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Science news in brief: From talking to plants to a beluga-narwhal hybrid

Watch soap bubbles turn into tiny snow globes as they freeze

You may have seen the viral videos of photographers freezing soap bubbles during a recent Snowmageddon in the US. They’re magical, turning into ethereal globes filled with ice crystals when the surrounding temperature is just right.

Unlike water droplets, puddles or other liquid surfaces, the thin, rounded shape of bubbles makes them poor heat conductors. So when soap bubbles freeze, lacy crystals break off from cooler points on the surface and swirl around on currents of warmer liquid. Recently, scientists set out to explain the transfer of heat that affects how bubbles freeze.

“We’ve seen the unique freezing dynamics of bubbles in nature, but we’ve never understood the physics behind it,” says Jonathan Boreyko, who studies condensation and frost phenomena at Virginia Tech.

Boreyko and colleagues’ results, published in Nature Communications, make for fascinating viewing. The study could also have applications for flash freezing food, creating tastier ice cream or even developing antifreeze materials.

How bubbles behave on ice poses many questions, Boreyko says, but “you can only study that by looking at bubbles in carefully controlled situations in the lab”.

The team started by pipetting tiny soap bubbles onto an ice block that they chilled to -20C and kept in a walk-in freezer. Using high-speed cameras, the team then filmed the soap bubbles as they froze from the bottom up.

They noticed that as soon as the bubble came into contact with the icy surface, water that was sandwiched inside the soap began flowing upward from the base. As the bottom of the bubble cooled and solidified, ice crystals also formed a boundary between the frozen and unfrozen part of the bubble – a freeze front – that inched up the surface. But within milliseconds, chunks of ice crystals started breaking off from the freeze front. These were swept up by tiny water streams, known as Marangoni currents, until hundreds of ice crystals danced across the bubble.

After about 10 seconds, the Marangoni flow dissipated and died out as the floating ice grew and crystals became interlocked. At that point, the rest of the bubble froze over.

In a bubble that’s slowly freezing, the changes in temperature change the surface tension, too. That results in Marangoni currents that produce swirls of liquid and ice crystals, resulting in a dramatic snow globe effect.

You can talk to plants but maybe you should listen

Plants communicate with each other (Alamy)
Plants communicate with each other (Alamy)

What does a plant sound like?

An art installation on display at the Brooklyn Botanic Garden in New York attempts to answer this question. This veggie-lullaby plays from large, yellow horns planted with corn seeds in a plot of soil. As the seedlings grow, their sounds will also be recorded.

“They’re communicating to each other,” says Adrienne Adar, the artist who designed this installation, “Sonic Succulents: Plant Sounds and Vibrations,” on display until 27 October. “We are not their audience.”

But she asks us to listen to plants and reflect on how we feel: “How does it make us think about them differently? How does it change our minds and our relationship to them? Because they’re doing their thing, and what are we going to feel like if they’re not there anymore?”

On a quiet night, farmers say they can hear corn grow. But for most others, the constant sounds plants make are inaudible without technology like Adar’s to bring them to life. By allowing visitors to interact with audible plants, she hopes to evoke a new perception of these photosynthesising organisms: not as inanimate objects for humans to control, but as living co-inhabitants, just as important to this planet as we are.

To make the invisible visible, Adar “audiolises” plants. At the garden, she has also planted sensors with succulents and cactuses indoors. When visitors touch the plants, sensors pick up vibrations, normally inaudible to humans. For a one-on-one experience, these sounds travel through a wire into a machine for amplification and delivery through headphones. For others, a prerecorded track of these plant bodies plays through a large speaker mounted in the room.

“That way the plants can listen to each other,” Adar says.

These vibrations are just physical reactions to touch. But in nature, quiet vibrations inside and outside plant bodies are daily soundtracks and important communication signals, scientists are starting to learn.

For instance, scientists have found that corn grows better when exposed to sounds at frequencies between 200 and 300 hertz. Playing sounds for mustard plants enhanced survival in the face of simulated drought. Sound delayed tomato ripening. Mung beans, cucumbers and rice have all sprouted more in response to certain sounds. Strawberries have grown bushier; kiwi and rice roots, longer. Sound has guided roots to water.

Who liked Hurricane Sandy? These tiny, endangered birds

The piping plover population has increased by 93 per cent (Alamy)
The piping plover population has increased by 93 per cent (Alamy)

The wrath of Hurricane Sandy’s powerful winds and violent storm surge left considerable damage across New York and New Jersey in October 2012. But for one tiny bird, the cataclysmic storm has been a big help.

“Hurricane Sandy was really good for piping plovers,” says Katie Walker, a graduate student in wildlife conservation at Virginia Tech.

The piping plover is a small, migratory shorebird that nests along North America’s great lakes and Atlantic coast. The species, which is listed as endangered in New York state and threatened federally, has been the focus of intensive conservation efforts for decades. But on one island that was heavily damaged by the big storm, the piping plover population has increased by 93 per cent, Walker and colleagues reported in the journal Ecosphere this month.

The finding highlights how major weather events can benefit wildlife on barrier islands that humans have engineered to resist storm damage.

Fire Island, a 32-mile-long barrier island off the southern coast of Long Island that is popular with vacationers, was hit particularly hard by Hurricane Sandy. The storm washed sand and seawater across the island, flooding homes, flattening dunes and breaching the island in three places.

Sand deposited from Fire Island’s oceanside onto its bayside created a number of new sand flats. Some areas were also breached by seawater but most were filled by the army corps of engineers shortly after the storm as part of the recovery effort, and to help make the island better able to withstand future storms.

For the threatened birds, this was great news. Piping plovers like to nest on dry, flat sand close to the shoreline, where the insects and crustaceans they feed on are easily accessible. But over the past century, coastal development and recreational use of shorelines have vastly reduced the amount of waterfront property available to the sand-coloured shorebirds.

Walker and her colleagues analysed aerial photographs of Fire Island taken before and after Hurricane Sandy and discovered that the storm, and the coastal engineering that followed it, increased the amount of suitable habitat for plovers by roughly 50 per cent.

“It’s not surprising,” says Jonathan Cohen, assistant professor at Suny College of Environmental Science and Forestry, who was not involved with the study. “When storms like Sandy flatten dunes and scour away vegetation, they create open sandy areas where plovers can lay their eggs.”

Meet the hybrid son of a narwhal and a beluga whale

An artist’s impression of what a narluga may have looked like. The species is thought to have fed from the seafloor, like a walrus (Markus Bühler)
An artist’s impression of what a narluga may have looked like. The species is thought to have fed from the seafloor, like a walrus (Markus Bühler)

On a remote island in Disko Bay, Greenland, a scientist in 1990 was collecting specimens of narwhals, the whales with unicorn-like tusks. He noticed an unusual skull on a hunter’s roof.

The teeth were bizarre: the top ones pointed forward, a couple spiralled out. They looked like a mix of narwhal and beluga, but with too many for a narwhal, too few for a beluga.

The hunter told the scientist that the skull had belonged to a strange animal he’d killed in the late 1980s. He had also killed two other similarly strange whales the same day. All had beluga-like flippers, narwhal-like tails and solid grey skin, he said.

Mads Peter Heide-Jørgensen, the narwhal scientist, persuaded the hunter to donate it to the Natural History Museum of Denmark for analysis. But at the time, he could only conclude it was a possible hybrid or deformed beluga.

Thirty years later, he and others have finally cracked this cold case. A genomic analysis of DNA extracted from the John Doe skull revealed that it belonged to an adult, first-generation son of a narwhal mother and beluga father. The study, published in Scientific Reports, shows how a little DNA can go a long way, that hybridisation isn’t that unusual and that as long as museums keep storing mysterious stuff, the right technology might one day set their stories free.

“There are certainly things lying around that can tell us about the natural world around us and how it shifts and changes,” says Eline Lorenzen, the museum collection curator who first decided to pull the skull off its shelf.

Her lab extracted DNA from the dust of its teeth and bones and compared it to genomes derived from tissue samples of belugas and narwhals from the same area. The analysis, conducted by Mikkel Skovrind, a graduate student, revealed it was a male and a 50/50 narwhal and beluga mix.

The hybrid whale’s combined features are completely weird, Lorenzen says. “It’s like if you took 50 per cent beluga and 50 per cent narwhal and shoved their teeth in a blender, that’s what would come out.”

The fish egg that travelled through a swan’s gut and hatched

Killifish eggs make it through the digestive tract intact (iStock)
Killifish eggs make it through the digestive tract intact (iStock)

Killifish manage to endure a variety of environments. The wee freshwater fish survive in isolated desert pools, lakes made by floodwater, even seasonal ponds that are little more than puddles.

One place scientists didn’t expect to find them was in swan poop. But an international team of researchers reported this month in the journal Ecology that whole killifish eggs make it through the digestive tract of water birds intact, with one egg in the study even hatching more than a month after its transit through a swan. The findings suggest that bird faeces may be capable of carrying fish eggs far from their original locations.

Giliandro Silva, a graduate student at Unisinos University in Brazil, and colleagues found last year that small flowering water plants in bird faeces were still alive and able to grow. While they were completing that study, they found a killifish egg in a frozen faecal sample from a wild coscoroba swan. They realised that what was true for plants might also be true for fish eggs.

To test this hypothesis, they mixed eggs of two killifish species found in Brazil into the feed of swans living in a zoo. Over the next two days, they collected what the swans excreted and looked for intact eggs. They found five, about 1 per cent of the 650 eggs they’d mixed in.

Then, they kept the eggs in the lab to see if they would continue developing. One hatched into a young killifish 49 days after its emergence from a swan’s gut, apparently none the worse for wear.

When the water they live in dries up, killifish eggs drop into a hibernation-like state, able to revive and hatch months later if water returns. This special ability is often why the fish sometimes seem to appear out of nowhere when a seasonal pool forms.

“They’re famous because of their amazing ability to survive in the mud,” says Andrew Green, a researcher at Estación Biológica de Doñana in Seville, Spain, and a co-author of the new paper.

But the fact that a small fraction of all killifish eggs consumed can make it through a bird unharmed may explain the appearance of fish in places where no one can imagine a plausible arrival story, he continues. In some cases, the fish may have literally fallen from the sky.

Additional reporting Veronique Greenwood, Knvul Sheikh, JoAnna Klein and Annie Roth

© New York Times