Development of a consistent thermodynamic model of trace element - organic matter interactions in the Ocean.

• Applicants: Dr. Martha Gledhill; Professorin Dr. Andrea Koschinsky
• Subject Area: Oceanography
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 393829236

• Final Report Year: 2024

Final Report Abstract

Trace elements can limit productivity in the ocean, and thus influence the amount of carbon dioxide that marine phytoplankton remove from the atmosphere. The most critical trace element for phytoplankton growth is iron, which limits productivity in approximately 30 % of the worlds' ocean. Iron is included as limiting nutrient in many biogeochemical models and some climate models, in order to account for its influence on the impact of carbon dioxide on the earths' climate. Incorporation of iron into biogeochemical and climate models needs to be underpinned by a fundamental understanding of the chemistry of iron in seawater, since iron chemistry is affected by ocean pH, temperature and dissolved organic matter (DOM). Organic matter is known to have a major influence on iron chemistry, but interactions between DOM and iron are typically described in a simplistic, empirical way that is not linked to the intrinsic chemical properties of DOM or iron. In this project we investigated the intrinsic acid-base properties of DOM, which underpin DOM-iron interactions. We determined proton binding parameters for DOM sampled from brackish waters of the Baltic Sea and open ocean waters of the North Atlantic, via application of the non-ideal competitive adsorption (NICA) - Donnan model. Alongside these parameters, we determined the molecular and elemental properties of marine DOM. We found that the NICA parameters of DOM could be linked to changes in elemental and molecular properties. We further applied the NICA-Donnan model to determine carbon:trace metal ratios in the Amazon Plume. We found determined ratios were consistent with ratios observed on analysis of extracted DOM with high performance liquid chromatography – electrospray ionisation/inductively coupled – mass spectrometry. The application of the NICA model for interpretation of trace metal (including iron) chemistry in seawater improved our ability to link the biogeochemistry of the metals in the Amazon Plume to their fundamental chemical properties, as determined by their positions in the periodic table of elements.

Publications

• Acid-base properties of dissolved organic matter extracted from the marine environment. Science of The Total Environment, 729, 138437.
  Lodeiro, Pablo; Rey-Castro, Carlos; David, Calin; Achterberg, Eric P.; Puy, Jaume & Gledhill, Martha
  
• Contrasting behaviour of dissolved organic iron, aluminium and phosphorous fractions in the Amazon estuary. Ocean Sciences
  Gledhill, Martha; Lodeiro, Pablo; Hollister, Adrienne & Seidel, Michael
  
• Dissolved concentrations and organic speciation of Cu in the Amazon River estuary and mixing plume. Ocean Sciences Meeting, San Diego.
  Hollister, Adrienne; Whitby, Hannah; Gledhill, Martha & Koschinsky, Andrea
  
• Exploring the Iron‐Binding Potential of the Ocean Using a Combined pH and DOC Parameterization. Global Biogeochemical Cycles, 34(6).
  Ye, Y.; Völker, C. & Gledhill, M.
  
• A fungal siderophore hotspot on the Amazon Shelf. ASLO
  Gledhill, Martha; Hollister, Adrienne; Koschinsky, Andrea; Walter, J.; Nobreg, M.S.; Thompson, Fabiano L. & de Rezende, Carlos E.
  
• Are the binding groups of Baltic coastal dissolved organic matter affected by seasonal variabilities? 11th International Conference Interfaces Against Pollution (IAP2021).
  Lodeiro, Pablo; Rey-Castro, Carlos; David, Calin; Puy, Jaume; Achterberg, Eric P. & Gledhill, Martha
  
• Carbon and alkalinity outwelling across the groundwater‐creek‐shelf continuum off Amazonian mangroves. Limnology and Oceanography Letters, 6(6), 369-378.
  Cabral, Alex; Dittmar, Thorsten; Call, Mitchell; Scholten, Jan; de Rezende, Carlos E.; Asp, Nils; Gledhill, Martha; Seidel, Michael & Santos, Isaac R.
  
• Dissolved concentrations and organic speciation of copper in the Amazon River estuary and mixing plume. Marine Chemistry, 234, 104005.
  Hollister, Adrienne Patricia; Whitby, Hannah; Seidel, Michael; Lodeiro, Pablo; Gledhill, Martha & Koschinsky, Andrea
  
• Distribution and size fractionation of nickel and cobalt species along the Amazon estuary and mixing plume. Marine Chemistry, 236, 104019.
  de Carvalho, Leandro M.; Hollister, Adrienne Patricia; Trindade, Cristina; Gledhill, Martha & Koschinsky, Andrea
  
• Modelling protocols for derivation of Fe(III) NICA constants and calculations of ambient Fe speciation and apparent Fe(III) solubility in seawater v1. ZappyLab, Inc..
  Zhu, Kechen
  
• Seasonal Variations in Proton Binding Characteristics of Dissolved Organic Matter Isolated from the Southwest Baltic Sea. Environmental Science & Technology, 55(23), 16215-16223.
  Lodeiro, Pablo; Rey-Castro, Carlos; David, Calin; Puy, Jaume; Achterberg, Eric P. & Gledhill, Martha
  
• Updated estimates of sedimentary potassium sequestration and phosphorus release on the Amazon shelf. Chemical Geology, 560, 120017.
  Spiegel, Timo; Vosteen, Paul; Wallmann, Klaus; Paul, Sophie A.L.; Gledhill, Martha & Scholz, Florian
  
• Distribution of dissolved and soluble Ti along the salinity gradients in the Pará and Amazon estuaries and plume. Goldschmidt Conference
  A.B. Schneider; Koschinsky, Andrea; Krause, Cristian H. & Gledhill, Martha
  
• Dynamic behavior of dissolved and soluble titanium along the salinity gradients in the Pará and Amazon estuarine system and associated plume. Marine Chemistry, 238, 104067.
  Schneider, Alexandre B.; Koschinsky, Andrea; Krause, Cristian H.; Gledhill, Martha & de Carvalho, Leandro M.
  
• The Fate of Sedimentary Reactive Iron at the Land‐Ocean Interface: A Case Study From the Amazon Shelf. Geochemistry, Geophysics, Geosystems, 23(11).
  Vosteen, Paul; Spiegel, Timo; Gledhill, Martha; Frank, Martin; Zabel, Matthias & Scholz, Florian
  
• The impact of chemical heterogeneity on the binding of trace metals by marine dissolved organic matter. Goldschmidt Conference
  Lodeiro, Pablo; Rey-Castro, Carlos; David, Calin; Puy, Jaume & Gledhill, Martha
  
• Trace metal stoichiometry of dissolved organic matter in the Amazon plume. Science Advances, 8(31).
  Gledhill, Martha; Hollister, Adrienne; Seidel, Michael; Zhu, Kechen; Achterberg, Eric P.; Dittmar, Thorsten & Koschinsky, Andrea
  
• Trace metals and organic matter in the Amazon-Pará River Estuary. PhD thesis, Jacobs University Bremen (now Constructor University), 256 pages.
  Hollister, Adrienne
  
• Estimation of uncertainty in calcu lations of apparent iron solubility in seawater. protocols.io
  Zhu, Kechen, Hopwood, Mark J. & Gledhill, Martha
  
• Influence of Changes in pH and Temperature on the Distribution of Apparent Iron Solubility in the Oceans. Global Biogeochemical Cycles, 37(5).
  Zhu, Kechen; Achterberg, Eric P.; Bates, Nicholas R.; Gerringa, Loes J. A.; Middag, Rob; Hopwood, Mark J. & Gledhill, Martha
  
• Proton Binding Characteristics of Dissolved Organic Matter Extracted from the North Atlantic. Environmental Science & Technology, 57(50), 21136-21144.
  Lodeiro, Pablo; Rey-Castro, Carlos; David, Calin; Humphreys, Matthew P. & Gledhill, Martha