Methane Meltdown: Thawing Permafrost Could Release More Potent Greenhouse Gas Than Expected
A study published in Nature Climate Change Monday shows that thawing permafrost in the Arctic might produce more methane than previously thought. Methane has 28 times the Global Warming Potential (GWP) of carbon dioxide, so the findings indicate scientists might have to reassess how thawing permafrost will contribute to climate change.
The research contradicts previous studies that suggested dry permafrost would contribute more to global warming than water-saturated permafrost, and it would do so mostly by releasing carbon dioxide. By studying samples of water-saturated permafrost in the laboratory over a seven-year period, the study's authors found that the samples produced equal amounts of carbon dioxide and methane. They were then able to derive models that predicted water-saturated permafrost would release about 2.4 times the greenhouse gases that dry permafrost would.
"What we can definitely say is that the importance of methane was underestimated until now in the carbon studies," the study's lead author and Universität Hamburg researcher Christian Knobloch, told The Washington Post.
The reason this study found different results is likely due to its length. Permafrost releases carbon as it melts due to microbial decomposition; previous studies did not pick up on the production of methane in water-saturated soils because they only lasted days or weeks. The laboratory observations, however, found that methane-producing communities of microorganisms did not activate in the permafrost samples until weeks to years had passed.
More methane release has been observed in field studies of the Arctic. Last summer, for example, EcoWatch reported that scientists found 7,000 methane-filled mounds in thawing permafrost in Siberia that bounced when researchers pressed on them.
"What's remarkable about this study is the length of time they spent tracking the communities, and I think that offers a potential reason for why field and lab studies have disagreed with each other," University of Guelph ecologist Merritt Turetsky, who studies permafrost but was not involved in this particular study, told the Post.
However, the authors of Monday's study point out that more work needs to be done to determine how their laboratory observations will play out in the Arctic. While they predict that there will be a significant amount of water-saturated permafrost thawing in the region, since permafrost tends to impede drainage, they still say further research is needed to determine how much of the thawing ground will actually be wetlands.
Róisín Commane, an Arctic-atmosphere researcher at Harvard University, who was also not part of the study, told the Post that many factors could prevent the methane observed in the laboratory from reaching the atmosphere in the real world. Permafrost might not retain water as the ice melts, and organisms in the soil could turn the methane into carbon dioxide before it reaches the air.
"Ecosystems will probably produce more methane as they stay wet. The big question we have is, how much of that makes it into the atmosphere, and I don't think they get to that question here," Commane told the Post.
However, whether or not melting permafrost releases more methane or carbon dioxide, the Post reported that as much as 10 percent of permafrost carbon could be released into the atmosphere this century, which would disrupt global climate change goals.
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By Jacob L. Steenwyk and Antonis Rokas
From the mythical minotaur to the mule, creatures created from merging two or more distinct organisms – hybrids – have played defining roles in human history and culture. However, not all hybrids are as fantastic as the minotaur or as dependable as the mule; in fact, some of them cause human diseases.
When Looking Through a Microscope Isn’t Close Enough.<p>For the last few years, <a href="http://www.rokaslab.org/" target="_blank">our team at Vanderbilt University</a>, <a href="https://www.researchgate.net/lab/Gustavo-Goldman-Lab" target="_blank">Gustavo Goldman's team at São Paulo University in Brazil</a> and many other collaborators around the world have been collecting samples of fungi from patients infected with different species of <em>Aspergillus</em> molds. One of the species we are particularly interested in is <a href="https://doi.org/10.1006/rwgn.2001.0082" target="_blank"><em>Aspergillus nidulans</em>, a relatively common and generally harmless fungus</a>. Clinical laboratories typically identify the species of <em>Aspergillus</em> causing the infection by examining cultures of the fungi under the microscope. The problem with this approach is that very closely related species of <em>Aspergillus</em> tend to look very similar in their broad morphology or physical appearance when viewing them through a microscope.</p><p>Interested in examining the varying abilities of different <em>A. nidulans</em> strains to cause disease, we decided to analyze their total genetic content, or genomes. What we saw came as a total surprise. We had not collected <em>A. nidulans</em> but <em>Aspergillus latus</em>, a close relative of <em>A. nidulans</em> and, as we were to soon find out, <a href="https://doi.org/10.1016/j.cub.2020.04.071" target="_blank">a hybrid species that evolved through the fusion of the genomes</a> of two other <em>Aspergillus</em> species: <em>Aspergillus spinulosporus</em> and an unknown close relative of <em>Aspergillus quadrilineatus</em>. Thus, we realized not only that these patients harbored infections from an entirely different species than we thought they were, but also that this species was the first ever <em>Aspergillus</em> hybrid known to cause human infections.</p>
Several Different Fungal Hybrids Cause Human Disease.<p>Hybrid fungi that can cause infections in humans are well known to occur in several different lineages of single-celled fungi known as yeasts. Notable examples include multiple different species of <a href="https://doi.org/10.1002/yea.3242" target="_blank">yeast hybrids</a> that cause the human diseases <a href="https://rarediseases.info.nih.gov/diseases/6218/cryptococcosis" target="_blank">cryptococcosis</a> and <a href="https://www.cdc.gov/fungal/diseases/candidiasis/index.html" target="_blank">candidiasis</a>. Although pathogenic yeast hybrids are well known, our discovery that the <em>A. latus</em> pathogen is a hybrid is a first for molds that cause disease in humans.</p>
(Left) Candida yeasts live on parts of the human body. Imbalance of microbes on the body can allow these yeasts, some of which are hybrids, to grow and cause infection. (Right) Cryptococcus yeasts, including ones that are hybrids, can cause life-threatening infections in primarily immunocompromised people. Centers for Disease Control and Prevention<p><a href="https://doi.org/10.1371/journal.ppat.1008315" target="_blank">Why certain <em>Aspergillus</em> species are so deadly</a> while others are harmless remains unknown. This may in part be because <a href="https://doi.org/10.1016/j.fbr.2007.02.007" target="_blank">combinations of traits, rather than individual traits</a>, underlie organisms' ability to cause disease. So why then are hybrids frequently associated with human disease? Hybrids inherit genetic material from both parents, which may result in new combinations of traits. This may make them more similar to one parent in some of their characteristics, reflect both parents in others or may differ from both in the rest. It is precisely this mix and match of traits that hybrids have inherited from their parental species that <a href="https://www.nytimes.com/2010/09/14/science/14creatures.html" target="_blank">facilitates their evolutionary success</a>, including their ability to cause disease.</p>
The Evolutionary Origin of an Aspergillus Hybrid.<p>Multiple evolutionary paths can lead to the emergence of hybrids. One path is through mating, just as the horse and donkey mate to create a mule. Another path is through the merging or fusion of genetic material from cells of different species.</p><p>It is this second path that appears to have been taken by our fungus. <em>A. latus</em> appears to have two of almost everything compared to its parental species: twice the genome size, twice the total number of genes and so on. But unlike other hybrids, which are often sterile like the mule, we found that <em>A. latus</em> is capable of reproducing both asexually and sexually.</p><p>But how distinct were the parents of <em>A. latus</em>? By comparing the parts contributed by each parent in the <em>A. latus</em> genome, we estimate that its parents are approximately 93% genetically similar, which is about as related as we humans are with lemurs. In other words, <em>A. latus</em>, an agent of infectious disease, is the fungal equivalent of a human-lemur hybrid.</p>
How A. Latus Differs From its Parents.<p>Elucidating the identity of closely related fungal pathogens and how they differ from each other in infection-relevant characteristics is a key step toward reducing the burden of fungal disease. For example, we found that <em>A. latus</em> was three times more resistant than <em>A. nidulans</em>, the species it was originally identified as using microscopy-based methods, to one of the most common antifungal drugs, <a href="https://www.drugbank.ca/drugs/DB00520" target="_blank">caspofungin</a>. This result provides a clear example of the potential importance of accurate identification of the <em>Aspergillus</em> pathogen causing an infection.</p><p>We also examined how <em>A. latus</em> and <em>A. nidulans</em> interact with cells from our immune system. We found that immune cells were less efficient at combating <em>A. latus</em> compared to <em>A. nidulans</em>, suggesting the hybrid fungus may be trickier for our immune systems to identify and destroy.</p><p>In the midst of the COVID-19 pandemic, our quest to understand <em>Aspergillus</em> pathogens is becoming more urgent. Growing evidence suggests that <a href="https://doi.org/10.1111/myc.13096" target="_blank">a fraction of COVID-19 patients are also infected with <em>Aspergillus</em>.</a> More worrying is that these <a href="https://doi.org/10.3201/eid2607.201603" target="_blank">secondary <em>Aspergillus</em> infections</a> can worsen the clinical outcomes for those infected with the novel coronavirus. That being said, we stress that little is known about <em>Aspergillus</em> infections in COVID-19 patients due to a lack of systematic testing, and none of the infections identified so far appear to have been caused by hybrids.</p><p>So, when it comes to hybrids, some are fantastic (the minotaur), some are helpful (the mule) and some are dangerous (<em>Aspergillus latus</em>). Understanding more about the biology of <em>Aspergillus latus</em> may help in our understanding of how microbial pathogens arise and how to best prevent and combat their infections.</p>
This Saturday, June 6, marks National Trails Day, an annual celebration of the remarkable recreational, scenic and hiking trails that crisscross parks nationwide. The event, which started in 1993, honors the National Trail System and calls for volunteers to help with trail maintenance in parks across the country.
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By John Letzing
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The Navajo Nation covers the corners of three different states. Google Maps
Growing Contribution<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM3NDY5Ny9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0NjM4MTgyM30.IuQTKQs1stvYYKD6vaVTrqAyoBsUG0BhDvlhxsyKwPA/img.png?width=980" id="02a05" class="rm-shortcode" data-rm-shortcode-id="2841f82b1785df5d5ed7bf64d3bb882b" data-rm-shortcode-name="rebelmouse-image" />
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Scuba divers around the world are holding their metaphorical breath to see if a coronavirus infection affects the ability to dive.
DAN medical experts explained the difference between normal lungs, on the left, and "very serious lungs caused by COVID-19," on the right. Matias Nochetto / Divers Alert Network (DAN)
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