Inside Science | Warming Tropical Soils May Release Huge Amounts of Stored Carbon

October 2nd, 2019 @

The heat-trapping gases humans release into the air are warming the planet. But humble soil-dwelling bacteria and fungi also release heat-trapping gases, and those gases could determine just how hot it gets. Now new research adds to the worry that the microbes will make climate change worse.

Soil microbes digest dead plants and animals. And, like us, they "breathe out" carbon dioxide. Some scientists predict that as temperatures rise, bacteria and fungi will speed up their metabolisms, spewing vast stores of carbon from the soil into the atmosphere. Others think heat could slow soil microbes down, heading off this potential carbon burp.

A team of scientists has now taken an important step toward lowering the uncertainty about the microbes' likely response. The researchers conducted the first tropical soil carbon warming experiment by carting tubes of soil up and down a mountainside and measuring how the soil’s carbon content changed. The research suggests a huge carbon bomb may be waiting to explode, the team said, possibly boosting carbon dioxide in the atmosphere by almost 10% over a century -- an amount that would have severe impacts on life on the planet.

“This experiment adds to our insight as to what could go on in future,” said Jerry Melillo, a biogeochemist at the Marine Biological Laboratory in Woods Hole, Massachusetts, who was not involved in the study. “It’s definitely an important contribution.”

Melillo launched one of the earliest soil warming experiments in 1991, using buried electrical cables to heat soil by 5 degrees Celsius in a Massachusetts forest. He sought to determine whether underground microbes digest dead animals and plants faster when things get hot. Dozens more experiments have since come online. A 2016 analysis of 49 of these experiments estimated that warming soils globally could belch a whopping 55 billion metric tons of carbon by 2050 -- about as much as the expected human-caused emissions from the U.S. over that period.

But all soil warming experiments to date have been done in the temperate and boreal zones, which are cold much of the year. The tropics, where about a third of Earth’s soil carbon resides, are already warm year-round. Some scientists have hypothesized that warming tropical soils might release little additional carbon because microbes' digestive enzymes may function sluggishly at hotter temperatures; others believe tropical microbes will respond similarly to their boreal and temperate counterparts.

Without experimental data, computer simulations come to wildly different conclusions about how much carbon tropical soil microbes will release. Differences in such estimates for this century vary by a greater amount than the total carbon emitted by humans to date, making it hard for bodies like the Intergovernmental Panel on Climate Change, or IPCC, to pin down how much warming to expect. Data from tropical soils, said Melillo, “is absolutely critical.”

To fill this gap, Andrew Nottingham, an ecologist at the University of Edinburgh in the United Kingdom, devised a way to warm soils without expensive, complicated underground infrastructure. In 2010, he and his research team extracted 50-centimeter-long, 10-centimeter-wide cylinders of soil from different heights on a heavily forested mountainside in Peru’s Manu National Park. The environments ranged from steamy Amazon rainforest 200 meters above sea level to high-elevation cloud forest 3,000 meters up the slope. They carted the high-elevation ones down to the bottom (and vice versa) and reburied them. The journeys involved hours of hiking, long bus rides and even a canoe trip down a river.

The approach allowed the researchers to hit the highest-elevation soils with temperatures 15 degrees Celsius (27 degrees Fahrenheit) warmer, on average, than they would normally see.

The researchers also installed filters and funnels to ensure each soil core received the same average rainfall it would have had it not been moved.

Five years later, the research team measured the carbon in each soil core and compared it to the amounts in soils that had not been moved. They also studied variables such as the makeup of bacterial and fungal communities and the activity of the microbial enzymes.

They found that for each 1 degree C (1.8 degrees F) uptick in temperature, soil carbon declined by 4%. They also found evidence that the microbes in the warmed soils produced enzymes that allowed them to decompose plant and animal remains more efficiently. If this pattern holds for soils throughout the tropics, which span much of Latin America, Africa and Asia, atmospheric carbon dioxide could balloon over this century by an additional 9% above what humans and other sources will emit, Nottingham said. Though studies in other sites are needed to verify this prediction, the result suggests tropical soils will see “a very large loss of carbon,” he said. “It’s larger than we expected.”

Nottingham noted that his experiment had limitations: He and his colleagues did not transport plants growing atop their soil cores, which could affect how much carbon microbes have to feast on. And they did not attempt to mimic non-temperature-related conditions of the future.

They also could not heat soils beyond the average temperature of the low-lying forest, about 26 degrees C (79 degrees F). To see how tropical soils might respond to the even higher temperatures expected as the climate warms, Nottingham has installed electrical coils that are heating rainforest soil at a Smithsonian Tropical Research Institute site in Panama. (A separate warming experiment is underway in Puerto Rico, though it was knocked offline for a year by 2017’s Hurricane Maria.)

Kathe Todd-Brown, a soil ecologist at the University of Florida in Gainesville who co-authored the 2016 analysis, praised the researchers for devising a way to produce a big soil carbon change in a short time.

In one sense, she said, the result is “reassuring”: it suggests that climate models that assume tropical soils will behave similarly to temperate and boreal ones -- including many of those used by the IPCC -- do not need to be rewritten.

But the study’s implications for future climate change, said Todd-Brown, are not reassuring.

“Soils will not save us.”

There is hope, however, that with smart management, soil microbes could at least help us. Some scientists believe practices such as reforestation and no-till farming could help restore tropical soils and cause them to sequester carbon instead of release it.

Beyond carbon storage, soil microbes are also critical to biodiversity and forest health, added Norma Salinas, an ecologist at Pontifical Catholic University of Peru in Lima and a member of the research team. “People say the microbiome is important for your health,” she said. “For the ecosystem, it is the same -- if you see very healthy soils, you can see a very good ecosystem.”

Originally published on Inside Science by Gabriel Popkin, Contributor.

The work is published on "early view" in Ecology Letters.

Editor's Note: This story was updated on Oct. 1, 2019 to include additional information about the location of the soil warming experiment in Panama.

WBUR | MBL’s Anne Giblin Comments on U.N. Climate Report on Oceans

September 26th, 2019 @

The Intergovernmental Panel on Climate Change published a report Wednesday detailing how climate change is affecting oceans and the frozen world. It’s the final of three special reports, and, like the previous two, it has implications for New England.MBL's Anne Giblin Comments on U.N. Climate Report on Oceans | WBUR

If you’re picturing a polar bear standing on a small ice floe and wondering what this has to do with you, just know that what happens in one corner of the world — even somewhere as remote and inhospitable as the Arctic Ocean — can have a profound effect on ecosystems and humans thousands of miles away.

With that in mind, here are five takeaways for New England in the report: Read more and listen to radio spot…

By Miriam Wasser. This segment aired on September 25, 2019.

Photo: A wave crashes high above a house on Oceanside Avenue in Scituate during a 2018 nor’easter. (Jesse Costa/WBUR)

Source: Here’s What The New U.N. Report On Oceans And Ice Means For New England | WBUR

Hurricane Nicole Sheds Light on How Storms Impact Deep Ocean

September 19th, 2019 @

Hurricane Nicole bears down on Bermuda on Oct. 12, 2016. Credit: NASA Goddard MODIS Rapid Response Team

In early October 2016, a tropical storm named Nicole formed in the middle of the Atlantic Ocean. It roamed for six days, reaching Category 4 hurricane status with powerful 140 mile-per hour-winds, before hitting the tiny island of Bermuda as a Category 3.

Hurricanes like Nicole can cause significant damage to human structures on land, and often permanently alter terrestrial landscapes. But these powerful storms also affect the ocean.

Scientists have a good understanding of how hurricanes impact the surface layer of the ocean, the sunlit zone, where photosynthesis can occur. Hurricanes’ strong winds churn colder water up from below, bringing nutrients such as nitrogen and phosphorus to the surface and stimulating short-lived algae blooms. However, until recently, we didn’t know much about how hurricanes impact the deep ocean.

A new study of Hurricane Nicole by researchers at the Marine Biological Laboratory (MBL), Woods Hole, and the Bermuda Institute of Ocean Sciences (BIOS) has provided novel insight on those impacts. Nicole had a significant effect on the ocean’s carbon cycle and deep sea ecosystems, the team reports.

Read the full story on The Well | MBL Scientists Study Impact on Nitrate in Salt Marshes

September 9th, 2019 @

Great Sippewissett Marsh in Falmouth. Salt marshes store carbon at higher rates than in ecosystems on land. Photo: Daniel Buckley

WOODS HOLE – Scientists at the Marine Biological Laboratory have studied salt marshes and concluded that nitrate, a common coastal water pollutant, stimulates the decomposition of organic matter in these marshes.

The matter would normally have remained stable over a long period of time.

The increase of decomposition might alter the salt marshes’ carbon capacity due to the release of carbon dioxide. Normally, salt marshes storing carbon could offset effects of climate change due to carbon dioxide building up in the atmosphere.

The study was led by scientists from the MBL in Woods Hole and Northeastern University. It was published in Global Change Biology.

The research team is now looking to analyze the microbial that has decreased the carbon build up in salt marshes.

Author: Brendan Patrick

Originally published in

Salt Marshes' Capacity to Store Carbon may be Threatened by Nitrogen Pollution

August 23rd, 2019 @
Salt marshes sequester carbon at rates more than an order of magnitude greater than their terrestrial counterparts. Core samples for this study where taken from this marsh in Rowley, Mass., part of the Plum Island Ecosystems NSF-LTER site. Credit: Aber, Aber, and Valentine 2009.

Salt marshes sequester carbon at rates more than an order of magnitude greater than their terrestrial counterparts. Core samples for this study where taken from this marsh in Rowley, Mass., part of the Plum Island Ecosystems NSF-LTER site. Credit: Aber, Aber, and Valentine 2009.

Deep in the waterlogged peat of salt marshes, carbon is stored at much greater rates than in land ecosystems, serving as an offset to climate change due to carbon dioxide (CO2) build-up in the atmosphere.

However, a new study indicates that a common pollutant of coastal waters, nitrate, stimulates the decomposition of organic matter in salt marsh sediments that normally would have remained stable over long periods of time. This increase in decomposition, which releases CO2, could alter the capacity of salt marshes to sequester carbon over the long term. The study, led by scientists at the Marine Biological Laboratory (MBL), Woods Hole, and Northeastern University, is published in Global Change Biology.

“Traditionally, we have viewed salt marshes as resilient to nitrogen pollution, because the microbes there remove much of the nitrogen as gas through a process called denitrification,” writes first author Ashley Bulseco, a postdoctoral scientist at the MBL.

“But this research suggests that when nitrate is abundant, a change occurs in the microbial community in salt marsh sediments that increases the microbes’ capacity to degrade organic matter. This potentially reduces the ability of the marsh to store carbon,” Bulseco writes.

Ashley Bulseco, pictured, and team used a controlled flow-through reactor experiment to determine how nitrate affected organic matter decomposition and microbial community structure in salt marsh sediments. Credit: MBL Ecosystems Center

Ashley Bulseco, pictured, and co-authors used a controlled flow-through reactor experiment to determine how nitrate affected organic matter decomposition and microbial community structure in salt marsh sediments. Credit: MBL Ecosystems Center

As global temperatures continue to rise, a number of carbon capture strategies have been proposed, including sequestering CO2 in “blue carbon” habitats such as salt marshes, mangroves and seagrass meadows. However, coastal nitrogen pollution is also still rising in many areas due to agricultural and urban runoff, and sewage.

“Given the extent of nitrogen loading along our coastlines, it is imperative that we better understand the resilience of salt marsh systems to nitrate, especially if we hope to rely on salt marshes and other blue carbon systems for long-term carbon storage,” the authors write.

The next phase of this research, already in progress, is to analyze the microbial community responsible for degrading carbon in a salt marsh ecosystems, especially when exposed to high concentrations of nitrate.

Among Bulseco’s co-authors are Jennifer Bowen, professor of marine and environmental sciences at Northeastern University, and Anne Giblin, director of the Ecosystems Center at the MBL, who were her PhD advisors.


Ashley N. Bulseco et al (2019) Nitrate addition stimulates microbial decomposition of organic matter in salt marsh sediments. Global Change Biology, DOI: 10.1111/gcb.14726

Originally published in The Well.

Team Explores the Recovery, Resilience of a Stressed Salt Marsh

July 29th, 2019 @

Day in and day out for 13 years, scientists slowly dripped fertilizers into a pristine section of salt marsh north of Boston. They were simulating, in a controlled experiment, the pollution that marshes in densely Team Explores the Recovery, Resilience of a Stressed Salt Marshpopulated areas receive from sewage, lawn fertilizer, and other human sources.

By the time they stopped dripping the nutrients — nitrogen and phosphorus — in 2016, they had observed changes in the marsh’s plant and animal community and even in its physical structure.

The creek banks had begun to crack and slump down, indicating that the over the long term, nutrient pollution could be a factor in converting “a vegetated marsh into a mudflat, which is a much less productive ecosystem,” said MBL Fellow Linda Deegan, lead investigator of the project at the Plum Island Ecosystems Long-Term Ecological Research Site (PIE-LTER).

Losses of healthy salt marsh have accelerated in recent decades, with some losses caused by sea-level rise and development. “Salt marshes are a critical interface between the land and sea,” Deegan said. “They provide habitat for fish, birds, and shellfish; protect coastal cities from storms; and take nutrients out of water coming from upland areas, which protects coastal bays from pollution.”

Now, the team wants to know, “Will this marsh be able to recover?” Buoyed by a new, three-year grant from the National Science Foundation, they are watching how the marsh is responding now that the nutrient addition has stopped.

Nutrient addition over 13 years led to cracking and slumping of creek banks in the experimental site. Now, the TIDE team is studying how the salt marsh responds to a reduced nutrient load. Credit: Shanna Baker, MBL Logan Science Journalism Program

“We want to see how microbes, plants and animals respond to a decrease in nutrients,” said Anne Giblin, who directs the MBL Ecosystems Center as well as the PIE-LTER. “We will also see if the changes in the marsh’s physical structure that we observed after fertilization began will continue in the same direction, or reverse course.”

This marks the latest phase in the ecosystem-scale TIDE Project, which began in 2002. The scientists now hope to illuminate “the legacy effects of stress-induced changes (genotypic to landscape) on ecosystem recovery, and the limits of landscape resilience.”

Giblin received this collaborative NSF grant with Deegan, a senior scientist at Woods Hole Research Center, and James A. Nelson, assistant professor at University of Louisiana.

Top photo: Lush cordgrass (Spartina patens) at a salt marsh in Ipswich, Mass., part of the Plum Island Ecosystems study site. Credit: David S. Johnson, TIDE Project

Originally published in: The Well: MBL News from the Source

Scientists Urge Formation of National Network to Accelerate Climate Change Action

April 4th, 2019 @

A non-federal network that will leverage science to manage climate change risks in the United States is urgently needed, recommends a report released today by a group of 36 climate researchers, state/local/tribal officials, and other experts including Jerry Melillo, Distinguished Scientist at the Marine Biological Laboratory (MBL) and former chairman of the U.S. National Climate Assessments.

An early online version of the report, “Evaluating Knowledge to Support Climate Action,” is published today by the Bulletin of the American Meteorological Society. The report summary and a full press release are available here.

The report’s key recommendations are to establish a non-federal network to assess how to apply science in making and implementing decisions; focus these assessments on the common problems and challenges that climate risk managers face; and use new methods such as artificial intelligence to support climate risk management.

“This network will build off the U.S. National Climate Assessments to help communities establish pragmatic, science-based actions and pathways to manage the climate risks that are specific to their region,” said Melillo.

To provide interim leadership for this national network, the group also announced today the establishment of the Science for Climate Action Network (SCAN), which will coordinate preparation of a next-generation of climate assessments and serve as a backbone organization for groups that already are beginning to incorporate climate science in their work.

In 2016, a Federal Advisory Committee was convened to recommend how to increase the application of the National Climate Assessments to inform action. This committee was disbanded by the Trump Administration in 2017, but members and additional experts reconvened as the Independent Advisory Committee to complete the present report.

by Diana Kenney

Originally posted on The Well


Rooted in research: A study looks at effects of climate change on a less visible matter

January 15th, 2019 @

Global warming brings to mind scenes of devastating natural disasters and polar bears on shrinking ice caps. But new research is studying the effects of climate change on a less visible matter — interactions between plant roots and the surrounding soil, particularly relative to carbon.

The results of the study could shed light on global warming’s influence on food production and carbon storage.

“This is the frontier of what we don’t understand,” said Marco Keiluweit, a biogeochemist and assistant professor at the University of Massachusetts Amherst. “It will give us the opportunity to explore these broader problems of climate change.”

Full article by Ysabelle Kempe, Globe Correspondent, available on

Team Studies how Viral Infections in Plants may Affect Carbon Storage in Soil

January 9th, 2019 @

Photo illustration by Zoe Cardon

MBL Senior Scientist Zoe Cardon has received a collaborative grant from the Department of Energy to study how viral infections in plants can affect the fate of the largest pool of organic carbon stored in soils: organic carbon bound to minerals.

As carbon dioxide (CO2) concentrations in the atmosphere continue to rise, driving further climate change, it becomes more and more urgent to understand how plant roots, soil microbes, and soil minerals interact to control whether soils store carbon or release CO2.

One way that plant roots strongly contribute to soil carbon storage is by producing sugars, organic acids, and even whole cells that are lost to soil. But there is a twist in the story. Certain types of compounds derived from roots may also destabilize the bonds between soil  minerals and existing soil organic matter (SOM), making that SOM more vulnerable to microbial attack and decomposition. Soil carbon loss, instead of storage, may result.

The question then becomes what types of compounds, and how much of them, are lost from plant roots to soils. Cardon and colleagues have found that, upon infection with particular plant viruses, plant roots can lose so many compounds to their surroundings that they become literally “sticky” to the touch. Understanding whether and how these “sticky roots” drive increased decomposition of existing mineral-stabilized soil carbon promises to transform our understanding of the importance of common virus infection for soil carbon dynamics and global change.

Co-principal investigators with Cardon, the lead principal investigator on this project, include Marco Keiluweit, University of Massachusetts, Amherst; Carolyn Malmstrom, Michigan State University; and William J Riley, Lawrence Berkeley National Laboratory.


Originally published in The Well

Improving Predictions of Soil Microbe Responses to Global Change

November 27th, 2018 @

In most soil microbial communities, the controls on growth and metabolism are poorly understood and are simply too complex to be included in computer models of climate, soil fertility for agriculture, or waste Improving Predictions of Soil Microbe Responses to Global Changemanagement.

To determine the principles by which soil microbial communities function under varying environmental constraints, development of a scalable biogeochemical modeling approach is critical.

In a new collaborative project funded by the National Science Foundation (NSF), MBL Senior Scientists Joe Vallino and Zoe Cardon will develop a flexible framework for analyzing microbial biogeochemistry from the perspective of maximum entropy production (MEP) (a concept that proposes complex systems will likely organize to maximize dissipation of useful energy).

The work takes advantage of the high diversity of microbial communities to enable thermodynamically based predictions about system-level biogeochemical responses to global change.

Ultimately, the goal is to integrate sensor-derived information of soil properties with the MEP model to predict shifting activities of microbial communities in soils using far fewer model parameters than would be required with conventional modeling. The project will also support undergraduate research activities as part of the MBL’s Semester in Environmental Science program.

This grant is through the NSF’s “Signals in the Soil” program.

Caption: Example of a simplified soil metabolic network model representing the conversion of soil organic matter (SOM) to methane (CH4) or carbon dioxide (CO2) overlaying an image of methanogens stained with SYBR green. Credit: Joe Vallino and Zoe Cardon

Originally Posted in The Well.

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