mapping unexplored areas of the seabed.”
In the studyeight adult Australian female sea lions from the Olive Island And Colonies of seal bay were equipped with small, lightweight cameras. The team taped 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 film and tracking equipment weighed less than 1 percent of the sea lions’ body weight. This prevented additional drag and allowed them to move without restriction. The sea lions recorded over two to three days.
“We put the instruments on adult females so that we could retrieve the equipment a few days later when they returned to land to nurse their pups,” Angelakis said. “We used satellite-linked GPS loggers on the sea lions, which meant that we could track their position in real time and know when they had returned to the colony.”
How do you predict a habitat?
In total the team collected 89 hours of animal video footageThe 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 major habitats on the South Australian continental shelf. They did this by incorporating oceanographic and environmental data collected over 21 years in the models. These factors may be important drivers of the structure and distribution of these habitats.
(Related: Scientists have attached tiny cameras to beetles to see the world from an insect’s perspective.)
“The sea lions from both sites covered fairly broad areas around the colonies. In our calculations, we kept the area in which we predicted habitats small to maximize the precision 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 sea lions
The Sea Lion Cams also filmed different habitats than in some of the previously mapped regions of southern Australia. The pinnipeds may not use or swim through certain habitats or may prefer certain areas over others. The researchers also point out that some regions may have been missed.
However, the images still fill a number of knowledge gaps about the seabed, while at the same time providing crucial information about endangered marine animals. Marine populations has decreased by more than 60 percent over the past 40 yearsThis method can also be used to investigate and evaluate other interesting marine animals that the sea lions have captured on camera.
According to the teamBy assessing the marine environment from the perspective of a predator rather than a human, we can better understand the benthic environment and develop a more complete map of the seafloor.
