Phytoplankton communities influence the dissolved organic matter composition of the sea-surface microlayer

2020 ◽  
Author(s):  
Lea Oeljeschlaeger ◽  
Nils Hintz ◽  
Jutta Niggemann ◽  
Oliver Wurl ◽  
Thorsten Dittmar
Keyword(s):  
Boundary Layer ◽  
Organic Matter ◽  
Chemical Composition ◽  
Solid Phase ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Exchange Processes ◽  
Sea Surface Microlayer ◽  
Phytoplankton Communities ◽  
External Forces

<p>The sea surface microlayer (SML) is the boundary layer at the ocean and atmosphere interface and plays a crucial role in air-sea gas exchange processes and global climate. It is enriched in dissolved organic matter (DOM) compared to the underlying water, but the chemical composition of this material has been insufficiently studied. For improved understanding of the exchange processes it is of utmost importance knowing the molecular composition of the SML. Studying the microlayer is very challenging due to its thinness and strong influence of external forces as wind, UV light and atmospheric deposition on the chemical and microbial composition. The complex and dynamic nature of the microlayer and the enrichment of hydrophobic substances led to the assumption that we find unique chemical composition and distinct compound groups. SML samples of the Indo-Pacific Ocean from R/V Falkor cruise FK161010 (October 2016) were studied with respect to molecular composition of DOM. We analyzed solid-phase extracted DOM with high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The results were compared to the underlying water (ULW, 1m depth). We found similar molecular DOM composition in the ULW, whereas microlayer extracts were more variable and diverse. This can be related to the influence of changing weather conditions during the cruise on the SML. To reveal molecular changes without interfering external forces, a 5-week indoor mesocosm experiment with induced marine phytoplankton blooms was conducted. A modified solid-phase extraction approach was used to chemically fractionate the microlayer DOM prior to molecular analysis. Our experiment showed that the DOM enrichment in the SML is linked to different phytoplankton communities. In addition, it revealed that depending on the predominant community the DOM concentration can be even depleted in the SML compared to the ULW. Based on the outcome of our field and laboratory studies we conclude that molecular level analysis of surface microlayers is essential to understand the chemical diversity of this highly dynamic boundary layer.</p>

scholarly journals The organic sea-surface microlayer in the upwelling region off the coast of Peru and potential implications for air–sea exchange processes

2016 ◽  
Vol 13 (4) ◽  
pp. 989-1007 ◽  
Author(s):  
Anja Engel ◽  
Luisa Galgani
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Wind Speed ◽  
Coastal Upwelling ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Close Coupling ◽  
Exchange Processes ◽  
Sea Surface Microlayer ◽  
Almost All

Abstract. The sea-surface microlayer (SML) is at the uppermost surface of the ocean, linking the hydrosphere with the atmosphere. The presence and enrichment of organic compounds in the SML have been suggested to influence air–sea gas exchange processes as well as the emission of primary organic aerosols. Here, we report on organic matter components collected from an approximately 50 µm thick SML and from the underlying water (ULW),  ∼  20 cm below the SML, in December 2012 during the SOPRAN METEOR 91 cruise to the highly productive, coastal upwelling regime off the coast of Peru. Samples were collected at 37 stations including coastal upwelling sites and off-shore stations with less organic matter and were analyzed for total and dissolved high molecular weight (> 1 kDa) combined carbohydrates (TCCHO, DCCHO), free amino acids (FAA), total and dissolved hydrolyzable amino acids (THAA, DHAA), transparent exopolymer particles (TEP), Coomassie stainable particles (CSPs), total and dissolved organic carbon (TOC, DOC), total and dissolved nitrogen (TN, TDN), as well as bacterial and phytoplankton abundance. Our results showed a close coupling between organic matter concentrations in the water column and in the SML for almost all components except for FAA and DHAA that showed highest enrichment in the SML on average. Accumulation of gel particles (i.e., TEP and CSP) in the SML differed spatially. While CSP abundance in the SML was not related to wind speed, TEP abundance decreased with wind speed, leading to a depletion of TEP in the SML at about 5 m s−1. Our study provides insight to the physical and biological control of organic matter enrichment in the SML, and discusses the potential role of organic matter in the SML for air–sea exchange processes.

scholarly journals The organic sea surface microlayer in the upwelling region off Peru and implications for air–sea exchange processes

2015 ◽  
Vol 12 (13) ◽  
pp. 10579-10619 ◽  
Author(s):  
A. Engel ◽  
L. Galgani
Keyword(s):  
Organic Matter ◽  
Organic Compounds ◽  
Coastal Upwelling ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Surface Ocean ◽  
Gel Particles ◽  
Exchange Processes ◽  
Sea Surface Microlayer

Abstract. The sea surface microlayer (SML) is at the very surface of the ocean, linking the hydrosphere with the atmosphere, and central to a range of global biogeochemical and climate-related processes. The presence and enrichment of organic compounds in the SML have been suggested to influence air–sea gas exchange processes as well as the emission of primary organic aerosols. Among these organic compounds, primarily of plankton origin, are dissolved exopolymers, specifically polysaccharides and proteins, and gel particles, such as Transparent Exopolymer Particles (TEP) and Coomassie Stainable Particles (CSP). These organic substances often accumulate in the surface ocean when plankton productivity is high. Here, we report results obtained in December 2012 during the SOPRAN Meteor 91 cruise to the highly productive, coastal upwelling regime off Peru. Samples were collected from the SML and from ~ 20 cm below, and were analyzed for polysaccharidic and proteinaceous compounds, gel particles, total and dissolved organic carbon, bacterial and phytoplankton abundance. Our study provides insight to the physical and biological control of organic matter enrichment in the SML, and discusses the potential role of organic matter in the SML for air–sea exchange processes.

scholarly journals Enriching particles on a bubble through drainage: Measuring and modeling the concentration of microbial particles in a bubble film at rupture

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Peter L. L. Walls ◽  
James C. Bird
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
High Speed ◽  
Ocean Surface ◽  
Sea Surface ◽  
Bulk Liquid ◽  
Surface Microlayer ◽  
Exchange Processes ◽  
Sea Surface Microlayer ◽  
The Moment

The concentration of microbes and other particulates is frequently enriched in the droplets produced by bursting bubbles. As a bubble rises to the ocean surface, particulates in the bulk liquid can be transported to the sea surface microlayer by attaching to the bubble’s interface. When the bubble eventually ruptures, a fraction of these particulates is often ejected into the surroundings in film droplets with a particulate concentration that is higher than in the liquid from which they formed. The precise mechanisms responsible for this enrichment are unclear, yet such enrichment at the ocean surface influences important exchange processes with the atmosphere. Here we provide evidence that drainage, coupled with scavenging, is responsible for the enrichment. By simultaneously recording the drainage and rupture effects with high-speed and standard photography, we directly measured the particulate concentrations in the thin film of a bubble cap at the moment before it ruptures. We observed that the enrichment factor strongly depends on the film thickness at rupture, and developed a physical model, based on scavenging and drainage, that is consistent with our observations. We have also demonstrated that this model is quantitatively consistent with prior observations of film drop enrichment, indicating its potential for a broader range of applications in the study of the sea surface microlayer and related phenomena.

scholarly journals Plastic Accumulation in the Sea Surface Microlayer: An Experiment-Based Perspective for Future Studies

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 66 ◽  
Author(s):  
Luisa Galgani ◽  
Steven Loiselle
Keyword(s):  
Organic Matter ◽  
Marine Environment ◽  
Bulk Water ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Surface Ocean ◽  
Marine Organic Matter ◽  
Sea Surface Microlayer ◽  
Preliminary Study ◽  
The Impact

Plastic particles are ubiquitous in the marine environment. Given their low density, they have the tendency to float on the sea surface, with possible impacts on the sea surface microlayer (SML). The SML is an enriched biofilm of marine organic matter, that plays a key role in biochemical and photochemical processes, as well as controlling gas exchange between the ocean and the atmosphere. Recent studies indicate that plastics can interfere with the microbial cycling of carbon. However, studies on microplastic accumulation in the SML are limited, and their effects on organic matter cycling in the surface ocean are poorly understood. To explore potential dynamics in this key ocean compartment, we ran a controlled experiment with standard microplastics in the surface and bulk water of a marine monoculture. Bacterial abundance, chromophoric dissolved organic matter (CDOM), and oxygen concentrations were measured. The results indicate an accumulation of CDOM in the SML and immediate underlying water when microplastic particles are present, as well as an enhanced oxygen consumption. If extrapolated to a typical marine environment, this indicates that alterations in the quality and reactivity of the organic components of the SML could be expected. This preliminary study shows the need for a more integrated effort to our understanding the impact of microplastics on SML functioning and marine biological processes.

Organic matter characterization in the Northern adriatic sea with special reference to the sea surface microlayer

1988 ◽  
Vol 25 (3) ◽  
pp. 243-263 ◽  
Author(s):  
J.C. Marty ◽  
V. Ẑutić ◽  
R. Precali ◽  
A. Saliot ◽  
B. Ćosović ◽  
...  
Keyword(s):  
Organic Matter ◽  
Special Reference ◽  
Adriatic Sea ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
Sea Surface Microlayer

scholarly journals Variability of the Sea Surface Microlayer Across a Filament’s Edge and Potential Influences on Gas Exchange

2021 ◽  
Vol 8 ◽  
Author(s):  
Theresa Barthelmeß ◽  
Florian Schütte ◽  
Anja Engel
Keyword(s):  
Organic Matter ◽  
Gas Exchange ◽  
Surfactant Concentration ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Fresh Organic Matter ◽  
Heterotrophic Microorganisms ◽  
Sea Surface Microlayer ◽  
Established Relationship ◽  
Autochthonous Production

Major uncertainties in air-sea gas flux parameterizations may arise from a yet unpredictable sea surface microlayer (SML). Its influence on gas exchange is twofold as organic matter, in particular surfactants, on one side and organisms enriched in the SML on the other can alter air-sea gas fluxes. However, spatial heterogeneity of the SML and its potential consequences for gas exchange are not well understood. This study examines the SML’s surfactant pool and the dynamics of microbial enrichment across the sharp hydrological front of a newly upwelled filament off Mauritania. The front was marked by a distinct decrease in temperature and salinity compared to the stratified water column outside the filament. Distinct chemical and microbial SML properties were observed and associated with the filament. Overall, organic matter in the SML was significantly higher concentrated inside the filament and in equivalence to the underlying water. Degradation indices derived from total amino acids (TAA) composition indicated production of fresh organic matter inside and increased degradation outside the filament. Moreover, a shift in the microbial community was observed, for instance Synechococcus spp. prevailed outside the filament. Autotrophic and heterotrophic microorganisms preferably colonized the SML outside the filament. Organic matter enrichment in the SML depended largely on the chemical nature of biomolecules. Total organic carbon (TOC), total nitrogen and total combined carbohydrates were only slightly enriched while glucose, TAA and surfactants were considerably enriched in the SML. Surfactant concentration was positively correlated to TAA, in particular to arginine and glutamic acid, indicating that fresh organic matter components enhanced surface activity. Further, TOC and surfactant concentration correlated significantly (r2 = 0.47, p-value < 0.001). The lower limit of this linear correlation hits approximately the lowest TOC concentration expected within the global surface ocean. This suggests that surfactants are primarily derived from autochthonous production and most refractory components are excluded. Using a previously established relationship between surfactants and CO2 gas exchange (Pereira et al., 2018), we estimated that surfactants suppressed gas exchange by 12% inside the filament. This could be of relevance for freshly upwelled filaments, which are often supersaturated in greenhouse gases.

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