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

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.

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

Biogeosciences Discussions ◽

10.5194/bgd-12-10579-2015 ◽

2015 ◽

Vol 12 (13) ◽

pp. 10579-10619 ◽

Cited By ~ 4

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.

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High concentrations of mycosporine-like amino acids and colored dissolved organic matter in the sea surface microlayer off the Iberian Peninsula

Limnology and Oceanography ◽

10.4319/lo.2010.55.5.1835 ◽

2010 ◽

Vol 55 (5) ◽

pp. 1835-1850 ◽

Cited By ~ 35

Author(s):

Gavin H. Tilstone ◽

ruth L. Airs ◽

Victor Martinez Vicente ◽

Claire Widdicombe ◽

Carole Llewellyn

Keyword(s):

Amino Acids ◽

Organic Matter ◽

Dissolved Organic Matter ◽

Iberian Peninsula ◽

Sea Surface ◽

Surface Microlayer ◽

Colored Dissolved Organic Matter ◽

Sea Surface Microlayer ◽

High Concentrations

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

10.5194/egusphere-egu2020-19041 ◽

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&#160;been&#160;insufficiently&#160;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>

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Formation and distribution of sea-surface microlayers

Biogeosciences Discussions ◽

10.5194/bgd-7-5719-2010 ◽

2010 ◽

Vol 7 (4) ◽

pp. 5719-5755 ◽

Cited By ~ 4

Author(s):

O. Wurl ◽

E. Wurl ◽

L. Miller ◽

K. Johnson ◽

S. Vagle

Keyword(s):

Wind Speed ◽

Primary Production ◽

Sea Surface ◽

Surface Microlayer ◽

Average Wind Speed ◽

Wind Speeds ◽

Average Wind ◽

The Pacific ◽

Sea Surface Microlayer ◽

Natural Surfactants

Abstract. Results from a study of surfactants in the sea-surface microlayer (SML) in different regions of the ocean (subtropical, temperate, polar) suggest that this interfacial layer between the ocean and atmosphere covers the ocean's surface to a significant extent. Threshold values at which primary production acts as a significant source of natural surfactants have been derived from the enrichment of surfactants in the SML relative to underlying water and local primary production. Similarly, we have also derived a wind speed threshold at which the SML is disrupted. The results suggest that surfactant enrichment in the SML is typically greater in oligotrophic regions of the ocean than in more productive waters. Furthermore, the enrichment of surfactants persisted at wind speeds of up to 10 m s−1 without any observed depletion above 5 m s−1. This suggests that the SML is stable enough to exist even at the global average wind speed of 6.6 m s−1. Global maps of primary production and wind speed are used to estimate the ocean's SML coverage. The maps indicate that wide regions of the Pacific and Atlantic Oceans between 30° N and 30° S are more significantly affected by the SML than northern of 30° N and southern of 30° S due to higher productivity (spring/summer blooms) and wind speeds exceeding 12 m s−1 respectively.

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

Elem Sci Anth ◽

10.1525/elementa.230 ◽

2017 ◽

Vol 5 ◽

Cited By ~ 3

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.

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Large Enrichment of Anthropogenic Organic Matter Degrading Bacteria in the Sea-Surface Microlayer at Coastal Livingston Island (Antarctica)

Frontiers in Microbiology ◽

10.3389/fmicb.2020.571983 ◽

2020 ◽

Vol 11 ◽

Author(s):

Alícia Martinez-Varela ◽

Gemma Casas ◽

Benjamin Piña ◽

Jordi Dachs ◽

Maria Vila-Costa

Keyword(s):

Organic Matter ◽

Sea Surface ◽

Surface Microlayer ◽

Livingston Island ◽

Sea Surface Microlayer ◽

Degrading Bacteria

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

Geosciences ◽

10.3390/geosciences9020066 ◽

2019 ◽

Vol 9 (2) ◽

pp. 66 ◽

Cited By ~ 7

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.

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