|
Growing Marine Plants Need Their VitaminsVitamin B12 has impacts on the ocean food web and Earth's climate |
|
|
 | |  |
|
| Enlarge ImageWHOI biogeochemists and colleagues found evidence that vitamin B12 plays a vital and previously overlooked role in the ocean food web and Earth's climate. Their research was published in the May 2007 issue of Limnology & Oceanongraphy. From right to left: MIT/WHOI Joint Program graduate students, Erin Bertrand and Abigail Noble, and assistant scientist Mak Saito, aboard the icebreaker Nathaniel B. Palmer. |
|
|  |
|
| Enlarge ImageScientists from research institutions around the world convened for expeditions in 2005 and 2006 aboard the icebreaker Nathaniel B. Palmer to the Ross Sea near Antarctica, 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 taking 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. (Yuanyuan Feng, University of Delaware ) |
|
|  |
|
| Enlarge ImageScientists use a long pole and scooper to capture samples of algae found under the sea ice in the Ross Sea. (Rob Dunbar, Stanford University) |
|
|  |
|
| Enlarge ImageB12 contains the metal cobalt and is required by many living things. Both cobalt and the vitamin are rare in the oceans, and scientists wondered if they played a role in marine ecosystems. (Mak Saito, Woods Hole Oceanographic Institution) |
|
|  |
|
| Enlarge ImageAs well as bountiful plant life, the Ross Sea is also filled with mammoth icebergs. (Rob Dunbar, Stanford University) |
|
|
Related Files |
|
|
|
|
|
Related Links |
|
|
Your mother was right: You need your vitamins. And that turns out to be true for life in the oceans, too.
B12—an essential vitamin for land-dwelling animals, including
humans—also plays a vital and previously overlooked role in determining
how microscopic plants will bloom in the sea, according to a new study
led by biogeochemists at Woods Hole Oceanographic Institution.
These plants (called phytoplankton) have critical impacts on the marine
food web and on Earth’s climate. Via photosynthesis, they draw huge
amounts of carbon dioxide, a greenhouse gas, from the air,
incorporating carbon into their bodies. When they die or are eaten,
much of the carbon ends up sinking 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 scientists wondered whether the vitamin was also important in the
ocean, where B12 and cobalt are both found in exceedingly low
concentrations—especially around Antarctica, where the only nearby
continent (a usual 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.
Bertrand, Saito, and colleagues collected water samples from three
locales in the highly fertile Ross Sea off Antarctica during a 2005
expedition 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,” wrote Bertrand and Saito
in the May 2007 issue of the journal Limnology and Oceanography.
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 that the adding more B12 benefits
diatoms—indicate that Phaeocystis
may have a competitive advantage over diatoms in the Ross Sea in
spring, when populations of B12-manufacturing
bacteria and archaea (and therefore B12 supplies) are low.
Phaeocystis effectively
monopolize the B12 supply by forming colonies cemented by sticky mucous
that attracts B12-making bacteria, the scientists 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, the bacteria are eaten or decomposed, and B12 is released
back to the ocean, becoming available to be used by diatoms.
The finding underscores the complexities of the marine food web and
raises questions about how climate change could affect the delicately
balanced ecosystem—and vice versa.
— Lonny Lippsett
The National Science Foundation
funded the 2005 Controls on Ross Sea Algal Community Structure
expedition. Erin Bertrand was a Carl and Pancha Peterson Summer Research
Fellow at WHOI and is now a graduate student in the MIT/WHOI Joint
Program.
Posted: June 7, 2007 [top] |
|
