Ocean micronutrient cycles: UK GEOTRACES
Lead Research Organisation:
University of Oxford
Department Name: Earth Sciences
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.
Organisations
Publications
Browning T
(2015)
Volcanic ash supply to the surface oceanâ€"remote sensing of biological responses and their wider biogeochemical significance
in Frontiers in Marine Science
Browning T
(2014)
Strong responses of Southern Ocean phytoplankton communities to volcanic ash
in Geophysical Research Letters
Browning T
(2014)
Satellite-detected fluorescence: Decoupling nonphotochemical quenching from iron stress signals in the South Atlantic and Southern Ocean
in Global Biogeochemical Cycles
Browning T
(2014)
Nutrient regimes control phytoplankton ecophysiology in the South Atlantic
in Biogeosciences
Casacuberta N
(2016)
First 236U data from the Arctic Ocean and use of 236U/238U and 129I/236U as a new dual tracer
in Earth and Planetary Science Letters
Deng F
(2018)
Evolution of <sup>231</sup>Pa and <sup>230</sup>Th in overflow waters of the North Atlantic
in Biogeosciences
Henderson G
(2018)
Changing Trace Element Cycles in the 21st Century Ocean
in Elements
Henderson G
(2015)
Recommendations for future measurement and modelling of particles in GEOTRACES and other ocean biogeochemistry programmes
in Progress in Oceanography
Homoky WB
(2016)
Quantifying trace element and isotope fluxes at the ocean-sediment boundary: a review.
in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
Horner T
(2011)
Isotopic fractionation of cadmium into calcite
in Earth and Planetary Science Letters
Hsieh Y
(2011)
Combining seawater 232Th and 230Th concentrations to determine dust fluxes to the surface ocean
in Earth and Planetary Science Letters
Hsieh Y
(2011)
Precise measurement of 228Ra/226Ra ratios and Ra concentrations in seawater samples by multi-collector ICP mass spectrometry
in Journal of Analytical Atomic Spectrometry
Le Moigne F
(2014)
Where is mineral ballast important for surface export of particulate organic carbon in the ocean?
in Geophysical Research Letters
Olivelli A
(2023)
Decline of anthropogenic lead in South Atlantic Ocean surface waters from 1990 to 2011: New constraints from concentration and isotope data
in Marine Pollution Bulletin
Paul M
(2015)
Tracing the Agulhas leakage with lead isotopes LEAD ISOTOPES TRACE AGULHAS LEAKAGE
in Geophysical Research Letters
Paul M
(2015)
High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry.
in Analytica chimica acta
Sabadel A
(2017)
Determination of picomolar dissolved free amino acids along a South Atlantic transect using reversed-phase high-performance liquid chromatography
in Marine Chemistry
Schlitzer R
(2018)
The GEOTRACES Intermediate Data Product 2017
in Chemical Geology
Wyatt N
(2021)
Seasonal cycling of zinc and cobalt in the south-eastern Atlantic along the GEOTRACES GA10 section
in Biogeosciences
Zheng X
(2016)
Rare earth elements (REEs) in the tropical South Atlantic and quantitative deconvolution of their non-conservative behavior
in Geochimica et Cosmochimica Acta
Zheng X
(2014)
A Robust Procedure for High-Precision Determination of Rare Earth Element Concentrations in Seawater
in Geostandards and Geoanalytical Research
Živkovic I
(2022)
Enhanced mercury reduction in the South Atlantic Ocean during carbon remineralization
in Marine Pollution Bulletin
Description | As submitted last year |
Exploitation Route | many |
Sectors | Environment |
Description | In many ways to advance understanding of ocean chemistry and its role in biological and climate cycles. |
First Year Of Impact | 2014 |
Sector | Environment |
Impact Types | Societal |