Characterization of dissolved organic matter across the Subtropical Convergence off the South Island,New Zealand |
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| Authors: | Michael Gonsior Barrie M Peake William T Cooper David C Podgorski Juliana D'Andrilli Thorsten Dittmar William J Cooper |
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| Institution: | 1. Hydrothermal Geomicrobiology Group, MARUM — Center for Marine Environmental Sciences, University of Bremen, PO Box 330440, 28334, Bremen, Germany;2. Research Group for Marine Geochemistry (ICBM-MPI Bridging Group), Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Carl-von-Ossietzky-Str. 9-11, 26129 Oldenburg, Germany;3. Geochemistry and Hydrogeology Group, University of Bremen, PO Box 330440, 28334, Bremen, Germany;1. Department of Limnology and Oceanography, University of Vienna, Vienna, Austria;2. Research Group for Marine Geochemistry (ICBM-MPI Bridging Group), Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, Oldenburg, Germany;3. Max Planck Institute for Marine Microbiology (MPI), Bremen, Germany;4. Department of Biological Oceanography, Royal Netherlands Institute for Sea Research (NIOZ), Den Burg, The Netherlands;1. Research Group for Marine Geochemistry (ICBM-MPI Bridging Group), Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Oldenburg, Germany;2. Jacobs University Bremen, Earth and Space Sciences, Bremen, Germany;3. Department of Geosciences, University of Bremen, Bremen, Germany;1. University of MD Center for Environmental Science, Chesapeake Biological Laboratory, Solomons, USA;2. Linköping University, Department of Thematic Studies — Water and Environmental Studies, Linköping, Sweden;3. Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany;4. Bermuda Institute of Ocean Sciences, Ferry Reach, St. Georges GE01, Bermuda;5. Urban Water Research Center, Department of Environmental and Civil Engineering, University of CA, Irvine, USA;6. Department of Earth System Science, University of CA, Irvine, USA;7. Department for Chemical–Technical Analysis, Research Center Weihenstephan for Brewing and Food Quality, Technische Universität München, D-85354 Freising-Weihenstephan, Germany |
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| Abstract: | Dissolved organic matter (DOM) was investigated along a gradient across the Subtropical Convergence (STC) off the South Island, New Zealand. Ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), excitation emission matrix fluorescence (EEM) spectroscopy, and molecular lignin analysis techniques were used to study this DOM. The analysis revealed a group of compounds found only in the coastal DOM samples, which were also characterized by an elevated terrestrial DOM fluorescence pattern and elevated lignin content if compared to the offshore samples. This group exhibited a high degree of carbon unsaturation, as evident from high double bond equivalence minus oxygen values (DBE-O > 9) and maximum fluorescence intensity. Sulfur-containing molecular formulae for summer DOM samples were much more abundant across the entire transect of the STC compared to winter and exhibited distinctly different hydrogen:carbon and oxygen:carbon elemental ratios, suggesting a possible correlation between biological activity and sulfur compounds. The molecular formulae common to all STC samples were compared with those calculated for DOM extracted from freshwater collected from a stream discharging into Doubtful Sound (West Coast, New Zealand). ESI-FT-ICR-MS measurements undertaken in negative electrospray ionization (ESI?) mode indicated that 30% of the molecular formulae were present in both types of DOM, while in positive ESI mode (ESI+) over 90% of the formulae were present in all samples. Hence, a significant portion of the molecular formulae assigned to the solid-phase extractable DOM pool (SPE-DOM) appear to be identical in oceanic and freshwater samples. |
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