Angelakis, N., Grammer, G. L., Connell, S. D., Bailleul, F., Durante, L. M., Kirkwood, R., Holman, D., & Goldsworthy, S. D. (2024). Using sea lion-borne video to map diverse benthic habitats in southern Australia. Frontiers in Marine Science, 11, 1425554. https://doi.org/10.3389/fmars.2024.1425554
The depths of our vast ocean are largely undiscovered. However, as technology continues to advance, new methods of deep sea exploration are being developed. Previously, researchers have used remotely operated underwater vehicles (ROVs) and cameras dropped from ships to collect video footage of and map unreachable habitats. These methods are cost- and time- consuming. Additionally, in Australia, these methods provided very little information about the underwater world. What if, instead, we utilized animals who call these depths home to explore the ocean?
In this study, researchers posit a new approach to benthic (sea floor) surveying and mapping: attaching cameras to Australian sea lions (scientific name Neophoca cinerea) to view the seafloor through their eyes. This novel method is quicker, cheaper and more far-reaching than traditional exploration methods.
Seal Bay Conservation Park. Image credits: Roger Smith via Flickr Creative Commons
Seeing the World Through Sea Lions’ Eyes
Australian sea lions are endangered predators that spend most of their time hunting on the seafloor. They roam multiple habitats, including sand plains and seagrass meadows. Because of their diverse range, researchers in this study chose to survey the South Australian continental shelf by attaching video cameras to eight female sea lions.
The study took place over the course of nine months off of two islands hosting the biggest sea lion colonies in Australia: Olive Island Conservation Park and Seal Bay Conservation Park. Sea lions were sedated and anesthetized while the cameras, GPS, and acceleration and magnetic field measurement devices were attached to neoprene (rubber) patches on their fur. Their vitals were checked frequently to ensure that they remained physically healthy. Sea lions were released and then recaptured after 2-10 days.
Researchers collected video footage during daylight hours, only when the sea lions ventured lower than 5 meters below the surface. The GPS tracked the locations at which the sea lions surfaced. Depth was measured every second and time spent and distance traveled in each habitat type were recorded. This data was used to measure percent cover of each habitat. The animal-borne data was combined with environmental data, such as sea surface temperature and bathymetry, to predict how environmental factors may influence habitat distribution in the study area.
So What Does The Australian Seafloor Look Like?
Researchers collected a total of 89 hours of footage and 560 km of habitat. The footage captured six distinct habitats: macroalgae reef, macroalgae meadow, bare sand, sponge/sand, invertebrate reef, and invertebrate boulder habitats. Percent cover of each of these habitat types varied between the two study sites.
Combining the data captured by the sea lion footage with environmental data, models were able to predict benthic habitats 99.5% and 98.6% accurately for Olive Island and Seal Bay, respectively. Specifically, the models predicted that most of the southern Australian continental shelf is covered by invertebrate reef, bare sand, and sponge/sand habitats.
Notably, the findings of this study revealed more about benthic habitats in Australia than previous studies have, even those that have used animal-borne video for mapping.
Australian sea lion. Image credits: Sheila Thomson via Flickr Creative Commons
What Do We Know About Benthic Habitats Now?
The methods in this study provided new insights into the features of benthic habitats where Australian sea lions forage. For example, when macroalgae reefs and meadows were not present, the seafloor was dominated by invertebrates.The distribution of these invertebrate communities could be predicted by the environmental variables used in the models for the study.
The camera footage from this study also showed a variety of coral communities off the Australian coast. The researchers hypothesized that the impressive size of these communities was likely due to the nutrient-rich water provided by seasonal upwelling and water circulation changes. The models created in this study supported this theory as they suggested that chlorophyll-a (an indicator of high rates of photosynthesis) was an important predictor of benthic habitat. Further, bare sand plains were another common habitat that appeared on the video footage. These areas could receive fewer nutrients than benthic habitats, explaining why fewer animals were found there.
So What?
Mapping and surveying efforts reveal changes in the marine environment, especially negative changes that have been caused by human activity. Discovering new methods by which to view and explore the ocean can help scientists identify these issues more quickly, leading to better restoration projects and policy changes. These methods can also be used to discover new habitats and communities, especially for species like the Australian sea lion, whose population has decreased by more than half in the past 40 years.
What next?
Future research should utilize animal-borne video surveying in addition to existing methods to ensure that the benefits of all methods are taken advantage of. Applying this study to other locations and other marine mammals could also provide a more comprehensive understanding of our ocean, especially parts that are unreachable by traditional methods.
Cover photo by Brian M. Hunt via Wikimedia Commons
I received my MPS in Marine Biology & Ecology from the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Sciences in May 2024. I plan to use my education and experience to pursue a career in science writing or film production to help communicate the importance of the ocean to the general public.
