The vast reservoir of carbon stored in Arctic permafrost is gradually being converted to carbon dioxide (CO2) after entering the freshwater system in a process thought to be controlled largely by microbial activity. However, a new study – funded by the National Science Foundation and published in the journal Science – concludes that sunlight and […]Read more...
The vast reservoir of carbon stored in Arctic permafrost is gradually being converted to carbon dioxide (CO2) after entering the freshwater system in a process thought to be controlled largely by microbial activity.
However, a new study – funded by the National Science Foundation and published in the journal Science – concludes that sunlight and not bacteria is the key to triggering the production of CO2 from material released by Arctic soils.
The finding is particularly important, scientists say, because climate change could affect when and how permafrost is thawed, which begins the process of converting the organic carbon into CO2.
“Arctic permafrost contains about half of all the organic carbon trapped in soil on the entire Earth – and equals an amount twice of that in the atmosphere,” said Byron Crump, an Oregon State University microbial ecologist and co-author on the Science study. “This represents a major change in thinking about how the carbon cycle works in the Arctic.”
Converting soil carbon to carbon dioxide is a two-step process, notes Rose Cory, an assistant professor of earth and environmental sciences at the University of Michigan, and lead author on the study. First, the permafrost soil has to thaw and then bacteria must turn the carbon into greenhouse gases – carbon dioxide or methane. While much of this conversion process takes place in the soil, a large amount of carbon is washed out of the soils and into rivers and lakes, she said.
“It turns out, that in Arctic rivers and lakes, sunlight is faster than bacteria at turning organic carbon into CO2,” Cory said. “This new understanding is really critical because if we want to get the right answer about how the warming Arctic may feedback to influence the rest of the world, we have to understand the controls on carbon cycling.
“In other words, if we only consider what the bacteria are doing, we’ll get the wrong answer about how much CO2 may eventually be released from Arctic soils,” Cory added.
The research team measured the speed at which both bacteria and sunlight converted dissolved organic carbon into carbon dioxide in all types of rivers and lakes in the Alaskan Arctic, from glacial-fed rivers draining the Brooks Range to tannin-stained lakes on the coastal plain. Measuring these processes is important, the scientists noted, because bacteria types and activities are variable and the amount of sunlight that reaches the carbon sources can differ by body of water.
In virtually all of the freshwater systems they measured, however, sunlight was always faster than bacteria at converting the organic carbon into CO2.
“This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river – and most lakes – so that no dissolved organic carbon is kept in the dark,” said Crump, an associate professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “Also, there is little shading of rivers and lakes in the Arctic because there are no trees.”
Another factor limiting the microbial contribution is that bacteria grow more slowly in these cold, nutrient-rich waters.
“Light, therefore, can have a tremendous effect on organic matter,” University of Michigan’s Cory pointed out.
The source of all of this organic carbon is primarily tundra plants – and it has been building up for hundreds of thousands of years, but doesn’t completely break down immediately because of the Arctic’s cold temperatures. Once the plant material gets deep enough into the soil, the degradation stops and it becomes preserved, much like peat.
“The level of thawing only gets to be a foot deep or so, even in the summer,” Crump said. “Right now, the thaw begins not long before the summer solstice. If the seasons begin to shift with climate change – and the thaw begins earlier, exposing the organic carbon from permafrost to more sunlight – it could potentially trigger the release of more CO2.”\
The science community has not yet been able to accurately calculate how much organic carbon from the permafrost is being converted into CO2, and thus it will be difficult to monitor potential changes because of climate change, they acknowledge.
“We have to assume that as more material thaws and enters Arctic lakes and rivers, more will be converted to CO2,” Crump said. “The challenge is how to quantify that.”
Some of the data for the study was made available through the National Science Foundation’s Arctic Long-Term Ecological Research project, which has operated in the Arctic for nearly 30 years.
Other authors on the study are Collin Ward and George Kling of the University of Michigan.
The research was supported by the following National Science Foundation grants: NSF-OPP 1023270/1022876; NSF-PLR 1107593; and NSF DEB-1026843 and 1147378/1347042.
The phrase, ‘Eat your vitamins,’ applies to marine animals just like humans. Many vitamins are elusive in the ocean environment. University of Washington researchers used new tools to measure and track B-12 vitamins in the ocean. Once believed to be manufactured only by marine bacteria, the new results show that a whole different class of […]Read more...
The phrase, ‘Eat your vitamins,’ applies to marine animals just like humans. Many vitamins are elusive in the ocean environment.
University of Washington researchers used new tools to measure and track B-12 vitamins in the ocean. Once believed to be manufactured only by marine bacteria, the new results show that a whole different class of organism, archaea, can supply this essential vitamin. The results were presented Feb. 24 at the Ocean Sciences meeting in Honolulu.
“The dominant paradigm has been bacteria are out there, making B-12, but it turns out that one of the most common marine bacteria doesn’t make it,” said Anitra Ingalls, a UW associate professor of oceanography.
All marine animals, some marine bacteria and some tiny marine algae, or phytoplankton, need B-12, but only some microbes can produce the large, complex molecule. So like human vegetarians on land, marine organisms may be scouring for food that can help stave off vitamin deficiency.
“If only certain bacteria can make B vitamins, that can make B-12 a controlling factor in the environment. Is it present or not?” said Katherine Heal, a UW oceanography graduate student. “Studying the marine microbiome can help us understand what microbial communities could be supported where, and how that affects things like the ocean’s capacity to absorb atmospheric CO2.”
The UW team is the first to show that marine archaea, a single-celled organism that evolved totally separate from bacteria and all other living things, are making B-12. Relatives of these tiny critters are known for unusual behavior like living inside hot springs and underwater volcanoes.
The Seattle team managed to grow a common type of open-ocean archaea in the lab, no mean feat, and show that it not only makes enough B-12 to support its own growth but can supply some to the environment.
“It’s hard to quantify their contribution,” Ingalls said. “This is a first glimpse at their potential to contribute to this pool of vitamins.”
The analysis was done at a new UW marine chemistry center that does detailed analysis of proteins and other carbon-based chemicals in the ocean. The researchers used high-tech tools, including liquid chromatography and mass spectrometry, to identify the tiny amount of vitamins among all the dissolved matter and salt in the seawater. The UW method is unique in that it is the only one that can distinguish among the four forms of B-12 vitamins.
Field experiments involved sampling seawater in Hood Canal, near Seattle, and in the Pacific Ocean hundreds of miles offshore. The results showed that B-12 was present in small amounts in all water samples. Concentrations were low enough in some places that vitamin deficiency among tiny marine algae, or phytoplankton, is likely.
“Having a very small amount doesn’t mean there’s a very small supply,” Ingalls said. “Low concentrations can indicate something that’s highly desirable to marine organisms.”
The next step, researchers said, is to connect different microbes’ activity with the production of B vitamins, to see which organisms are responsible where, and to look at how ocean vitamins affect the type and amount of phytoplankton growing in the water.
Recent sequencing of the genomes of marine microbes has revealed genetic pathways in bacteria and archaea for creating B vitamins, but just because the gene is there doesn’t mean it’s being used. Marine microbes often adapt their behavior depending on the environment. In the case of vitamins, some bacteria make more B-12 if a phytoplankton is nearby, supporting their eventual food source.
Making a B-12 vitamin, which has a metal core and complex surrounding structure, involves 30-some steps.
“People think that’s why many organisms have lost it from their genomes,” Heal said. “It’s just too expensive to make it, and it’s easier to get it from food.”
The UW team hopes to learn which microbes are producing B-12 vitamins where, to better understand how the base of the marine food web works, how it might alter in a changing environment, how oceans might help regulate atmospheric carbon dioxide, and where marine animals could go to get a well-balanced diet.
“The public really has a very strange relationship to microorganisms,” Ingalls said. “People know they cause disease, so they want to kill them. But they’re also the only reason that we – or whales, fish or coral reefs – are alive.”
Collaborators are David Stahl, E. Virginia Armbrust, Allan Devol, Wei Qin and Laura Carlson at the UW, James Moffett at the University of Southern California and Willow Coyote, an undergraduate from Evergreen State College who will also present a poster at the meeting.