Featured Research

from universities, journals, and other organizations

Iron Controls Patterns Of Nitrogen Fixation In The Atlantic

Date:
January 7, 2010
Source:
National Oceanography Centre, Southampton (UK)
Summary:
Scientists have discovered that interactions between iron supply, transported through the atmosphere from deserts, and large-scale oceanic circulation control the availability of a crucial nutrient, nitrogen, in the Atlantic. Their findings have potentially important implications for understanding global climate, both past and future.

This is the experimental set-up on the Royal Research Ship Discovery.
Credit: Dr Mark Moore (NOCS)

Scientists including researchers from the National Oceanography Centre, Southampton and the University of Essex have discovered that interactions between iron supply, transported through the atmosphere from deserts, and large-scale oceanic circulation control the availability of a crucial nutrient, nitrogen, in the Atlantic. Their findings have potentially important implications for understanding global climate, both past and future.

Nitrogen is an essential element for life, but in its gaseous form (N2) cannot be used by most organisms. To be useful, nitrogen has to be 'fixed' by combining it with other chemicals to form compounds such as ammonium. 'Diazotrophic' microbes such as the blue-green bacterium Trichodesmium are equipped with the enzymes needed to perform these energy-demanding transformations.

Nevertheless, over most of the ocean, a relative shortage of fixed nitrogen limits the growth of phytoplankton -- microscopic marine plants -- and their uptake of the greenhouse gas carbon dioxide through photosynthesis. Fixed nitrogen is ultimately removed by denitrification, whereby it is converted back to N2. The rate at which it is replaced depends on many factors including the availability of other crucial nutrients such as iron and phosphate needed by nitrogen-fixing microbes for growth.

Work over the last decade or so has hinted at iron availability being a significant control on oceanic nitrogen fixation, primarily because the enzyme responsible contains a lot of this element. However, other recent research had reinforced the long held view that phosphorus is the more important controlling factor. The new findings reaffirm the view that an adequate supply of iron is crucial, which, although frequently quoted, had previously been supported by little clear evidence.

"Our new data provides some of the first really conclusive evidence that iron availability is playing a significant roll in controlling the input of fixed nitrogen, at least to the Atlantic Ocean," said lead author Dr Mark Moore of the University of Southampton's School of Ocean and Earth Science based at the National Oceanography Centre.

Detailed measurements of nutrients and microbiology were made by an international team aboard the Royal Research Ship RRS Discovery during a 10,000-kilometre cruise along a meridional transect between 37°N -- 35°S in the Atlantic Ocean in 2005.

Iron-rich dust blown over the North Atlantic from the Sahara desert allows the growth of diazotrophic Trichodesmium species, which fix large amounts of nitrogen and use up excess phosphate. In contrast, diazotrophs in the South Atlantic appear more severely limited by iron availability.

These observations, backed up by a large-scale physical analysis of the Atlantic circulation, also indicated that the North Atlantic is a net source of fixed nitrogen to the world's oceans.

In addition to highlighting the importance of iron in controlling global patterns of nitrogen fixation, the potential for interaction with the overturning circulation leads to novel conclusions concerning the global nitrogen cycle.

Specifically, it appears that nitrogen fixation in the north Atlantic basin, immediately upstream of the formation region for half the global deep waters, will have a much greater influence on ocean-atmosphere partitioning of carbon dioxide than recently proposed hotspots of nitrogen fixation around the edges of denitrification zones.

"Any interactions between large-scale overturning circulation and nitrogen fixation may potentially have important consequences for understanding how the nitrogen cycle reacted to past climate change, and also how it might react in the future," says Dr Moore.

He acknowledges, however, that there is still a lot of work to be done and that many of the details concerning the supply of nutrients for nitrogen fixation remain to be worked out: "We still need to identify the sources of iron which are presumably required to support nitrogen fixation in other regions, alongside making further improvements to our understanding of how oceanic circulation supplies the required excess phosphorus."

But what is clear from the study is that past and future climate changes in both atmospheric dust transport and ocean circulation may impact the fixed nitrogen inventory and consequently have a global-scale influence on the ability of the ocean to sequester carbon dioxide.

The work was supported by the European Union Carboocean integrated project, the UK Natural Environment Research Council and the Atlantic Meridional Transect consortium.

The researchers are: C. Mark Moore (SOES/NOCS and University of Essex), Matthew Mills (Stanford University), Eric P. Achterberg (SOES/NOCS), Richard Geider (University of Essex), Julie La Roche (Leibniz-Institut für Meereswissenschaften, Kiel), Mike Lucas (University of Cape Town), Elaine L. McDonagh (NOCS), Xi Pan (NOCS), Alex Poulton (NOCS), Micha Rijkenberg (NOCS), David Suggett (University of Essex), Simon Ussher (University of Plymouth), and E. Malcolm S. Woodward (Plymouth Marine Laboratory).


Story Source:

The above story is based on materials provided by National Oceanography Centre, Southampton (UK). Note: Materials may be edited for content and length.


Journal Reference:

  1. Moore, C. M., et al. Large-scale distribution of Atlantic nitrogen fixation controlled by iron supply. Nature Geoscience, Published online 1 November 2009 DOI: 10.1038/Ngeo667

Cite This Page:

National Oceanography Centre, Southampton (UK). "Iron Controls Patterns Of Nitrogen Fixation In The Atlantic." ScienceDaily. ScienceDaily, 7 January 2010. <www.sciencedaily.com/releases/2009/11/091102121628.htm>.
National Oceanography Centre, Southampton (UK). (2010, January 7). Iron Controls Patterns Of Nitrogen Fixation In The Atlantic. ScienceDaily. Retrieved August 29, 2014 from www.sciencedaily.com/releases/2009/11/091102121628.htm
National Oceanography Centre, Southampton (UK). "Iron Controls Patterns Of Nitrogen Fixation In The Atlantic." ScienceDaily. www.sciencedaily.com/releases/2009/11/091102121628.htm (accessed August 29, 2014).

Share This




More Earth & Climate News

Friday, August 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) — State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Scientists Have Figured Out Why Rocks Move In Death Valley

Scientists Have Figured Out Why Rocks Move In Death Valley

Newsy (Aug. 28, 2014) — The mystery of the moving rocks in Death Valley, California, has finally been solved. Scientists are pointing to a combo of water, ice and wind. Video provided by Newsy
Powered by NewsLook.com
Big Waves, Minor Flooding from Hurricane

Big Waves, Minor Flooding from Hurricane

AP (Aug. 27, 2014) — Thundering surf spawned by Hurricane Marie pounded the Southern California coast Wednesday, causing minor flooding in a low-lying beach town. High surf warnings were posted for Los Angeles County south through Orange County. (Aug. 27) Video provided by AP
Powered by NewsLook.com
Calif. Quake Underscores Need for Early Warning

Calif. Quake Underscores Need for Early Warning

AP (Aug. 26, 2014) — Researchers at UC Berkeley are testing a prototype of an earthquake early warning system that California is pursuing years after places like Mexico and Japan already have them up and running. (August 26) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins