There’s a ‘Desert’ in the Middle of the Pacific Ocean, and Now We Know What Lives There

In the middle of the South Pacific, there is a place as far from the earth as anyone on Earth could hope for. The ocean is different there.

These distant waters are located in the heart of the South Pacific gyre, the center of which holds the ‘oceanic pole of inaccessibility’: the ocean’s remotest extreme, aka Point Nemo (a name meaning ‘no-one’), otherwise famous for being a spaceship cemetery.

Although it occupies 10% of the ocean’s surface, the South Pacific Gyre (SPG) – Earth’s five giant ocean-spanning current systems – is generally considered a ‘desert’ in terms of Marine biology.

“Biological deserts” is the name given to these portions of the ocean due to the low amount of life.

In truth, however, we don’t know much about the life forms that populate the GSP, largely because of the difficulty of studying this ocean desert – due to its extreme remoteness and size, covering approximately 37 million square kilometers (14 million square miles).

We saw that the low-productivity area of the west Pacific was expanding, and we wondered if it was unique or if it was happening globally,” said ocean biologist and satellite data enthusiast Jeffrey Polovina.

Polovina explained:

The climate models are on century timescales and suggest that the rate of expansion of these expected low-productivity areas will be slow.

Despite the challenges, a recent international research effort has given us what scientists claim to be an unprecedented glimpse of the microbial creatures that exist in these waters.

Scientists at the Max Planck Institute for Marine Microbiology in Bremen, Germany, have compiled an inventory of microbial life in this remote ocean region.

A cruise from Chile to New Zealand tested the pipeline used to study organisms living in this area and found that the overall SPG microbial community was very similar to that of other oceanic gyres.

Chile to New Zealand. The picture also shows chlorophyll concentrations derived from NASA imagery. Dark areas show the gyre middle or “desert”. (© modified from Google Earth / NASA)

Along the way, they sampled microbial populations in distant waters at depths between 20 and 5,000 meters (65 feet to 16,400 feet), using a new analysis system that allowed researchers sequencing and identifying organic samples en route in as little as 35 hours.

“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.”

The SPG was dominated by 20 major bacterial clades such as SAR11 ( part of the Pelagibacterals, composed of free-living bacteria, making up roughly one in three cells at the ocean’s surface ). The distribution pattern showed that most of the bacterial clades had a strong vertical concentration (20 m to 5,000 m) but only a weak longitudinal concentration (80 ° W to 160 ° W).

“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.”

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