Science/Revelations
Tiny Plankton May Have Perilous Impact by Alex Kirby Tags: carbon carbon dioxide climate change climate news network global warming ocean acidification oceans

 

This story originally appeared at Climate News Network. LONDON—Some of the most minute forms of marine life may have a significant effect both on more developed creatures and on the oceans’ ability to absorb carbon dioxide.

An international team of scientists has found that the smallest species of plankton thrive when levels of CO2, the main greenhouse gas from human sources, rise and increase the acidity of the oceans.

Writing in Biogeosciences, a journal of the European Geosciences Union, they say this could knock the marine food web off balance and also lessen the oceans’ uptake of CO2, a mechanism which helps to regulate the global climate by absorbing gas which would otherwise heat the atmosphere.

The study took place off the coast of Svalbard, the Norwegian high Arctic archipelago, and was led by Ulf Riebesell, a professor of biological oceanography at the GEOMAR Helmholtz Centre for Ocean Researct Kiel in Germany.

 “If the tiny plankton blooms, it consumes the nutrients that are normally also available to larger plankton species,” he says.

But the bigger plankton play an important role in transferring carbon down to the ocean depths. So in a system dominated by the minute pico- and nanoplankton, less carbon will leave surface waters and the oceans could in future absorb less CO2, says Riebesell.

The potential imbalance in the food web may have an even bigger impact. Large plankton are also important as producers of a climate-cooling gas called dimethyl sulphide, which stimulates cloud formation over the oceans. Less dimethyl sulphide will mean more sunlight reaches the Earth’s surface, adding to the greenhouse effect.

The root of the problem is the growing acidity of the Arctic. This, coupled with the availability of nutrients, allows the very smallest plankton to thrive at the expense of their larger cousins.

Natural laboratory

The Arctic seas are among those most vulnerable to acidification, because the cold allows them to absorb more CO2. This increasing acidity is already known to affect some Arctic creatures which use calcium to build their shells, including some sea snails, mussels and other molluscs.

But scientists had not known unil now how acidification alters both the base of the marine food web and oceanic carbon transport. The five week-long field study, conducted in the Kongsfjord in Svalbard, sought to close this knowledge gap.

For the experiment the scientists deployed nine large “mesocosms” – eight-metre long flotation frames carrying plastic bags with a capacity of 50 cubic metres. These bags let researchers study plankton communities in their natural environment under controlled conditions, rather than in a laboratory.

The scientists gradually added CO2 to the mesocosm water so that it reached the acidity levels expected in 20, 40, 60, 80 and 100 years, with two bags left as controls. They also added nutrients to simulate a natural plankton bloom.

They found that, with higher CO2, pico- and, to a lesser extent, nanoplankton grew, consuming nutrients and leaving fewer for larger plankton. “The different responses we observed made it clear that the communities’ sensitivity to acidification depends strongly on whether or not nutrients are available,” Riebesell says.

“…the tiniest plankton benefit from the surplus CO2, they produce more biomass and more organic carbon, and dimethyl sulphide production and carbon export decrease.”

Researchers at two UK universities reported earlier this month that they had found that rising temperatures in the oceans would affect plankton development, upsetting the natural cycles of carbon dioxide, nitrogen and phosphorous.

Lake Vostok mysteries: Biologists find over 3,500 life forms in isolated Antarctic basin Tags: Planet Earth Lake Vostok
Published time: July 07, 2013 02:39 
Edited time: July 07, 2013 09:54
 
RADARSAT image of Lake Vostok, Antarctica. (NASA)

RADARSAT image of Lake Vostok, Antarctica. (NASA)

Scientists have discovered more than 3,500 unique gene sequences in Lake Vostok – the underground Antarctic water reservoir isolated from the outside world for 15 million years – revealing a complex ecosystem far beyond anything they could have expected.

"The bounds on what is habitable and what is not are changing," said Scott Rogers, Bowling Green State University professor of biological sciences, who led a genetic study of the contents of half a liter of water brought back from the lake after it was drilled by Russian scientists last year. 

"We found much more complexity than anyone thought," Rogers said. "It really shows the tenacity of life, and how organisms can survive in places where a couple dozen years ago we thought nothing could survive." 

There are few places on Earth more hostile to life forms than Lake Vostok, the largest subglacial lake in the Antarctic, and initially Rogers believed that the water from it may have been completely sterile. 

Water is located 4,000 meters below the ice, which completely blocks sunlight, and creates huge pressure on the liquid. It is also literally located in the coldest place on Earth: the world’s lowest temperature of -89.2C was recorded at Vostok Station above the reservoir.

 

Image from the study

Image from the study

 

 

But after using bleach to remove outer layers of the ice (the form in which the water was extracted from the lake) which could potentially have been contaminated during the drilling, and conducting RNA and DNA testing, thousands of microscopic life forms, predominantly bacteria, were detected.

Many had expected that if any life forms were to be found in the frozen crypt, they would be uniquely adapted to the harsh environment, and perhaps entirely different as a result of being shielded from evolution of life elsewhere on the planet for millions of years.

Rogers, who has just published his findings in PLOS One magazine, says this has not turned out to be the case. 

"Many of the species we sequenced are what we would expect to find in a lake. Most of the organisms appear to be aquatic (freshwater), and many are species that usually live in ocean or lake sediments." 

 

A handout photo provided by the Russia’s Arctic and Antarctic Research Institute taken at the Vostok station in Antarctica on February 5, 2012, shows Russian researchers posing for a picture after reaching the subglacial lake Vostok (AFP Photo)

A handout photo provided by the Russia’s Arctic and Antarctic Research Institute taken at the Vostok station in Antarctica on February 5, 2012, shows Russian researchers posing for a picture after reaching the subglacial lake Vostok (AFP Photo)

 

Rogers’ team believes the relative ordinariness of the organisms discovered may be due to the fact that they are left there as a legacy of when Antarctica had a temperate climate 35 million years ago, rather than as a result of evolution inside the lake. 

Some of the organisms found in Lake Vostok commonly exist in ocean environments (in the digestive systems of fish and crustaceans) suggesting that the reservoir was once connected to a bigger body of saltwater. 

But Rogers believes “two huge drops of temperature” cut it off and conserved it in its present state.

Yet the study is not excluding the possibility of startling discoveries. 

"It's a very challenging project and the more you study, the more you want to know. Every day you are discovering something new and that leads to more questions to be answered,” said Yury Shtarkman, who conducted many of the analyses, and believes it could take a lifetime to untangle the secrets of the lake.

Hints of Lost Continent Found Beneath Indian Ocean Tags: Earth Science

Hints of Lost Continent Found Beneath Indian Ocean

Geological detectives are piecing together an intriguing seafloor puzzle. The Indian Ocean and some of its islands, scientists say, may lie on top of the remains of an ancient continent pulled apart by plate tectonics between 50 million and 100 million years ago. Painstaking detective work involving gravity mapping, rock analysis, and plate movement reconstruction has led researchers to conclude that several places in the Indian Ocean, now far apart, conceal the remnants of a prehistoric land mass they have named Mauritia. In fact, they say, the Indian Ocean could be “littered” with such continental fragments, now obscured by lava erupted by underwater volcanoes.

The Seychelles, an archipelago of 115 islands about 1500 kilometers east of Africa, are something of a geological curiosity. Although a few of Earth’s largest islands, such as Greenland, are composed of the same continental crust as the mainland, most islands are made of a denser, chemically distinct oceanic crust, created mid ocean by magma welling up beneath separating tectonic plates. Geologists think they separated from the Indian subcontinent 80 million to 90 million years ago.

But those islands might not be so unique. Researchers from Norway, Germany, and Britain, writing in Nature Geoscience, now suggest that the Indian Ocean is harboring other fragments of ancient continental crust. Those fragments, the researchers say, lie buried beneath more recent oceanic crust erupted by underwater volcanoes.

 

 micro-continent

Earth’s gravity gave the first hints that led scientists to the hidden crust. A number of places in the Indian Ocean, such as Madagascar, Mauritius and the Seychelles, Maldives, and Lakshadweep islands, are known to display a slightly stronger gravitational field than expected. Abnormally thick crust could explain this anomaly. If that’s the reason, it could be because the crust is about 25 kilometers thick, resembling continental crust, compared with the 5 to 10 kilometers of oceanic crust elsewhere. However, thickness alone doesn’t prove that crust is continental, as oceanic crust can be thickened by processes such as underwater volcanism.

To collect additional evidence for the hidden continent idea, the researchers then took another tack. They reconstructed the movements of the tectonic plates to determine whether and how these fragments of undersea crust were once connected to continents. They were able to show that, until about 90 million years ago, the places with unexpectedly high gravity would all have been attached to India.

Next, in search of chemical evidence to back up their idea, the researchers took sand samples from several beaches in Mauritius, another African island nation located about 1700 kilometers southeast of the Seychelles. The surface rock of Mauritius is made from volcanic oceanic crust, or basalt. But its beach sands contained not just fragments of eroded lava but also zircons, a mineral associated with continental crust.

The zircons from Mauritius, it turned out, were hundreds or even thousands of millions of years old, although the island’s oceanic crust was less than 10 million years old.

So how did the zircons get there? The researchers, led by geophysicist Trond H. Torsvik of the University of Oslo, believe they had to have been in the lava itself. The magma, they suggest, punched its way through pieces of preexisting continental crust on the seafloor, and in the process it tore off zircons and incorporated them into the basalt lava. “Zircons don’t fly,” Torsvik says. “I don’t believe these could have been brought by other means—they must have been eroded from the basalt itself.”

Geochemist Andreas Stracke at the University of Münster in Germany is impressed, saying that while others have speculated on the possibility of buried continental crust under this part of the Indian Ocean, “this could be a smoking gun.” But he would like to see tests conducted into a wider range of rocks from the region to see if other geochemical signatures of continental crust can be found.

 

Source: www.sciencemag.org

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