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The air–sea exchange of ozone (O 3) is controlled by chemistry involving halogens, dissolved organic carbon, and sulfur in the sea surface microlayer. Calculations also indicate faster ozone photolysis at aqueous surfaces, but the role of clouds as an ozone sink is currently not well established. Fast-response ozone sensors offer opportunities to measure eddy covariance (EC) ozone fluxes in the marine boundary layer. However, intercomparisons of fast airborne O 3 sensors and EC O 3 fluxes measured on aircraft have not been conducted before. In April 2022, the Technological Innovation Into Iodine and GV Environmental Research (TI 3 GER) field campaign deployed three fast ozone sensors (gas chemiluminescence and a combination of UV absorption with coumarin chemiluminescence detection, CID) together with a fast water vapor sensor and anemometer to study iodine chemistry in the troposphere and stratosphere over Colorado and over the Pacific Ocean near Hawaii and Alaska. Here, we present an instrument comparison between the NCAR Fast O 3 instrument (FO3, gas-phase CID) and two KIT Fast AIRborne Ozone instruments (FAIRO, UV absorption and coumarin CID). The sensors have comparable precision < 0.4 % Hz -0.5 (0.15 ppbv Hz -0.5), and ozone volume mixing ratios (VMRs) generally agreed within 2 % over a wide range of environmental conditions: 10 < O 3 < 1000 ppbv, below detection < NO x < 7 ppbv, and 2 ppmv < H 2 O < 4 % VMR. Both instrument designs are demonstrated to be suitable for EC flux measurements and were able to detect O 3 fluxes with exchange velocities (defined as positive for upward) as slow as - 0.010 ± 0.004 cm s -1 , which is in the lower range of previously reported measurements. Additionally, we present two case studies. In one, the direction of ozone and water vapor fluxes was reversed (vO3 = + 0.134 ± 0.005 cm s -1), suggesting that overhead evaporating clouds could be a strong ozone sink. Further work is needed to better understand the role of clouds as a possibly widespread sink of ozone in the remote marine boundary layer. In the second case study, vO3 values are negative (varying by a factor of 6–10 from - 0.036 ± 0.006 to - 0.003 ± 0.004 cm s -1), while the water vapor fluxes are consistently positive due to evaporation from the ocean surface and spatially homogeneous. This case study demonstrates that the processes governing ozone and water vapor fluxes can become decoupled and illustrates the need to elucidate possible drivers (physical, chemical, or biological) of the variability in ozone exchange velocities on fine spatial scales (∼ 20 km) over remote oceans. [ABSTRACT FROM AUTHOR]

We report on the spatial distributions and optical characteristics of chromophoric dissolved organic matter (CDOM) in the sea surface microlayer (SML), subsurface seawater (SSW), and water column profiles down to 500 m across a range of Atlantic Ocean biogeochemical provinces during two cruises of the UK Atlantic Meridional Transect program (AMT24 and AMT25). We measured the CDOM absorption coefficient at 300 nm, aCDOM(300), and determined CDOM spectral slopes across two UV wavelength ranges: S1 (275-295 nm) and S2 (350-400 nm). We used spectral slope ratios (SR: S1/S2) to infer CDOM source characteristics and transformation history. During both cruises, SML aCDOM(300) was highest in the Northern Hemisphere, particularly in the North Atlantic Drift Region (NADR). CDOM was always enriched in the SML, with enrichment factors (SML aCDOM (300) / SSW aCDOM(300)) ranging from 1.03 to 2.00, reflecting preferential accumulation of CDOM in the SML. We also found a significant inverse correlation between aCDOM(300) and S1 in both the SML (Spearman's rank correlation coefficient, r2 = -0.75, p < 0.001, n = 114) and water column profiles (r2 = -0.74, p < 0.001, n = 845). Biogeochemical province-dependent variations in the relationships between CDOM and chlorophyll a were also observed. In high-latitude regions, elevated aCDOM(300) and low SR values indicated a dominance of terrestrially-derived CDOM, whereas oligotrophic subtropical areas showed lower aCDOM(300) and higher SR values, suggestive of aged, refractory, and photodegraded biologically-derived CDOM. Taken together, these findings reveal a complexity of drivers affecting CDOM distributions and spectral properties, which may limit the use of CDOM in predictive relationships in the oceans. However, the potential use of chlorophyll a as a CDOM proxy may prove most successful in open ocean regions devoid of terrestrial inputs, where biological production predominates. [ABSTRACT FROM AUTHOR]

This summary discusses the role of sea surface biofilm in regulating the Earth's climate. It highlights the importance of microbial communities in recycling carbon and producing biofilms, which can prevent the release of greenhouse gases. The article also emphasizes the role of the sea surface microlayer (SML) in air-sea gas exchange and the impact of marine organic matter on aerosol particles. Further research is needed to fully understand the role of biofilms and the SML in climate regulation and gas exchange. Another article reviews the effects of ocean warming on marine ecosystems, including changes in distribution, abundance, and behavior of marine species. Both articles provide valuable insights into the complex interactions between ocean warming, marine ecosystems, and the Earth's climate system. [Extracted from the article]

The emergence of antibiotic-resistant bacteria in coastal waters is a global health problem posing potential risks to the health of humans who depend on coastal resources. Monitoring and increased efforts are needed to maintain the health of marine ecosystems. The sea surface microlayer (SML) is poorly studied for antibiotic resistance of the inhabiting bacteria. Therefore, we examined the antibiotic resistance patterns of 41 bacterial strains isolated from the SML in a harbor in the southern North Sea. The strains are affiliated with 17 genera typically found in the marine environment. Using the disc diffusion assay, we found extensive resistance, particularly to gentamycin, kanamycin, nalidixic acid, penicillin, sulfadimidine, and streptomycin. A broth microdilution assay showed high minimum inhibitory concentrations (MICs) for most isolates for amikacin, aztreonam, ceftazidime, cefepime, minocycline, and tobramycin. Genome analysis of three strains affiliated with the genera Pseudoseohaeicola, Nereida, and Vibrio, all showing a highly resistant phenotype, revealed the presence of 57, 42, and 90 genes, respectively, associated with antibiotic resistance. Over 50 % of these genes are multidrug efflux pumps. Our study shows that the SML in anthropogenic-influenced coastal regions harbors a wide diversity of antibiotic-resistant bacteria equipped with a broad range of multidrug efflux pumps.

The reaction between ozone and iodide is one of the main drivers of tropospheric ozone deposition to the ocean due to the ubiquitous presence of iodide in the ocean surface and its rapid reaction with ozone. Despite the importance of this sea surface reaction for tropospheric ozone deposition and also as the major source of atmospheric iodine, there is uncertainty in its rate and dependence on aqueous-phase temperature. In this work, the kinetics of the heterogeneous second-order reaction between ozone and iodide are investigated using conditions applicable to coupled ocean–atmosphere systems (1 × 10 -7 –1 × 10 -5 M iodide; 40 ppb ozone; 288–303 K ; 15.0 psi). The determined Arrhenius parameters of A = 5.4 ± 23.0 × 10 10 M-1s-1 and Ea = 7.0 ± 10.5 kJmol-1 show that the reaction has a negligible positive temperature dependence, which could be weakly negative within errors. This is in contrast to a previous study that found a strong positive activation energy and a pre-exponential factor many orders of magnitude greater than determined here. The re-measured kinetics of ozone and iodide were used to constrain a state-of-the-art sea surface microlayer (SML) model. The model replicated results from a previous laboratory study of the temperature dependence of hypoiodous acid (HOI) and molecular iodine (I2) emissions from an ozone-oxidised iodide solution. This work has significance for the global modelling of the dry deposition of ozone to the ocean and the subsequent emissions of iodine-containing species, thus improving the understanding of the feedback between natural halogens, air quality and climate change. [ABSTRACT FROM AUTHOR]

Sea surface salinity may serve as a tracer for freshwater fluxes because it is linked to evaporation and precipitation that force the freshwater balance of the ocean's surface. The relationship between freshwater fluxes and salinity anomalies in the upper few centimeters remains widely unknown. In a mechanistic approach, we investigated how these anomalies develop by conducting experiments with artificial rain over a large basin. We measured conductivity and temperature at different depths and rain characteristics (intensity, rain temperature, droplet sizes, and velocities). In the absence of turbulence, the rain causes a strong salinity change of up to 6.02 g kg - 1 in 0–4 cm depth. At the highest rain intensity of 56 mm h - 1 , salinity changed thrice as fast as at an intensity of 18 mm h - 1 . At the sea surface microlayer (first millimeter of the surface) the anomalies are always highest and reached a maximum of 14.18 g kg - 1 . With mechanical mixing, salinity changes were less pronounced (maximum SML salinity anomaly: 6.17 g kg - 1 ), and freshwater was mixed fast with the existing seawater body. In general, our study shows that freshwater remains in the upper few centimeters, and even with induced turbulence, are not mixed below 16 cm. [ABSTRACT FROM AUTHOR]

Dry deposition of ozone (O 3) to the ocean surface and the ozonolysis of organics in the sea surface microlayer (SSML) are potential sources of volatile organic compounds (VOCs) to the marine atmosphere. We use a gas chromatography system coupled to a Vocus proton-transfer-reaction time-of-flight mass spectrometer to determine the chemical composition and product yield of select VOCs formed from ozonolysis of coastal seawater collected from Scripps Pier in La Jolla, California. Laboratory-derived results are interpreted in the context of direct VOC vertical flux measurements made at Scripps Pier. The dominant products of laboratory ozonolysis experiments and the largest non-sulfur emission fluxes measured in the field correspond to Vocus C x H y+ and C x H y O z+ ions. Gas chromatography (GC) analysis suggests that C 5 –C 11 oxygenated VOCs, primarily aldehydes, are the largest contributors to these ion signals. In the laboratory, using a flow reactor experiment, we determine a VOC yield of 0.43–0.62. In the field at Scripps Pier, we determine a maximum VOC yield of 0.04–0.06. Scaling the field and lab VOC yields for an average O 3 deposition flux and an average VOC structure results in an emission source of 10.7 to 167 Tg C yr -1 , competitive with the DMS source of approximately 20.3 Tg C yr -1. This study reveals that O 3 reactivity to dissolved organic carbon can be a significant carbon source to the marine atmosphere and warrants further investigation into the speciated VOC composition from different seawater samples and the reactivities and secondary organic aerosol (SOA) yields of these molecules in marine-relevant, low NO x conditions. [ABSTRACT FROM AUTHOR]

Carbohydrates, originating from marine microorganisms, enter the atmosphere as part of sea spray aerosol (SSA) and can influence fog and cloud microphysics as cloud condensation nuclei (CCN) or ice-nucleating particles (INP). Particularly in the remote Arctic region, significant knowledge gaps persist about the sources, the sea-to-air transfer mechanisms, atmospheric concentrations, and processing of this substantial organic group. In this ship-based field study conducted from May to July 2017 in the Fram Strait, Barents Sea, and central Arctic Ocean, we investigated the sea-to-air transfer of marine combined carbohydrates (CCHO) from concerted measurements of the bulk seawater, the sea surface microlayer (SML), aerosol particles and fog. Our results reveal a wide range of CCHO concentrations in seawater (22–1070 µ g L -1), with notable variations among different sea-ice-related sea surface compartments. Enrichment factors in the sea surface microlayer (SML) relative to bulk water exhibited variability in both dissolved (0.4–16) and particulate (0.4–49) phases, with the highest values in the marginal ice zone (MIZ) and aged melt ponds. In the atmosphere, CCHO was detected in super- and submicron aerosol particles (CCHO aer,super : 0.07–2.1 ng m -3 ; CCHO aer,sub : 0.26–4.4 ng m -3) and fog water (CCHO fog,liquid : 18–22 000 µ g L -1 ; CCHO fog,atmos : 3–4300 ng m -3). Enrichment factors for sea–air transfer varied based on assumed oceanic emission sources. Furthermore, we observed rapid atmospheric aging of CCHO, indicating both biological/enzymatic processes and abiotic degradation. This study highlights the diverse marine emission sources in the Arctic Ocean and the atmospheric processes shaping the chemical composition of aerosol particles and fog. [ABSTRACT FROM AUTHOR]

Isoprene is a crucial non-methane biogenic volatile organic compound (BVOC) that exhibits the largest emissions globally. It is chemically reactive in the atmosphere and serves as the primary source of generating secondary organic aerosols (SOA) in terrestrial and remote marine regions. However, a comprehensive estimation of marine isoprene emissions is currently lacking. Here we built a module to present a 20-year (2001–2020) global hourly dataset for marine isoprene emissions, including phytoplankton-generated biological emissions (BIO emissions) and photochemistry-generated emissions in the sea surface microlayer (SML emissions) based on the latest advancements in biological, physical, and chemical processes, with high spatial resolutions. Our dataset suggests the annual global marine isoprene emissions amount to 1.097±0.009 Tg yr -1. Among these, the BIO emissions are 0.481±0.008 Tg yr -1 while SML emissions contribute 0.616±0.003 Tg yr -1. The ability of this module to estimate marine isoprene emissions was evaluated through comparison with a series of observations of marine isoprene concentrations and emission fluxes. The annual total isoprene emissions across the tropical ocean show a declining trend from 2001 to 2020. Most ocean regions exhibit a 1-year emission period, whereas a significant intraseasonal period is found in the tropical ocean. This dataset can be employed as input for the simulation of marine SOA formation in earth system models. This work provides the foundation for further studies into the impact of the air–sea system on marine SOA formation and its climate effect. The DOI link for the dataset is 10.11888/Atmos.tpdc.300521 (Cui and Zhu, 2023). [ABSTRACT FROM AUTHOR]

The reaction between ozone and iodide is one of the main drivers of tropospheric ozone deposition to the ocean, due to the ubiquitous presence of iodide in the ocean surface and its rapid reaction with ozone. Despite the importance of this sea surface reaction for tropospheric ozone deposition, and also as the major source of atmospheric iodine, there is uncertainty in its rate and dependence on aqueous phase temperature. In this work, the kinetics of the heterogeneous second order reaction between ozone and iodide were investigated using conditions applicable to coupled ocean-atmosphere systems (1 × 10−7 – 1 × 10−5 M [iodide], 40 ppb ozone, 288 – 303 K, 15.0 psi). The Arrhenius parameters determined of A = 1.0 ± 4.6 ×1011 M−1 s−1 and Ea = 8.5 ± 10.9 kJ mol−1 show that the reaction has a negligible positive temperature dependence, which could be weakly negative within errors. This is in contrast to a previous study that found a strong positive activation energy and a pre-exponential factor many orders of magnitude greater than determined here. The re-measured kinetics of ozone and iodide were used to constrain a state-of-the-art sea surface microlayer (SML) model. The model replicated results from a previous laboratory study of the temperature dependence of hypoiodous acid (HOI) and molecular iodine (I2) emissions from an ozoneoxidised iodide solution. This work has significance for global modelling of dry deposition of ozone to the ocean and the subsequent emissions of iodine-containing species, thus improving understanding of the feedbacks between natural halogens, air quality, and climate change. [ABSTRACT FROM AUTHOR]

Dry deposition of ozone (O3) to the ocean surface and the ozonolysis of organics in the sea surface microlayer (SSML) is a potential source of volatile organic compounds (VOC) to the marine atmosphere. We use a gas chromatography system coupled to a Vocus proton transfer reaction time-of-flight mass spectrometer to determine the chemical composition and product yield of select VOC formed from ozonolysis of coastal seawater collected from Scripps Pier in La Jolla, California. Laboratory-derived results are interpreted in the context of direct VOC vertical flux measurements made at Scripps Pier. The dominant products of laboratory ozonolysis experiments and the largest non-sulfur emission fluxes measured in the field correspond to Vocus CxHy+ and CxHyOz+ ions. GC analysis suggests that C5–C11 oxygenated VOC, primarily aldehydes, are the largest contributors to these ion signals. In the laboratory, using a flow reactor experiment, we determine a VOC yield of 0.43–0.62. In the field at Scripps Pier, we determine a maximum VOC yield of 0.04–0.06. Scaling the field and lab VOC yields for an average O3 deposition flux and an average VOC structure results in an emission source of 12.6 to 136 Tg C yr-1, competitive with the DMS source of 21.1 Tg C yr-1. This study reveals that O3 reactivity to dissolved organic carbon can be a significant carbon source to the marine atmosphere and warrants further investigation into the speciated VOC composition from different seawater samples, and the reactivities and secondary organic aerosol yields of these molecules in marine-relevant, low NOx conditions. [ABSTRACT FROM AUTHOR]

Marine viruses in seawater have frequently been studied, yet their dispersal from neuston ecosystems at the air-sea interface towards the atmosphere remains a knowledge gap. Here, we show that 6.2% of the studied virus population were shared between air-sea interface ecosystems and rainwater. Virus enrichment in the 1-mm thin surface microlayer and sea foams happened selectively, and variant analysis proved virus transfer to aerosols collected at ~2 m height above sea level and rain. Viruses detected in rain and these aerosols showed a significantly higher percent G/C base content compared to marine viruses. CRISPR spacer matches of marine prokaryotes to foreign viruses from rainwater prove regular virus-host encounters at the air-sea interface. Our findings on aerosolization, adaptations, and dispersal support transmission of viruses along the natural water cycle. Here, the authors provide evidence that marine viruses spread via aerosolization and rain through the natural water cycle. Hosts from the first centimeters of the marine water column show signs of immunity against rain viruses. Those have DNA adaptations facilitating their stay in the air. [ABSTRACT FROM AUTHOR]

The air-sea exchange of ozone is controlled by chemistry involving halogens, dissolved organic carbon and sulfur in the sea surface microlayer. Calculations also indicate faster ozone photolysis at aqueous surfaces, but the role of clouds as ozone sink is currently not well established. Fast response ozone sensors offer opportunities to measure eddy covariance (EC) ozone fluxes in the marine boundary layer. However, intercomparisons of fast airborne O3 sensors, and EC O3 fluxes measured on aircraft have not been conducted before. In April 2022, the TI³GER (Technical Innovation Into Iodine and GV aircraft Environmental Research) field campaign deployed three fast ozone sensors (gas chemiluminescence and a combination of UV absorption with coumarin chemiluminescence detection, CID) together with a fast water vapor sensor and anemometer to study iodine chemistry in the troposphere and stratosphere over Colorado and over the Pacific Ocean near Hawaii and Alaska. Here, we present an instrument comparison between the NCAR Fast O3 instrument (FO3, gas-phase CID) and two KIT Fast AIRborne Ozone instruments (FAIRO, UV absorption and coumarin CID). The sensors have comparable precision <0.4% Hz- 0.5 (0.15 ppbv Hz-0.5), and ozone volume mixing ratios (vmr) generally agreed within 2% over a wide range of environmental conditions: 10 < O3 < 1000 ppbv; below detection < NOx < 7 ppbv; and 2 ppmv < H2O < 4% VMR. Both instrument designs are demonstrated to be suitable for EC flux measurements and were able to detect O3 fluxes with exchange velocities (defined as positive for upward) as slow as -0.010 ± 0.004 cm s-1, which is in the lower range of previously reported measurements. Additionally, we present two case studies: one in which the direction of ozone and water vapor fluxes were reversed (vO3 = +0.134 ± 0.005 cm s-1), suggesting that overhead evaporating clouds could be a strong ozone sink; and another in which ozone fluxes vO3 are negative (varying by a factor of 6-10 from -0.036 ± 0.006 to -0.003 ± 0.004 cm s-1), while the water vapor fluxes are consistently positive due to evaporation from the ocean surface and spatially homogeneous. Future work is needed to better understand the role of clouds as a possibly widespread sink of ozone in the remote marine boundary layer, and to elucidate possible drivers (physical, chemical, or biological) of the variability in ozone exchange velocities on fine spatial scales (~20 km) over remote oceans. [ABSTRACT FROM AUTHOR]

Visible surface films, termed slicks, can extensively cover freshwater and marine ecosystems, with coastal regions being particularly susceptible to their presence. The sea-surface microlayer (SML), the upper 1-mm at the air-water interface in slicks (herein slick SML) harbors a distinctive bacterial community, but generally little is known about SML viruses. Using flow cytometry, metagenomics, and cultivation, we characterized viruses and bacteria in a brackish slick SML in comparison to non-slick SML as well as seawater below slick and non-slick areas (subsurface water = SSW). Size-fractionated filtration of all samples distinguished viral attachment to hosts and particles. The slick SML contained higher abundances of virus-like particles, prokaryotic cells, and dissolved organic carbon compared to non-slick SML and SSW. The community of 428 viral operational taxonomic units (vOTUs), 426 predicted as lytic, distinctly differed across all size fractions in the slick SML compared to non-slick SML and SSW. Specific metabolic profiles of bacterial metagenome-assembled genomes and isolates in the slick SML included a prevalence of genes encoding motility and carbohydrate-active enzymes (CAZymes). Several vOTUs were enriched in slick SML, and many virus variants were associated with particles. Nine vOTUs were only found in slick SML, six of them being targeted by slick SML-specific clustered-regularly interspaced short palindromic repeats (CRISPR) spacers likely originating from Gammaproteobacteria. Moreover, isolation of three previously unknown lytic phages for Alishewanella sp. and Pseudoalteromonas tunicata, abundant and actively replicating slick SML bacteria, suggests that viral activity in slicks contributes to biogeochemical cycling in coastal ecosystems. [ABSTRACT FROM AUTHOR]

A Gram-negative, strictly aerobic, non-motile, slightly curved rod-shaped bacterial strain, designated as HL-RS19T, was isolated from a sea surface microlayer (SML) sample of the brackish Lake Shihwa. Here, we characterized the new strain HL-RS19T using a polyphasic approach to determine its taxonomic position. A phylogenetic analysis of its 16S rRNA gene sequence revealed that strain HL-RS19T belonged to the genus Lacinutrix and was closely related to L. mariniflava AKS432T (97.9%), L. algicola AKS293T (97.8%), and other Lacinutrix species (<97.3%). The complete genome sequence of strain HL-RS19T comprised a circular chromosome of 3.9 Mbp with a DNA G+C content of 35.2%. Genomic comparisons based on the average nucleotide identity and digital DNA-DNA hybridization showed that strain HL-RS19T was consistently discriminated from its closely related taxa in the genus Lacinutrix. Strain HL-RS19T showed optimal growth at 20–25 °C, pH 6.5–7.0, and 3.0–3.5% (w/v) sea salts. The major fatty acids (>5%) of strain HL-RS19T were identified as iso-C15:1 G (16.5%), iso-C16:0 3-OH (12.9%), anteiso-C15:1 A (9.9%), anteiso-C15:0 (9.7%), iso-C15:0 (9.0%), and iso-C15:0 3-OH (8.3%). The polar lipids consisted of phosphatidylethanolamine, three unidentified aminolipids, an unidentified phospholipid, and two unidentified lipids. The major respiratory quinone was MK-6. Based on phylogenetic, genomic, phenotypic, and chemotaxonomic data, strain HL-RS19T represents a novel species belonging to the genus Lacinutrix, for which the name Lacinutrix neustonica sp. nov. is proposed. The type strain is HL-RS19T (=KCCM 90497T = JCM 35710T). The genome sequence analysis of strain HL-RS19T suggests that it may be well adapted to a harsh SML environment and is likely involved in arsenic cycling, potentially contributing to the bioremediation of anthropogenic arsenic pollution. [ABSTRACT FROM AUTHOR]

Isoprene is a crucial non-methane biogenic volatile organic compound (BVOC) that exhibits the largest emissions globally. It is chemically reactive in the atmosphere and serves as the primary source to generate of secondary organic aerosols (SOA) in terrestrial and remote marine regions. However, a comprehensive estimation of marine isoprene emissions is currently lacking. Here we built a module to present a twenty-year (2001-2020) global hourly dataset for marine isoprene emissions, including phytoplankton-generated biological emissions (BIO emissions) and photochemistry-generated emissions in the sea surface microlayer (SML emissions) based on the latest advancements in biological, physical, and chemical processes, with high spatial and temporal resolutions. The ERA5-hourly meteorological reanalysis (0.25°×0.25° horizontal spatial resolution) from the European Centre for Medium-Range Weather Forecasts (ECMWF) for the period of 2001-2020 were used as input for meteorological factors. Chlorophyll concentration data and the downwelling radiative flux diffuse attenuation coefficient data were collected from the National Aeronautics and Space Administration's (NASA) Ocean Color Web MODIS Level-3 data, with a resolution of 9 km, covering the same period. Additionally, monthly normalized water-leaving radiance at 410 nm data from the Visible and Infrared Imager/Radiometer Suite (VIIRS) were provided by the National Oceanic and Atmospheric Administration (NOAA). Our dataset suggests the annual global marine isoprene emissions amount to 1.049 ± 0.009 Tg·yr -1. Among these, the BIO emissions are 0.433 ± 0.007 Tg·yr -1 while SML emissions contribute 0.616 ± 0.003 Tg·yr -1. The ability of this module to estimate marine isoprene emissions was evaluated through comparison with a series of observations of marine isoprene concentrations and emission fluxes. Annual total isoprene emission across tropical ocean shows a declining trend from 2001 to 2020. Most ocean regions exhibit a one-year emission period, whereas a significant intraseasonal period is found in the tropical ocean. This dataset can be employed as input for the simulation of marine SOA formation in earth system models. This work provides the foundation for further studies into the impact of the air-sea system on marine SOA formation and its climate effect. The DOI link for the dataset is http://dx.doi.org/10.11888/Atmos.tpdc.300521 (Cui and Zhu., 2023). [ABSTRACT FROM AUTHOR]

This study examines carbohydrates, amino acids, and lipids as important contributors to organic carbon (OC) in the tropical Atlantic Ocean at the Cape Verde Atmospheric Observatory (CVAO). The above compounds were measured in both surface seawater and in ambient sub-micron aerosol particles to investigate their sea-to-air transfer, including their enrichment in the sea surface microlayer (SML), potential atmospheric in situ formation or degradation, and their oceanic contribution to the ambient marine aerosol particles. In bulk seawater and the SML, similar distributions among species were found for the lipids and carbohydrates with moderate SML enrichments (enrichment factors EF SML = 1.3 ± 0.2 and 1.1 ± 0.5 respectively). In contrast, the amino acids exhibited a higher enrichment in the SML with an average EF SML of 2.3 ± 0.4, although they are less surface-active than lipids. The same compounds studied in the seawater were found on the ambient sub-micron aerosol particles, whereas the lipids' enrichment was more pronounced (EF aer.=1.6×105) compared to the amino acids and carbohydrates (EF aer.=1.5×103 and 1.3×103 respectively), likely due to their high surface activity and/or the lipophilic character. Detailed molecular analysis of the seawater and aerosol particles revealed changes in the relative abundance of the individual organic compounds. They were most pronounced for the amino acids and are likely related to an in situ atmospheric processing by biotic and/or abiotic reactions. On average, 49 % of the OC on the aerosol particles (=∧97 ng m -3) could be attributed to the specific components or component groups investigated in this study. The majority (43 %) was composed of lipids. Carbohydrates and amino acids made up less than 1 % of the OC. This shows that carbohydrates, at least when resolved via molecular measurements of single sugars, do not comprise a very large fraction of OC on marine aerosol particles, in contrast to other studies. However, carbohydrate-like compounds are also present in the high lipid fraction (e.g. as glycolipids), but their chemical composition could not be revealed by the measurements performed here. Previously determined OC components at the CVAO, specifically amines, oxalic acid, and carbonyls, comprised an OC fraction of around 6 %. Since the identified compounds constituted about 50 % of the OC and belong to the rather short-lived biogenic material probably originating from the surface ocean, a pronounced coupling between ocean and atmosphere was indicated for this oligotrophic region. The remaining, non-identified OC fraction might in part contain recalcitrant OC; however, this fraction does not constitute the vast majority of OC in the aerosol particles investigated here. [ABSTRACT FROM AUTHOR]

We present the results of salinity (ΔS) and temperature (ΔT) anomalies in the sea surface microlayer (SML) in relation to the underlying mixed bulk water (bulk). Several light to moderate rain events were recorded in the southern Pacific near Fiji using our remotely operated catamaran. Precipitation and evaporation drive freshwater fluxes across the sea surface (i.e., the SML) and are the most essential processes of the hydrologic cycle. However, measurements of the SML during precipitation are rare, but necessary to fully understand freshwater exchange at the air‐sea interface. Here we show that freshwater can mix rapidly with the bulk water through wind‐induced mixing, as ΔS and ΔT show a clear dependence on wind speed. At high wind speeds (5.1–11.6 m s−1), anomalies approach zero (ΔS = −0.02 ± 0.49 g kg−1, ΔT = −0.09 ± 0.46°C) but can reach ΔS = 1.00 ± 0.20 g kg−1 and ΔT = −0.37 ± 0.09°C at lower wind speeds (0–2 m s−1). We find shallow freshwater lenses and fronts, likely caused by past rainfall, with ΔS and ΔT of up to −1.11 g kg−1 and 1.77°C, respectively. Our observations suggest that freshwater lenses can be very shallow (<1 m depth) and missed by conventional measurements. In addition, the temperature and salinity in the SML respond to freshwater fluxes instantaneously. It highlights the role of the SML in a mechanistic understanding of the fate of freshwater over the ocean and, therefore, the global hydrologic cycle. Plain Language Summary: Rain and evaporation are the most important processes in the global water cycle, causing either the supply to or the removal of freshwater from the upper ocean, thereby changing the salinity of the sea surface. Evaporation also removes heat and lowers the temperature on the ocean surface. We used the measurements of sea surface microlayer (SML) salinity and temperature as key indicators to study hydrologic cycle processes during our cruise with the RV Falkor in the South Pacific and found that freshwater mixes rapidly with the underlying bulk water during strong winds (5.1–11.6 m s−1). We also detected shallow freshwater lenses and fronts, most likely caused by past rainfall, with ΔS and ΔT of up to −1.11 g kg−1 and 1.77°C, respectively. Our observations suggest that freshwater lenses can occur at the sea surface and that the SML respond to freshwater fluxes instantaneously. It highlights the role of the SML for future studies of the global hydrologic cycle. Key Points: Small scale air‐sea interactions (freshwater fluxes) during precipitation were investigated in the southern PacificTemperature and salinity anomalies occur with a high spatial variabilityMeasurements with remote controlled catamaran revealed shallow freshwater lenses, which were not detectable with ship based measurements [ABSTRACT FROM AUTHOR]

We present the characterisation and distribution of organic matter (OM) within the sea surface microlayer (SML) and underlying water (ULW) collected in October 2015 at nine stations in the Baltic Sea, Gulf of Gdańsk, encompassing the Vistula River plume. The salinity of >7 throughout the transect indicated Vistula plume was possibly displaced westward by the preceding northerly and easterly winds between 5.7 and 10.7 ms–1 during the sampling campaign. Spectral analysis pointed to the highest contribution of aromatic and high molecular weight molecules (lowest spectral slope (SR) ratios and highest absorption coefficient at 254 nm (aCDOM(254)) at the first two stations near the river mouth, demonstrating a very limited influence of the river plume. Concentrations of surface-active organic substances (SAS) ranged from 0.28 to 0.60 mg L−1 in eq. Triton-X-100 in SML, and from 0.22 to 0.47 mg L−1 in eq. Triton-X-100 in the ULW, while POC concentrations ranged from 0.27 to 0.84 mg L−1 in SML and from 0.20 to 0.37 mg L−1 in ULW. Enrichment of SAS and POC detected at the highest wind speeds indicates rapid SML recovery by OM transported from the ULW. Low lipids to POC contribution, on average 5% and 7% in SML and ULW respectively, points to eutrophic conditions. Statistically significant negative correlation between SR and the Lipid:PIG ratio in SML and ULW suggests the production of lower molecular weight OM by phytoplankton living under favourable environmental conditions. Accumulation of lipid reserves triacylglycerols (TG) in the SML indicates more stressful plankton growth conditions compared to ULW.

The microbial cycling of dimethylsulfoniopropionate (DMSP) and the resulting gaseous catabolites dimethylsulfide (DMS) or methylmercaptan (MeSH) play key roles in the global sulfur cycle and potentially climate regulation. As the ocean–atmosphere boundary, the sea surface microlayer (SML) is important for the generation and emission of DMS and MeSH. However, understanding of the microbial DMSP metabolism remains limited in the SML. Here, we studied the spatiotemporal differences for DMS/DMSP, bacterial community structure and the key bacterial DMSP metabolic genes between SML and subsurface seawater (SSW) samples in the eastern China marginal seas (the East China Sea and Yellow Sea). In general, DMSPd and DMSPt concentrations, and the abundance of total, free-living and particle-associated bacteria were higher in SML than that in SSW. DMSP synthesis (~7.81-fold for dsyB, ~2.93-fold for mmtN) and degradation genes (~5.38-fold for dmdA, ~6.27-fold for dddP) detected in SML were more abundant compared with SSW samples. Free-living bacteria were the main DMSP producers and consumers in eastern Chinese marginal sea. Regionally, the bacterial community structure was distinct between the East China Sea and the Yellow Sea. The abundance of DMSP metabolic genes (dsyB, dmdA, and dddP) and genera in the East China Sea were higher than those of the Yellow Sea. Seasonally, DMSP/DMS level and DMSP metabolic genes and bacteria were more abundant in SML of the East China Sea in summer than in spring. Different from those in spring, Ruegeria was the dominant DMSP metabolic bacteria. In conclusion, the DMSP synthesis and degradation showed significant spatiotemporal differences in the SML of the eastern China marginal seas, and were consistently more active in the SML than in the SSW. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) in the ocean represents about 662 billion tons of C, 200 times more than the living biomass. It is produced mainly by microbial primary production. The largest fraction of this DOM is old (>weeks to months) and both chemically and biologically recalcitrant. The remainder is young (seconds to weeks), more labile and surface active. Part of the latter fraction changes the rheological properties in the bulk phase of the water and at interfaces including the sea surface microlayer (SML). In order of abundance, this DOM consists of sugars, amino acids, fatty acids and nucleic acids, often incorporated into complex polymers. The DOM molecules are produced by microbial genes, and are further modified by enzymes themselves produced by genes. The properties of ocean water and its interfaces as well as biogeochemical fluxes may thus be modified by ocean plankton genes. These fluxes influence ocean and atmospheric climate, which in return acts on the biota. Viral infection may furthermore modify prokaryotic and eukaryotic genes and their expression. Therefore, the ocean plankton genomes and the fluxes and climates they influence may be subject to Darwinian-type selection. Research programs need to integrate ocean ecology, rheology, biogeochemistry and genomics, to find the associations among them. [ABSTRACT FROM AUTHOR]

We report on airborne limb and nadir measurements of vertical profiles and total vertical column densities (VCDs) of glyoxal (C2H2O2) in the troposphere, which were performed aboard the German research aircraft HALO (High Altitude and LOng Range) in different regions and seasons around the globe between 2014 and 2019. The airborne nadir and integrated limb profiles agree excellently among each other. Our airborne observations are further compared to collocated glyoxal measurements of the TROPOspheric Monitoring Instrument (TROPOMI), with good agreement between both data sets for glyoxal observations in (1) pristine terrestrial, (2) pristine marine, (3) mixed polluted, and (4) biomass-burning-affected air masses with high glyoxal concentrations. Exceptions to the overall good agreement are observations of (1) faint and aged biomass burning plumes over the oceans and (2) of low-lying biomass burning or anthropogenic plumes in the terrestrial or marine boundary layer, both of which contain elevated glyoxal that is mostly not captured by TROPOMI. These differences in airborne and satellite-detected glyoxal are most likely caused by the overall small contribution of plumes of a limited extent to the total glyoxal absorption in the atmosphere and the difficulty in remotely detecting weak absorbers located close to low reflective surfaces (e.g. the ocean in the visible wavelength range) or within dense aerosol layers. Observations of glyoxal in aged biomass burning plumes (e.g. observed over the tropical Atlantic off the coast of West Africa in summer 2018, off the coast of Brazil by the end of the dry season 2019, and the East China Sea in spring 2018) could be traced back to related wildfires, such as a plume crossing over the Drake Passage that originated from the Australian bushfires in late 2019. Our observations of glyoxal in such aged biomass burning plumes confirm recent findings of enhanced glyoxal and presumably secondary organic aerosol (SOA) formation in aged wildfire plumes from yet-to-be-identified, longer-lived organic precursor molecules (e.g. aromatics, acetylene, or aliphatic compounds) co-emitted in the fires. Furthermore, elevated glyoxal (median 44 ppt – parts per trillion), as compared to other marine regions (median 10–19 ppt), is observed in the boundary layer over the tropical oceans, which is well in agreement with previous reports. The airborne data sets are further compared to glyoxal simulations performed with the global atmosphere chemistry model EMAC (ECHAM/MESSy Atmospheric Chemistry). When using an EMAC set up that resembles recent EMAC studies focusing on complex chemistry, reasonable agreement is found for pristine air masses (e.g. the unperturbed free and upper troposphere), but a notable glyoxal overestimation of the model exists for regions with high emissions of glyoxal and glyoxal-producing volatile organic compounds (VOCs) from the biosphere (e.g. the Amazon). In all other investigated regions, the model underpredicts glyoxal to varying degrees, in particular when probing mixed emissions from anthropogenic activities (e.g. over continental Europe, the Mediterranean, and East China Sea) and potentially from the sea (e.g. the tropical oceans). Also, the model tends to largely underpredict glyoxal in city plumes and aged biomass burning plumes. The potential causes for these differences are likely to be multifaceted, but they all point to missing glyoxal sources from the degradation of the mixture of potentially longer-chained organic compounds emitted from anthropogenic activities, biomass burning, and from the organic microlayer of the sea surface. [ABSTRACT FROM AUTHOR]

Elevated dimethyl sulfide (DMS) concentrations in the sea surface microlayer (SML) have been previously related to DMS air–sea flux anomalies in the southwestern Pacific. To further address this, DMS, its precursor dimethylsulfoniopropionate (DMSP), and ancillary variables were sampled in the SML and also subsurface water at 0.5 m depth (SSW) in different water masses east of New Zealand. Despite high phytoplankton biomass at some stations, the SML chlorophyll a enrichment factor (EF) was low (< 1.06), and DMSP was enriched at one station with DMSP EF ranging from 0.81 to 1.25. DMS in the SML was determined using a novel gas-permeable tube technique which measured consistently higher concentrations than with the traditional glass plate technique; however, significant DMS enrichment was present at only one station, with the EF ranging from 0.40 to 1.22. SML DMSP and DMS were influenced by phytoplankton community composition, with correlations with dinoflagellate and Gymnodinium biomass, respectively. DMSP and DMS concentrations were also correlated between the SML and SSW, with the difference in ratio attributable to greater DMS loss to the atmosphere from the SML. In the absence of significant enrichment, DMS in the SML did not influence DMS emissions, with the calculated air–sea DMS flux of 2.28 to 11.0 µ mol m -2 d -1 consistent with climatological estimates for the region. These results confirm previous regional observations that DMS is associated with dinoflagellate abundance but indicate that additional factors are required to support significant enrichment in the SML. [ABSTRACT FROM AUTHOR]

This study examines carbohydrates, amino acids, and lipids as important contributors to organic carbon (OC) in the tropical Atlantic Ocean at the Cape Verde Atmospheric Observatory (CVAO). The above compounds were measured in both surface seawater and in ambient submicron aerosol particles to investigate their sea-to-air transfer, including their enrichment in the sea surface microlayer (SML), potential atmospheric in situ formation or degradation, and their oceanic contribution to the ambient marine aerosol particles. In bulk seawater and the SML, similar distributions among species were found for the lipids and carbohydrates with moderate SML enrichments (enrichment factor EFSML = 1.3±0.2 and 1.1±0.5 respectively). In contrast, the amino acids exhibited a higher enrichment in the SML with an averaging EFSML of 2.4±0.3 although being less surface-active than lipids. The same compounds studied in the seawater were found on the ambient submicron aerosol particles whereas the lipids were more pronounced enriched (EFaer. = 1.6x105) compared to the amino acids and carbohydrates (EFaer. = 1.5x10³ and 1.3x10³ respectively), likely due to their high surface activity and/or the lipophilic character. Detailed molecular analysis of the seawater and aerosol particles revealed changes in the relative composition of the single organic compounds. They were most pronounced for the amino acids and are likely related to an in situ atmospheric processing by biotic and/or abiotic reactions. On average 49 % of the OC on the aerosol particles (≙ 97 ng m-3) could be attributed to the specific components or component groups investigated in this study. The majority (43 %) was composed of lipids. Carbohydrates and amino acids made up less than 1 % of the OC. This shows that carbohydrates, at least resolved via molecular measurements of single sugars, do not comprise a very large fraction of OC on marine aerosol particles, in contrast to other studies. However, carbohydrate-like compounds are also present in the high lipid fraction (e.g., as glycolipids), but their chemical composition could not be revealed by the measurements performed here. Previously determined OC components at the CVAO, in detail amines, oxalic acid, and carbonyls, comprised an OC fraction of around 6 %. Since the identified compounds constituted about 50 % of the OC and belong to the rather short-lived biogenic material probably originating from the surface ocean, a pronounced coupling between ocean and atmosphere was indicated for this oligotrophic region. The remaining, non-identified OC fraction might in part contain recalcitrant OC, however, this fraction does not constitute the vast majority of OC in the here investigated aerosol particles. [ABSTRACT FROM AUTHOR]

Sea salt aerosols play an important role in the radiation budget and atmospheric composition over the Arctic, where the climate is rapidly changing. Previous observational studies have shown that Arctic sea ice leads are an important source of sea salt aerosols, and modeling efforts have also proposed blowing snow sublimation as a source. In this study, size-resolved atmospheric particle number concentrations and chemical composition were measured at the Arctic coastal tundra site of Utqiaġvik, Alaska, during spring (3 April–7 May 2016). Blowing snow conditions were observed during 25 % of the 5-week study period and were overpredicted by a commonly used blowing snow parameterization based solely on wind speed and temperature. Throughout the study, open leads were present locally. During periods when blowing snow was observed, significant increases in the number concentrations of 0.01–0.06 µ m particles (factor of 6, on average) and 0.06–0.3 µ m particles (67 %, on average) and a significant decrease (82 %, on average) in 1–4 µ m particles were observed compared to low wind speed periods. These size distribution changes were likely caused by the generation of ultrafine particles from leads and/or blowing snow, with scavenging of supermicron particles by blowing snow. At elevated wind speeds, both submicron and supermicron sodium and chloride mass concentrations were enhanced, consistent with wind-dependent local sea salt aerosol production. At moderate wind speeds below the threshold for blowing snow as well as during observed blowing snow, individual sea spray aerosol particles were measured. These individual salt particles were enriched in calcium relative to sodium in seawater due to the binding of this divalent cation with organic matter in the sea surface microlayer and subsequent enrichment during seawater bubble bursting. The chemical composition of the surface snowpack also showed contributions from sea spray aerosol deposition. Overall, these results show the contribution of sea spray aerosol production from leads on both aerosols and the surface snowpack. Therefore, if blowing snow sublimation contributed to the observed sea salt aerosol, the snow being sublimated would have been impacted by sea spray aerosol deposition rather than upward brine migration through the snowpack. Sea spray aerosol production from leads is expected to increase, with thinning and fracturing of sea ice in the rapidly warming Arctic. [ABSTRACT FROM AUTHOR]

Environmental context: Saccharides contribute substantially to dissolved organic carbon in the ocean and are enriched at the ocean surface. In this study, we demonstrate that saccharides are more enriched in persistent whitecap foam compared to the sea surface. The maturation of bubbles at the air–water interface is thus expected to enhance the enrichment of organic matter at the ocean surface and ultimately in the sea spray aerosol that forms when bubbles burst at the ocean surface. Rationale: Organic matter accumulates at the ocean surface. Herein, we provide the first quantitative assessment of the enrichment of dissolved saccharides in persistent whitecap foam and compare this enrichment to the sea surface microlayer (SSML) during a 9 day mesocosm experiment involving a phytoplankton bloom generated in a Marine Aerosol Reference Tank (MART). Methodology: Free monosaccharides were quantified directly, total saccharides were determined following mild acid hydrolysis and the oligo/polysaccharide component was determined as the difference between total and free monosaccharides. Results: Total saccharides contributed a significant fraction of dissolved organic carbon (DOC), accounting for 13% of DOC in seawater, 27% in SSML and 31% in foam. Median enrichment factors (EFs), calculated as the ratio of the concentrations of saccharides relative to sodium in SSML or foam to that of seawater, ranged from 1.7 to 6.4 in SSML and 2.1–12.1 in foam. Based on median EFs, xylitol, mannitol, glucose, galactose, mannose, xylose, fucose, rhamnose and ribose were more enriched in foam than SSML. Discussion: The greatest EFs for saccharides coincided with high chlorophyll levels, indicating increasing ocean surface enrichment of saccharides during phytoplankton blooms. Higher enrichments of organic matter in sea foam over the SSML indicate that surface active organic compounds become increasingly enriched on persistent bubble film surfaces. These findings help to explain how marine organic matter becomes highly enriched in sea spray aerosol that is generated by bursting bubbles at the ocean surface. Environmental context. Saccharides contribute substantially to dissolved organic carbon in the ocean and are enriched at the ocean surface. In this study, we demonstrate that saccharides are more enriched in persistent whitecap foam compared to the sea surface. The maturation of bubbles at the air–water interface is thus expected to enhance the enrichment of organic matter at the ocean surface and ultimately in the sea spray aerosol that forms when bubbles burst at the ocean surface. [ABSTRACT FROM AUTHOR]

The concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), total dissolved carbohydrates (TDCHO), and total hydrolyzable amino acids (THAA) in the sea surface microlayer (SML) and subsurface water (SSW) were measured in the Yellow Sea and East China Sea. Concentrations of DOC and TDCHO in the SML were correlated with their respective concentrations in the SSW (Pearson's correlations: DOC, r2 = 0.17, n = 45, p < 0.01; TDCHO, r2 = 0.32, n = 45, p < 0.01). In contrast, DON and THAA concentrations in the SML and SSW were not correlated, suggesting that processes other than exchange with SSW dominated their loss or gain in the SML. Both THAA and TDCHO were significantly enriched in the SML, with mean enrichment factors (EFs) of 2.24 ± 1.17 and 1.98 ± 1.08, respectively. The EFs of dissolved organic matter (DOM) were not correlated with wind speed under the influence of complex processes (e.g., bubbling and turbulence). THAA‐C% and TDCHO‐C% in the SML were 3.38 ± 1.71% and 8.49 ± 4.81%, respectively, which were significantly higher than those in the SSW (Mann‐Whitney U test, p < 0.05), suggesting that DOM in the SML was fresher than that in the SSW. While the high bioavailability of DOM in the SML should be conducive to neuston proliferation in this unique environment, no significant correlations were observed between degradation indicators and neuston abundances. In contrast, the changes of temperature and pH may have an important impact on the degradation of DOM. Plain Language Summary: The sea surface microlayer (SML) is a thin layer (1–1,000 μm) and unique biological, physical and chemical habitat at the interface between the atmosphere and the hydrosphere. Compared with the subsurface water (SSW, depth <1 m), the SML is generally enriched with various organisms and surface‐active material. In this study, the distribution, enrichment and potential links between neuston abundances with the dissolved organic matter (DOM) bioavailability were studied, providing the most extensive data set pertaining to the SML in the Yellow Sea and East China Sea to date. Due to the riverine input, phytoplankton production and SSW replenishment, elevated concentrations of DOM mostly appeared in the Changjiang Estuary and other coastal areas. Total dissolved carbohydrates (TDCHO) and total hydrolyzable amino acids (THAA) were significantly enriched in the SML. Several physical and biological processes, including turbulent mixing, rising bubbles and in situ primary production, contribute to the enrichment of DOM. THAA‐C% and TDCHO‐C% were consistently higher in the SML relative to the SSW, indicating that DOM in the SML was fresher than that in the SSW. However, there were no significant correlations between degradation indicators and neuston abundances, indicating that DOM bioavailability was not the main factor affecting neuston abundances. Key Points: In addition to phytoplankton production and bacterial degradation, changes in temperature and pH also affect the degradation state of dissolved organic matter (DOM)Dissolved organic nitrogen and total hydrolyzable amino acids were highly enriched in the sea surface microlayer and their concentrations were more likely affected by in situ productionDOM bioavailability was not the main factor affecting neuston abundances in the microlayer [ABSTRACT FROM AUTHOR]

The sea surface microlayer (SML), particularly in monsoon-influenced regions, remains largely unexplored. This study aims to determine the concentrations, enrichment, and factors controlling the enrichment processes of surface-active substances (SASs), which include surfactants, dissolved monosaccharides (MCHOs), polysaccharides (PCHOs), total dissolved carbohydrates (TDCHOs), and transparent exopolymer particles (TEPs) around the coastal area of Malaysian Peninsula. The SML samples and underlying water (ULW) from a depth of 1 m were collected during the southwest (August and September 2023) and northeast (November 2023) monsoons. Surfactants, TEPs, and dissolved carbohydrates were measured spectrometrically using methylene blue, the Alcian blue assay, and 2,4,6-Tri(2-pyridyl)- s -triazine (TPTZ), respectively. The results showed that stations influenced by anthropogenic activities were generally enriched with surfactants (Enrichment factor, EF = 1.40 ± 0.91) and carbohydrate species (TDCHOs = 1.38 ± 0.28, MCHOs = 1.54 ± 0.57, PCHOs = 1.85 ± 1.43). However, TEP enrichment was not observed in our study (EF = 0.68 ± 0.24). The SASs in the SML were correlated with their underlying concentrations, implying that transport from underlying water could be a major source of substances in the SML. High carbohydrate concentrations and enrichment were found during the northeast monsoon, implying that rain and runoff water affect concentrations in the SML. Besides, the enrichment of SASs persists at moderate wind speeds and is depleted at high wind speeds. • The SML is enriched with surfactants and dissolved carbohydrates, persisting at moderate wind speeds. • Higher input of substances through wet deposition and photodegradation could explain higher SASs in Port Dickson. • Concentrations of SASs in the SML were positively correlated to those in ULW implying the upward flux from underlying water. • Carbohydrates enriched in the SML during NE monsoon are likely due to precipitation, run-off, and low wind speed. [ABSTRACT FROM AUTHOR]

A Gram-negative, strictly aerobic, non-motile, slightly curved rod-shaped bacterial strain, designated as HL-RS19T, was isolated from a sea surface microlayer (SML) sample of the brackish Lake Shihwa. Here, we characterized the new strain HL-RS19T using a polyphasic approach to determine its taxonomic position. A phylogenetic analysis of its 16S rRNA gene sequence revealed that strain HL-RS19T belonged to the genus Lacinutrix and was closely related to L. mariniflava AKS432T (97.9%), L. algicola AKS293T (97.8%), and other Lacinutrix species (T comprised a circular chromosome of 3.9 Mbp with a DNA G+C content of 35.2%. Genomic comparisons based on the average nucleotide identity and digital DNA-DNA hybridization showed that strain HL-RS19T was consistently discriminated from its closely related taxa in the genus Lacinutrix. Strain HL-RS19T showed optimal growth at 20–25 °C, pH 6.5–7.0, and 3.0–3.5% (w/v) sea salts. The major fatty acids (>5%) of strain HL-RS19T were identified as iso-C15:1 G (16.5%), iso-C16:0 3-OH (12.9%), anteiso-C15:1 A (9.9%), anteiso-C15:0 (9.7%), iso-C15:0 (9.0%), and iso-C15:0 3-OH (8.3%). The polar lipids consisted of phosphatidylethanolamine, three unidentified aminolipids, an unidentified phospholipid, and two unidentified lipids. The major respiratory quinone was MK-6. Based on phylogenetic, genomic, phenotypic, and chemotaxonomic data, strain HL-RS19T represents a novel species belonging to the genus Lacinutrix, for which the name Lacinutrix neustonica sp. nov. is proposed. The type strain is HL-RS19T (=KCCM 90497T = JCM 35710T). The genome sequence analysis of strain HL-RS19T suggests that it may be well adapted to a harsh SML environment and is likely involved in arsenic cycling, potentially contributing to the bioremediation of anthropogenic arsenic pollution.

Dust emitted from North Africa is transported over long distances and has a strong impact on large areas over the North Tropical Atlantic Ocean. Sea salt emitted by the sea surface is the second source of essential elements transported in the atmosphere and plays a major role in the cycles of alkaline‐earth metals in the ecosystems of tropical North Atlantic Islands. The total atmospheric deposition fluxes were continuously sampled on a weekly basis in Guadeloupe, Lesser Antilles, from March 2015 to August 2018 (41 months). Elemental deposition fluxes, including Al, Ca, K, Mg, Fe, Na, P, S, and Zn, were measured for all samples to provide the first long time series of atmospheric elemental deposition fluxes over the Lesser Antilles region. It is shown that: (a) the three sources of atmospheric deposits in Guadeloupe for the presented elements are sea salt (for K, Ca, Mg, Na, and S), long‐range transported Saharan dust (for Al, Ca, K, and Fe), and biogenic particles (for P and Zn); (b) the average deposition mass fluxes of sea salt and Saharan dust are 17.4 and 11.2 g.m−2.year−1, respectively, without noticeable inter‐annual variations; (c) a pronounced seasonality is found for the Saharan dust deposition, for which maximum flux values are observed between June and July each year and 85% of the annual deposition flux occurs between April and September; (d) the deposition flux of sea salt is strongly correlated to local wind speed, without seasonality. Plain Language Summary: Saharan dust and sea salt contribute toward feeding trees living on Caribbean Island ground with alkaline, alkaline‐earth cations and other important elements. Saharan dust is transported time to time from North Africa with a higher frequency of events in summer. Sea salt is continuously locally emitted from the sea surface by the action of trade winds and storms on the sea surface that produces sea water brine. For the first time, we have measured the Saharan dust and sea salt deposition flux continuously for 3 years in Guadeloupe. We have found that Saharan dust brings iron, calcium, and potassium, and sea salt brings sodium, magnesium, sulfur, and potassium. The high flux of phosphorus is due to the local recycling of living debris and zinc which probably come from sea surface micro‐layer torn by the wind. These results enhance our knowledge of nutrients cycles in the North Atlantic region. Key Points: We have monitored atmospheric deposition in Guadeloupe over a 3‐year period with measurements of Al, Na, Mg, P, S, K, Ca, Fe, and ZnStrong seasonality for Saharan dust, no inter‐annual deposition flux variations for both sea salt and Saharan dustWe suggest that the contributions of Saharan dust, sea salt, and biogenic emissions explain the origin of the deposited elements [ABSTRACT FROM AUTHOR]

Surfactants can hamper gas exchange by up to 50 % in coastal seas; however, their small-scale temporal and spatial dynamics are poorly constrained. This study investigated possible biogenic sources of surfactants in the sea surface microlayer (SML) and the underlying water at a coastal Baltic Sea site. To relate surfactant dynamics to biogenic production, we conducted two field studies (June and September 2018) and focused on amino acids and carbohydrates as the main components of organic matter derived from phytoplankton. Furthermore the composition of the biochemicals provided insights into microbial degradation dynamics and was complemented by flow-cytometry-based community analysis. In total, 76 samples were collected within an area of approximately 50 km 2 , allowing for high spatial resolution. Moreover, morning and afternoon sampling enabled us to investigate diel cycles. Our results reveal that surfactant concentrations were tightly coupled to the abundance of nano-phytoplankton and generally higher in September than in June, with cell abundance 3 times higher. Surfactant concentration in June was best explained by the combined effect of the particulate fraction of the non-essential amino acid serine, the concentration of particulate combined carbohydrates (PCHO), and dissolved organic carbon (DOC). Surfactant and PCHO concentrations were significantly enriched in the SML and followed a pronounced diel cycle, possibly linked to microbial processing and/or photo-processing. In contrast to June, the surfactant pool in September correlated to a diverse mixture of semi-labile organic matter components, represented best by dissolved glucose and the essential amino acid isoleucine. We conclude that the surfactant pool in surface seawater is mainly composed of organic matter components that resist rapid microbial degradation. Elevated surfactant concentrations are triggered by the release of fresh organic matter. While the effect of the resistant but less surface-active stock is potentially longer-lasting, the additive effect of labile, highly surface-active agents on gas exchange may diminish on short timescales. [ABSTRACT FROM AUTHOR]

As the sea surface microlayer (SML) is the uppermost oceanic layer and differs in biogeochemical composition to the underlying subsurface water (SSW), it is important to determine whether processes in the SML modulate gas exchange, particularly for climate active gases. Enrichment of dimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) has been reported in the SML, but it remains unclear how this is maintained whilst DMS is lost to the atmosphere. To examine this, a comprehensive study of DMS source and sink processes, including production, consumption, and net response to irradiance, was carried out in deck-board incubations of SML water at five locations in different water masses in the southwestern Pacific east of New Zealand. Net consumption of DMSP and production of DMS in the light and dark occurred at all sites. The net response of DMS and DMSP to irradiance varied between stations but was always lower than conversion of DMSP to DMS in the dark. In addition, DMS photolytic turnover was slower than reported elsewhere, which was unexpected given the high light exposure in the SML incubations. Although no relationships were apparent between DMS process rates and biogeochemical variables, including chlorophyll a , bacteria, and phytoplankton groups, net bacterial DMSP consumption was correlated with DMSP and DMS concentrations and also dinoflagellate and Gymnodinium spp. biomass, supporting the findings of a companion study that dinoflagellates play an important role in DMS cycling in the SML. However, net DMS production rates and accumulation were low relative to regional air–sea DMS loss, indicating that DMS cycling within the SML is unlikely to influence regional DMS emissions. [ABSTRACT FROM AUTHOR]

The emergence of antibiotic-resistant bacteria in coastal waters is a global health problem posing potential risks to the health of humans who depend on coastal resources. Monitoring and increased efforts are needed to maintain the health of marine ecosystems. The sea surface microlayer (SML) is poorly studied for antibiotic resistance of the inhabiting bacteria. Therefore, we examined the antibiotic resistance patterns of 41 bacterial strains isolated from the SML in a harbor in the southern North Sea. The strains are affiliated with 17 genera typically found in the marine environment. Using the disc diffusion assay, we found extensive resistance, particularly to gentamycin, kanamycin, nalidixic acid, penicillin, sulfadimidine, and streptomycin. A broth microdilution assay showed high minimum inhibitory concentrations (MICs) for most isolates for amikacin, aztreonam, ceftazidime, cefepime, minocycline, and tobramycin. Genome analysis of three strains affiliated with the genera Pseudoseohaeicola, Nereida, and Vibrio, all showing a highly resistant phenotype, revealed the presence of 57, 42, and 90 genes, respectively, associated with antibiotic resistance. Over 50 % of these genes are multidrug efflux pumps. Our study shows that the SML in anthropogenic-influenced coastal regions harbors a wide diversity of antibiotic-resistant bacteria equipped with a broad range of multidrug efflux pumps., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Blooms of Ostreopsis cf. ovata pose an emerging health threat, causing respiratory disorders in various coastal regions. This dinoflagellate produce potent phycotoxins named ovatoxins that can be transferred from the seawater to the atmosphere. However, the biotic and abiotic conditions affecting their transfer are still unknown. In this study, we investigate the sea-to-air transfer of O. cf ovata phycotoxins using a process study in an aerosol reference tank (MART) and field observations. The process study exhibited a positive correlation between the phycotoxin content in sea spray aerosol (up to 832.59 ng m -3 ) and the particulate phycotoxin fraction in the water column and surface microlayer. In contrast, in the natural system, aerosolized phycotoxins were only observed in one out of six air collection (total toxins 0.59 ng m -3 ) despite optimal wind conditions. In both the process study and the natural system, ovatoxins represented only a minor fraction of the total toxin content, which was comprised of up to 90% liguriatoxins. In seawater, while no solubilized ovatoxins were detected, the concentration in dissolved liguriatoxin-a reached up to 19.07 μg L -1 . These results underscore the need for future research on the liguriatoxins, and on their toxicity to establish safe exposure thresholds for beachgoers.

Volatile organic compounds (VOCs) form ozone (O3) and secondary organic aerosols (SOAs) in the atmosphere under favourable conditions. Biogenic VOC levels in the marine atmosphere are significantly lower compared with levels in the atmosphere above terrestrial ecosystems. However, much less is known about the marine biogenic VOC sea-to-air flux, specifically at the sea surface level. Therefore, here we describe a newly developed and cost-effective floating chamber system that has the capacity to measure the VOC sea-to-air flux near the sea surface (< 1 m). The floating chamber is coupled with adsorbent cartridges, and samples were analysed in the laboratory using commercial thermal desorption and gas chromatography mass spectrometry (TD-GC–MS). The structural performance of the floating flux chamber was evaluated, and it was shown to have the capacity to stay continuously afloat for up to 72 h in various conditions (e.g., rainy, windy) and with wave heights up to approximately 1 m in coastal waters. Preliminary measurements of isoprene (3-Methyl-1,2-butadiene) (C5H8) sea-to-air flux using the floating flux chamber in the coastal waters off the east coast of Peninsular Malaysia found values in the region of 107 molecules/cm2/s, comparable with most published values based on various flux measurement techniques. We suggest the proposed floating chamber system could serve as a cost-effective VOC flux technique that allows measurements near the sea surface. [ABSTRACT FROM AUTHOR]

Atmospheric deposition represents a major input for micronutrient trace elements (TEs) to the surface ocean and is often quantified indirectly through measurements of aerosol TE concentrations. Sea spray aerosol (SSA) dominates aerosol mass concentration over much of the global ocean, but few studies have assessed its contribution to aerosol TE loading, which could result in overestimates of "new" TE inputs. Low‐mineral aerosol concentrations measured during the U.S. GEOTRACES Pacific Meridional Transect (GP15; 152°W, 56°N to 20°S), along with concurrent towfish sampling of surface seawater, provided an opportunity to investigate this aspect of TE biogeochemical cycling. Central Pacific Ocean surface seawater Al, V, Mn, Fe, Co, Ni, Cu, Zn, and Pb concentrations were combined with aerosol Na data to calculate a "recycled" SSA contribution to aerosol TE loading. Only vanadium was calculated to have a SSA contribution averaging >1% along the transect (mean of 1.5%). We derive scaling factors from previous studies on TE enrichments in the sea surface microlayer and in freshly produced SSA to assess the broader potential for SSA contributions to aerosol TE loading. Maximum applied scaling factors suggest that SSA could contribute significantly to the aerosol loading of some elements (notably V, Cu, and Pb), while for others (e.g., Fe and Al), SSA contributions largely remained <1%. Our study highlights that a lack of focused measurements of TEs in SSA limits our ability to quantify this component of marine aerosol loading and the associated potential for overestimating new TE inputs from atmospheric deposition. Plain Language Summary: Sea spray aerosol (SSA) generated by breaking waves and bursting bubbles can dominate the particle population in the marine atmosphere. We investigated whether this mechanism could mobilize significant amounts of trace elements (TEs)—nutrient and pollutant elements present in the surface ocean in very low concentrations. Previous studies have suggested that TEs could become enriched on SSA during its formation, relative to their concentrations in seawater, and this could make the process a more significant source for aerosol concentrations of some elements. But for others, the SSA contribution is always likely to be insignificant. Our calculations based on sea salt and TE aerosol concentrations in the atmosphere and dissolved TEs in the surface ocean suggest that SSA does not contribute significantly to total aerosol TE loading, with the possible exception of vanadium, which has relatively higher concentrations in seawater than the other elements considered. This study highlights that this process remains poorly quantified due to limited direct measurements. Key Points: Sea spray aerosol (SSA) concentration was quantified along a meridional Pacific Ocean transect during low mineral aerosol conditionsSea spray‐derived aerosol trace elements (TEs) are negligible unless significant enrichment occurs during formation; only vanadium is >1%SSA contributions to aerosol TEs of >100% calculated by applying enrichments from earlier studies suggests these are not widely applicable [ABSTRACT FROM AUTHOR]

Deposition of aerosols to the surface ocean is an important factor affecting primary production in the surface ocean. However, the sources and fluxes of aerosols and associated trace elements remain poorly defined. Aerosol 210Pb, 210Po, and 7Be data were collected on US GEOTRACES cruise GP15 (Pacific Meridional Transect, 152°W; 2018). 210Pb fluxes are low close to the Alaskan margin, increase to a maximum at ∼43°N, then decrease to lower values. There is good agreement between 210Pb fluxes and long‐term land‐based fluxes during the SEAREX program (1970–1980s), as well as between GP15 and GP16 (East Pacific Zonal Transect, 12°S; 2013) at adjacent stations. A normalized fraction f(7Be, 210Pb) is used to discern aerosols with upper (high f) versus lower (low f) troposphere sources. Alaskan/North Pacific aerosols show significant continental influence while equatorial/South Pacific aerosols are supplied to the marine boundary layer from the upper troposphere. Lithogenic trace elements Al and Ti show inverse correlations with f(7Be, 210Pb), supporting a continental boundary layer provenance while anthropogenic Pb shows no clear relationship with f(7Be, 210Pb). All but four samples have 210Po/210Pb activity ratios <0.2 suggesting short aerosol residence time. Among the four samples (210Po/210Pb = 0.42–0.88), two suggest an upper troposphere source and longer aerosol residence time while the remaining two cannot be explained by long aerosol residence time nor a significant component of dust. We hypothesize that enrichments of 210Po in them are linked to Po enrichments in the sea surface microlayer, possibly through Po speciation as a dissolved organic or dimethyl polonide species. Key Points: North Pacific aerosols are influenced by continental sources while South Pacific aerosols have upper troposphere sources7Be/210Pb shows that Al, Ti, and Fe have continental‐influenced lower troposphere sources; Pb has lower‐ and upper troposphere sourcesElevated aerosol 210Po/210Pb may indicate addition of Po from the sea surface as an organic Po or dimethyl polonide species [ABSTRACT FROM AUTHOR]

As the sea surface microlayer (SML) is the uppermost oceanic layer and differs in biogeochemical composition to the underlying subsurface water (SSW), it is important to determine whether processes in the SML modulate gas exchange, particularly for climate reactive gases. Enrichment of dimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) have been reported in the SML, but it remains unclear how this is maintained whilst DMS is lost to the atmosphere. To examine this, a comprehensive study of DMS source and sink processes, including production, consumption and net response to irradiance, were carried out in deck-board incubations of SML water at five locations in different water masses in the South West Pacific east of New Zealand. Net consumption of DMSP and production of DMS in the light and dark occurred at all sites. The net response of DMS and DMSP to irradiance varied between stations but was always lower than conversion of DMSP to DMS in the dark. In addition, DMS photolytic turnover was slower than reported elsewhere, which was unexpected given high light exposure in the SML incubations. Although no relationships were apparent between DMS process rates and biogeochemical variables, including chlorophyll- a , bacteria and phytoplankton group, net bacterial DMSP consumption was correlated with DMSP and DMS concentrations, and also dinoflagellate and Gymnodinium spp. biomass, supporting the findings of a companion study that dinoflagellates play an important role in DMS cycling in the SML. However, net DMS production rates and accumulation were low relative to calculated air-sea DMS loss, confirming that the DMS cycling within the SML is unlikely to influence regional DMS emissions. [ABSTRACT FROM AUTHOR]

Elevated dimethyl sulfide (DMS) concentrations in the sea surface microlayer (SML) have been previously related to DMS air-sea flux anomalies in the South West Pacific. To further address this, DMS, its precursor dimethylsulfoniopropionate (DMSP), and ancillary variables were sampled in the SML and also subsurface water at 0.5 m depth (SSW) in different water masses east of New Zealand. Despite high phytoplankton biomass at certain stations significant chlorophyll a and DMSP enrichments were only apparent at one of six stations, with the DMSP enrichment factor (EF) ranging from 0.81 to 1.25. DMS in the SML was determined using a novel gas-permeable tube technique which measured consistently higher concentrations than with the traditional glass plate technique; however, DMS enrichment was also present at only one station, with the EF ranging from 0.40 to 1.22. SML DMSP and DMS were influenced by phytoplankton community composition, with correlations with dinoflagellate and Gymnodinium biomass, respectively. DMSP and DMS concentrations were also correlated between the SML and SSW, with the difference in ratio attributable to greater DMS loss to the atmosphere from the SML. DMS in the SML did not significantly influence regional DMS emissions, with the calculated air-sea DMS flux of 1.0 to 11.0 µmol m-2 d-1 consistent with climatological estimates for the region. These results extend previous regional observations that DMS is associated with dinoflagellate abundance but indicate that additional factors are required for significant enrichment in the SML. [ABSTRACT FROM AUTHOR]

Ocean waves transfer sea spray aerosol (SSA) to the atmosphere, and these SSA particles can be enriched in organic matter relative to salts compared to seawater ratios. A fundamental understanding of the factors controlling the transfer of biogenic organic matter from the ocean to the atmosphere remains elusive. Field studies that focus on understanding the connection between organic species in seawater and SSA are complicated by the numerous processes and sources affecting the composition of aerosols in the marine environment. Here, an isolated ocean–atmosphere system enables direct measurements of the sea–air transfer of different classes of biogenic organic matter over the course of two phytoplankton blooms. By measuring excitation–emission matrices of bulk seawater, the sea surface microlayer, and SSA, we investigate time series of the transfer of fluorescent species including chlorophyll-a, protein-like substances, and humic-like substances. Herein, we show the emergence of different molecular classes in SSA at specific times over the course of a phytoplankton bloom, suggesting that SSA chemical composition changes over time in response to changing ocean biological conditions. We compare the temporal behaviors for the transfer of each component, and discuss the factors contributing to differences in transfer between phases. [ABSTRACT FROM AUTHOR]

Terrestrial anionic surfactants (AS) enter the marine environment through coastal region. Despite that, in general limited knowledge is available on the coastal AS transfer pathway. This paper aims to assess the distributions and exchange of AS in the Peninsular Malaysia coastal environments, adjacent to the southern waters of South China Sea and Strait of Malacca. An assessment case study was conducted by a review on the available data from the workgroup that span between the year 2008 and 2019. The findings showed that AS dominated in the sea surface microlayer (SML, 57%) compared to subsurface water (SSW, 43 %). AS were also found to have dominated in fine mode (FM, 71 %) compared to coarse mode (CM, 29 %) atmospheric aerosols. SML AS correspond to the SSW AS (p < 0.01); however, highest enrichment factor (EF) of the SML AS was not consistent with highest SSW AS. Direct AS exchange between SML and FM and CM was not observed. Furthermore, the paper concludes AS mainly located in the SML and FM and could potentially be the main transfer pathway in the coastal environment. [ABSTRACT FROM AUTHOR]

Studies over the last two decades have shown that submicron particulates (SMPs) can be transferred from the seawater into sea spray aerosol (SSA), potentially impacting SSA cloud seeding ability. This work reports the first concurrent bulk and sea surface microlayer (SSML) SMP (0.4–1.0 μm) measurements, made during two mesocosm phytoplankton blooms in a region devoid of active wave breaking and bubble formation, providing insight into how biological and physicochemical processes influence seawater SMP distributions. Modal analyses of the SMP size distributions revealed contributions from multiple, biologically related particulate populations that were controlled by the microbial loop. With negligible bubble scavenging occurring, SSML enrichment of SMPs remained low throughout both experiments, suggesting scavenging is vital for SMP enrichment in the SSML. Our findings are discussed in the context of SMP transfer into SSA and its potential importance for SSA cloud seeding ability. Plain Language Summary: Research has shown that particulates can be transferred from the ocean into sea spray aerosol (SSA) when bubbles burst at the ocean surface. This transfer is important because incorporation of seawater particulates into SSA can impact its ability to seed water and ice clouds. During the Sea Spray Chemistry and Particulate Evolution (SeaSCAPE) study, submicron particulates (SMPs, 0.4–1.0 μm) were measured daily in the sea surface microlayer (SSML), the topmost 1–1,000 μm of the ocean surface, and the underlying bulk seawater over the course of two phytoplankton growth experiments. The objective of this study was to assess the influence of biological activity on SMP concentrations and distributions in the seawater. Our results indicate that biological growth led to increased SMP production, and the size distribution of SMPs produced was dependent on the phase of the bloom growth. Additionally, almost no SSML enrichment of SMPs occurred without active wave breaking and bubble formation, highlighting the significance of biological activity and bubble scavenging/bursting for particulate transfer into SSA. These findings are discussed in the context of potential SMP impacts on SSA cloud forming ability. Key Points: The concentration of 0.4–1.0 μm seawater particulates is higher during a phytoplankton bloomThe biologically induced increase in seawater submicron particulates is size dependent and influenced by the phase of the bloomParticulate enrichment in the sea surface microlayer is low in the absence of wave breaking and bubble scavenging [ABSTRACT FROM AUTHOR]

We present a framework for estimating concentrations of episodically elevated high-temperature marine ice nucleating particles (INPs) in the sea surface microlayer and their subsequent emission into the atmospheric boundary layer. These episodic INPs have been observed in multiple ship-based and coastal field campaigns, but the processes controlling their ocean concentrations and transfer to the atmosphere are not yet fully understood. We use a combination of empirical constraints and simulation outputs from an Earth system model to explore different hypotheses for explaining the variability of INP concentrations, and the occurrence of episodic INPs, in the marine atmosphere. In our calculations, we examine the following two proposed oceanic sources of high-temperature INPs: heterotrophic bacteria and marine biopolymer aggregates (MBPAs). Furthermore, we assume that the emission of these INPs is determined by the production of supermicron sea spray aerosol formed from jet drops, with an entrainment probability that is described by Poisson statistics. The concentration of jet drops is derived from the number concentration of supermicron sea spray aerosol calculated from model runs. We then derive the resulting number concentrations of marine high-temperature INPs (at 253 K) in the atmospheric boundary layer and compare their variability to atmospheric observations of INP variability. Specifically, we compare against concentrations of episodically occurring high-temperature INPs observed during field campaigns in the Southern Ocean, the Equatorial Pacific, and the North Atlantic. In this case study, we evaluate our framework at 253 K because reliable observational data at this temperature are available across three different ocean regions, but suitable data are sparse at higher temperatures. We find that heterotrophic bacteria and MBPAs acting as INPs provide only a partial explanation for the observed high INP concentrations. We note, however, that there are still substantial knowledge gaps, particularly concerning the identity of the oceanic INPs contributing most frequently to episodic high-temperature INPs, their specific ice nucleation activity, and the enrichment of their concentrations during the sea–air transfer process. Therefore, targeted measurements investigating the composition of these marine INPs and drivers for their emissions are needed, ideally in combination with modeling studies focused on the potential cloud impacts of these high-temperature INPs. [ABSTRACT FROM AUTHOR]

Spatiotemporal heterogeneities in the concentrations of alkaline gases and their particulate counterparts in the marine atmosphere over China's marginal seas were investigated in terms of causes and chemical conversion during two winter cruise campaigns, using semi-continuous measurements made by an onboard URG-9000D Ambient Ion Monitor-Ion Chromatograph (AIM-IC, Thermo Fisher). During the cruise campaign over the East China Sea from 27 December 2019 to 6 January 2020, the concentrations of gas-phase atmospheric trimethylamine (TMA gas) varied by approximately 1 order of magnitude, with an average (± standard deviation) of 0.10±0.04 µ g m -3 corresponding to a mixing ratio of 26±17 pptv. Corresponding mean values were 0.037±0.011 µ g m -3 (14±5 pptv in mixing ratio) over the Yellow Sea during the period from 7 to 16 January 2020 and 0.031±0.009 µ g m -3 (12±4 pptv in mixing ratio) over the Yellow Sea and Bohai Sea from 9 to 22 December 2019. By contrast, the simultaneously observed concentrations of TMA in PM 2.5 , detected as TMAH + , over the East China Sea were 0.098±0.069 µ g m -3 and substantially smaller than the 0.28±0.18 µ g m -3 observed over the Yellow Sea and Bohai Sea from 9 to 22 December 2019. A significant correlation between TMA gas and particulate TMAH + was observed over the East China Sea, but no correlation was found over the Yellow Sea and Bohai Sea. Proportional or disproportional variations in concentrations of TMA gas with particulate TMAH + over the sea zones were probably attributed to the difference in the enrichment of TMAH + in the sea surface microlayer. In addition, spatiotemporal heterogeneities in concentrations of atmospheric ammonia (NH 3gas), atmospheric dimethylamine (DMA gas), and DMA in PM 2.5 , detected as DMAH + , were investigated. Case analyses were performed to illustrate the formation and chemical conversion of particulate aminium ions in marine aerosols. Finally, we hypothesized the release of basic gases and particulate counterparts from the ocean to the atmosphere, together with the secondary formation of DMAH + and chemical conversion of TMAH + , in the marine atmosphere. [ABSTRACT FROM AUTHOR]

Comparing measurements of the natural sea surface microlayer (SML) and artificial surface films made of Triton-X-100 and oleyl alcohol can provide a fundamental understanding of diffusive gas fluxes across the air–water boundary layers less than 1 mm thick. We investigated the impacts of artificial films on the concentration gradients and diffusion of oxygen (O2) across the SML, the thickness of the diffusive boundary layer (DBL), and the surface tension levels of natural seawater and deionized water. Natural and artificial films led to approximately 78 and 81% reductions in O2 concentration across the surfaces of natural seawater and deionized water, respectively. The thicknesses of the DBL were 500 and 350 µm when natural SML was added on filtered and unfiltered natural seawater, respectively, although the DBL on filtered seawater was unstable, as indicated by decreasing thickness over time. Triton-X-100 and oleyl alcohol at a concentration of 2000 µg L−1 in deionized water persistently increased the DBL thickness values by 30 and 26% over a period of 120 min. At the same concentration, Triton-X-100 and oleyl alcohol decreased the surface tension of deionized water from ~72 mN m−1 to 48 and 38 mN m−1, respectively; 47% recovery was recorded after 30 min with Triton-X-100, although low surface tension persisted for 120 min with oleyl alcohol. The critical micelle concentration values of Triton-X-100 ranged between 400 and 459 µg L−1. We, therefore, suggest that Triton-X-100 resembles natural SML because the reduction and partial recovery of the surface tension of deionized water with the surfactant resembles the behavior observed for natural slicks. Temperature and salinity were observed to linearly decrease the surface tension levels of natural seawater, artificial seawater, and deionized water. Although several factors leading to O2 production and consumption in situ are excluded, experiments carried out under laboratory-controlled conditions are useful for visualizing fine-scale processes of O2 transfer from water bodies through the surface microlayer. [ABSTRACT FROM AUTHOR]

The content of heavy metals and Al in the aerosol matter over the Sea of Azov has been studied. According to the special test the vast majority of samples were attributed to the type of marine aerosol. The ranges of contents were determined as following: Fe (200 – 2000 ng/m3), Al (20 – 200 ng/m3), Zn (10 – 280 ng/m3), Cu (2 – 23 ng/m3), Ni (1 – 16 ng/m3), Pb (3 -30 ng/m3), Cd (0.4 –2.8 ng/m3); Mn (3 – 23 ng/m3), Cr (1 – 15 ng/m3). The spatial distribution of HMs in the marine aerosol of the Sea of Azov depends on the influence of the river-sea geochemical barrier zone in the Taganrog Bay and the anthropogenic impact of the coastal industrial cities. HM concentrations decrease from the northern coast of the bay and the mouth of the Don River towards the open sea. The maximum HM content in marine aerosol observed in the mouth area of the Don River. It may be associated with the HM accumulation at the river-sea geochemical barrier, and also with the anthropogenic impact of the cities of Rostov-on-Don, Azov and Taganrog. Anthropogenic impact of the city of Mariupol cause the maximum values of Fe, Cr, and Cd in marine aerosol matter of the western part of the Taganrog Bay.

Bursting of bubbles at a liquid surface is ubiquitous in a wide range of physical, biological, and geological phenomena, as a key source of aerosol droplets for mass transport across the interface. However, how a structurally complex interface, widely present in nature, mediates the bursting process remains largely unknown. Here, we document the bubble-bursting jet dynamics at an oil-covered aqueous surface, which typifies the sea surface microlayer as well as an oil spill on the ocean. The jet tip radius and velocity are altered with even a thin oil layer, and oily aerosol droplets are produced. We provide evidence that the coupling of oil spreading and cavity collapse dynamics results in a multi-phase jet and the follow-up droplet size change. The oil spreading influences the effective viscous damping, and scaling laws are proposed to quantify the jetting dynamics. Our study not only advances the fundamental understanding of bubble bursting dynamics, but also may shed light on the airborne transmission of organic matters in nature related to aerosol production. How structurally complex interfaces mediate bubble bursting might significantly impact environmental and industrial processes. Here, authors investigate the bubble-bursting jets dynamics of oil-covered aqueous surface and show how these can also disperse insoluble organic contaminants. [ABSTRACT FROM AUTHOR]

Plankton and neuston microbes produce organic matter (OM), which accumulates in the sea surface microlayer (SML). Fluxes of heat and momentum exchange across the sea-air interface, as do fluxes of matter, including greenhouse gases, aerosols, microbes (algae, bacteria sensu lato and viruses) and other substances. At least at calm to moderate windspeeds, microbial OM (MOM) in the SML reduces these fluxes. Another MOM fraction, foam, covers a part of the ocean surface. Ocean foam increases mean ocean albedo because it reflects solar radiation, thus cooling the ocean and the Earth. The rheological properties of MOM and the reduction of sea-air fluxes depend on microbial abundance and taxonomic composition, as do the formation and persistence of foam. Genomic regulation of MOM secretion may thus be helping to regulate air-sea fluxes and climate. Unpredictable changes in abundance and taxonomic composition of these microbial communities may be adding uncertainty to global and more local climate. Some of this uncertainty could be mitigated by studying the ecology and genomics of the surface microbial community together with chemical and rheological properties of their secreted MOM and its effects on sea-air fluxes and foam coverage, to incorporate into climate models. [ABSTRACT FROM AUTHOR]

A wide range of materials including mineral dust, soil dust, and bioaerosols have been shown to act as ice nuclei in the atmosphere. During atmospheric transport, these materials can become coated with inorganic and organic solutes which may impact their ability to nucleate ice. While a number of studies have investigated the impact of solutes at low concentrations on ice nucleation by mineral dusts, very few studies have examined their impact on non-mineral dust ice nuclei. We studied the effect of dilute (NH 4)2 SO 4 solutions (0.05 M) on immersion freezing of a variety of non-mineral dust ice-nucleating substances (INSs) including bacteria, fungi, sea ice diatom exudates, sea surface microlayer substances, and humic substances using the droplet-freezing technique. We also studied the effect of (NH 4)2 SO 4 solutions (0.05 M) on the immersion freezing of several types of mineral dust particles for comparison purposes. (NH 4)2 SO 4 had no effect on the median freezing temperature (ΔT50) of 9 of the 10 non-mineral dust materials tested. There was a small but statistically significant decrease in ΔT50 (- 0.43 ± 0.19 ∘ C) for the bacteria Xanthomonas campestris in the presence of (NH 4)2 SO 4 compared to pure water. Conversely, (NH 4)2 SO 4 increased the median freezing temperature of four different mineral dusts (potassium-rich feldspar, Arizona Test Dust, kaolinite, montmorillonite) by 3 to 9 ∘ C and increased the ice nucleation active site density per gram of material (nm(T)) by a factor of ∼ 10 to ∼ 30. This significant difference in the response of mineral dust and non-mineral dust ice-nucleating substances when exposed to (NH 4)2 SO 4 suggests that they nucleate ice and/or interact with (NH 4)2 SO 4 via different mechanisms. This difference suggests that the relative importance of mineral dust to non-mineral dust particles for ice nucleation in mixed-phase clouds could potentially increase as these particles become coated with (NH 4)2 SO 4 in the atmosphere. This difference also suggests that the addition of (NH 4)2 SO 4 (0.05 M) to atmospheric samples of unknown composition could potentially be used as an indicator or assay for the presence of mineral dust ice nuclei, although additional studies are still needed as a function of INS concentration to confirm the same trends are observed for different INS concentrations than those used here. A comparison with results in the literature does suggest that our results may be applicable to a range of mineral dust and non-mineral dust INS concentrations. [ABSTRACT FROM AUTHOR]