In a study published this week in the journal Global Change Biology, SF State Assistant Professor of Biology Jonathon Stillman and colleagues show how climate-driven changes in nitrogen sources and carbon dioxide levels in seawater could work together to make Emiliania huxleyi a less effective agent of carbon storage in the deep ocean, the world's largest carbon sink.
Changes to this massive carbon sink could have a critical effect on the planet's future climate, Stillman said, especially as atmospheric carbon dioxide levels continue to rise sharply as a result of fossil fuel burning and other human activities.
While floating free in the sunny top layers of the oceans, the phytoplankton develop elaborate plates of calcified armor called coccoliths. The coccoliths form a hard and heavy shell that eventually sinks to the ocean depths. "About 80 percent of inorganic carbon trapped down there is from coccoliths like these," said Stillman.
Stillman and his colleagues wanted to discover how ocean acidification and changes in the ocean's nitrogen cycle—both hallmarks of climate warming—might effect coccolith development. So they raised more than 200 generations of Emiliania huxleyi in the lab, adjusting carbon dioxide levels and the type of nitrogen in the phytoplankton's seawater bath.
They found that high levels of carbon dioxide—which make the water more acidic—along with a shift in the prevailing nitrogen type from nitrates to ammonium—"had a synergistic effect" on the phytoplankton's biology and growth.
In particular, coccoliths formed under conditions of high carbon dioxide and high ammonium levels were incomplete or hollow, and contained less than the usual amount of inorganic carbon, the researchers noted.
"The ratio of inorganic to organic carbon is important," Stillman explained. "As inorganic carbon increases, it adds more ballast to the hard shell, which makes it sink and makes it more likely to be transported to the deep ocean. Without this, the carbon is more likely to be recycled into the Earth's atmosphere."
"Our results suggest in the future there will be overall lower amounts of calcification and overall lower amount of transport of carbon to the deep ocean," he added.
Emiliania huxleyi typically use nitrates to make proteins, but this form of nitrogen may be in shorter supply for the phytoplankton as the world's oceans grow warmer and more acidic, Stillman and colleagues suggest. In the open ocean, nitrates are upwelled from deep waters, but a thickening layer of warmer surface water could inhibit this upwelling. At the same time, the warmer temperatures favor bacteria that turn recycled nitrogen from surface waters and the atmosphere into ammonium, and acidification inhibits the bacteria that turn ammonium into nitrate.
"It is likely that in the future, the ocean surface will contain more ammonium," which the phytoplankton will assimilate instead of nitrates, Stillman suggested. "Metabolizing nitrogen as ammonium versus nitrates requires different biochemical constituents that impact how well the cells make their coccoliths. They will survive just fine, but their biology will be different as a result."
The study by Stillman and colleagues is the first to look at the intertwined effects of ocean acidification and changes in nitrogen on phytoplankton like Emiliania huxleyi. It's also one of the first studies to observe these effects continuously over a long time scale, "so the responses of the phytoplankton are likely what we'll see in the ocean itself," Stillman said.
Stephane Lefebrve, the SF State postdoctoral student who developed the experiments for the study, said he is now looking for phytoplankton genes that "will help us to build the genetic blueprint of their responses to elevated carbon dioxide and a nitrogen source"
Lefebvre, Ina Benner, Alexander Parker, Michelle Drake, Pascale Rossignol, Kristine Okimura, Tomoko Komada, and Edward Carpenter, all from SF State's Romberg Tiburon Center for Environmental Studies, were co-authors on the Global Change Biology study.
"Nitrogen source and pCO2 synergistically affect carbon allocation, growth and morphology of the coccolithophore Emiliania huxleyi: implications of ocean acidification for the carbon cycle," was published online in October by the journal Global Change Biology.
Jonathon Stillman and Stephane Lefebvre may be reached by contacting Nan Broadbent at SF State: firstname.lastname@example.org or at 415-338-7108.
Nan Broadbent | EurekAlert!
New catalyst controls activation of a carbon-hydrogen bond
21.11.2017 | Emory Health Sciences
The main switch
21.11.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
21.11.2017 | Physics and Astronomy
21.11.2017 | Physics and Astronomy
21.11.2017 | Life Sciences