Ocean micronutrient cycles: UK GEOTRACES

Lead Research Organisation: Imperial College London
Department Name: Earth Science and Engineering

Abstract

A paradigm developed during the 20th Century that the amount and type of life in the oceans depended to a large degree on the supply to the surface ocean of three nutrients - phosphate, nitrate, and silica (the macronutrients). International research efforts mapped the distribution of these macronutrients in detail and developed a full understanding of how these macronutrients are chemically cycled into, out-of, and within the oceans. Models of ocean biology and the global carbon cycle now incorporate this understanding. In the early 1990s, however, it became clear that this view of ocean nutrients was incomplete. New ability to sample seawater without contaminating it, and to make sensitive measurements, demonstrated that a range of metals, present at low concentrations in seawater, were required by life. Of these 'micronutrients', the most prominent is iron which is now known to be the major limitation on life in large areas of the ocean. Other micronutrients, such as zinc and cobalt, are also essential for critical biological processes. Despite their importance, our knowledge of the chemical cycle of these micronutrients is rudimentary, particularly compared to that of the macronutrients. We know micronutrients enter the ocean in dust, but the size of other inputs (from rivers, alteration of sediments, or from undersea volcanoes) is not known. Even the distribution of these micronutrients in the ocean is poorly known and measurements are sparse, particularly in the deep ocean. To understand controls on life and the carbon cycle in the ocean, there is an urgent need to dramatically improve knowledge of the distribution and cycling of micronutrients. This is the goal of a major new international research programme - GEOTRACES. The programme seeks to develop an understanding of micronutrient cycles as comprehensive as that of the macronutrients, through a series of sections spanning all the ocean basins. This proposal represent the UK contribution to that programme. We will map the concentration of the seven most important micronutrients through the full water column along an east-west section at 40oS in the Atlantic. This ocean is little studied but is an important region for ocean biogeochemical cycles. In the surface at this latitude the ocean is very productive, requiring addition of micronutrients, but the source of these micronutrients is not known. At depth are found three different water masses. The uppermost flows northwards and upwells to the surface at the equator to provide micronutrients to this very productive region, while the middle layer flows southward before upwelling in the Southern Ocean where low iron supply is known to be the primary limitation on life. Understanding micronutrient inputs to these deep water masses is therefore important for life in a much broader region, and will teach us generally about the processes that control cycling of micronutrients into surface and deep waters around the globe. We will study the inputs of micronutrients from four ocean boundaries - from the atmosphere as dust blown from South America; from rivers (the large Plata River); from sediments; and from the active volcanoes found in the mid Atlantic. We will use a variety of tools - including other chemicals that act as tracers of the micronutrients, and computer models - to assess how micronutrients get from their sources into the open ocean. And we will study the relationship between these micronutrients and the nature of the ecosystems that occur in the productive seas of 40oS. This work will rely on co-operation between 10 leading UK institutes, including universities and research centres, and also involves leading scientists from other countries (partially through the GEOTRACES programme). This national and international effort will lead to a significant improvement in our understanding of the cycles of the metals that control the biology and carbon system in the ocean.

Publications


10 25 50
Bridgestock L (2016) Return of naturally sourced Pb to Atlantic surface waters. in Nature communications
Mawji E (2015) The GEOTRACES Intermediate Data Product 2014 in Marine Chemistry
Paul M (2015) Tracing the Agulhas leakage with lead isotopes in Geophysical Research Letters
 
Description This project has facilitated the analytical development work to perform the first precise and accurate lead isotope analyses in seawater and to produce the first high quality data set for trace and major elements in aerosols in the Southern Atlantic Ocean (SAO). Such measurements are only performed by a few laboratories world-wide, but hold the potential for unprecedented insights (i) in tracking anthropogenic lead and using it as an tracer for water mass exchange and movement in the ocean and (ii) into the sources of micronutrients into the SAO. A paper detailing the results has been published in 2015 (Paul et al., Anal Chim Acta, 2015)
Samples from depth profiles and surface seawater along the UK GEOTRACES 40S transect in the South Atlantic have been successfully analysed and results are currently being written up for publication. A first paper on the has now been published (2015) where we show that lead isotopes successfully identify the transport of water masses from the Indian Ocean to the Atlantic Ocean through the Aghuelas Current - that is a very important finding with respect to trace element dynamics in the ocean. (Paul et al., Geophys Res Letters, 2015)

Work on aerosol samples collected from the same cruise is in progress and will upon completion complement the seawater analysis by providing additional constraints on sources of anthropogenic and natural Pb to the South Atlantic.
Exploitation Route The Pb isotope data established for the Southern Atlantic Ocean is currently used by physical oceanographers to develop the first model for Pb circulation in the world oceans. A proposal has also been submitted by Rehkamper and van de Flierdt.

The analytical methods implemented during the project are used by the various investigators for developing their research portfolio.
PI Weiss has set up a air monitoring system in the Amazon forest with follow up funding from the EU
Co-I Rehkamper has developed his research into the dynamics of nanoparticles in collaboration with a wide range of scientists (biologists, toxicologists)
Co-I van de Flierdt has been developing work into nuclear forensics and is a key part of the Pb modeling efforts
The Geotraces Programm has also led to further work into the ocean chemistry of trace elements such as As, Sb, Cd, Zn by the three investigators
Sectors Environment
URL http://www.ukgeotraces.com
 
Description We have used the findings of this work and the technique and experience developed to install and develop a passive sampler that we have been employing in the Amazon. That led to a monitoring network for particulate matter in the Amazon. We used this passive sampler technology now also to study aerosols in London and test its air quality. In a very recent paper, we showed that Cu and Zn isotopes suggest that tires and brakes are the main sources of these toxic metals in the atmospheric environment in London.
First Year Of Impact 2015
Sector Environment
Impact Types Societal,Economic
 
Description RS Meeting of Young Scientists between Australia and the United Kingdom
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a national consultation
 
Description CLIM AMAZON
Amount £90,000 (GBP)
Organisation European Research Council (ERC) 
Sector Public
Country European Union (EU)
Start 11/2012 
End 10/2015
 
Description PhD scholarship from Islamic Development Bank
Amount £70,000 (GBP)
Organisation Islamic Development Bank (IDB) 
Sector Private
Country Saudi Arabia, Kingdom of
Start 03/2017 
End 02/2021
 
Description Revisiting the Neodymium Paradox
Amount £365,608 (GBP)
Funding ID NE/J021636/1 
Organisation Natural Environment Research Council (NERC) 
Sector Public
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 09/2012 
End 03/2017
 
Description SOUTHERNCHANGE
Amount £180,000 (GBP)
Organisation European Research Council (ERC) 
Sector Public
Country European Union (EU)
Start 10/2016 
End 09/2018
 
Title Geotraces Data base 
Description Data base for geotraces data bank 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact this data is now used to develop a Pb ocean model 
URL http://www.bodc.ac.uk/geotraces/
 
Description UK Geotracers Consortium 
Organisation University of East Anglia
Department School of Environmental Sciences UEA
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution work on work package 4
Collaborator Contribution consortium partners
Impact papers further funding
Start Year 2010
 
Description UK Geotracers Consortium 
Organisation University of Oxford
Department Department of Earth Sciences
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution work on work package 4
Collaborator Contribution consortium partners
Impact papers further funding
Start Year 2010
 
Title Basin Change point Model 
Description application for change point modeling in geological data sets 
Type Of Technology Software 
Year Produced 2011 
Open Source License? Yes  
Impact change point modeling is now widely used in the peat archive community 
URL http://www.iearth.org.au/codes/
 
Title High precision Pb isotope measurements 
Description double spike for high precision isotope ratio measurements 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2015 
Impact improvement of precision and accuracy of Pb isotope measurements in seawater 
 
Description Insights into improved provenance tracing using Pb isotopic ratios of aerosols into the South Atlantic Ocean 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Talk presented by Roulin Khondoker, who works on the tied studentship project of the grant for her PhD. The talk was presented at the 'Research in progress' meeting organised by the Geochemistry section of the Geological Society at the Open University in March 2013.
Year(s) Of Engagement Activity 2013
 
Description Lead isotopes in South Atlantic seawater: insights on anthropogenic inputs and ocean circulation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Goldschmidt conference 2012, abstract for poster presentation by Maxence Paul (PDRA on the project)
Year(s) Of Engagement Activity 2012
 
Description Lead isotopes in South Atlantic seawater: insights on anthropogenic inputs and ocean circulation from the UK GEOTRACES transect along 40°S 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Poster presentation at the Challenger Conference 2012 in Norwich, East Anglia by Maxence Paul (PDRA on the projec).
Year(s) Of Engagement Activity 2012
 
Description Ocean Chemistry: Now and Then 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Policymakers/politicians
Results and Impact Invited talk at a one day symposium on ocean research at Imperial College London, organised to stimulate UK collaborations in ocean research.
Year(s) Of Engagement Activity 2012
 
Description Ocean chemistry as a mediator in the dialogue between geology and oceanography ? 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk at an INQUA AND IGBP sponsored workshop on contourites, Hull, 2013.
Year(s) Of Engagement Activity 2013
 
Description Why measuring isotope ratios on every single GEOTRACES cruise? 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Plenary talk at the 'Frontiers of Science' meeting 2010 in Perth, Australia. 'Frontiers of Science' is a series of prestigious international meetings for outstanding early career scientists, organised by the Royal Society in conjunction with other national academies. These meetings bring together future leaders to encourage innovative science and international and cross-disciplinary collaboration. I highlighted the value of isotope work within the context of the international GEOTRACES program, as well as the ongoing UK activities.
Year(s) Of Engagement Activity 2010
 
Description  
Form Of Engagement Activity
Part Of Official Scheme? No
Primary Audience
Year(s) Of Engagement Activity