Questions remain about the biolability of dissolved black carbon

The heating and partial combustion of organic matter produces a diverse suite of organic compounds that range from sugar-like molecules to graphite. Charcoal formed at high temperatures, here termed “black carbon”, tends to be less biolabile (i.e. less degradable by microbes) than charcoal formed at low temperatures. Consider how you make and enjoy a piece of toast: Lightly singed bread is quite tasty (or “biolabile”), whereas bread burnt to a crisp is bitter and unpalatable. When charred material interacts with water, some of it dissolves and is carried away by rivers to the ocean. Therefore, understanding the relative biolability (or “tastiness”) of dissolved black carbon is important for understanding whether or not it is degraded in rivers before entering ocean waters.

A gradient of toast.

Isolating and tracking different molecular components of charcoal and black carbon in the environment is very challenging from an analytical perspective - Different methods measure different fractions of charcoal along the “combustion continuum”. Therefore, charcoal and black carbon are operationally defined by the method used to quantify and characterize it. Questions still remain about exactly how, or to what degree, the analytical windows of these methods overlap … if they overlap at all.

Sasha Wagner and colleagues recently published a Matters Arising in Nature Communications entitled “Questions remain about the biolability of dissolved black carbon along the combustion continuum” that dives into discussion about the comparison of black carbon analytical windows, biolabile charcoal fractions, and the terminology used to describe this important yet enigmatic compound class.

Stories of Carbon Cycling as Told by Dissolved Organic Matter

The Wagner Lab put together a short video for the Passport To Rensselaer – a virtual guide to the research, pedagogy, students, and faculty who collaborate across disciplines at RPI – as part of the 2021 Virtual Reunion and Homecoming Event. It’s a great 2-minute overview of the research we do!

Click here to view the full Passport To Rensselaer virtual booklet.

Hudson River sampling kicks off after spring thaw

Collecting water samples from the Mohawk River tributary.

Fieldwork is more fun when the whole lab is involved!

NSF RAPID GRANT to capture "first flush" of carbon and nutrients after wildfire

Post-fire landscape.

Sasha Wagner has teamed up with principal investigator Margaret Zimmer, a University of California Santa Cruz hydrologist who had been studying the path of water starting from rainfall on a hillside in Blue Oak reserve. Zimmer’s lab equipped the hillside with multiple instruments, including sensors that detect and measure the flow of water, and automated sample collecting equipment. A wildfire burned through the site in August 2020, but the instruments were resurrected with minor repairs, and researchers are now anticipating the first rainfall to follow the fire.

“What we call the ‘first flush’ of carbon and nutrients from the land after a wildfire has never been captured before,” said Wagner. “So what’s in that first flush? When does it get to the ocean? Is the fraction of black carbon that arrives in the ocean more or less reactive than what was flushed from the landscape? Part of filling in these gaps on this aspect of the carbon cycle requires us to track black carbon from the headwaters through the larger branches of the river into coastal environments.”

With mountains that drain directly into the sea, southern California is the perfect location for a clean track of the connection between charring on the landscape and the ocean. And by combining organic geochemical analysis with hydrological analysis, the research will create an informed picture of how black carbon is moving from the hillside overland or into groundwater. “These kinds of connections are really important in telling the story of what’s happening in streams, extrapolating more broadly to what’s happening in other areas, and also making predictions should a wildfire happen again,” Wagner said.

Read the full Rensselaer News article here: “West Coast Wildfires Create Rare Opportunity To Track Black Carbon” - Originally published by M. L. Martialay on 17 December 2020.

Project funding information: National Science Foundation – Hydrologic Sciences (EAR). RAPID: Collaborative Research: Hydrologically driven export of pyrogenic carbon and nutrients in fire-impacted watersheds. Award No. 2100269. M. Zimmer (PI), S. Wagner (CoI).

Western wildfires touch the east coast

View of hazy sun from RPI campus. Photo by S. Wagner

This week, the sky took on a distinctive haze – Smoke from the western US wildfires officially reached the east coast.  The frequency and intensity of west coast wildfires is increasing – A trend driven by fire suppression (fuel accumulation) and exacerbated by a warming climate.  Wildfires release carbon to the atmosphere in the form of carbon dioxide, smoke, and other aerosols.  This atmospheric carbon release is somewhat buffered by the simultaneous production of charcoal, which converts fast-cycling (relatively reactive) biomass carbon to slow-cycling (relatively inert) charcoal.  In the Wagner lab, we study the formation, transport, and environmental fate of this slowly-cycling pool of fire-derived carbon.

In New York, it is unusual to experience fire at all, let alone the effects of wildfires burning ~3000 miles away – A visual reminder that local burn events have widespread and global impacts.

Source and flux of dissolved black carbon from the Congo River

The Congo River Basin forest-savanna mosaic landscape. Smoke from burning vegetation can also be seen. Photo by T. Drake.

The charring of terrestrial biomass (e.g., trees and grasses) produces black carbon, which is resistant to microbial degradation and thus cycles differently than its unburned precursor material. A portion of this charred biomass enters waterways as dissolved black carbon (DBC), which is then routed through river networks and subsequently delivered to coastal oceans. Since river systems are a globally significant sink for this refractory component of terrestrial carbon, we set out to constrain sources and fluxes of DBC from the second-largest watershed on Earth: the Congo River Basin.

Sasha Wagner and Travis Drake (ETH Zurich) led a paper entitled “Du feu à l'eau: Source and flux of dissolved black carbon from the Congo River” that was recently published in Global Biogeochemical Cycles. In this study, they found that the Congo River exports over 800,000 metric tons of DBC per year and was largely controlled by the basin’s unique North‐South bimodal hydrologic regime. Compound-specific stable carbon isotopes also revealed a seasonal shift in DBC source from forest-dominant landscapes early in the year to mixed forest-savanna landscapes later in the year. Detailed assessments of the production, mobility, and fate of DBC produced by fires within the Congo River Basin is key to balancing fire-derived carbon budgets globally.

Discussing dissolved organic matter for the hudson Mohawk Magazine

The Mohawk River, a tributary of the Hudson River, that borders Peebles Island State Park (Cohoes, NY). Photo by S. Wagner

Dissolved organic matter (DOM) is a mixture of millions of organic molecules and gives water its color. DOM is mobilized by water and plays an integral role in connecting aquatic systems to the landscapes they drain.  Collectively, DOM molecules tell stories about water history and catchment health. 

Sasha Wagner was interviewed by Jared Wesley Singer of the Water Justice Laboratory for the Hudson Mohawk Magazine, a news and public affairs show produced daily in the studios of WOOC 105.3 FM at The Sanctuary for Independent Media in Troy, NY. Here, Sasha discusses the importance and intersectionality of DOM across terrestrial, aquatic, and human-engineered systems.

This interview first aired on WOOC 105.3 FM on July 6, 2020 and is available via the Sanctuary for Independent Media or can be listed to below:

The liberation of RNA

Brandon Ogbunu shares his story with the Story Collider audience at the Evolution 2019 event co-organized by the Diversity Committees of the ASN, SSB, and SSE in Providence, RI. Photo by Davide DelPoio.

Brandon Ogbunu is an Assistant Professor at Brown University. His research focuses on evolutionary genetics and the ecology of disease. A New York City native, Brandon enjoys film, hip-hop, jazz and science fiction. He's an ex-very mediocre light heavy weight boxer, and slightly less mediocre experimental virologist. He has higher hopes for humanity than he does the New York Knicks.

In June of 2019, Brandon got on stage and told a story about the role race has played in his academic career. Starting when he was a senior in college being shook down by a couple cops, Brandon tells us about navigating his ups and downs of a career in science, his startling connection to scientific racism, and his battle against biology's central dogma.

This story was originally produced by The Story Collider and shared by Radiolab.

A key part of dismantling racism is listening to and amplifying Black voices. Listen to Brandon’s story below or read the transcript at The Story Collider.

A current perspective on the future of oceanic dissolved organic carbon

A conceptual diagram of major environmental processes which change the quantity and quality of dissolved organic carbon (DOC) stored in the global ocean.

The vast majority of freshly produced oceanic dissolved organic carbon (DOC) is derived from marine phytoplankton, then rapidly recycled by heterotrophic microbes.  A small fraction of this DOC survives long enough to be routed to the interior ocean, which houses the largest and oldest DOC reservoir.  The oceanic DOC cycle is an essential part of the global carbon cycle, however Earth system models currently lack a coherent implementation of oceanic DOC.

Sasha Wagner and co-authors recently published a review entitled “Soothsaying DOM: A current perspective on the future of oceanic dissolved organic carbon” in Frontiers in Marine Science. The review paper synthesizes current budgets of oceanic DOC, considers what is meant by the term “DOC recalcitrance,” spotlights new isotopic approaches for probing DOC cycling, and discusses potential changes to oceanic DOC budgets that are expected to occur in response to our changing climate.

Formative discussions for this review took place at the Marine Organic Geochemistry Workshop held at the Hanse-Wissenschaftskolleg Institute for Advanced Study (Delmenhorst, Germany) in April 2019.

California wildfire burns boundaries between science and art

Artwork by Celia Jacobs, who illustrated portraits of the crew, the science team, and the science itself during this project.

The Across the Channel: Investigating Diel Dynamics (ACIDD) project was designed to examine day-night fluctuations in microbial, chemical, and biological cycles within the Santa Barbara Channel located off the coast of Southern California. However, just 10 days before the cruise was scheduled to embark on its mission, the Thomas Fire ignited in the Santa Barbara mountains. The timing of this major wildfire presented a rare opportunity to incorporate a direct investigation of how dry ash deposition impacts the Southern California coastal oceanic ecosystem.

The commentary “California wildfire burns boundaries between science and art,” led by Kelsey Bisson and Nick Baetge and co-authored by Sasha Wagner, was published in the journal Oceanography last month. The commentary describes the challenges of scientific research at sea and opportunities to integrate artistic perspectives that enable scientific findings to reach a broader community. The ACIDD team’s documentary “Aquatic Cathartic” is freely available online and offers an outsider’s perspective to seagoing oceanographic research in all of its glories and shortcomings.