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News Release : B12 Is Also an Essential Vitamin for Marine LifeThe vitamin has impacts on the marine food web and Earth’s climate |
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May 18, 2007
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Woods Hole Oceanographic Institution
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Enlarge Image Erin Bertrand (right) and Mak Saito, biogeochemists at Woods Hole Oceanographic Insitution, have found evidence that B12, an essential vitamin for people, also plays a critical role in ocean food web. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)
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WHOI biogeochemists (from right, MIT/WHOI Joint Program graduate students, Erin Bertrand and Abigail Noble, assistant scientist Mak Saito, aboard the icebreaker Nathaniel B. Palmer) found that vitamin B plays a vital and previously overlooked role in in the ocean food web and Earth's climate. The research was published in the May 2007 issue of Limnology & Oceanongraphy.
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Enlarge Image Scientists from research institutions around the world convened for expeditions in 2005 and 2006 aboard the icebreaker Nathaniel B. Palmer to the Ross Sea near Antartica, which teems with small plants, known as algae, in spring and summer. The algae have an impact on Earth's climate by using carbon dioxide, a greenhouse gas, from the atmosphere and then bringing carbon down to the depths when they die and sink. The CORSACS (Controls on Ross Sea Algal Community Structure) project, funded by the National Science Foundation, explored the myriad factors that regulate the Ross Sea ecosystem. (Photo by Yuanyuan Feng, University of Delaware )
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Enlarge Image Scientists use a long pole and scooper to capture samples of algae found under the sea ice in the Ross Sea. (Photo by Rob Dunbar, Stanford University )
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Enlarge Image As well as bountiful plant life, the Ross Sea is also filled with mammoth icebergs. (Photo by Rob Dunbar, Stanford University)
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Enlarge Image The structure of Vitamin B12 (Mak Saito, Woods Hole Oceanographic Institution)
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| May 18, 2007Source: Media Relations
B12—an essential vitamin for land-dwelling
animals, including humans—also turns out to be an essential ingredient
for growing marine plants that are critical to the ocean food web and
Earth’s climate, scientists have found.
The presence or absence of B12 in the ocean plays
a vital and previously overlooked role in determining where, how much,
and what kinds of microscopic algae (called phytoplankton) will bloom
in the sea, according to a study published in the May issue of the
journal Limnology and Oceanography.
These photosynthesizing plants, in turn, have a critical impact on
Earth’s climate: They draw huge amounts of carbon dioxide, a greenhouse
gas, from the air, incorporating carbon into their bodies. When they
die or are eaten, carbon is transferred to the ocean depths, where it
cannot re-enter the atmosphere.
B12 contains the metal cobalt and can be
synthesized only by certain singled-celled bacteria and archaea.
Humans, animals, and many algae require B12 to
manufacture essential proteins, but they cannot make it and must either
acquire it from the environment or eat food that contains B12, said the study’s lead authors, Erin
Bertrand and Mak Saito. The two biogeochemists at the Woods Hole
Oceanographic Institution wondered whether the vitamin was also
important in the ocean, where B12 and cobalt are
both found in exceedingly low concentrations.
Bertrand, Saito, and colleagues collected water samples from three
locales in the highly fertile Ross Sea off Antarctica during an
expedition in 2005 aboard the icebreaker Nathaniel B. Palmer. To one
set of samples, they added B12 and iron (another
essential nutrient for plant growth); to a second set, they added just
iron; and to a third, they added neither. Samples stimulated with both
iron and B12 showed significantly higher
concentrations of plant life in general and greater concentrations of a
particular type of marine algae called diatoms.
“The possibility that a vitamin could substantially influence
phytoplankton growth and community composition in the marine
environment is a novel and exciting finding,” the study’s authors
wrote.
The finding underscores the complexities of the marine food web and
raises questions about the delicately balanced ecosystem’s
vulnerabilities to changing climate. It also sheds light on the sources
and cycling of vitamin B12 and cobalt in the
ocean, especially in the Southern Ocean around Antarctica, where the
only nearby continent—a standard source of metal particles blown into
the sea—is largely ice-covered.
Nevertheless, polar regions harbor some of the most extensive
phytoplankton blooms in the world and are believed to play a
significant role in exporting carbon to the deep ocean. In the Ross
Sea, spectacular spring blooms of marine algae called Phaeocystis
antarctica dissipate by summer and are followed by blooms of diatoms.
The scientists’ experiments—showing more diatom growth with the
addition of B12—indicate that Phaeocystis may
have a competitive advantage over diatoms in the Ross Sea’s springtime.
The sea contains bacteria and archaea that make B12, but their populations are low, particularly
in the spring, and so B12 supplies are limited.
Phaeocystis effectively monopolize the B12
supply by forming colonies cemented by sticky mucous that attracts B12 -making bacteria, Bertrand and Saito
theorize. In a symbiotic relationship, the algae get their required
vitamin and the bacteria get a steady supply of carbon made by the
plants. When Phaeocystis dies off and the bacteria are eaten or
decomposed, B12 is released once again to the
ocean and is available to be used by diatoms.
Any disruption in the timing or abundances of these microbial
populations has ramifications on the ecosystem and the climate, the
scientists said. For example, Phaeocystis antarctica in the Ross Sea
takes up more carbon dioxide than diatoms, so if the marine community
shifts to diatoms, the Ross Sea would likely remove less carbon dioxide
from the atmosphere. Unlike diatoms, Phaeocystis also produce a
compound called dimethylsulfioniopriopionate, or DMSP, which is
released into the air and helps produce clouds that block solar
radiation.
Polar oceans do not have large bacterial populations to produce B12, making the vitamin a critical factor
influencing the food web, the cycling of carbon in the ocean, and the
climate, Bertrand and Saito said. At the same time, climate changes
could affect the availability of B12 by causing
changes in ocean temperatures, bacterial populations, and other
factors. The ozone hole produced in the austral spring above Antarctica
could also induce a cascade of effects by allowing more penetration of
ultraviolet radiation that is known to degrade B12, they said.
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The National Science Foundation
Office of Polar Program provided funding for the 2005 Controls on Ross
Sea Algal Community Structure (CORSACS) expedition. Erin Bertrand was a
Carl and Pacha Peterson Summer Research Fellow at WHOI and is now a
graduate student in the MIT/WHOI Joint Program.
Last updated: November 20, 2009 |
