Fish that live in the twilight zone region of the ocean are a crucial part of a vastly under-studied ecosystem. When fish are brought up to the surface for study, the change in pressure between their native depth (200-500 feet) and sea level often causes fatal damages to their anatomy. Watch how a team of scientists from the California Academy of Sciences designs and builds a portable chamber that creates a pressure-controlled environment for these animals, so they can safely transport them from the twilight zone to the aquarium.
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- One of the most interesting parts of the ocean for me is this area that we call the Twilight Zone, which is this narrow band of the ocean between about 200 and 500 feet below the surface of the water. It's mysterious, it's unknown, it's sort of enchanting and captivating, but also it's an area where literally, the light is like twilight.
- This twilight zone is part of the coral reef, but it's a part that's very understudied. About half of the fish are not known, and nobody goes down there because there's a lot of technical difficulties associated in going there. So a lot of the times, those deep reefs are being destroyed even before we identify what's down there.
- It wasn't until really recent years that we've had sophisticated and reliable diving equipment that allowed people to actually go down there and come back. One of the most challenging aspects of this diving really is the pressure. The deeper you go in the ocean, the more and more pressure is stacking up, and that's essentially just all of that water that's over your head pressing down on your body. One of the first things we recognized is that the fish that we wanted to bring up from the depths were subject to the same decompression issues that humans are.
- So most fish have swim bladders. It's a little chamber filled with gas that keeps them neutrally buoyant, so if they didn't have a swim bladder because the fish, their tissues, are heavier than water, it will just sink. If you capture a fish at those depths and just bring him to the surface, that swim bladder is going to inflate. The gas expands inversely to the pressure. The swim bladder expands, it pushes the stomach away, it pushes the heart, the heart stops beating, and then everything else collapses just because the swim bladder takes the space of everything.
- And then there's an antheus in here somewhere. It's from Hawaii.
- I had started to hear about the idea of the academy going down and exploring deep under the ocean with divers and possibly collecting fish down there, and since my job is to make sure that those fish come back healthy, I thought about different ways that we could make sure that they could handle that pressure change. Is there a way that we can seal the fish up at pressure, keep them at the pressure that they were collected at, and then bring them to the surface and slowly decompress them over a period of a few days, so that we don't have to have any of that trauma. What we wanted to do was to take the pressure chamber underwater with us. We knew that if we wanted to dive with it, it needed to be sturdy yet sleek yet light yet all these things that's sort of our design compromises. And it also needs to, of course, be able to handle the immense amount of pressure that's on it. The first sort of flash bulb over the head idea that we had was to use a water filter housing. They're used for home water filtration. It's about two gallons, it's enough space for our fish to live in that space for about 24 hours while we decompress them, and that's a cheap off the shelf unit, you can get one for about $100, but then we just heavily modified it. This is the main pressure canister, or the main pressure chamber. I mean it's basically tinkering on a grand scale. I mean I played with Legos as a kid, and this is like real adult Legos, right? Putting all these things together and seeing how they work and seeing how an idea that is brand new that nobody's ever done before, seeing how it works in the real world is great. It's a dream job.
- [Bart] It's a portable, submersible, deep compression chamber. You just pull the velcro up and stick the fish in and seal the velcro. And then once we were done with the collecting, make sure that we sealed it all up tight, make sure it holds the pressure, and then we start our ascent.
- [Matt] They bring it up to the boat, and then we connect it to a water supply and our pressure generating pump, and that pushes water through the canister, so that the fish start to get a water change. We keep it like that for the next 24 hours while we slowly start to bleed off that pressure until it's at surface pressure.