The Amazon River is the biggest river in the world, and it is an important source for terrestrial dissolved organic matter (DOM), nutrients and trace metals to the Atlantic Ocean. The riverine nutrient fluxes affect large areas in the Atlantic Ocean, stimulating phytoplankton blooms that can even be seen from space. In this German-Brazilian project we study the distribution of DOM and the speciation of trace metals along the salinity gradient, starting from the Amazon River mouth along its freshwater plume into the tropical North Atlantic Ocean. We aim to understand how the complexation with organic matter enhances the trace metal fluxes between the river and the ocean. By looking at different size fractions of organic matter (dissolved and particulate phases) we are trying to identify possible removal mechanisms in the river plume, such as colloidal coagulation and sedimentation during estuarine mixing.

Funding:

DFG

List of people involved:

Michael Seidel
Thorsten Dittmar
Jomar Marques da Silva Junior
Melina Knoke
Hannelore Waska

Collaborators:

Andrea Koschinsky-Fritsche (www.jacobs-university.de/directory/koschinsky-fritsche)
Martin Frank (www.geomar.de/mfrank)
Carlos Eduardo de Rezende (uenf.br/cbb/lca/professor/carlos-eduardo-de-rezende/)
Martha Gledhill (https://www.geomar.de/mgledhill)

Key publications:

Gledhill M, Hollister A, Seidel M, Zhu K, Achterberg EP, Dittmar T, Koschinsky A (2022) “Trace metal stoichiometry of dissolved organic matter in the Amazon Estuary“, Science Advances, 8: eabm2249; doi.org/10.1126/sciadv.abm2249

Hollister AP, Whitby H, Seidel M, Lodeiro P, Gledhill M, Koschinsky A (2021) “Dissolved concentrations and organic speciation of copper in the Amazon River estuary and mixing plume”, Marine Chemistry, 234:104005; doi.org/10.1016/j.marchem.2021.104005 doi.org/10.1016/j.marchem.2021.104005

Seidel M, Yager PL, Ward ND, Carpenter EJ, Gomes HR, Krusche AV, Richey JE, Dittmar T, Medeiros PM (2015). “Molecular-level changes of dissolved organic matter along the Amazon River-to-ocean-continuum”, Marine Chemistry, Marine Chemistry, 177: 218-231; doi.org/10.1016/j.marchem.2015.06.019

Medeiros PM, Seidel M, Ward ND, Carpenter EJ, Gomes HR, Niggemann J, Krusche AV, Richey JE, Yager PL, Dittmar T (2015). “Fate of the Amazon River dissolved organic matter in the Tropical Atlantic Ocean”, Global Biogeochemical Cycles, 29:677–690; onlinelibrary.wiley.com/doi/10.1002/2015GB005115/full

Seidel M, Dittmar T, Ward ND, Krusche AV, Richey JE, Yager PL, Medeiros PM (2016). “Seasonal and spatial variability of the dissolved organic matte composition in the lower Amazon River”, Biogeochemistry, 131:281-302; doi.org/10.1007/s10533-016-0279-4

Waska H, Koschinsky A, Dittmar T (2016) “Fe- and Cu-complex formation with artificial ligands investigated by ultra-high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS): implications for natural metal-organic complex studies”, Frontiers in Marine Science, 3:119. doi: 10.3389/fmars.2016.00119; doi.org/10.3389/fmars.2016.00119