TY  - JOUR
AB  - Solid-phase extracted dissolved organic matter (SPE-DOM) was isolated 
      from two depth profiles at the core and at the edge of an anticyclonic 
      eddy (ACE) in the northern South China Sea. Non-target nuclear magnetic 
      resonance (NMR) spectroscopy and Fourier transform ion cyclotron mass 
      spectrometry (FTICR/MS) of SPE-DOM revealed a higher uniformity of DOM 
      molecules within the ACE than at the edge of the ACE. Small-scale 
      upwelling of external nutrients may have contributed to higher 
      productivity and production of fresher DOM, with higher proportions of 
      CHNO and CHNOS compounds and low molecular weight species at the edge of
       the eddy. Common SPE-DOM molecules of supposedly biological origin such
       as carbohydrates and olefins were most abundant in the chlorophyll 
      maximum layer in both stations. An unusual suite of ~10 abundant and ~35
       less abundant tert-butyl benzene derivatives with potential to act as 
      endocrine disruptors within a marine food chain and ~two dozen ketones 
      of putative bacterial origin was recognized at meso- and bathypelagic 
      depths in single-digit micromolar concentrations, with a distinct 
      maximum at 1000 m depth at the edge of ACE. Downwelling might bring 
      temporary large volumes of productive marine waters into deep waters, 
      with micromolar concentration of abundant, microbial food web-specific 
      metabolites (e.g. 2,4-di-tert-butylphenol et al.). In our study, these 
      eventually added up to one quarter of common background biogeochemical 
      marine organic matter even at bathypelagic depths and beneath and are 
      significant food and energy sources for marine biota. Mesoscale chemical
       heterogeneity of marine water columns might extend to larger depths 
      than currently anticipated and may create activity hotspots influencing 
      biota, processing of DOM, and cycling of nutrients and trace elements.
AU  - Zhang, M.*
AU  - Li, S.
AU  - Hertkorn, N.
AU  - Harir, M.
AU  - Xu, D.*
AU  - Schmitt-Kopplin, P.
AU  - Wu, Y.*
C1  - 65500
C2  - 52279
TI  - Substantial biogeochemical and biomolecular processing of dissolved organic matter in an anticyclonic eddy in the Northern South China Sea down to bathypelagic depths.
JO  - Front. Mar. Sci.
VL  - 9
PY  - 2022
ER  - 

TY  - JOUR
AB  - Chromophoric dissolved organic matter (CDOM) is the dominant absorber of ultraviolet radiation in the ocean, but its sources within the ocean, as well as its chemical composition, remain uncertain. One source of marine CDOM is Sargassum, an epipelagic marine macro brown alga common to the Gulf of Mexico, Caribbean, and Western North Atlantic. Furthermore, Sargassum contains phlorotannins, a class of polyphenols that may have similar optical properties to terrestrial polyphenols. Here, we analyze Sargassum CDOM optical properties, acquired from absorption and fluorescence spectra of filtered samples collected during Sargassum exudation experiments in seawater tanks. To further evaluate the structural basis of Sargassum CDOM optical properties, Sargassum CDOM was collected by solid phase extraction (SPE) and its chemical composition was tested by pH titration and sodium borohydride reduction. These chemical tests revealed that Sargassum CDOM absorption spectra respond similarly to pH titration and borohydride reduction when compared to terrestrially-derived materials, but Sargassum CDOM has unique absorbance peaks in difference spectra that have not been observed in terrestrially-derived CDOM. These absorbance features are consistent with the deprotonation of modified Sargassum phlorotannins, which are likely highly related phenolic acids and polyphenols. Sargassum CDOM was also more rapidly photodegraded when compared to terrestrial CDOM such as Suwannee River Natural Organic Matter. Similar to terrestrial DOM, ultrahigh resolution mass spectrometry revealed that sunlight decreases relative abundances of m/z ions and molecular formulas with an average O/C ratio of 0.6 and an average H/C ratio of 0.9, suggesting preferential photodegradation and/or phototransformation of hydrogen-deficient and oxygenated compounds, such as Sargassum phlorotannins. Assuming a large fraction of Sargassum CDOM is quickly mineralized to CO2 during its rapid photodegradation, Sargassum could play a major role in marine photochemical carbon mineralization during its annual growth cycle.
AU  - Powers, L.C.*
AU  - Del Vecchio, R.*
AU  - Blough, N.V.*
AU  - McDonald, N.*
AU  - Schmitt-Kopplin, P.
AU  - Gonsior, M.*
C1  - 60686
C2  - 49441
CY  - Avenue Du Tribunal Federal 34, Lausanne, Ch-1015, Switzerland
TI  - Optical properties and photochemical transformation of the dissolved organic matter released by Sargassum.
JO  - Front. Mar. Sci.
VL  - 7
PB  - Frontiers Media Sa
PY  - 2020
ER  - 

TY  - JOUR
AB  - Despite the huge extent of the ocean's surface, until now relatively little attention has been paid to the sea surface microlayer (SML) as the ultimate interface where heat, momentum and mass exchange between the ocean and the atmosphere takes place. Via the SML, large-scale environmental changes in the ocean such as warming, acidification, deoxygenation, and eutrophication potentially influence cloud formation, precipitation, and the global radiation balance. Due to the deep connectivity between biological, chemical, and physical processes, studies of the SML may reveal multiple sensitivities to global and regional changes. Understanding the processes at the ocean's surface, in particular involving the SML as an important and determinant interface, could therefore provide an essential contribution to the reduction of uncertainties regarding ocean-climate feedbacks. This review identifies gaps in our current knowledge of the SML and highlights a need to develop a holistic and mechanistic understanding of the diverse biological, chemical, and physical processes occurring at the ocean-atmosphere interface. We advocate the development of strong interdisciplinary expertise and collaboration in order to bridge between ocean and atmospheric sciences. Although this will pose significant methodological challenges, such an initiative would represent a new role model for interdisciplinary research in Earth System sciences.
AU  - Engel, A.M.*
AU  - Bange, H.W.*
AU  - Cunliffe, M.*
AU  - Burrows, S.M.*
AU  - Friedrichs, G.*
AU  - Galgani, L.*
AU  - Herrmann, H.*
AU  - Hertkorn, N.
AU  - Johnson, M.A.*
AU  - Liss, P.S.*
AU  - Quinn, P.K.*
AU  - Schartau, M.*
AU  - Soloviev, A.*
AU  - Stolle, C.*
AU  - Upstill-Goddard, R.C.*
AU  - van Pinxteren, M.*
AU  - Zäncker, B.*
C1  - 51349
C2  - 43191
TI  - The ocean's vital skin: Toward an integrated understanding of the sea surface microlayer.
JO  - Front. Mar. Sci.
VL  - 4
IS  - MAY
PY  - 2017
ER  - 

TY  - JOUR
AB  - Marine dissolved organic matter (DOM) in surface and deep waters of the eastern Atlantic Ocean and Sargasso Sea was analyzed by excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC). Photo-degradation with semi-continuous monitoring of EEMs and absorbance spectra was used to measure the photo-degradation kinetics and changes of the PARAFAC components in a depth profile of DOM at the Bermuda Atlantic Time Series (BATS) station in the Sargasso Sea. A five component model was fit to the EEMs, which included traditional terrestrial-like, marine-like, and protein-like components. Terrestrial-like components showed the expected high photo-reactivity, but surprisingly, the traditional marine-like peak showed slight photo-production in surface waters, which may account for its prevalence in marine systems. Surface waters were depleted in photo-labile components while protein-like fluorescent components were enriched, consistent with previous studies. Ultra-high resolution mass spectrometry detected unique aliphatic compounds in the surface waters at the BATS site, which may be photo-produced or photo-stable. Principle component and canonical analysis showed strong correlations between relative contributions of unsaturated/aromatic molecular formulas and depth, with aliphatic compounds more prevalent in surface waters and aromatic compounds in deep waters. Strong correlations were seen between these aromatic compounds and humic-like fluorescent components. The rapid photo-degradation of the deep-sea fluorescent DOM in addition to the surface water relative depletion of aromatic compounds suggests that deep-sea fluorescent DOM may be too photochemically labile to survive during overturning circulation.
AU  - Timko, S.A.*
AU  - Maydanov, A.*
AU  - Pittelli, S.L.*
AU  - Conte, M.H.*
AU  - Cooper, W.J.*
AU  - Koch, B.P.*
AU  - Schmitt-Kopplin, P.
AU  - Gonsior, M.*
C1  - 50329
C2  - 42266
TI  - Depth-dependent photodegradation of marine dissolved organic matter.
JO  - Front. Mar. Sci.
VL  - 2
IS  - SEP
PY  - 2015
ER  -