Shark cameras find new largest seagrass plain
The field of marine biology has been recruiting new members to study and measure marine life: the marine life itself. A study off the coast of the Bahamas has discovered the largest seagrass colony in the world. So large, in fact, that it pushes the total amount of known seagrass on the planet up by 40%. This seagrass forest was discovered when a team of scientists strapped cameras to Tiger sharks, which is no mean feat, and watched where they went about their day. Dr Ollie Shipley, from organisation Beneath The Waves, spoke to Will Tingle about their new recruits’ findings, including the obvious question: How do you attach a camera to a shark?
Ollie - The way that we explain it to people, it's almost like a NASCAR pit crew. And what we basically do is we strap the camera or the package because it's not just a camera, remember we've got other sensors. We've got a satellite tag, a radio tag on this package as well so we can find it when it falls off the animal. And we use biodegradable cable ties to basically fix that camera package through the fin of the animal. And the cable ties are secured by a piece of equipment that's called a galvanic time release. And what that is, is it's basically a dissolvable link that dissolves in seawater and the kind of dissolution time is pre-programmed. So that thing will dissolve within about four to six hours typically. And then the whole package basically falls off the animal and through a satellite and a radio tag, we can basically then go and locate that package. Once it's off the shark, we then remove all of the hook, take the cables off, and let the animal swim on its merry way. So all of that happens in about eight to 10 minutes typically.
Will - Given that all of the technology we have, all the sensory equipment we have available to us, satellites and ocean scanning equipment. Why did you feel the need to strap a camera to a shark?
Ollie - We've been putting tags on animals for the last 30-40 years, some of these satellite tags. But we really don't know a lot about what goes into their daily routine. And I think the way that the technology has developed over the last five to six years, we're now able to explore and observe high precision information on what these animals are doing every minute of every day for this study, whenever you strap a tag onto an animal, it's likely going to take you to a really important place because these animals are making calculated decisions every day of their life. They're trading off energy versus the cost of actually moving from one place to another. And so all of their decisions are calculated. So the chances are, if you strap a tag onto an animal, it's gonna take you to somewhere that's pretty important for that individual or that population or that species. For this study, we kind of utilized that concept and we used the cameras strapped onto these tiger sharks to quantify the density of seagrass that they were swimming over. And we were able to extrapolate those kinds of seagrass density measurements and use it to 'ground truth' information from satellites to basically quantify or measure the largest seagrass ecosystem in the world.
Will - And when you say ground truthing, what does that mean?
Ollie - Ground truthing is basically confirming.Because a lot of these measurements are made from satellite and there's sometimes quite a bit of error associated with that, and that that can be used to things like cloud cover or if the water isn't particularly clear on a certain day, for example. And so you actually have to go in there and empirically measure the density of the seagrass in this case. So you can confirm that what the satellite derived data is telling you is true.
Will - What have the cameras on these sharks reveal to us about seagrass distribution?
Ollie - Well, they've revealed that the area that we were working in, that The Bahamas, houses an incredible abundance of seagrass. We had an idea that it was there, but we weren't really sure how much. And so through strapping these cameras on these tiger sharks, they've really revealed how kind of expansive and dense these seagrass ecosystems are on The Bahamas banks. And it's only through that that we're able to confirm that this is the most significant, largest seagrass ecosystem in the world, which is crazy.
And do you know of any other shark camera equipment that's going on? Maybe new discoveries could be made somewhere else?
Ollie - This is a technique that has been utilized in a few different species before. So there's a group that are using them in sea turtles to kind of map similar things because sea turtles also interact quite abundantly with seagrass meadows. But I think this is where innovation really gets exciting. This is a proof of concept that has led us to an incredible discovery. And so I think the world really is our oyster in applying this sort of technology to other animals as well. And we certainly have plans to do that in various parts of the world.