June 17, 2024

Deep Sea Freezers Could Revolutionize Marine Biology

This story was originally published by The same magazine.

During Japan’s sweltering summers, nothing hits the spot like a frozen orange. The popular treat tastes great when made at home. But it tastes even better when it is made 850 meters below sea level. “A little bit salty, but very tasty,” says Shinsuke Kawagucci, a deep-sea geochemist at Japan’s Agency for Marine Science and Technology.

The frozen fruit was the result of a very tasty scientific experiment. In 2020, Kawagucci and his colleagues designed a very unusual freezer – a freezer built to work in the intense pressure of the deep sea. The frozen orange, chilled in the depths of Japan’s Sagami Bay, was proof that such a thing is even possible.

Kawagucci and his colleagues’ prototype deep-sea freezer is essentially a pressure-resistant tube with a thermoelectric cooling device inside. By running an electric current through a pair of semiconductors, the device creates a temperature difference thanks to a phenomenon known as the Peltier effect. The device can cool its contents to -13 degrees Celsius – well below the freezing point of sea water. Because it does not require liquid nitrogen or refrigerants to cool its housing, the freezer can be built compactly and with minimal engineering skill.

With a few adjustments, Kawagucci and his colleagues wrote in a recent paper, their prototype freezer can be more than a fancy snack machine. By offering a way to deep-freeze samples, such a device could improve scientists’ ability to study life in the deep sea.

Bringing animals up from the earth is often destructive, leaving them damaged and disfigured. The best example is the smoothhead blobfish, a sad lump of fish that gets its name from the bloblike shape it takes when it stretches from its home, which can be more than 1,000 meters below. (In the deep sea habitat, the fish look like many other fish and his name is not real.)

While scientists have previously designed tools to keep deep-sea specimens cold on their way to the surface, the new prototype freezer is the first device capable of freezing specimens in the deep sea. Similarly, there are other tools that allowing scientists to collect creatures from the earth unharmedas pressurized collection rooms. But these often don’t work well for small and soft-bodied deep-sea animals that are prone to death and decay when kept in such containers for too long – which is often unavoidable, says Luiz Rocha, curator of ichthyology at the California Academy of Sciences, in San Francisco. “It can take hours to bring up samples,” says Rocha.

A device that first freezes samples would stop degradation, allowing for better scientific analysis of everything from anatomy to gene expression. Although the freezing process would undoubtedly damage the tissues of some of the more sensitive life forms on earth, freeze-damaged specimens are often more useful to scientists than decaying specimens—at least when it comes to DNA analysis.

The prototype freezer takes more than an hour to freeze a sample, which is probably “too slow to be generally useful,” says Steve Haddock, a marine biologist with the Monterey Bay Aquarium Research Institute who studies bioluminescence in jellyfish and ctenophores. Every minute of deep-sea exploration is precious, he says: “We usually spend our time searching for animals, and we bring them to the surface in great shape using insulated chambers.” If the freezing time could be improved, however, Haddock believes such a device could “empower” those who study deep-sea creatures that are extremely sensitive to changes in pressure and temperature, such as microbes that live in hydrothermal vents.

Kawagucci says he and his team plan to improve their freezer before testing any live specimens. But he hopes that with such improvements, their tool will give scientists a way to collect even the most delicate deep-sea organisms.

Meanwhile, Kawagucci is happy that his device has proven that deep sea freezing is possible through a thermoelectric cooler. “I wanted to be the first to generate and see the ice in the deep sea with my freezer,” he says. And when he finally sank his teeth into that tangy, salty, sweet frozen orange, he says, “One of my dreams came true.”

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