Featured Research

from universities, journals, and other organizations

Mapping Nutrient Distributions Over The Atlantic Ocean

Date:
December 30, 2009
Source:
National Oceanography Centre, Southampton (UK)
Summary:
Large-scale distributions of two important nutrient pools -- dissolved organic nitrogen and dissolved organic phosphorus have been systematically mapped for the first time over the Atlantic Ocean in a new study. The findings have important implications for understanding nitrogen and phosphorus biogeochemical cycles and the biological carbon pump in the Atlantic Ocean.

Shows in the two upper panels the distribution of the dissolved inorganic nutrients, nitrate (NO3) and phosphate (PO4). Here one can appreciate the vast areas of the Atlantic where inorganic nutrients are very low (most of it looks pinky, and pink colour indicated extremely low concentrations). The middle panels show the distributions of dissolved organic nitrogen and dissolved organic phosphorus, where the regions where these are produced can be appreciated. Also the way the ocean circulation and eddies redistribute these nutrients can be clearly seen. Finally, the lower panels show the contribution (in percent) of dissolved organic nutrients towards the Total nutrient pools in the surface ocean.
Credit: Image courtesy of Dr. Rory Howlett

Large-scale distributions of two important nutrient pools -- dissolved organic nitrogen and dissolved organic phosphorus (DON and DOP) have been systematically mapped for the first time over the Atlantic Ocean in a study led by Dr Sinhue Torres-Valdes of the National Oceanography Centre, Southampton. The findings have important implications for understanding nitrogen and phosphorus biogeochemical cycles and the biological carbon pump in the Atlantic Ocean.

Tiny marine plants called phytoplankton living in the sunlit surface waters of the oceans produce organic matter through the process of photosynthesis, thereby drawing carbon dioxide down from the atmosphere. Much of this organic matter is recycled, but some of it -- the so-called export production -- sinks as 'marine snow' to the deep ocean. This is also known as the biological carbon pump, and it helps to significantly reduce the CO2 released by the burning of fossil fuels (oil, gas and coal), that would otherwise accumulate in the atmosphere.

In addition to light, phytoplankton growth requires nutrients for growth. However, inorganic nutrients are in short supply in vast areas of the oceans known as oligotrophic regions or oligotrophic oceans. This means that phytoplankton must get the nutrients from somewhere else and therefore "understanding the sources and distribution of nutrients is of major interest to oceanographers," says Torres-Valdes. The new study involved scientists based at the National Oceanography Centre, Southampton and the University of Liverpool.

The scientists studied the distributions of dissolved organic nutrients during eight research cruises in the Atlantic between spring 2000 and autumn 2005. Six of these cruises sampled north-south transects between 50 degrees N and 50 degrees S, while the other two sampled east-west transects at 24 and 36 degrees N. In this way, they were able systematically to cover large tracts of the Atlantic Ocean.

"This big effort combines observations and a modelling study in order to understand the role dissolved organic nutrients play in export production" said Torres-Valdes: "The large scale distributions revealed very interesting things: First, nutrient pools in surface waters are dominated by dissolved organic nutrients, making up typically more that 75% of the total nutrient pools in the upper 100 metres of the oligotrophic Atlantic Ocean. Second, patterns emerged showing differences exist between the extensive oligotrophic North and South Atlantic subtropical gyres. DON and DOP concentrations are lower in the North Atlantic. These differences are more striking in the case of DOP, which is very low in the North Atlantic subtropical gyre."

This is important because export production over the nutrient poor, or 'oligotrophic' subtropical gyres is thought to account for up to half of global oceanic carbon export. The patterns observed probably reflect differences in how dissolved organic nutrients are recycled, with DON being mostly refractory. DOP seems more easily taken up by organisms than DON. In the North Atlantic subtropical gyre, DOP may actually provide the extra phosphorus required by microbes that 'fix' nitrogen.

The researchers also used a computer model to study the effect of cycling and transport on export production. The modelling work shows that both DON and DOP are important. While DON contributes up to 40% of the particulate nitrogen export, DOP contributes up to 70% of the modelled particulate phosphorus export. This also shows that DOP is more easily used by microbes than DON.

The observations and model results are consistent with the hypothesis that DON and DOP are important for sustaining export production in surface layers of oligotrophic gyres. Specifically, these dissolved organic nutrients are produced as a result of enhanced primary production over upwelling regions -- the tropical Atlantic more or less along the equator, off the Northwest African Coast and the North Atlantic subpolar gyre. These nutrients are then distributed by the ocean circulation, with a very important eddy component, and are then used and recycled as they are transported.

"It's very likely that this situation also applies to many nutrient-poor marine systems, including other subtropical gyres, the Mediterranean Sea, and summer, stratified shelf seas," said Torres-Valdes.

The study was supported by the UK Natural Environment Research Council.

The researchers are Sinhue Torres-Valdes NOCS), V. Roussenov (University of Liverpool), Richard Sanders (NOCS), S. Reynolds, S. (U. Liverpool; now at the British Oceanographic Data Centre, Liverpool, X. Pan (NOCS; now at the British Oceanographic Data Centre), R. Mather U. (Liverpool), A. Landolfi (NOCS; now at Leibniz-Institut Fur Meereswissenschaften, Marine), G. Wolff (U. Liverpool), Eric Achterberg (NOCS) and R. G. Williams (U. of Liverpool).


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. Torres-Valdιs et al. Distribution of dissolved organic nutrients and their effect on export production over the Atlantic Ocean. Global Biogeochemical Cycles, 2009; 23 (4): GB4019 DOI: 10.1029/2008GB003389

Cite This Page:

National Oceanography Centre, Southampton (UK). "Mapping Nutrient Distributions Over The Atlantic Ocean." ScienceDaily. ScienceDaily, 30 December 2009. <www.sciencedaily.com/releases/2009/11/091103112237.htm>.
National Oceanography Centre, Southampton (UK). (2009, December 30). Mapping Nutrient Distributions Over The Atlantic Ocean. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2009/11/091103112237.htm
National Oceanography Centre, Southampton (UK). "Mapping Nutrient Distributions Over The Atlantic Ocean." ScienceDaily. www.sciencedaily.com/releases/2009/11/091103112237.htm (accessed October 22, 2014).

Share This



More Earth & Climate News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) — He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com
How Detroit's Money Woes Led To U.N.-Condemned Water Cutoffs

How Detroit's Money Woes Led To U.N.-Condemned Water Cutoffs

Newsy (Oct. 20, 2014) — The United Nations says water is a human right, but should it be free? Detroit has cut off water to residents who can't pay, and the U.N. isn't happy. Video provided by Newsy
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) — Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
White Rhino's Death In Kenya Means Just 6 Are Left

White Rhino's Death In Kenya Means Just 6 Are Left

Newsy (Oct. 20, 2014) — Suni, a rare northern white rhino at Ol Pejeta Conservancy, died Friday. This, as many media have pointed out, leaves people fearing extinction. Video provided by Newsy
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:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

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