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1.
Dimethylsulfide enrichment in the surface microlayer of the South China Sea   总被引：5，自引：0，他引：5  
A total of 22 sea surface microlayer samples collected from the Nansha Islands waters of the South China Sea were analyzed for dimethylsulfide (DMS), chlorophyll a and nutrients including nitrate, phosphate and silicate. The DMS concentrations in surface microlayer samples ranged from 82 to 280 ng S/l with a mean of 145 ng S/l. A significant correlation was found between DMS and chlorophyll a data both in the surface microlayer as well as in the subsurface water. However, no correlation was observed between DMS and nutrient concentrations in the surface microlayer. The DMS concentrations were higher in all surface microlayer samples, compared with subsurface samples. The enrichment factor (EF) of DMS in the surface microlayer varied from 1.21 to 3.08 with an average of 1.95. The EF of DMS was significantly correlated with that of chlorophyll a in the microlayer. The enrichment of DMS in the microlayer may be due to two factors, including the in situ production from phytoplankton and the transportation from the underlying seawater. The diel variations in DMS and chlorophyll a concentrations were studied at a fixed station. The highest concentrations of DMS in the surface microlayer and subsurface water were simultaneously observed in the late afternoon (1800 h), while the highest levels of chlorophyll a were simultaneously found at night (0200 h).  相似文献   

2.
The distributions of DMS and its precursor dimethylsulfoniopropionate, in both dissolved (DMSPd) and particulate fractions (DMSPp) were determined in the seasurface microlayer and corresponding subsurface water of the Jiaozhou Bay, China and its adjacent area in May and August 2006. The concentrations of all these components showed a clear seasonal variation, with higher concentrations occurring in summer. This can be mainly attributed to the higher phytoplankton biomass observed in summer. Simultaneously, the enrichment extents of DMSPd and DMSPp in the microlayer also exhibited seasonal changes, with higher values in spring and lower ones in summer. Higher water temperature and stronger radiant intensity in summer can enhance their solubility and photochemical reaction in the microlayer water, reducing their enrichment factors (the ratio of concentration in the microlayer to that in the corresponding subsurface water). A statistically significant relationship was found between the microlayer and subsurface water concentrations of DMS, DMSP and chlorophyll a, demonstrating that the biogenic materials in the microlayer come primarily from the underlying water. Moreover, our data show that the concentrations of DMSPp and DMS were significantly correlated with the levels of chlorophyll a, indicating that phytoplankton biomass might play an important role in controlling the distributions of biogenic sulfurs in the study area. The ratios of DMS/chlorophyll a and DMSPp/chlorophyll a varied little from spring to summer, suggesting that there was no obvious change in the proportion of DMSP producers in the phytoplankton community. The mean sea-to-air flux of DMS from the study area was estimated to be 5.70 μmol/(m2·d), which highlights the effects of human impacts on DMS emission.  相似文献   

3.
以胶州湾及青岛近海为研究区域,利用吹扫-捕集气相色谱法研究了二甲基硫(DMS)和二甲巯基丙酸(DMSP,分为溶解态DMSPd和颗粒态DMSPp)在微表层与次表层中的浓度以及它们在微表层中的富集行为。结果表明,DMS、DMSPd和DMSPp在微表层中的浓度高于次表层,它们在微表层中的富集因子分别为1.17、1.84和1.51。研究发现,DMS及DMSPp浓度与叶绿素a(Chl-a)浓度有很好的相关性,但它们的周日变化与Chl-a并不完全同步。DMS/Chl-a和DMSPp/Chl-a的比值在次表层和微表层分别为4.35、13.47mmol/g和3.99、15.88mmol/g。胶州湾及青岛近海生态环境受人为活动干扰严重,使本海域DMS含量较高,从而贡献出较大的DMS海-气通量。  相似文献   

4.
Twenty-eight sea surface microlayer samples, along with subsurface bulk water samples were collected in Funka Bay, Japan during October 2000–March 2001 and analyzed for dimethylsulfoniopropionate, dissolved (DMSPd) and particulate (DMSPp), and chlorophyll a. The aim of the study was to examine the extent of enrichment of DMSP in the microlayer and its relationship to chlorophyll a, as well as the production rate of dimethylsulfide (DMS) from DMSP and the factors that influence this. The enrichment factor (EF) of DMSPd in the surface microlayer ranged from 0.81 to 4.6 with a mean of 1.85. In contrast, EF of DMSPp in the microlayer varied widely from 0.85–10.5 with an average of 3.21. Chlorophyll a also appeared to be enriched in the microlayer relative to the subsurface water. This may be seen as an important cause of the observed enrichment of DMSP in the microlayer. The concentrations of DMSPp in the surface microlayer showed a strong temporal variation, basically following the change in chlorophyll a levels. Moreover, the microlayer concentrations of DMSPp were, on average, 3-fold higher than the microlayer concentrations of DMSPd and there was a significant correlation between them. Additionally, there was a great variability in the ratios of DMSPp to chlorophyll a over the study period, reflecting seasonal variation in the proportion of DMSP producers in the total phytoplankton assemblage. It is interesting that the production rate of DMS was enhanced in the microlayer and this rate was closely correlated with the microlayer DMSPd concentration. Microlayer enrichment of chlorophyll a and higher DMS production rate in the microlayer provide favorable evidence supporting the view that the sea surface microlayer has a greater biological activity than the underlying water.  相似文献   

5.
Spatial variations in dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) were surveyed in the surface microlayer and in the subsurface waters of the low productivity South China Sea in May 2005. Overall, average subsurface water concentrations of DMS and DMSP of dissolved (DMSPd) and particulate (DMSPp) fractions were 1.74 (1.00-2.50), 3.92 (2.21-6.54) and 6.06 (3.40-8.68) nM, respectively. No enrichment in DMS and DMSPp was observed in the microlayer. In contrast, the microlayer showed a DMSPd enrichment, with an average enrichment factor (EF, defined as the ratio of the microlayer concentration to subsurface water concentration) of 1.40. In the study area, none of the sulfur components were correlated with chlorophyll a. An important finding in this study was that DMS, DMSP and chlorophyll a concentrations in the surface microlayer were respectively correlated with those in the subsurface water, suggesting a close linkage between these two water bodies. The ratios of DMS:Chl-a and DMSPp:Chl-a showed a gradually increasing trend from North to South. This might be due to changes in the proportion of DMSP producers in the phytoplankton community with the increased surface seawater temperature. A clear diurnal variation in the DMS and DMSP concentrations was observed at an anchor station with the highest concentrations appearing during the day and the lowest concentrations during the night. The higher DMS and DMSP concentrations during daytime might be attributed to the light-induced increase in both algal synthesis and exudation of DMSP and biological production of DMS. The mean flux of DMS from the investigated area to the atmosphere was estimated to be 2.06 micromo lm(-2)d(-1). This low DMS emission flux, together with the low DMS surface concentrations was attributed to the low productivity in this sea.  相似文献   

6.
The distribution and chemical properties of chromophoric dissolved organic matter (CDOM) in the Jiaozhou Bay, China were examined during four cruises in 2010-2011. The influence of freshwater and industrial and municipal sewage along the eastern coast of the bay was clearly evident as CDOM levels (defined as a 305 ), and dissolved organic carbon (DOC) concentrations were well correlated with salinity during all the cruises. Moreover, DOC concentrations were significantly correlated with chlorophyll a concentrations in the surface microlayer as well as in the subsurface water. The concentrations of DOC and CDOM displayed a gradually decreasing trend from the northwestern and eastern coast to the central bay, and the values and gradients of their concentrations on the eastern coast were generally higher than those on the western coast. In addition, CDOM and DOC levels were generally higher in the surface microlayer than in the subsurface water. In comparison with DOC, CDOM exhibited a greater extent of enrichment in the microlayer in each cruise, with average enrichment factor (E F ) values of 1.38 and 1.84, respectively. Four fluorescent components were identified from the surface microlayer and subsurface water samples and could be distinguished as peak A, peak T, peak B and peak M. For all the cruises, peak A levels were higher in the surface microlayer than in the subsurface water. This pattern of variation might be attributed to the terrestrial input.  相似文献   

7.
The production of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) by marine microalgae was investigated to elucidate more on the role of marine phytoplankton in ocean-atmosphere interactions in the global biogeochemical sulfur cycle.Axenic laboratory cultures of four marine microalgae–Isochrysis galbana 8701,Pavlova viridis,Platymonas sp.and Chlorella were tested for DMSP production and conversion into DMS.Among these four microalgae,Isochrysis galbana 8701 and Pavlova viridis are two species of Haptophyta,while Chlorella and Platymonas sp.belong to Chlorophyta.The results demonstrate that the four algae can produce various amounts of DMS(P),and their DMS(P) production was species specific.With similar cell size,more DMS was released by Haptophyta than that by Chlorophyta.DMS and dissolved DMSP (DMSPd) concentrations in algal cultures varied significantly during their life cycles.The highest release of DMS appeared in the senescent period for all the four algae.Variations in DMSP concentrations were in strong compliance with variations in algal cell densities during the growing period.A highly significant correlation was observed between the DMS and DMSPd concentrations in algal cultures,and there was a time lag for the variation trend of the DMS concentrations as compared with that of the DMSPd.The consistency of variation patterns of DMS and DMSPd implies that the DMSPd produced by phytoplankton cells has a marked effect on the production of DMS.In the present study,the authors’ results specify the significant contribution of the marine phytoplankton to DMS(P) production and the importance of biological control of DMS concentrations in oceanic water.  相似文献   

8.
于2012年7—9月现场测定了北极挪威海和格陵兰海区域海水二甲基硫(DMS)及其前体物质二甲巯基丙酸内盐(DMSP,分溶解态DMSPd和颗粒态DMSPp)的含量,研究了其空间分布格局及其影响因素,探讨了表层海水DMS的生物周转和去除途径。结果表明,表层海水DMS、DMSPd和DMSPp的平均浓度分别为5.36nmol/L、15.63nmol/L和96.73nmol/L,受挪威海流和北极深层水影响,表层海水二甲基硫化物浓度呈现出由低纬度向高纬度海域递减的趋势。DMSPd和DMSPp浓度与Chl a浓度均有显著的相关性,说明浮游植物生物量是影响挪威海和格陵兰海二甲基硫化物生产的重要因素。表层海水DMS生物生产和消费速率平均值分别为18.19nmol/(L·d)、15.67nmol/(L·d)。DMS微生物周转时间变化范围为0.03~1.80d,平均值为0.49d,DMS海-气周转时间是微生物消费时间的90倍,说明夏季挪威海和格陵兰海表层海水中DMS微生物消费过程是比海-气扩散更具优势的去除机制。  相似文献   

9.
《Marine Chemistry》2001,76(3):137-153
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.  相似文献   

10.
《Marine Chemistry》2001,73(3-4):319-332
The accumulation of dissolved organic matter (DOM) at the air–sea interface is controlled by dynamic physical processes at the boundary between ocean and atmosphere. Much of the DOM concentrated in the surface microlayer is thought to be protein or glycoprotein. Enzymatic hydrolysis of these and other biopolymers is an important step in the microbial uptake of dissolved and particulate organic matter in many aquatic environments. We employed a sensitive fluorescence technique to investigate differences between extracellular enzymatic peptide hydrolysis in the sea surface microlayer and corresponding subsurface water from Stony Brook Harbor, NY. We separated the microlayer from its underlying water and thus measured hydrolysis potential rather than an in-situ process. Peptide turnover was always faster in the microlayer than in subsurface waters. This was confirmed by allowing a new surface film to form on subsurface water; hydrolysis was still faster in the new surface film. In a year-long study, we found the relative difference between turnover times in the surface film and subsurface waters to vary greatly with season. While rate constants of peptide hydrolysis were generally higher in both microlayer and bulk water samples in spring/summer than in fall/winter, the difference in activity between the two environments was greatest in winter. Enhanced hydrolysis in the sea surface microlayer is likely due to the greater concentrations of DOM in the microlayer. Seasonal changes in distribution of hydrolytic activity between surface film and subsurface water probably reflect seasonal variation in the mechanisms of DOM enrichment, which depend on water temperature, substance and energy fluxes across the water–air boundary, activity of aquatic organisms and other seasonal variables.  相似文献   

11.
Temporal distributions of dimethylsulfide(DMS) and dimethylsulfoniopropionate(DMSP) were studied in the southern Yellow Sea(SYS) during April and September 2010. The mean concentrations(range) of DMS, dissolved and particulate DMSP(DMSPd and DMSPp) in the surface waters in spring are 1.69(0.48–4.92), 3.18(0.68–6.75)and 15.81(2.82–52.33) nmol/L, respectively, and those in autumn are 2.80(1.33–5.10), 5.45(2.19–11.30) and 30.63(6.24–137.87) nmol/L. On the whole, the distributions of DMS and DMSP in spring are completely different from those in autumn. In the central part of the SYS, the concentrations of DMS and DMSP in spring are obviously higher than those in autumn, but the opposite situation is found on the south of 34°N, which can be attributed to the differences in nutrients and phytoplankton biomass and composition between spring and autumn. Besides,the seasonal variations of water column stability and the Changjiang diluted water also have significant impact on the distributions of DMS and DMSP in spring and autumn on the south of 34°N. DMS and DMSPp concentrations coincide well with chlorophyll a(Chl a) levels in the spring cruise, suggesting that phytoplankton biomass may play an important role in controlling the distributions of DMS and DMSPp in the study area. Annual DMS emission rates range from 0.015 to 0.033 Tg/a(calculated by S), respectively, using the equations of Liss and Merlivat(1986) and Wanninkhof(1992). This result implies a significant relative contribution of the SYS to the global oceanic DMS fluxes.  相似文献   

12.
本研究首次探究了西太平洋雅浦海沟北段从表层到超深渊海水中甲烷（CH4）及二甲基硫（DMS）的前体物质二甲基巯基丙酸内盐（DMSP）的浓度变化情况。结果表明:雅浦海沟海水甲烷浓度变化范围为1.49~3.87 nmol/L。其上层海水甲烷平均浓度最高，有明显的次表层极大现象。雅浦海沟氧最小层海水的甲烷平均浓度最低；在500~1 000 m中层水中甲烷浓度有一定程度的增大，1 000 m以下至底层甲烷浓度继续升高。研究海区溶解态DMSP（DMSPd）和总DMSP（DMSPt）平均浓度的垂直变化随深度呈先增大后减小趋势，颗粒态DMSP（DMSPp）的平均浓度随深度呈波动式变化，在中层达到最大。雅浦海沟CH4和DMSP浓度垂直变化受浮游生物、微生物、光照、温度、压力、大洋环流等的复杂影响。在真光层海水中，CH4浓度与DMSPd、DMSPp和DMSPt浓度表现为负相关关系，在200 m至底层海水中，CH4浓度与DMSPd、DMSPp和DMSPt浓度表现为正相关关系，显示光照条件是造成雅浦海沟不同深度海水CH4和DMSP浓度相关性差异的关键因素。  相似文献   

13.
Microlayer samples from a coastal marine area near Marseilles (France) collected in 1979 and 1980 have been analysed for POC, PON, chlorophyll a, ATP, cell counts, carbon fixation and in some cases for heterotrophic activity. Comparison of microlayer data with those of underlying water showed in most cases enrichment of organic matter and microorganisms in the surface microlayer. Carbon fixation values were comparable to those observed at 0·50 m except in the slicks, where phytoneustonic activity was higher than that of the underlying phytoplankton. Though total heterotrophic activity was higher in the surface film, the turnover time was not significantly different in both microlayer and underlying water. Our data show that enrichment is highly dependent on sea conditions; whenever slicks are present, the surface film seems to function like an eutrophic system, including active living material, although detritus is regularly present in large amounts.  相似文献   

14.
黄、渤海二甲基硫化物的浓度分布与迁移转化速率研究   总被引：2，自引：1，他引：1  
于2015年8-9月对黄、渤海海域进行现场调查，研究了海水中二甲基硫（DMS）、β-二甲巯基丙酸内盐（DMSP）、二甲亚砜（DMSO）的浓度分布、相互关系及影响因素，测定了DMS的生物生产与消耗、光化学氧化和海-气扩散速率，对DMS的迁移转化速率进行综合评价。结果表明:表层海水中DMS、溶解态DMSP（DMSPd）、颗粒态DMSP（DMSPp）、溶解态DMSO（DMSOd）和颗粒态DMSO（DMSOp）浓度的平均值分别为（6.12±3.01）nmol/L、（6.03±3.45）nmol/L、（19.47±9.15）nmol/L、（16.85±8.34）nmol/L和（14.37±7.47）nmol/L，整体呈现近岸高远海低，表层高底层低的趋势。DMS、DMSPd和DMSOp浓度与叶绿素（Chl a）浓度存在显著的相关性。表层海水中DMS光氧化速率顺序为:kUVA > kUVB > k可见，其中UVA波段占光氧化的70.8%。夏季黄、渤海微生物消耗、光氧化及海-气扩散对DMS去除的贡献率分别为32.4%、34.5%和33.1%，表明3种去除途径作用相当。黄、渤海DMS海-气通量变化范围为0.79~48.45 μmol/（m2·d），平均值为（11.87±11.35）μmol/（m2·d）。  相似文献   

15.
Coastal and oceanic surface microlayer samples were collected using a stainless steel screen, along with subsurface bulk seawater, and were analyzed for low-molecular-weight (LMW) carbonyl compounds, including formaldehyde, acetaldehyde, propanal, glyoxal, methylglyoxal, glyoxylic acid and pyruvic acid. The enrichment factor in surface microlayer compared to corresponding subsurface seawater ranged from 1.2 to 21. A time-series measurement at a coastal site showed strong diurnal variations in concentrations of the LMW carbonyl compounds in the surface microlayer and in the enrichment factor, with maxima in the early afternoon and minima in the early morning. Exposure of samples to sunlight resulted in the higher yields of these compounds in the surface microlayer than in the bulk seawater, by a factor of 1.1–25, suggesting that the higher photoproduction rate of LMW carbonyl compounds in the surface microlayer accounts for the majority of the observed enrichment in these samples. Potential sinks include biological uptake and mixing. Air-sea exchange may be a source for soluble compounds and a sink for less soluble compounds. The enrichment of the LMW carbonyl in surface microlayer may alter their net air-sea exchange direction e.g., from the ocean as a potential sink to a source for atmospheric acetaldehyde and acetone. The residence times of the LMW carbonyl compounds in the microlayer were estimated to be on the order of tens of seconds to minutes using a modified two-layer model. However, to maintain the observed microlayer enrichment factor, the residence time should be on the order of ˜ 1 hour. This prolonged residence time may be due to organic enrichment in the surface microlayer (‘organic film’) which inhibited molecular transfer of carbonyl compounds into and out of the microlayer. The deviated behavior from model prediction may also be due to changes in the apparent partition coefficients of these species as a result of thier physical and chemical interactions with organic matrix in the surface microlayer.  相似文献   

16.
A chemoreduction-purge-and-trap gas chromatographic method has been developed for the determination of trace dimethylsulfoxide (DMSO) in seawater. In the analysis procedure, DMSO was first reduced to dimethylsufide (DMS) by sodium borohydride and then the produced DMS was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. Under the optimum conditions, 97% DMSO was reduced in the standard solution samples with a standard deviation of 5% (n=5). The detection limit of DMSO was 2.7 pmol of sulfur, corresponding to a concentration of 0.75 nmol/L for a 40 ml sample. This method was applied to determine the dissolved DMSO (DMSOd) and particulate DMSO (DMSOp) concentrations in the surface seawater of the Jiaozhou Bay, and the results showed that the DMSOd and DMSOp concentrations varied from 16.8 to 921.1 nmol/L (mean:165.2 nmol/L) and from 8.0 to 162.4 nmol/L (mean:57.7 nmol/L), respectively. The high concentrations of DMSOp were generally found in productive regions. Consequently, a significant correlation was found between the concentrations of DMSOp and chlorophyll a, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMSOp in the bay. Moreover, in the study area, the concentrations of DMSOd were significantly correlated with the levels of DMS, implying that the production of DMSOd is mainly via photochemical and biological oxidation of DMS.  相似文献   

17.
为分析海洋微表层这一特殊生境中的细菌类群,于2010—2011年4个航次对北黄海微表层和次表层海水中的总菌丰度、可培养细菌丰度和群落结构进行了分析。采用流式细胞仪测定总菌丰度,平板计数法测定可培养细菌丰度,PCR-16SrDNA分析可培养细菌的群落结构。结果表明,调查海域微表层海水总菌均值为1.76×106 cell/mL,次表层海水总菌均值为1.07×106 cell/mL。可培养细菌丰度范围是1.00×102~1.70×106 CFU/mL,微表层和次表层可培养细菌所占总菌数量的百分比分别为13.05%和0.45%。微表层对总菌的富集因子(EF)均值为2.02,可培养细菌的EF均值为74.16。PCR-16SrDNA序列分析结果表明,该海域可培养细菌分属变形菌门(Proteobacteria)(94.34%)、厚壁菌门(Firmicutes)(1.89%)、拟杆菌门(Bacteroidetes)(1.89%)和放线菌门(Actinobacteria)(1.89%)4个类群。本研究初步发现,微表层对细菌具有较强的聚集作用,尤其对可培养细菌聚集作用更为明显。微表层中可培养细菌的群落结构与次表层有所不同,其种类丰富,来源和功能多样。由此可见,微表层独特的生境成就了其独特的微生物类群,其生态功能有待于进一步研究。  相似文献   

18.
Seasonal changes in oceanographic conditions related to primary productivity was investigated in the southwestern Okhotsk Sea during non-iced seasons, using the observation data conducted in 2000∼2006. Based on hydrographic characteristics, the studied area could be classified into two regions, the Coastal Region which is influenced under the Soya Warm Current and the Forerunner Water of the Soya Warm Current, and the Offshore Region where the Intermediate Cold Water was located in the subsurface layer. This study is the first report on seasonal change of nutrient and chlorophyll a concentrations in the offshore region of the southwestern Okhotsk Sea. Variability of concentrations of chlorophyll a and nutrients is temporally and regionally high in the Coastal Region. The maximum chlorophyll a concentration in April was observed at the surface layer of both regions. The most remarkable feature on the vertical structure in the Offshore Region was the consistent existence of the Intermediate Cold Water and the development of seasonal thermocline in the subsurface layer during summer and autumn. The stratification formed within the euphotic zone in the Offshore Region resulted in the formation of the subsurface chlorophyll a maximum (SCM) from May to October. Throughout the research period, although less amplitude of nutrients at the surface was observed in the Coastal Region than that in the Offshore Region, comparable amplitude of chlorophyll a concentration was observed between regions. These results suggested differences of environmental conditions for primary production between the two regions. Depending on the presence of SCM, relationships between chlorophyll a concentration at the sea surface and chlorophyll a standing stock within the euphotic layer were different. At most stations with SCM, the surface chlorophyll a concentration was lower than 0.6 mg m-3. This suggests that the presence of SCM and the chlorophyll a standing stock within the euphotic layer may be estimated using the surface chlorophyll a concentration from spring to autumn in the studied area.  相似文献   

19.
The impact of in situ iron fertilisation on the production of particulate dimethylsulphoniopropionate (DMSPp) and its breakdown product dimethyl sulphide (DMS) was monitored during the SOLAS air-sea gas exchange experiment (SAGE). The experiment was conducted in the high nitrate, low chlorophyll (HNLC) waters of the sub-Antarctic Southern Ocean (46.7°S 172.5°E) to the south-east of New Zealand, during March-April, 2004. In addition to monitoring net changes in the standing stocks of DMSPp and DMS, a series of dilution experiments were used to determine the DMSPp production and consumption rates in relation to increased iron availability. In contrast to previous experiments in the Southern Ocean, DMS concentrations decreased over the course of the 15-d iron-fertilisation experiment, from an integrated volume-specific concentration in the mixed layer on day 0 of 0.78 nM (measured values 0.65-0.91 nM) to 0.46 nM (measured values 0.42-0.47 nM) by day 15, in parallel with the surrounding waters. DMSPp, chlorophyll a and the abundance of photosynthetic picoeukaryotes exhibited indiscernible or only moderate increases in response to the raised iron availability, despite an obvious physiological response by the phytoplankton. High specific growth rates of DMSPp, equivalent to 0.8-1.2 doublings d−1, occurred at the simulated 60% light level of the dilution experiments. Despite the high production rates, DMSPp accumulation was suppressed in part by microzooplankton grazers who consumed between 61% d−1 and 126% d−1 of the DMSPp production. Temporal trends in the rates of production and consumption illustrated a close coupling between the DMSP-producing phytoplankton and their microzooplankton grazers. Similar grazing and production rates were observed for the eukaryotic picophytoplankton that dominated the phytoplankton biomass, partial evidence that picoeukaryotes contributed a substantial proportion of the DMSP synthesis. These rates for DMSPp and picoeukaryotes were considerably higher than for chlorophyll a, indicating higher cycling rates of the DMSP-producing taxa than for the bulk phytoplankton community. When compared to the total phytoplankton community, there was no evidence of selection against the DMSP-containing phytoplankton by the microzooplankton grazers; the opposite appeared to be the case. SAGE demonstrated that increased iron availability in the HNLC waters of the Southern Ocean does not invariably lead to enhanced DMS sea-air flux. The potential suppression of DMSPp accumulation by grazers needs to be taken into account in future attempts to elevate DMS emission through in situ iron fertilisation and in understanding the hypothesised link between levels of Aeolian iron deposition in the Southern Ocean, DMS emission and global albedo.  相似文献   

20.
Dimethylsulfide (DMS), chlorophyll a (Chl-a), accessory pigments (fucoxanthin, peridinin and 19-hexanoyloxyfucoxanthin), and bacterial production (BP) were measured in the surface layer (0–100 m) of the subarctic North Pacific, including the Bering Sea, during summer (14 July–5 September, 1997). In surface sewater, the concentrations of DMS and Chl-a varied widely from 1.3 to 13.2 nM (5.1 ± 3.0 nM, mean ± S.D., n = 48) and from 0.1 to 2.4 µg L–1 (0.6 ± 0.6 µg L–1, n = 24), respectively. In the subarctic North Pacific, DMS to Chl-a ratios (DMS/Chl-a) were higher on the eastern side than the western side (p < 0.0001). Below the euphotic zone, DMS/Chl-a ratios were law and the correlation between DMS and Chl-a was relatively strong (r 2 = 0.700, n = 27, p < 0.0001). In the euphotic zone, DMS/Chl-a ratios were higher and the correlation between DMS and Chl-a was weak (r 2 = 0.128, n = 50, p = 0.01). The wide variation in DMS/Chl-a ratios would be at least partially explained by the geographic variation in the taxonomic composition of phytoplankton, because of the negative correlation between DMS/Chl-a and fucoxanthin-to-Chl-a ratios (Fuc/Chl-a) (r 2 = 0.476, n = 26, p = 0.0001). Furthermore, there was a positive correlation between DMS and BP (r 2 = 0.380, n = 19, p = 0.005). This suggests that BP did not represent DMS and dimethylsulfoniopropionate (DMSP) removal by bacterial consumption but rather DMSP degradation to DMS by bacterial enzyme.  相似文献   

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