The Experts below are selected from a list of 5115 Experts worldwide ranked by ideXlab platform
Yoshio Utaka - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the Microlayer characteristics in the whole range of nucleate boiling for water by laser interferometry
International Journal of Heat and Mass Transfer, 2020Co-Authors: Zhihao Chen, Yoshio Utaka, Shoji MoriAbstract:Abstract During nucleate boiling, a thin liquid film (Microlayer) is formed beneath a boiling bubble when the bubble undergoes rapid growth/expansion. The linear distribution of the Microlayer has been previously confirmed, and its crest shape has been observed in the isolated bubble region of nucleate boiling. However, the Microlayer behavior in larger heat flux regions up to critical heat flux has not yet been elucidated. In this study, to further understand the Microlayer structure in the whole heat flux range of nucleate boiling, Microlayer configuration was measured using laser interferometry. Water was adopted as the test fluid, and it is confirmed that the Microlayer can be observed over a whole range of nucleate boiling containing the critical heat flux point. It is also confirmed that the deformation of the Microlayer from axisymmetric shape was caused by complicated, irregular bubble motions such as bubble coalescence, which was observed for relatively higher heat flux. The crest shape of the Microlayer, which appears near the periphery of its maximum diameter under relatively smaller heat flux, was not observed at a relatively higher heat flux. Finally, it is confirmed that heat flux does not obviously influence the thickness distribution of the initial Microlayer.
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numerical simulation of thermal property effect of heat transfer plate on bubble growth with Microlayer evaporation during nucleate pool boiling
International Journal of Heat and Mass Transfer, 2018Co-Authors: Zhihao Chen, Yoshio UtakaAbstract:Abstract It is well known that during nucleate boiling, a large amount of energy can be transferred under relatively small temperature difference between the heat transfer surface and fluid, indicating that high efficiency of heat transfer can be achieved. However, the mechanism of nucleate boiling is still not well elucidated owing to the complexity of the phenomenon. The thermal properties of heat transfer plate, which is directly in contact with the Microlayer, may have a significant impact on heat transfer and evaporation characteristics of the Microlayer. A volume of fluid (VOF) method based algorithm, in which the experimentally measured Microlayer structure was taken into account, has been developed to simulate Microlayer evaporation and single bubble behavior. The influence of thermal conductivity of heat transfer plates on the contribution of Microlayer evaporation was examined. It was concluded that more efficient heat supply to the heat transfer surface can be achieved for the heat transfer plate with higher thermal conductivity. Microlayer evaporation occupied approximately 30–70% of the bubble volume, indicating that Microlayer evaporation is a principal mechanism of boiling heat transfer.
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Measurement of contribution of Microlayer evaporation applying the Microlayer volume change during nucleate pool boiling for water and ethanol
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yoshio Utaka, Zhihao Chen, Takayuki MorokumaAbstract:Abstract The formation of Microlayer beneath boiling bubbles during nucleate pool boiling has been confirmed by many researchers. The vigorous evaporation of the Microlayer plays an important role in boiling heat transfer, because of the high thermal conductance of the micron-order thickness of liquid film. However, the experimental knowledge on the Microlayer evaporation has been limited owing to the difficulty of measuring the evaporation. In this study, the laser interferometric method was adopted to investigate the Microlayer structure during the nucleate pool boiling for ethanol. The Microlayer evaporation was determined from the variation of Microlayer volume. As a result, it was confirmed that Microlayer evaporation contributes significantly to total evaporation, and that its contribution ratio coincided with the previous results.
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Detailed structure of Microlayer in nucleate pool boiling for water measured by laser interferometric method
International Journal of Heat and Mass Transfer, 2017Co-Authors: Zhihao Chen, Atsushi Haginiwa, Yoshio UtakaAbstract:Abstract During nucleate pooling boiling, a Microlayer forms on the heat transfer surface beneath a growing bubble. In previous studies, the existence of a Microlayer was confirmed, and its structure was investigated by using several different experimental methods. However, the characteristics and mechanism of the formation of a Microlayer have not been thoroughly elucidated to date. In this study, in order to obtain further understanding on the Microlayer structure, a laser interferometric method was adopted for a more detailed observation. As a result, it was observed that the special bended shape of the Microlayer forms near its outer margin when the Microlayer radius is close to its maximum value. By analyzing the variation of the ratio of bubble height to diameter, it can be inferred that the detachment of a bubble causes a decrease of the initial Microlayer thickness when the Microlayer thickness is close to the maximum radius. This effect explains the formation of the bended shape of initial Microlayer.
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On heat transfer and evaporation characteristics in the growth process of a bubble with Microlayer structure during nucleate boiling
International Journal of Heat and Mass Transfer, 2015Co-Authors: Zhihao Chen, Yoshio UtakaAbstract:Abstract We have previously observed and experimentally measured a Microlayer formed beneath a growing bubble during nucleate pool boiling. The initial Microlayer thickness was of micrometer order and increased linearly with distance from the bubble inception site. The quantitative degree of contribution of the Microlayer evaporation to bubble growth was still not elucidated, although a large number of experimental studies have been conducted on the distribution and evaporation characteristics of the Microlayer. To clarify the heat transfer characteristics, especially the contribution of Microlayer evaporation in nucleate pool boiling, numerical simulations are performed here for two phase vapor–liquid flow induced by the growth of a single bubble using the volume of fluid method. Furthermore, a special model is proposed to combine the Microlayer and bulk liquid regions, the scales of which are extremely different in the simulations. The Microlayer was neglected in the volume fraction calculation, while the evaporation from the Microlayer was included by applying the source terms of the basic equations for the presence of a virtual Microlayer. Similar tendencies were observed between the calculated and experimental results on the variations in the Microlayer radius and bubble volume. The proportion of Microlayer evaporation to total bubble volume was generally in agreement with the previous results, and the ratio of Microlayer evaporation to the change in the total bubble volume was approximately 40 percent.
Zhihao Chen - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the Microlayer characteristics in the whole range of nucleate boiling for water by laser interferometry
International Journal of Heat and Mass Transfer, 2020Co-Authors: Zhihao Chen, Yoshio Utaka, Shoji MoriAbstract:Abstract During nucleate boiling, a thin liquid film (Microlayer) is formed beneath a boiling bubble when the bubble undergoes rapid growth/expansion. The linear distribution of the Microlayer has been previously confirmed, and its crest shape has been observed in the isolated bubble region of nucleate boiling. However, the Microlayer behavior in larger heat flux regions up to critical heat flux has not yet been elucidated. In this study, to further understand the Microlayer structure in the whole heat flux range of nucleate boiling, Microlayer configuration was measured using laser interferometry. Water was adopted as the test fluid, and it is confirmed that the Microlayer can be observed over a whole range of nucleate boiling containing the critical heat flux point. It is also confirmed that the deformation of the Microlayer from axisymmetric shape was caused by complicated, irregular bubble motions such as bubble coalescence, which was observed for relatively higher heat flux. The crest shape of the Microlayer, which appears near the periphery of its maximum diameter under relatively smaller heat flux, was not observed at a relatively higher heat flux. Finally, it is confirmed that heat flux does not obviously influence the thickness distribution of the initial Microlayer.
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numerical simulation of thermal property effect of heat transfer plate on bubble growth with Microlayer evaporation during nucleate pool boiling
International Journal of Heat and Mass Transfer, 2018Co-Authors: Zhihao Chen, Yoshio UtakaAbstract:Abstract It is well known that during nucleate boiling, a large amount of energy can be transferred under relatively small temperature difference between the heat transfer surface and fluid, indicating that high efficiency of heat transfer can be achieved. However, the mechanism of nucleate boiling is still not well elucidated owing to the complexity of the phenomenon. The thermal properties of heat transfer plate, which is directly in contact with the Microlayer, may have a significant impact on heat transfer and evaporation characteristics of the Microlayer. A volume of fluid (VOF) method based algorithm, in which the experimentally measured Microlayer structure was taken into account, has been developed to simulate Microlayer evaporation and single bubble behavior. The influence of thermal conductivity of heat transfer plates on the contribution of Microlayer evaporation was examined. It was concluded that more efficient heat supply to the heat transfer surface can be achieved for the heat transfer plate with higher thermal conductivity. Microlayer evaporation occupied approximately 30–70% of the bubble volume, indicating that Microlayer evaporation is a principal mechanism of boiling heat transfer.
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Measurement of contribution of Microlayer evaporation applying the Microlayer volume change during nucleate pool boiling for water and ethanol
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yoshio Utaka, Zhihao Chen, Takayuki MorokumaAbstract:Abstract The formation of Microlayer beneath boiling bubbles during nucleate pool boiling has been confirmed by many researchers. The vigorous evaporation of the Microlayer plays an important role in boiling heat transfer, because of the high thermal conductance of the micron-order thickness of liquid film. However, the experimental knowledge on the Microlayer evaporation has been limited owing to the difficulty of measuring the evaporation. In this study, the laser interferometric method was adopted to investigate the Microlayer structure during the nucleate pool boiling for ethanol. The Microlayer evaporation was determined from the variation of Microlayer volume. As a result, it was confirmed that Microlayer evaporation contributes significantly to total evaporation, and that its contribution ratio coincided with the previous results.
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Detailed structure of Microlayer in nucleate pool boiling for water measured by laser interferometric method
International Journal of Heat and Mass Transfer, 2017Co-Authors: Zhihao Chen, Atsushi Haginiwa, Yoshio UtakaAbstract:Abstract During nucleate pooling boiling, a Microlayer forms on the heat transfer surface beneath a growing bubble. In previous studies, the existence of a Microlayer was confirmed, and its structure was investigated by using several different experimental methods. However, the characteristics and mechanism of the formation of a Microlayer have not been thoroughly elucidated to date. In this study, in order to obtain further understanding on the Microlayer structure, a laser interferometric method was adopted for a more detailed observation. As a result, it was observed that the special bended shape of the Microlayer forms near its outer margin when the Microlayer radius is close to its maximum value. By analyzing the variation of the ratio of bubble height to diameter, it can be inferred that the detachment of a bubble causes a decrease of the initial Microlayer thickness when the Microlayer thickness is close to the maximum radius. This effect explains the formation of the bended shape of initial Microlayer.
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On heat transfer and evaporation characteristics in the growth process of a bubble with Microlayer structure during nucleate boiling
International Journal of Heat and Mass Transfer, 2015Co-Authors: Zhihao Chen, Yoshio UtakaAbstract:Abstract We have previously observed and experimentally measured a Microlayer formed beneath a growing bubble during nucleate pool boiling. The initial Microlayer thickness was of micrometer order and increased linearly with distance from the bubble inception site. The quantitative degree of contribution of the Microlayer evaporation to bubble growth was still not elucidated, although a large number of experimental studies have been conducted on the distribution and evaporation characteristics of the Microlayer. To clarify the heat transfer characteristics, especially the contribution of Microlayer evaporation in nucleate pool boiling, numerical simulations are performed here for two phase vapor–liquid flow induced by the growth of a single bubble using the volume of fluid method. Furthermore, a special model is proposed to combine the Microlayer and bulk liquid regions, the scales of which are extremely different in the simulations. The Microlayer was neglected in the volume fraction calculation, while the evaporation from the Microlayer was included by applying the source terms of the basic equations for the presence of a virtual Microlayer. Similar tendencies were observed between the calculated and experimental results on the variations in the Microlayer radius and bubble volume. The proportion of Microlayer evaporation to total bubble volume was generally in agreement with the previous results, and the ratio of Microlayer evaporation to the change in the total bubble volume was approximately 40 percent.
Philippe Lebaron - One of the best experts on this subject based on the ideXlab platform.
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Biochemical characteristics and bacterial community structure of the sea surface Microlayer in the South Pacific Ocean
Biogeosciences, 2008Co-Authors: Ingrid Obernosterer, F Van Wambeke, Joséphine Ras, Philippe Catala, Annick Bricaud, J. Caparros, Raphaël Lami, Christine Dupuy, Philippe LebaronAbstract:The chemical and biological characteristics of the surface Microlayer were determined during a transect across the South Pacific Ocean in October-December 2004. Concentrations of particulate organic carbon (1.3 to 7.6-fold) and nitrogen (1.4 to 7-fold), and POC:PON ratios were consistently higher in the surface Microlayer as compared to surface waters (5 m). The large variability in particulate organic matter enrichment was negatively correlated to wind speed. No enhanced concentrations of dissolved organic carbon were detectable in the surface Microlayer as compared to 5 m, but chromophoric dissolved organic matter was markedly enriched (by 2 to 4-fold) at all sites. Based on pigment analysis and cell counts, no consistent enrichment of any of the major components of the autotrophic and heterotrophic microbial community was detectable. CE-SSCP fingerprints and CARD FISH revealed that the bacterial communities present in the surface Microlayer had close similarity (>76%) to those in surface waters. By contrast, bacterial heterotrophic production ( 3 H-leucine incorporation) was consistently lower in the surface Microlayer than in surface waters. By applying CARD-FISH and microautoradiography, we observed that Bacteroidetes and Gammaproteobacteria dominated leucine uptake in the surface Microlayer, while in surface waters Bacteroidetes and Alphaproteobacteria were the major groups accounting for leucine incorporation. Our results demonstrate that the microbial community in the surface Microlayer closely resembles that of the surface waters of the open ocean. Even a short residence in the surface Microlayer influences leucine incorporation by different bacterial groups, probably as a response to the differences in the physical and chemical nature of the two layers.
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Biochemical characteristics and bacterial community structure of the sea surface Microlayer in the South Pacific Ocean
Biogeosciences, 2008Co-Authors: Ingrid Obernosterer, Philippe Catala, Annick Bricaud, J. Caparros, Raphaël Lami, Christine Dupuy, France Van Wambeke, Philippe LebaronAbstract:The chemical and biological characteristics of the surface Microlayer were determined during a transect across the South Pacific Ocean in October-December 2004. Concentrations of particulate organic carbon (1.3 to 7.6-fold) and nitrogen (1.4 to 7-fold), and POC:PON ratios were consistently higher in the surface Microlayer as compared to surface waters (5 m). The large variability in particulate organic matter enrichment was negatively correlated to wind speed. No enhanced concentrations of dissolved organic carbon were detectable in the surface Microlayer as compared to 5 m, but chromophoric dissolved organic matter was markedly enriched (by 2 to 4-fold) at all sites. Based on pigment analysis and cell counts, no consistent enrichment of any of the major components of the autotrophic and het-erotrophic microbial community was detectable. CE-SSCP fingerprints and CARD FISH revealed that the bacterial communities present in the surface Microlayer had close similarity (>76%) to those in surface waters. By contrast, bacterial heterotrophic production (3 H-leucine incorporation) was consistently lower in the surface Microlayer than in surface waters. By applying CARD-FISH and microautoradiogra-phy, we observed that Bacteroidetes and Gammaproteobac-teria dominated leucine uptake in the surface Microlayer, while in surface waters Bacteroidetes and Alphaproteobacte-ria were the major groups accounting for leucine incorporation. Our results demonstrate that the microbial community in the surface Microlayer closely resembles that of the surface Correspondence to: I. Obernosterer (ingrid.obernosterer@obs-banyuls.fr) waters of the open ocean. Even a short residence in the surface Microlayer influences leucine incorporation by different bacterial groups, probably as a response to the differences in the physical and chemical nature of the two layers.
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Biochemical characteristics and bacterial community structure of the sea surface Microlayer in the South Pacific Ocean
Biogeosciences Discussions, 2007Co-Authors: Ingrid Obernosterer, F Van Wambeke, Joséphine Ras, Philippe Catala, Annick Bricaud, J. Caparros, Corinne Dupuy, Raphaël Lami, Philippe LebaronAbstract:The chemical and biological characteristics of the surface Microlayer were determined during a transect across the South Pacific Ocean in October-December 2004. Concentrations of particulate organic carbon (1.3 to 7.6-fold) and nitrogen (1.4 to 7), and POC:PON ratios were consistently higher in the surface Microlayer as compared to subsurface waters (5 m). The large variability in particulate organic matter enrichment was negatively correlated to wind speed. No enhanced concentrations of dissolved organic carbon were detectable in the surface Microlayer as compared to 5 m, but chromophoric dissolved organic matter was markedly enriched (by 2 to 4-fold) at all sites. Based on pigment analysis and cell counts, no consistent enrichment of any of the major components of the autotrophic and heterotrophic microbial community was detectable. CE-SSCP fingerprints and CARD FISH revealed that the bacterial communities present in the surface Microlayer had close similarity (>76%) to those in subsurface waters. By contrast, bacterial heterotrophic production (3H-leucine incorporation) was consistently lower in the surface Microlayer than in subsurface waters. By applying CARD-FISH and microautoradiography, we observed that Bacteroidetes and Gammaproteobacteria dominated leucine uptake in the surface Microlayer, while in subsurface waters Bacteroidetes and Alphaproteobacteria were the major groups accounting for leucine incorporation. Our results demonstrate that the microbial community in the surface Microlayer closely resembles that of the surface waters of the open ocean. However, even short time periods in the surface Microlayer result in differences in bacterial groups accounting for leucine incorporation, probably as a response to the differences in the physical and chemical nature of the two layers.
Gui-peng Yang - One of the best experts on this subject based on the ideXlab platform.
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Distribution of dimethylsulfide and dimethylsulfoniopropionate and its relation with phytoneuston in the surface Microlayer of the western North Atlantic during summer
Biogeochemistry, 2009Co-Authors: Gui-peng Yang, Maurice Levasseur, Sonia Michaud, Anissa Merzouk, Martine Lizotte, Michael ScarrattAbstract:One of the key steps towards predicting dimethylsulfide (DMS) emission to the atmosphere is to understand the distribution and cycling of biogenic sulfur in the Microlayer. In this study, we examined the distribution of DMS and dissolved and particulate fractions of dimethylsulfoniopropionate (DMSPd and DMSPp) in the surface Microlayer and bulk water of the western North Atlantic during July 2003. DMS concentrations in the bulk water varied from 0.71 to 7.65 nM. In contrast, DMS concentrations in the surface Microlayer were fairly low (0.17-1.33 nM). Average concentrations of DMSPd and DMSPp in the bulk water were 2.09 (1.87-6.25) and 44.1 (8.06-119.8) nM, respectively, and those in the surface Microlayer were 15.4 (4.06-54.3) and 29.9 (7.32-97.0) nM. In general, DMS was depleted in the Microlayer (mean concentration: 0.60 nM) relative to the bulk water (mean concentration: 2.38 nM) with enrichment factors (the ratio of the Microlayer concentration to bulk water concentration) ranging from 0.13 to 0.54. There was no consistent enrichment of DMSPp and chlorophyll a in the Microlayer. On the contrary, DMSPd appeared to be highly enriched in the Microlayer with an average EF of 4.89. The concentration of phaeopigments was also generally greater in the Microlayer than in the bulk water, presumably due to enhanced photo-oxidation of chlorophyll a under high surface light intensities in the Microlayer. In the study area, the concentration of DMSPp was significantly correlated with the abundance of dinoflagellates in the Microlayer. Moreover, a significant correlation between the distributions of DMS, DMSPp, chlorophyll a and phaeopigment concentrations in the Microlayer and the bulk water demonstrated that the biogenic materials in the Microlayer come primarily from the bulk water below.
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distribution and cycling of dimethylsulfide dms and dimethylsulfoniopropionate dmsp in the sea surface Microlayer of the yellow sea china in spring
Continental Shelf Research, 2008Co-Authors: Honghai Zhang, Gui-peng Yang, Tong ZhuAbstract:Abstract The distributions of dimethylsulfide (DMS) and its precursor, dimethylsulfoniopropionate (DMSP), were examined in the surface Microlayer and corresponding subsurface water of the Yellow Sea, China, in April 2006. The average concentrations of DMS and DMSP of dissolved (DMSPd) and particulate (DMSPp) forms were 5.42 (1.78–12.75), 9.22 (2.85–19.73) and 17.50 (4.33–36.09) nmol L −1 in the subsurface water, and those in the surface Microlayer were 4.92 (1.69–10.66), 17.08 (3.13–38.82) and 22.54 (4.85–47.24) nmol L −1 , respectively. The enrichment factor (EF) of DMS in the Microlayer ranged from 0.47 to 2.24 with a mean of 0.98. In contrast, DMSPd and DMSPp appeared to be enriched in the Microlayer with average EFs of 1.98 and 1.39, respectively. A close correlation of integrated DMS, DMSPp and chlorophyll a concentrations for compiled data from all stations in the Microlayer and the subsurface water indicated that phytoplankton biomass might play an important role in controlling the distributions of biogenic sulfurs in the study area. Moreover, a statistically significant relationship was found between the Microlayer concentrations of DMS, DMSP and chlorophyll a and their subsurface water concentrations, suggesting a close linkage between these two water compartments. Interestingly, we observed higher biological production rates and consumption rates of DMS in the Microlayer relative to the subsurface water. Furthermore, the DMS production rates were closely correlated both with DMSPd and chlorophyll a concentrations. Our study showed that the major sink of DMS in Microlayer was escape into the atmosphere, which greatly exceeded its bacterial consumption. A preliminary estimate for average flux of DMS from the Yellow Sea to the atmosphere was 6.41 μmol m −2 d −1 during spring.
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Biogeochemistry of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in the surface Microlayer and subsurface water of the western North Atlantic during spring
Marine Chemistry, 2005Co-Authors: Gui-peng Yang, Maurice Levasseur, Sonia Michaud, Michael ScarrattAbstract:Abstract Sixteen surface Microlayer samples and corresponding subsurface water samples were collected in the western North Atlantic during April–May 2003 to study the distribution and cycling of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) and the factors influencing them. In the surface Microlayer, high concentrations of DMS appeared mostly in the samples containing high levels of chlorophyll a , and a significant correlation was found between DMS and chlorophyll a concentrations. In addition, Microlayer DMS concentrations were correlated with Microlayer DMSPd (dissolved) concentrations. DMSPd was found to be enriched in the Microlayer with an average enrichment factor (EF) of 5.19. However, no Microlayer enrichment of DMS was found for most samples collected. Interestingly, the DMS production rates in the Microlayer were much higher than those in the subsurface water. Enhanced DMS production in the Microlayer was likely due to the higher concentrations of DMSPd in the Microlayer. A consistent pattern was observed in this study in which the concentrations of DMS, DMSPd, DMSPp (particulate) and chlorophyll a in the Microlayer were closely related to their corresponding subsurface water concentrations, suggesting that these constituents in the Microlayer were directly dependent on the transport from the bulk liquid below. Enhanced DMS production in the Microlayer further reinforces the conclusion that the surface Microlayer has greater biological activity relative to the underlying water.
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Biogeochemistry of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in the surface Microlayer of the western North Pacific
Deep Sea Research Part I: Oceanographic Research Papers, 2005Co-Authors: Gui-peng Yang, Shizuo TsunogaiAbstract:Abstract Twenty-eight sea-surface Microlayer samples as well as the bulk surface water samples were collected at seven stations in the western North Pacific in early June 2001 for studying the behavior of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in the surface water. The average concentrations of DMS and DMSP of dissolved (DMSPd) and particulate (DMSPp) forms were, respectively, 2.8 (0.5–12.2), 13.9 (7.3–39) and 23.4 (6.6–100.5) nM in the surface Microlayer, and those in the bulk surface water were 2.6 (0.8–6.9), 11.2 (5.2–23.4) and 19.1 (6.2–72.8) nM. In the bulk surface water, the concentrations of DMS were positively well correlated with the concentrations of chlorophyll a . The enrichment factors (EF) of DMS in the surface Microlayer ranged from 0.38 to 2.94 with a mean of 1.10, and those of chlorophyll a ranged from 0.72 to 2.61 with a mean of 1.28. The mean EFs of DMSPd and DMSPp in the Microlayer were 1.24 and 1.14, respectively. A striking finding in this study is that the concentrations of DMS, DMSPd and DMSPp in the Microlayer were closely correlated with them in the corresponding bulk surface water, suggesting that the Microlayer DMS, DMSPd and DMSPp are directly controlled by the bulk surface water below. It is noted that the production and consumption rates of DMS in the Microlayer were generally higher than those in the bulk surface water and the production rates of DMS were significantly well correlated with the concentrations of DMSPd. In addition, our study showed that the major sink of DMS in the Microlayer was escape into the atmosphere, which greatly exceeded its bacterial consumption.
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Distribution and cycling of dimethylsulfide in surface Microlayer and subsurface seawater
Marine Chemistry, 2001Co-Authors: Gui-peng Yang, Shuichi Watanabe, Shizuo TsunogaiAbstract:Abstract Laboratory experiments, along with in situ investigation in Funka Bay, Japan, were conducted to determine the enrichment factor (EF) of dimethylsulfide (DMS) in the sea surface Microlayer, as well as its the production and consumption rates. The EF of DMS in the Microlayer was largely affected by various factors including sampling methods, sampling thickness, temperature, salinity, and DMS concentration in bulk water. In all cases but the sealed system, a part of DMS in the Microlayer was always unavoidably lost during sampling. High temperature, great wind speed, and slow sampling would increase the extent of loss of DMS due to volatilization. In the field, the screen-collected samples usually exhibited greater Microlayer enrichment for DMS than the plate-collected samples, showing that the screen sampler might be more effective for collecting the in situ Microlayer DMS. The production and consumption rates of DMS in the surface Microlayer were higher than those in the bulk water and these two rates were significantly correlated with the Microlayer DMS concentrations. Moreover, the EF of DMS appeared to be related to the Microlayer production rate of DMS, providing evidence supporting the observed DMS enrichment in the Microlayer. The DMS production and consumption rates were not directly related to its concentrations in the bulk water, suggesting that the processes of production and consumption of DMS were very complex. In the surface Microlayer, the biological turnover time of DMS varied from 0.4 to 1.9 days, with an average of 0.9 days, which was about 540-fold greater than the mean DMS sea–air turnover time (2.4 min). Thus, the biological process occurring within the Microlayer can be neglected when we consider the sea–air exchange of DMS. Considering the Microlayer production rate of DMS (an average of 9.7 nM day−1) to be too small to counteract the sea-to-air removal of DMS, the main source of DMS in the Microlayer appears to be through vertical transport by turbulent diffusion from the underlying water.
Ingrid Obernosterer - One of the best experts on this subject based on the ideXlab platform.
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Biochemical characteristics and bacterial community structure of the sea surface Microlayer in the South Pacific Ocean
Biogeosciences, 2008Co-Authors: Ingrid Obernosterer, F Van Wambeke, Joséphine Ras, Philippe Catala, Annick Bricaud, J. Caparros, Raphaël Lami, Christine Dupuy, Philippe LebaronAbstract:The chemical and biological characteristics of the surface Microlayer were determined during a transect across the South Pacific Ocean in October-December 2004. Concentrations of particulate organic carbon (1.3 to 7.6-fold) and nitrogen (1.4 to 7-fold), and POC:PON ratios were consistently higher in the surface Microlayer as compared to surface waters (5 m). The large variability in particulate organic matter enrichment was negatively correlated to wind speed. No enhanced concentrations of dissolved organic carbon were detectable in the surface Microlayer as compared to 5 m, but chromophoric dissolved organic matter was markedly enriched (by 2 to 4-fold) at all sites. Based on pigment analysis and cell counts, no consistent enrichment of any of the major components of the autotrophic and heterotrophic microbial community was detectable. CE-SSCP fingerprints and CARD FISH revealed that the bacterial communities present in the surface Microlayer had close similarity (>76%) to those in surface waters. By contrast, bacterial heterotrophic production ( 3 H-leucine incorporation) was consistently lower in the surface Microlayer than in surface waters. By applying CARD-FISH and microautoradiography, we observed that Bacteroidetes and Gammaproteobacteria dominated leucine uptake in the surface Microlayer, while in surface waters Bacteroidetes and Alphaproteobacteria were the major groups accounting for leucine incorporation. Our results demonstrate that the microbial community in the surface Microlayer closely resembles that of the surface waters of the open ocean. Even a short residence in the surface Microlayer influences leucine incorporation by different bacterial groups, probably as a response to the differences in the physical and chemical nature of the two layers.
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Biochemical characteristics and bacterial community structure of the sea surface Microlayer in the South Pacific Ocean
Biogeosciences, 2008Co-Authors: Ingrid Obernosterer, Philippe Catala, Annick Bricaud, J. Caparros, Raphaël Lami, Christine Dupuy, France Van Wambeke, Philippe LebaronAbstract:The chemical and biological characteristics of the surface Microlayer were determined during a transect across the South Pacific Ocean in October-December 2004. Concentrations of particulate organic carbon (1.3 to 7.6-fold) and nitrogen (1.4 to 7-fold), and POC:PON ratios were consistently higher in the surface Microlayer as compared to surface waters (5 m). The large variability in particulate organic matter enrichment was negatively correlated to wind speed. No enhanced concentrations of dissolved organic carbon were detectable in the surface Microlayer as compared to 5 m, but chromophoric dissolved organic matter was markedly enriched (by 2 to 4-fold) at all sites. Based on pigment analysis and cell counts, no consistent enrichment of any of the major components of the autotrophic and het-erotrophic microbial community was detectable. CE-SSCP fingerprints and CARD FISH revealed that the bacterial communities present in the surface Microlayer had close similarity (>76%) to those in surface waters. By contrast, bacterial heterotrophic production (3 H-leucine incorporation) was consistently lower in the surface Microlayer than in surface waters. By applying CARD-FISH and microautoradiogra-phy, we observed that Bacteroidetes and Gammaproteobac-teria dominated leucine uptake in the surface Microlayer, while in surface waters Bacteroidetes and Alphaproteobacte-ria were the major groups accounting for leucine incorporation. Our results demonstrate that the microbial community in the surface Microlayer closely resembles that of the surface Correspondence to: I. Obernosterer (ingrid.obernosterer@obs-banyuls.fr) waters of the open ocean. Even a short residence in the surface Microlayer influences leucine incorporation by different bacterial groups, probably as a response to the differences in the physical and chemical nature of the two layers.
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Biochemical characteristics and bacterial community structure of the sea surface Microlayer in the South Pacific Ocean
Biogeosciences Discussions, 2007Co-Authors: Ingrid Obernosterer, F Van Wambeke, Joséphine Ras, Philippe Catala, Annick Bricaud, J. Caparros, Corinne Dupuy, Raphaël Lami, Philippe LebaronAbstract:The chemical and biological characteristics of the surface Microlayer were determined during a transect across the South Pacific Ocean in October-December 2004. Concentrations of particulate organic carbon (1.3 to 7.6-fold) and nitrogen (1.4 to 7), and POC:PON ratios were consistently higher in the surface Microlayer as compared to subsurface waters (5 m). The large variability in particulate organic matter enrichment was negatively correlated to wind speed. No enhanced concentrations of dissolved organic carbon were detectable in the surface Microlayer as compared to 5 m, but chromophoric dissolved organic matter was markedly enriched (by 2 to 4-fold) at all sites. Based on pigment analysis and cell counts, no consistent enrichment of any of the major components of the autotrophic and heterotrophic microbial community was detectable. CE-SSCP fingerprints and CARD FISH revealed that the bacterial communities present in the surface Microlayer had close similarity (>76%) to those in subsurface waters. By contrast, bacterial heterotrophic production (3H-leucine incorporation) was consistently lower in the surface Microlayer than in subsurface waters. By applying CARD-FISH and microautoradiography, we observed that Bacteroidetes and Gammaproteobacteria dominated leucine uptake in the surface Microlayer, while in subsurface waters Bacteroidetes and Alphaproteobacteria were the major groups accounting for leucine incorporation. Our results demonstrate that the microbial community in the surface Microlayer closely resembles that of the surface waters of the open ocean. However, even short time periods in the surface Microlayer result in differences in bacterial groups accounting for leucine incorporation, probably as a response to the differences in the physical and chemical nature of the two layers.