Even in the Oceans, Living Things Need Their Vitamins

Article excerpt

Your mother was right: You need your vitamins. And that turns out to be true for life in the oceans, too.

[B.sub.12]--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 is transferred to the ocean depths, where it cannot re-enter the atmosphere.

[B.sub.12] contains the metal cobalt and can be synthesized only by certain singled-celled bacteria and archaea. Humans, animals, and many algae require [B.sub.12] to manufacture essential proteins, but they cannot make it and must either acquire it from the environment or eat food that contains [B.sub.12], said the study's lead authors, Erin Bertrand and Mak Saito.

The scientists wondered whether the vitamin was also important in the ocean, where [B.sub.12] and cobalt are both found in exceedingly low concentrations--especially around Antarctica, where the only nearby continent (a common 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 [B.sub.12] and iron (another essential nutrient for plant growth); to a second set, they added just iron; and to a third, they added neither. …