From The Oregon State University (US): “Oregon State microbiology research furthers understanding of ocean’s role in carbon cycling”

From The Oregon State University (US)

October 07, 2021

Story By:
Steve Lundeberg

Ryan Mueller


Microbiology researchers at The Oregon State University (US) have shed new light on the mechanisms of carbon cycling in the ocean, using a novel approach to track which microbes are consuming different types of organic carbon produced by common phytoplankton species.

The research is an important step toward forecasting how much carbon will leave the ocean for the atmosphere as greenhouse gas carbon dioxide and how much will end up entombed in marine sediments, said Ryan Mueller, associate professor in The Oregon State University’s Department of Microbiology and the leader of the study.

Findings were published today in the PNAS.

“Our research shows that different species of microbes in the ocean are very particular yet predictable in the food sources they prefer to eat,” said first author Brandon Kieft, a recent Oregon State Ph.D. graduate who is now a postdoctoral researcher at The University of British Columbia (CA). “As global climate change continues to alter oceanic environments at a rapid pace, the availability of food sources for microbes will also change, ultimately favoring certain types over others.”

Phytoplankton are microscopic organisms at the base of the ocean’s food chain and a key component of a critical biological carbon pump. Most float in the upper part of the ocean, where sunlight can easily reach them.

The tiny autotrophic plants–they make their own food–have a big effect on the levels of carbon dioxide in the atmosphere by sucking it up during photosynthesis. It’s a natural sink and one of the primary ways that CO2, the most abundant greenhouse gas, is scrubbed from the atmosphere; atmospheric carbon dioxide has increased 40% since the dawn of the industrial age, contributing heavily to a warming planet.

“We’re studying the consumers–the heterotrophic microbes–of the organic material made by the primary producers-the microbial phytoplankton,” Mueller said. “Both groups are microbes, the former primarily consumes organic carbon as a food source, while the latter ‘fix’ their own organic carbon. Microbes form the basis of the food web and biological carbon pump, and our work is primarily focused on exploring what the consumers are doing in this system.”

The surface ocean stores nearly as much carbon as exists in the atmosphere. As the ocean pulls in atmospheric carbon dioxide, phytoplankton use the CO2 and sunlight for photosynthesis: They convert them into sugars and other compounds the cells can use for energy producing oxygen in the process.

This so-called fixed carbon makes up the diet of heterotrophic microbes and higher organisms of the marine food web such as fish and mammals, which ultimately convert the carbon back to atmospheric CO2 through respiration or contribute to the carbon stock at the bottom of the ocean when they die and sink.

The collective respiratory activity of the heterotrophic microbial consumers is the main way that fixed dissolved organic carbon from phytoplankton is returned to the atmosphere as CO2.

Mueller, Kieft and collaborators at the DOE’s Oak Ridge National Laboratory (US) and DOE’s Lawrence Livermore National Laboratory (US) and The University of Tennessee (US), The University of Washington (US) and The University of Oklahoma(US) used stable isotope labeling to track carbon as it made its way into the organic matter produced by the phytoplankton and, ultimately, the heterotrophic microbes that consume it.

The scientists used those isotopes to tell which organisms were eating diatoms and which were consuming cyanobacteria, two species of phytoplankton that combine to produce a majority of the ocean’s fixed carbon. The researchers could also tell when the consumption was happening – for example, at times the phytoplankton cells were producing substances known as lysates during their death phase or exudates during their growth phase.

“Our findings have important implications for understanding how marine microbes and photosynthetic algae function together to impact global carbon cycling and how this oceanic food web may respond to continued environmental change,” Kieft said. “This will help us predict how much carbon will go back into the atmosphere and how much will be buried in marine sediments for centuries.”

The research was funded by the Gordon and Betty Moore Foundation Marine Microbiology Initiative and the U.S. Department of Energy.

See the full article here.


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The Oregon State University(US) is a public land-grant research university in Corvallis, Oregon. The university currently offers more than 200 undergraduate-degree programs along with a variety of graduate and doctoral degrees. Student enrollment averages near 32,000, making it the state’s largest university. Since its founding over 230,000 students have graduated from OSU. It is classified among “R1: Doctoral Universities – Very high research activity” with an additional, optional designation as a “Community Engagement” university.

The Oregon State University a land-grant university and it also participates in the sea-grant, space-grant and sun-grant research consortia; it is one of only four such universities in the country (The University of Hawaii at Manoa (US), Cornell University (US) and The Pennsylvania State University (US) are the only others with similar designations). OSU consistently ranks as the state’s top earner in research funding.


Research has played a central role in the university’s overall operations for much of its history. Most of The Oregon State University’s research continues at the Corvallis campus, but an increasing number of endeavors are underway at various locations throughout the state and abroad. Research facilities beyond the campus include the John L. Fryer Aquatic Animal Health Laboratory in Corvallis, the Seafood Laboratory in Astoria and the Food Innovation Laboratory in Portland.

The university’s College of Earth, Ocean and Atmospheric Sciences (CEOAS) operates several laboratories, including the Hatfield Marine Science Center and multiple oceanographic research vessels based in Newport. CEOAS is now co-leading the largest ocean science project in U.S. history, the Ocean Observatories Initiative (OOI). The OOI features a fleet of undersea gliders at six sites in the Pacific and Atlantic Oceans with multiple observation platforms. CEOAS is also leading the design and construction of the next class of ocean-faring research vessels for The National Science Foundation (US), which will be the largest grant or contract ever received by any Oregon university. The Oregon State University also manages nearly 11,250 acres (4,550 ha) of forest land, including the McDonald-Dunn Research Forest.

The 2005 Carnegie Classification of Institutions of Higher Education recognized The Oregon State University as a “comprehensive doctoral with medical/veterinary” university. It is one of three such universities in the Pacific Northwest to be classified in this category. In 2006, Carnegie also recognized The Oregon State University as having “very high research activity,” making it the only university in Oregon to attain these combined classifications.

The National Sea Grant College Program was founded in the 1960s. The Oregon State University is one of the original four Sea Grant Colleges selected in 1971.

In 1967 the Radiation Center was constructed at the edge of campus, housing a 1.1 MW TRIGA Mark II Research Reactor. The reactor is equipped to utilize Highly Enriched Uranium (HEU) for fuel. U.S. News & World Report’s 2008 rankings placed The Oregon State University eighth in the nation in graduate nuclear engineering.

The Oregon State University was one of the early members of the federal Space Grant program. Designated in 1991, the additional grant program made The Oregon State University one of only 13 schools in the United States to serve as a combined Land Grant, Sea Grant and Space Grant university. Most recently, The Oregon State University was designated as a federal Sun Grant institution. The designation, made in 2003, makes The Oregon State University one of only three such universities (the others being Cornell University (US) and The Pennsylvania State University (US)) and the first of two public institutions with all four designations (the other being Penn State).

In 2001, The Oregon State University’s Wave Research Laboratory was designated by The National Science Foundation (US) as a site for tsunami research under the Network for Earthquake Engineering Simulation. The O. H. Hinsdale Wave Research Laboratory is on the edge of the campus and is one of the world’s largest and most sophisticated laboratories for education, research and testing in coastal, ocean and related areas.

The National Institute of Environmental Health Sciences funds two research centers at The Oregon State University. The Environmental Health Sciences Center has been funded since 1969 and the Superfund Research Center has been funded since 2009.

The Oregon State University administers the H.J. Andrews Experimental Forest, a United States Forest Service facility dedicated to forestry and ecology research. The Andrews Forest is a UNESCO International Biosphere Reserve.

The Oregon State University’s Open Source Lab is a nonprofit founded in 2003 and funded in part by corporate sponsors that include Facebook, Google, and IBM. The organization’s goal is to advance open source technology, and it hires and trains The Oregon State University students in software development and operations for large-scale IT projects. The lab hosts a number of projects, including a contract with the Linux Foundation.