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: email@example.com or at 415-338-7108.
Nan Broadbent | EurekAlert!
Atomic-level motion may drive bacteria's ability to evade immune system defenses
24.04.2017 | Indiana University
Two-dimensional melting of hard spheres experimentally unravelled after 60 years
24.04.2017 | University of Oxford
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Physics and Astronomy
24.04.2017 | Materials Sciences
24.04.2017 | Life Sciences