Ocean micronutrient cycles: UK GEOTRACES
Lead Research Organisation:
Plymouth Marine Laboratory
Department Name: Plymouth Marine Lab
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
Wyatt N
(2014)
Biogeochemical cycling of dissolved zinc along the GEOTRACES South Atlantic transect GA10 at 40°S
in Global Biogeochemical Cycles
Tuerena R
(2015)
Nutrient cycling in the Atlantic basin: The evolution of nitrate isotope signatures in water masses
in Global Biogeochemical Cycles
Schlosser C
(2019)
Distribution of dissolved and leachable particulate Pb in the water column along the GEOTRACES section GA10 in the South Atlantic
in Deep Sea Research Part I: Oceanographic Research Papers
Schlitzer R
(2018)
The GEOTRACES Intermediate Data Product 2017
in Chemical Geology
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
Hernández-Sánchez M
(2014)
Variations in GDGT distributions through the water column in the South East Atlantic Ocean
in Geochimica et Cosmochimica Acta
Browning T
(2014)
Strong responses of Southern Ocean phytoplankton communities to volcanic ash
in Geophysical Research Letters
Browning T
(2014)
Nutrient regimes control phytoplankton ecophysiology in the South Atlantic
in Biogeosciences
Artigue L
(2020)
Water mass analysis along 22 °N in the subtropical North Atlantic for the JC150 cruise (GEOTRACES, GApr08)
in Deep Sea Research Part I: Oceanographic Research Papers
Description | The nutrient assessments made during this programme will go towards supporting Trace Metal understanding in the Southern Atlantic Ocean and hence to other world oceans. Scientific papers have resulted and in the future possible computer modelling with all supplementary data with come to fruition. |
First Year Of Impact | 2011 |
Sector | Environment |
Title | Geotraces Intermediate Data Product 2017 |
Description | Global database for Nutrients and trace metals along Geotraces survey lines. |
Type Of Material | Database/Collection of data |
Year Produced | 2017 |
Provided To Others? | Yes |
Impact | Presentation and release at Ocean Sciences meeting in Portland Oregon. |
URL | http://www.geotraces.org/dp/idp2017 |
Title | eGeotraces |
Description | GEOTRACES is an international programme which aims to improve the understanding of biogeochemical cycles and large-scale distribution of trace elements and their isotopes in the marine environment. Scientists from approximately 35 nations have been involved in the programme, which is designed to study all major ocean basins over the next decade. |
Type Of Material | Data analysis technique |
Year Produced | 2013 |
Provided To Others? | Yes |
Impact | 3D mobile images of nutrient structures. |
URL | http://www.egeotraces.org/ |