More than One: Long-Reigning Microbe Controlling Ocean Nitrogen Shares the Throne

Feb 25, 2010
More than One: Long-Reigning Microbe Controlling Ocean Nitrogen Shares the Throne
Surface accumulation of the nitrogen-fixing microbe Trichodesmium in the South Pacific Ocean. Credit: Pia Moisander

(PhysOrg.com) -- Marine scientists long believed that a microbe called Trichodesmium, a member of a group called the cyanobacteria, reigned over the ocean's nitrogen budget.

New research results reported on-line today in a paper in show that Trichodesmium may have to share its nitrogen-fixing throne: two others of its kind, small spherical species of nitrogen-fixing called UCYN-A and Crocosphaera watsonii, are also abundant in the oceans.

One of them, UCYN-A, is more widely distributed than Trichodesmium, and can live in cooler waters.

Different nitrogen-fixing cyanobacteria, scientists have discovered, have varying preferences for water temperature and other environmental factors.

Pia Moisander and Jon Zehr of the University of California at Santa Cruz and their co-authors showed that actively nitrogen-fixing UCYN-A "can be found in great abundance at higher latitudes and deeper waters than Trichodesmium," says Moisander.

"Where Trichodesmium might be thought of as a warm-water microbe, UCYN-A likes it cooler," says Zehr. "This has far-reaching implications for the geographic distribution of the ocean's 'nitrogen fixers,' and for the process of nitrogen fixation itself."

According to co-author Joseph Montoya of the Georgia Institute of Technology, "we're now beginning to develop an appreciation for the biogeography of marine nitrogen fixation, and the broad range of oceanic habitats where nitrogen fixation makes a significant contribution to the overall nitrogen budget."

Most previous estimates of global nitrogen fixation were based on distributions of or factors that control the growth of Trichodesmium.

A micrograph showing microbes called UCYN-A; they spangle the sea like a star constellation. Credit: Pia Moisander

"The results of this study," says David Garrison, program director in the National Science Foundation (NSF)'s Directorate for Geosciences, "show that these novel are found in the world's oceans in a distribution analogous to that of non-nitrogen-fixing cyanobacteria, which are widespread."

The research was also supported by NSF's Directorate for Biological Sciences and an NSF Science and Technology Center called C-MORE, the Center for Microbial Oceanography: Research and Education.

Trichodesmium, as well as UCYN-A and Crocosphaera watsonii, "fix" nitrogen in the seas, taking nitrogen gas from the air we breathe and converting it to chemical forms that other microorganisms can use to power their cellular machinery.

Nitrogen-fixing microorganisms are the key to the productivity of the oceans. Growth of microbes at the base of the food chain is dependent on nutrients like nitrogen, in the same way that agriculture on land depends on such nutrients.

Microorganisms that fix nitrogen play a central role, says Zehr, in the "vertical downward flux of organic matter to the deep ."

Life forms that are among our planet's smallest, he says, play a very large role. Through a series of steps in the process, they sequester carbon from the atmosphere, important in controlling Earth's climate.

Explore further: Stopping the leaks

Related Stories

Researchers explain nitrogen paradox in forests

Jun 18, 2008

Nitrogen is essential to all life on Earth, and the processes by which it cycles through the environment may determine how ecosystems respond to global warming. But certain aspects of the nitrogen cycle in temperate and tropical ...

Forest canopies help determine natural fertilization rates

May 29, 2008

In this week’s issue of Science, a team of researchers from the United States and Sweden report on a newly identified factor that controls the natural input of new nitrogen into boreal forest ecosystems. Nitrogen is the ...

Recommended for you

Stopping the leaks

30 minutes ago

When a big old cast-iron water main blows, it certainly makes for a spectacular media event.

Alpine lifelines on the brink

1 hour ago

Only one in ten Alpine rivers are healthy enough to maintain water supply and to cope with climate impacts according to a report by WWF. The publication is the first-ever comprehensive study on the condition ...

Research that holds water

2 hours ago

Water is a vulnerable resource coming under increasing pressure in many parts of the world. The Research Council of Norway is providing funding to a number of research projects seeking to solve challenges related to the supply ...

User comments : 0