For centuries, sea creatures have been heaved up from the depths into the deadly air. This can quickly destroy gelatinous, fragile and bioluminescent animals. Elyse Hauser meets a new generation of scientists peering through the darkness to examine the mysteries of the sea. This article first appeared in Cosmos Print Magazine, March 2025.
Visit your local natural history museum and you might see fragile creatures, such as jellyfish, floating in jars of preservative. These wet specimens have long been used to study marine life – and even describe new species.
But life in the sea, especially the deep sea, is often elusive and delicate: specimens are hard to get and tend to fall apart. Even if they’re kept in one piece, preservation changes how these animals look, erasing clues to how they live in their natural habitats.
That means many new marine species remain undescribed, and even known species are often poorly understood.
Scientists are developing new ways to unveil the mysteries of the deep. Emerging technologies and innovative techniques are allowing scientists to study fragile ocean life right where it lives – no jarred specimens required.
A bobtail squid. These squid recruit bioluminescent bacteria, allowing them to glow. Credit: Wildestanimal/ Getty Images.
Tagging and tracking
Researchers have long studied marine life using tags: attached sensors that track the movements of animals.
Traditionally, tags were designed for large, sturdy species, including whales and sharks. Squishier lifeforms – squid, jellyfish, even small fish – are more challenging. Stiff and bulky tags don’t move with them, while the tags’ suction cups or barbed anchors can damage them. Yet understanding these squishy species is important, and tags can help.
“Those animals are central to ecosystem function,” says Aran Mooney, associate scientist at the Woods Hole Oceanographic Institution (WHOI).
Dr Pedro Alfono returning a tagged squid to the water after using a traditional suture tag. Credit: Seth Cones, ©Woods Hole Oceanographic Institution.
Mooney notes that squid are key to marine food webs: most marine animals either eat or get eaten by squid at some point. And jellyfish seem to proliferate in some areas impacted by climate change and other human activities, in a process sometimes called ‘jellification’.
“We really have no idea of the daily life of a squid,” Mooney says. If they can be tagged, scientists can better understand marine ecosystems, and even predict what the future may hold.
At WHOI, Mooney’s working on tagging solutions for delicate marine life, including a fast-acting flexible hydrogel adhesive. “We wanted something that’s something that’s much more responsive to these soft animals,” he says.
Some new tag designs are modular, so they can be customised for different animals. A small fish may need a different tag shape than a jellyfish. A slippery squid may need vet-grade tissue adhesive to attach a tag. There are even customisable release times: “you can program the tag to pop off the animal whenever you want,” says Mooney.
With solutions like these, not only is there less risk of damage (which can influence behaviour), but there’s also a higher resolution of movement captured.
The improved tags might someday even be able to pick up details like heart rates and blood oxygen levels of squishy marine life.
A skate resting on the bottom of a large saltwater pool, equipped with BIMS. Credit: Kayla Gardner, ©Woods Hole Oceanographic Institution.
DNA in the environment
In recent decades, environmental DNA (eDNA) has emerged as a promising way to study life, even when lifeforms are not easy to spot. Lifeforms shed DNA into their environments all the time, through things like dead skin cells and pee. Scientists can find that DNA by sampling part of an environment, such as soil, air, or water. This tells them which species have recently been there, “kind of like forensics for animals,” as environmental geneticist Clare I. M. Adams puts it.
At James Cook University, PhD candidate Scott Morrissey uses eDNA to study the deadly Australian box jellyfish. These jellies are delicate and transparent: they’re hard to find and study up close.
Box jellyfish are the most venomous animals in the ocean, so it’s important to know where they are. “eDNA kind of removes that struggle, so you can simply take water samples to see if they’re around,” says Morrissey. It even lets scientists find box jellies while they’re still in the super-small polyp stage. With eDNA, scientists can track where these deadly jellies are and where they might be going, helping to keep people safe.
Even when the jellies aren’t deadly, eDNA is a useful tool. “The problem with jellyfish is that they’re so delicate,” says Charlotte Havermans, marine zoologist at the University of Bremen. “When you have trawls or nets, many are destroyed; you can’t really count them.”
Jellyfish can dominate areas impacted by climate change and other human activities. Credit: Dado Daniela / Getty Images.
When jellyfish populations move or grow, they can have drastic effects, sometimes even taking over an ecosystem. Yet even as they proliferate, scientists struggle to find these translucent and fragile creatures, and to discover details, like what they feed on. “We still don’t have a really good overview of how many jellyfish there are in the ocean – like, what are their numbers?” says Havermans.
Havermans’s research group combines eDNA with video surveys and net sampling, to get a clearer picture of jellyfish activity. Separately, eDNA, videos, and nets all miss some species – no method is a catch-all. But together, the combined methods can find all kinds of things: elusive jellies, delicate siphonophores (another tentacled and gelatinous lifeform), and tiny creatures smaller than a centimetre.
Researchers even took eDNA samples from the stomachs of creatures they’d caught, which showed species that had been nearby as the feeding creatures passed through. Many marine animals filter lots of water as they feed, doing the work of collecting eDNA for scientists. “You get sometimes 500 species in such a stomach just by looking at the DNA,” says Havermans.
Havermans works within polar ecosystems. She’s used eDNA on an Arctic research cruise into the polar night: the period of winter when the sun never rises. “This shows even more how cool environmental DNA can be, because it’s difficult to go there out on a boat to get nets deployed,” she says. “You are in the dark, you don’t see properly, you cannot go everywhere because there’s ice.”
Where other research methods became more difficult, eDNA was still extremely effective. Through these eDNA samples, the researchers could tell that not just jellyfish, but fish, algae, crustaceans, and even narwhals and walruses were all around them, hidden in the polar night.
Sampling in the deep
In the deep sea, where life is often fragile and gelatinous, “you see animals all the time that are actually undescribed by science,” says University of Rhode Island oceanographer Brennan Phillips. Traditionally, there was no good way to collect these mysterious, delicate animals for further research – a frustrating situation for marine scientists.
Undescribed species can’t be found with eDNA, since that requires matching to a database of known species. Yet a recent interdisciplinary project, with Phillips as principal investigator, suggests how to study unfamiliar deep-sea life, right where it lives.
While doing postdoctoral research at Harvard, Phillips met another postdoc who was working on origami-inspired robotics designs. One of the designs was a folding 11-sided shape that could open and close: a sort of robotic “catcher’s mitt.”
“I said, ‘That’s really cool, man,’” Phillips recalls. “‘That should be used for something underwater – can you make it bigger?’” The robotics designer, Zhi Ern Teoh, eventually developed a 12-sided robotic capsule that could quickly fold around marine life.
The remotely operated vehicle SuBastian, with its 12-sided capsule mounted on the front. Credit: Courtesy of Brennan Phillips.
This was one piece of the interdisciplinary method that emerged in the end from a years-long research project, which brought together 15 scientists from 6 different institutions.
When a deep-sea lifeform is found, the method begins with 3D images of the animal moving naturally in its habitat. Then, the robot encapsulates the animal, taking tissue samples to get DNA. This entire process can take just 10 minutes, after which the animal is released back into the wild.
Finally, the images and DNA are converted into a detailed digital ‘specimen’ that can be shared with other scientists, to describe new species.
Not only is this safer for the animals – it requires a piece of preserved tissue, not the whole lifeform – but it vastly speeds up the research process.
“We were able to collect 14 samples per dive. That’s actually quite efficient compared to how many jars you could fit on the front of the [remotely operated underwater vehicle],” says Phillips. “That means we could image 14 different animals, collect the DNA from 14 different animals, and potentially describe 14 different animals on an entire dive.”
Rather than catching a specimen and sending it around the world for identification, this method results in a digital file for each animal, which is fast and free to send everywhere.
The initial project demonstrated the method’s potential on 4 example species. Someday, with further refinement, a version of this method may become the go-to for identifying delicate deep-sea life.
“I would argue it’s the way to go, for at least this realm,” says Phillips. “You know, the gelatinous animals may be quite common, but the opportunities to access them are very hard to come by.”
With these new research methods, scientists can gain understanding from marine animals where they live, instead of pulling them into our realm. It’s only by looking into the sea itself that we can hope to someday understand it.