There's a 'Desert' in The Middle of The Pacific. Here's What Lives There

In the centre of the South Pacific, there's a place as far away from land as anyone on Earth could ever hope to get. The ocean is different there.

These distant waters lie at the heart of the South Pacific Gyre, the centre of which holds the 'oceanic pole of inaccessibility': the ocean's remotest extreme, aka Point Nemo (a name meaning 'no-one'), famous otherwise for being a spacecraft cemetery.

But aside from the ghosts of burnt-up satellites, what dwells under these far-off waves?

Not much, scientists have long thought. Despite taking up 10 percent of the ocean's surface, the South Pacific Gyre (SPG) – the largest of Earth's five giant ocean-spanning current systems – is generally considered a 'desert' in terms of marine biology.

Nonetheless, stuff does live there, even if organic life in these waters (and the seabed below it) is few and far between, due to a range of factors.

These include distance from land (and the nutrient matter it provides), the way water swirling currents isolate the centre of the gyre from the rest of the ocean, and high UV levels in this part of the ocean.

In truth, though, we don't actually know all that much about the life-forms that inhabit the SPG, largely because of how hard it is to study this oceanic desert – due to both its extreme remoteness, and also how large it is, covering about 37 million square kilometres (14 million square miles).

Despite the challenges, a recent international research effort has given us what the scientists claim is an unparalleled glimpse at the microbial creatures that exist in these waters.

During a six-week expedition aboard the German research vessel FS Sonne from December 2015 to January 2016, a crew led by the Max Planck Institute for Marine Microbiology sailed a 7,000-kilometre (4,350 miles) journey through the SPG from Chile to New Zealand.

En route, they sampled the microbial populations of the remote waters at depths between 20 to 5,000 metres (65 ft to 16,400 ft), using a newly developed analysis system that enabled the researchers to sequence and identify organic samples en route in as little as 35 hours.

 (Max Planck Institute for Marine Microbiology/Google Earth/NASA)

Above: FS Sonne's path crossing the SPG from Chile to New Zealand.

"To our surprise, we found about a third less cells in South Pacific surface waters compared to ocean gyres in the Atlantic", said one of the researchers, microbial ecologist Bernhard Fuchs, back in July 2019.

"It was probably the lowest cell numbers ever measured in oceanic surface waters."

Among the microbes the team found, 20 major bacterial clades dominated the lot. These were mostly organisms scientists have encountered in other gyre systems, such as SAR11, SAR116, SAR86, Prochlorococcus, and more.

The distribution of these microbe communities depended largely on water depth, based around factors such as changes in temperature, nutrient concentrations, and availability of light.

One of the populations identified, called AEGEAN–169, was particularly numerous in the surface waters of the SPG, whereas previous research had only discovered them at 500-metre depths.

"This indicates an interesting potential adaptation to ultraoligotrophic [low in biological productivity] waters and high solar irradiance", said one of the team, microbiologist Greta Reintjes.

"It is definitely something we will investigate further."

On the whole though, the sampling generally confirmed that the SPG is a "unique, ultraoligotrophic habitat", where low nutrient availability restricts growth to specialist oligotrophic organisms and creatures that have adapted to "extreme physicochemical conditions".

In other words, the SPG can't shake off its 'desert' reputation just yet, but there is a bright side to all that organic absence: these distant, almost lifeless waters are said to be the clearest ocean in all the world.

The findings were reported in Environmental Microbiology.

A version of this article was first published in July 2019.

Source: https://www.sciencealert.com

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[TC] Physicists just built the world's smallest optical switch - based on a single atom

As our need for more data and faster transmissions grows, existing network infrastructure is being put under more strain than ever before. As a result, scientists are working hard to miniaturise these systems and switch from current electron-based computers to super-fast optics-based communications, where data is quite literally sent at the speed of light.

Now scientists working at ETH Zurich in Switzerland have made crucial progress in the design of a modulator - the device that converts electronic signals into optical ones. These devices are currently around 3 cm wide, which means when you have a data centre full of them, they take up a substantial amount of room. But this new modulator is based on an optical switch that uses just one atom.

As Gizmag's Colin Jeffrey reports, that's a level of miniaturisation that's surprised even the scientists themselves - it essentially allows light to pass through a gap that's smaller than the wavelength of light itself. A modulator built around this switch could be some 100,000 times smaller than the devices in use today.

Here's how it works: silver and platinum pads are placed on top of an optical waveguide made of silicon with just an atom's gap between them. Once voltage is applied to the silver pad, a single atom is drawn towards its furthermost point, closing up the gap and creating a circuit between the two pads. When voltage is removed, the atom retracts, and thus the modulator can transmit millions of switch signals every second.

But what about the physics-bending light compression? As the light is beamed across the waveguide, it gets converted into surface plasmon, made up of electrons that oscillate at the frequency of the laser light. These electrons can pass through the single atom gap before being reconverted on the other side. By reconfiguring the design of the modulator, the light is effectively squashed to squeeze through the gap.

"Until recently, even I thought it was impossible for us to undercut this limit,"said lead researcher, Jürg Leuthold. "This allows us to create a digital switch, as with a transistor. We have been looking for a solution like this for a long time."

Now the team wants to improve the modulator production process so it's suitable for large-scale use and reliable in operation - at the moment, only one out of every six attempts at fabrication is successful. Eventually, though, this single atom modulator could be helping to shift data around the planet faster than ever before.

Source: Science Alert

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