Featured Research

from universities, journals, and other organizations

Iron Isotopes As A Tool In Oceanography

Date:
August 4, 2009
Source:
National Oceanography Centre, Southampton
Summary:
New research highlights the potential utility of iron isotopes for addressing important questions in ocean science.

William Homoky of NOCS measuring iron isotopes.
Credit: Image courtesy of National Oceanography Centre, Southampton

New research involving scientists from the National Oceanography Centre, Southampton (NOCS) highlights the potential utility of iron isotopes for addressing important questions in ocean science. The findings are published in the August edition of the journal Geology.

Large regions of the world’s oceans have low primary production despite having plenty of macronutrients such as phosphate, nitrate and silicate. This is due a shortage of the essential micro-nutrient iron, which is needed for the growth of phytoplankton. These tiny, plant-like organisms sit at the base of the marine food chain and collectively draw vast amounts of the greenhouse gas carbon dioxide down from the atmosphere through the process of photosynthesis. 

A proportion of the carbon is exported to the deep ocean, making the oceans a major carbon dioxide sink, without which global warming would rapidly accelerate. The natural supply of iron to such ‘High Nutrient Low Chlorophyll (HNLC) regions is therefore, albeit indirectly, an important determinant of climate.

The importance of dissolved iron in seawater derived from bottom (benthic) sediments is increasingly recognised as being important. Around the continental margins, in particular, iron is released from the sediments during the decomposition of organic carbon by dissimilatory iron-reducing bacteria - micro-organisms that use elemental iron to obtain energy. This leads to the enrichment of iron in pore fluids and bottom waters. However the ubiquity of sedimentary iron inputs to seawater remains unknown.

Different biological and chemical processes can leave behind characteristic isotopic ‘fingerprints’. Of specific interest here, iron isotopes in sediment pore fluids may be a unique tracer of sediment respiration by dissimilatory iron-reducing bacteria.

Dissimilatory iron reduction is thought to be one of the earliest metabolic pathways on Earth , thus sedimentary iron isotopes may also be useful in reconstructing past iron cycling in the ancient ocean.

Pore-fluid iron isotope measurements have so far been restricted to the continental shelves where the supply of carbon is typically high and dissimilatory iron reduction is extensive, precluding comparisons with low-carbon, deep-water environments.  William Homoky, who is a research student at the University of Southampton’s School of Ocean and Earth Sciences based at NOCS, and his colleagues have helped fill this gap be measuring iron isotopes in pore fluids from both the Eel River shelf on the northern California margin (120 m water depth), and deep-sea sediments from the Southern Ocean around the Crozet Island Plateau (3000–4000 m water depth), about 1400 miles southeast of South Africa.

"We are excited by our findings not only because they represent the first measurements of their kind, but because they are telling us something important about iron cycling processes in the deep-sea, which can inform future iron isotope investigations in ancient rocks and the modern oceans," said William Homoky.

They find that the composition of iron isotopes in the pore fluids reflects the different extent of sedimentary iron recycling between the two sites. Specifically, the pore-fluid iron isotope compositions reflect the extent of iron recycling during early diagenesis, which is driven by organic carbon inputs from the overlying water column.

The researchers believe that iron isotope processing in carbon-limited environments, such as the deep-sea, is important and that it should help future interpretations of the rock record. “Additionally,” they say, “the unique isotopic fingerprint of pore fluid iron in continental shelf settings is confirmed, highlighting the potential for iron isotopes to trace the inputs of continental shelf-derived iron in seawater.”

Current thesis research aims to improve our understanding of iron cycling between sediments and seawater and compares the affects of contrasting sediment geochemistry on iron flux generating processes.

"In the future I would like to examine processes of sedimentary iron cycling in the high-latitudes, where sediments are subject to enhanced rates of environmental change due to changing climate in these regions," said Homoky.

This work was supported by the UK Natural Environment Research Council (NERC) and the US National Science Foundation (NSF). Research cruises were undertaken on the RV Wecoma and the RRS Discovery.


Story Source:

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


Journal Reference:

  1. Homoky, W., S. Severmann, S., Mills, R., Statham, P. & Fones, G. Pore-fluid Fe isotopes reflect the extent of benthic Fe redox recycling: Evidence from continental shelf and deep-sea sediments. Geology, 37, 751-754 (2009)

Cite This Page:

National Oceanography Centre, Southampton. "Iron Isotopes As A Tool In Oceanography." ScienceDaily. ScienceDaily, 4 August 2009. <www.sciencedaily.com/releases/2009/07/090731090015.htm>.
National Oceanography Centre, Southampton. (2009, August 4). Iron Isotopes As A Tool In Oceanography. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2009/07/090731090015.htm
National Oceanography Centre, Southampton. "Iron Isotopes As A Tool In Oceanography." ScienceDaily. www.sciencedaily.com/releases/2009/07/090731090015.htm (accessed July 31, 2014).

Share This




More Earth & Climate News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) — Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Florida Panther Rebound Upsets Ranchers

Florida Panther Rebound Upsets Ranchers

AP (July 31, 2014) — With Florida's panther population rebounding, some ranchers complain the protected predators are once again killing their calves. (July 31) Video provided by AP
Powered by NewsLook.com
Big Waves In Arctic Ocean Threaten Polar Ice

Big Waves In Arctic Ocean Threaten Polar Ice

Newsy (July 30, 2014) — Big waves in parts of the Arctic Ocean are unprecedented, mainly because they used to be covered in ice. Video provided by Newsy
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) — Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) 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