夏季黄海不同水团溶解有机物分布特征

依据2017年8—9月对黄海海域溶解有机物(DOM)的调查，探讨了夏季黄海海水中溶解有机碳(DOC)和有色溶解有机物(CDOM)的空间分布特征。在表层海水中，受陆源影响较大的近岸海域CDOM含量相对较高，北黄海冷水团区域由于水产养殖的饵料引起DOC浓度升高，且该部分DOC以无色为主。DOC浓度随深度逐渐降低，而CDOM逐渐升高，该特征在冷水团区域更为显著，因此DOC和CDOM在冷水团区域的表底差异远大于浅水区的非冷水团区域。陆源输入和初级生产是引起表层DOC升高的主要原因，而光漂白则引起CDOM降低，同时光漂白还导致表层水体中CDOM分子量和芳香性低于底层。底层溶解氧饱和度在冷水团为80%～93%，均表现为弱不饱和状态。层化不仅阻碍了O₂向底层水体输送，还抑制了DOC和CDOM的垂向混合，这是引起冷水团区域表底层DOC和CDOM差异较大的主要原因。     

Relationship between the optical properties of chromophoric dissolved organic matter and total concentration of dissolved organic carbon in the southern Baltic Sea region

Absorption and fluorescence of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) measurements were performed during three oceanographic surveys in 1994 in the southern Baltic Sea (Polish area of the Baltic Proper). DOC was measured both by high-temperature catalytic oxidation (HTCO) and low-temperature oxidation (LTO) conventional persulphate methods. CDOM fluorescence was shown to be highly correlated with absorption, with the same regression parameters, despite the seasonal change in different hydrographic conditions and the fluorescence quantum yield variations (1.23 ± 0.07 in April and 0.97 ± 0.12 in September). The results show a good correlation between the optical parameters and DOC although ˜ 70% of the DOC does not display significant absorption in the UV-visible range (350–750 nm). The non-absorbing DOC measured with HTCO method appears unaffected by seasonal changes. Consequently, total DOC can be predicted by optical methods using remote sensing techniques. The non-absorbing DOC measured by LTO method varies from 62% (April) to 76% (September), which implies that there is requirement for estimates on a seasonal basis.     

Characterization of dissolved organic matter fluorescence in the South Atlantic Bight with use of PARAFAC model: Interannual variability

Systematic water sampling for characterization of chromophoric dissolved organic matter (CDOM) in the coastal South Atlantic Bight, was conducted as part of the long term Coastal Ocean Research and Monitoring Program (CORMP). Water samples were collected during a 3.5 year period, from October 2001 until March 2005, in the vicinity of the Cape Fear River (CFR) outlet and in adjacent Onslow Bay (OB). During this study there were two divergent hydrological and meteorological conditions in the CFR drainage area: a severe drought in 2002, followed by the very wet year of 2003. CDOM was characterized optically by the absorption coefficient at 350 nm, the spectral slope coefficient (S), and by Excitation Emission Matrix (EEM) fluorescence. Parallel Factor Analysis (PARAFAC) was used to assess CDOM composition from EEM spectra and six components were identified: three terrestrial humic-like components, one marine humic-like component and two protein-like components. Terrestrial humic-like components contributed most to dissolved organic matter (DOM) fluorescence in the low salinity plume of the CFR. The contribution of terrestrial humic-like components to DOM fluorescence in OB was much smaller than in the CFR plume area. Protein-like components contributed significantly to DOM fluorescence in the coastal ocean of OB and they dominated DOM fluorescence in the Gulf Stream waters. Hydrological conditions during the observation period significantly impacted both concentration and composition of CDOM found in the estuary and coastal ocean. In the CFR plume, there was an order of magnitude difference in CDOM absorption and fluorescence intensity between samples collected during the drought compared to the wet period. During the drought, CDOM in the CFR plume was composed of equal proportions of terrestrial humic-like components (ca. 60% of the total fluorescence intensity) with a significant contribution of proteinaceous substances (ca. 20% of the total fluorescence). During high river flow, CDOM was composed mostly of humic substances (nearly 75% of total fluorescence) with minor contributions by proteinaceous substances. The impact of changes in fresh water discharge patterns on CDOM concentration and composition was also observed in OB, though to a lesser degree.     

Variation of dissolved organic matter and fluorescence characteristics before,during and after phytoplankton bloom

The variation of dissolved organic matter (DOM) and fluorescence characteristics during the phytoplankton bloom were investigated in Yashima Bay, at the eastern part of the Seto Inland Sea, Japan. We found significant accumulations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), chromophoric dissolved organic matter (CDOM) fluorescence, and UV₂₆₀ during the phytoplankton bloom period in 2005, although lower accumulations of DOC and DON and only increases of CDOM fluorescence were observed during the bloom period in 2006. Little or no correlation between DOM and phytoplankton abundance might be due to the composition of DOM, which is a complex mixture of organic materials. The 3D-EEM results revealed that the DOM produced around the phytoplankton bloom period contained tyrosine, tryptophan, and humic-like substances. Our results showed that the occurrence of phytoplankton bloom contributed to the production of DOM in coastal water but the DOM accumulation depended on the type of phytoplankton bloom, the phytoplankton species in particular. From our results, we concluded that phytoplankton have a great role in the dynamics of DOM as a producer in a coastal environment.     

DOC遥感研究进展——基于全球大河DOC与CDOM保守性特征

目前,溶解有机碳(DOC)遥感反演研究主要集中在河口及陆源影响较大的边缘海区,大多数是利用DOC与有色溶解有机物(CDOM)或DOC与盐度的经验关系获取。为了较好的理解DOC的遥感反演机理,收集了全球主要大河(流量排名前25中16条)及边缘海DOC与CDOM浓度与保守性分布状况,发现大多数河口CDOM呈现保守性分布,DOC呈现非保守性分布。基于DOC与CDOM保守性行为的主要影响因素分析以及研究海区的生物地球化学特征,论述了DOC遥感反演算法的研究进展,提出了DOC遥感反演需要考虑DOC受不同主要控制因素(如保守混合与生物作用等)的影响,并对这些控制因素进行量化。     

DOC遥感研究进展——基于全球大河DOC与CDOM保守性特征

目前,溶解有机碳(DOC)遥感反演研究主要集中在河口及陆源影响较大的边缘海区,大多数是利用DOC与有色溶解有机物(CDOM)或DOC与盐度的经验关系获取。为了较好的理解DOC的遥感反演机理,收集了全球主要大河(流量排名前25中16条)及边缘海DOC与CDOM浓度与保守性分布状况,发现大多数河口CDOM呈现保守性分布,DOC呈现非保守性分布。基于DOC与CDOM保守性行为的主要影响因素分析以及研究海区的生物地球化学特征,论述了DOC遥感反演算法的研究进展,提出了DOC遥感反演需要考虑DOC受不同主要控制因素(如保守混合与生物作用等)的影响,并对这些控制因素进行量化。     

Photochemical production of ammonium and transformation of dissolved organic matter in the Baltic Sea

The release of ammonium from the photochemical degradation of dissolved organic matter (DOM) has been proposed by earlier studies as a potentially important remineralisation pathway for refractory organic nitrogen. In this study the photochemical production of ammonium from Baltic Sea DOM was assessed in the laboratory. Filtered samples from the Bothnian Bay, the Gulf of Finland and the Arkona Sea were exposed to UVA light at environmentally relevant levels, and the developments in ammonium concentrations, light absorption, fluorescence and molecular size distribution were followed. The exposures resulted in a decrease in DOM absorption and loss of the larger sized fraction of DOM. Analysis of the fluorescence properties of DOM using parallel factor analysis (PARAFAC) identified 6 independent components. Five components decreased in intensity as a result of the UVA exposures. One component was produced as a result of the exposures and represents labile photoproducts derived from terrestrial DOM. The characteristics of DOM in samples from the Bothnian Bay and Gulf of Finland were similar and dominated by terrestrially derived material. The DOM from the Arkona Sea was more autochthonous in character. Photoammonification differed depending on the composition of DOM. Calculated photoammonification rates in surface waters varied between 121 and 382 μmol NH₄⁺ L^− 1 d^− 1. Estimated areal daily production rates ranged between 37 and 237 μmol NH₄⁺ m^− 2 d^− 1, which are comparable to atmospheric deposition rates and suggest that photochemical remineralisation of organic nitrogen may be a significant source of bioavailable nitrogen to surface waters during summer months with high irradiance and low inorganic nitrogen concentrations.     

长江口溶解有机物光漂白和光矿化表观量子产率

溶解有机物(DOM)经太阳光照射导致其吸光度(光漂白)和溶解有机碳(光矿化)损失,从而影响水体生态系统光学特性及碳循环。本文通过测定冬季长江口及其邻近海域DOM光降解表观量子产率(AQY),初步探讨了DOM光反应活性在河口及陆架海的变化特征。DOM光降解AQY由口内至口外逐渐递减,且有色溶解有机物(CDOM)光漂白速率是溶解有机碳(DOC)光矿化速率的10倍。Φ_ble(CDOM光漂白表观量子产率)和Φ_min(DOC光矿化平均量子产率)在最大浑浊带以东海域与盐度和SUVA₂₅₄分别呈显著的线性负相关与正相关,表明DOM光反应活性在长江口外受物理混合影响为主,且陆源DOM光反应活性比海源高。此外,最大浑浊带下游DOM光降解AQY显著低于上游。DOM光降解速率随波长的变化呈现非高斯分布,且峰值出现在330 nm,积分结果表明UVA是DOM光降解的主要贡献者。本研究结果将为完善我国东海碳通量模型提供帮助。     

Photoreactivity of chromophoric dissolved organic matter transported by the Mackenzie River to the Beaufort Sea

The photoreactivity of chromophoric dissolved organic matter (CDOM) transported to Arctic shelf environments by rivers has only recently been studied and its quantitative role in Arctic shelf biogeochemistry has received little attention. Sunlight exposure experiments were performed on CDOM collected over a three year period (2002 to 2004) from river, estuary, shelf, and gulf regions of the Western Canadian Arctic. Decreases in CDOM absorption, synchronous fluorescence (SF), and dissolved organic carbon (DOC) concentration were followed after 3 days of exposure, and in two experiments, six optical cutoff filters were used to incrementally remove ultraviolet radiation incident on the samples. Apparent quantum yields for CDOM photobleaching (AQY_ble) and for DOC photomineralization (AQY_min) were computed, as were two AQY spectra (_ble and _min) for the Mackenzie River and a sample from the Mackenzie Shelf. The photoreactivity of Mackenzie River CDOM was highest after break-up and peak discharge and lowest in late summer. The half-lives of CDOM and DOC were estimated at 3.7 days and 4.8 days, respectively, when Mackenzie River water was exposed to full sunlight. Photobleaching of Mackenzie River CDOM fluorescence after most UV-B wavelengths were removed increased the correlation between the river and offshore waters in the Beaufort Sea. When light attenuation from particle- and CDOM-rich river water was considered for the Mackenzie Shelf, our photodegradation models estimated around 10% loss of absorption and < 1% DOC loss, suggesting that sunlight exposure does not substantially degrade CDOM on Arctic shelves.     

Characterization of chromophoric dissolved organic matter (CDOM) in the Baltic Sea by excitation emission matrix fluorescence spectroscopy

Chromophoric dissolved organic matter (CDOM) is the major light absorber in the Baltic Sea. In this study, excitation emission matrix (EEM) fluorescence spectra and UV–visible absorption spectra of CDOM are reported as a function of salinity. Samples from different locations and over different seasons were collected during four cruises in 2002 and 2003 in the Baltic Sea in both Pomeranian Bay and the Gulf of Gdansk. Absorption by CDOM decreased with increased distance from the riverine source and reached a relatively stable absorption background in the open sea. Regression analysis showed that fluorescence intensity was linearly related to absorption by CDOM at 375 nm and a_CDOM(375) absorption coefficients were inversely related to salinity. Analysis of CDOM-EEM spectra indicated that a change in composition of CDOM occurred along the salinity gradient in the Baltic Sea. Analysis of percent contribution of respective fluorophore groups to the total intensity of EEM spectra indicated that the fluorescence peaks associated with terrestrial humic components of the CDOM and total integrated fluorescence decreased with decreasing CDOM absorption. In contrast, the protein-like fraction of CDOM decreased to a lesser degree than the others. Analysis of the percent contribution of fluorescence peak intensities to the total fluorescence along the salinity gradient showed that the contribution of protein-like fluorophores increased from 2.6% to 5.1% in the high-salinity region of the transect. Fluorescence and absorption changes observed in the Baltic Sea were similar to those observed in similar transects that have been sampled elsewhere, e.g. in European estuaries, Gulf of Mexico, Mid-Atlantic Bight and the Cape Fear River plume in the South Atlantic Bight, although the changes in the Baltic Sea occurred over a much smaller salinity gradient.     

舟山海域陆源溶解有机质变化及其对近岸羽状流的响应

2007年夏季在东海舟山海域河口锋区开展了陆源溶解有机质的调查研究。测定了有色溶解有机质(CDOM)在激发波长370 nm/发射波长460 nm处的荧光强度和在λ=355 nm处的吸收系数,用于代表陆源CDOM浓度,并测定了荧光指数以指示CDOM来源。结果表明,CDOM的荧光值和紫外吸收系数之间呈显著正相关性,陆源CDOM浓度大体有向海方向降低的趋势,但是纵向上存在一些"突跃"现象。在舟山海域东北角不时观测到表层水体含有高浓度的CDOM,但变异性很大,推测可能该海区受到长江口羽状流的影响。在连续观测站发现陆源CDOM浓度在低平潮时往往比高平潮时要高。河海水在混合过程中CDOM浓度与盐度呈显著的线性负相关关系。在低盐度的悬沙锋区(S<24)CDOM浓度明显低于理论稀释值,而在较高盐度的羽状锋区,CDOM浓度接近于理论稀释值。在盐度为24~31范围内,大部分水样的荧光指数在1.50上下波动,表明其中CDOM来源以陆地来源为主;在较低盐度(S<24)的水样中荧光指数在1.70至1.90以上,表明CDOM以海洋来源为主,这与其陆源组分在高浊度的低盐度区存在显著的去除过程有关。研究表明,舟山海域水质存在着显著的变异性,与近岸羽状流密切相关,陆源溶解有机质的分布特征对此有较好的响应。     

红树林间隙水溶解态陆源有机质的光降解和生物降解行为分析

红树林输送的溶解态陆源有机质是海洋中陆源有机质的主要来源之一,对其光降解和生物降解过程的研究有助于进一步了解红树林生态系统输出的有机质在近岸的归宿以及对近岸水体生物地球化学过程的影响,因此于2010年4月在海南省清澜港红树林采集间隙水,并进行了光降解和生物降解培养实验。分析了光培养(光降解)和暗培养过程(生物降解)中溶解态有机碳(DOC)、细菌以及溶解态木质素等的变化。结果显示经历128 d的暗培养后,DOC由初始的2 216 μmol/L下降至718 μmol/L,表明红树林间隙水的生物可利用性约为70%左右;经历11 d的自然光照后,DOC下降至800 μmol/L。木质素在光降解过程中的移除速率(-0.132 d-1)远高于生物降解过程(-0.008 d-1)。光培养中,木质素的下降速率高于总体DOC。不同系列溶解态木质素的下降速率不同,随着培养的进行,紫丁香基酚类(S)与香草基酚类(V)的比值(S/V)呈下降趋势,而V系列的酸醛比值((Ad/Al)v)呈上升的趋势。对比光培养和暗培养过程中DOC和木质素的变化可以得出生物消耗是引起红树林间隙水DOC从水体中移除的主要因素;而光照则是陆源有机质从水体中移除的主要因素;光培养和暗培养过程中细菌变化的差异表明光照可以促进细菌对溶解态有机碳的利用。与其他地区比较发现,海南红树林间隙水的光降解速率与热带河流(刚果河)相近,高于温带密西西比河流,降解过程中各参数的变化[S/V和(Ad/Al)v]与其他区域接近。     

胶州湾海水中溶解有色物质的光脱色对光致生成一氧化碳速率的影响

利用在胶州湾中不同位置取得的3个水样,对溶解有色物质进行了不同时间的光脱色,探讨了有机物含量随脱色时间的变化趋势,得出有机物吸光系数和溶解有机碳随脱色时间的增长而呈指数减小,说明光脱色可以明显降低溶解有机物的含量。对不同光脱色程度的水样进行了光化学降解,测定了其主要产物一氧化碳的光致生成速率,发现在8个不同波段下一氧化碳光致生成速率与350 nm的吸光系数和溶解有机碳之间均有良好的线性关系。350 nm的吸光系数和溶解有机碳含量在一定程度上均可较好地表示海水中CDOM的含量。     

海草凋落叶的溶解有机物的释放及其生物地球化学意义

Dissolved organic matter(DOM) represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon(C), 70% nitrogen(N) and 38% phosphorus(P) of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon(DOC), dissolved organic nitrogen(DON) and dissolved organic phosphorus(DOP) of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides(MCHO), DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/(g·d). Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON: DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production(the Xincun Bay, South China Sea), the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter(POM)from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.     

北极孔斯峡湾表层沉积物中溶解有机质的来源与转化历史

在北极地区孔斯峡湾采集28个表层沉积物样品,测定了其中水溶性有机质(也称溶解有机质,DOM)的分子量分布、紫外/可见吸收光谱和三维荧光光谱特征,并利用平行因子分析(PARAFAC)模型对DOM的荧光组分和来源进行了解析。结果表明:孔斯峡湾表层沉积物中有色溶解有机质(CDOM)及其中的荧光溶解有机质(FDOM)含量均从内湾向外湾方向呈逐渐累积的趋势,但CDOM中的FDOM所占比例逐渐减小,与DOM趋于老龄化密切相关。沉积作用减弱以及长期的光化学降解和微生物降解作用对此起主要贡献,并导致腐殖质和小分子组分在沉积物DOM中所占的比例呈逐渐递增的趋势。沉积物DOM包含陆源类腐殖质、自生源类腐殖质和类蛋白等三个荧光组分,但是其组成比例空间差异很大。吸收光谱斜率比(S_R)随自生源所占百分比增加而减小,随DOM腐殖质组分中陆源与自生源的比值增加而增加;腐殖化指数(HIX)随类腐殖质与类蛋白质比值和水深的增加而增加,生物源指数(BIX)随自生源比例增加而增加。峡湾沉积物DOM的组成和来源存在着高度的空间差异,在冰川湾区由水体颗粒有机质(POM)的近期转化和迁移而来,而在峡湾中央及口门附近以较老的腐殖质为优势,主要源于水体DOM长期迁移和转化。研究表明,FDOM/CDOM,S_R,HIX和BIX等构成的CDOM光谱指纹信息可以作为揭露沉积物溶解有机质来源及迁移转化历史的工具,对探索海洋与冰川相互作用影响下的峡湾环境演变有着重要意义。     

Stocks and dynamics of dissolved and particulate organic matter in the southern Ross Sea, Antarctica

Dissolved and particulate organic matter was measured during six cruises to the southern Ross Sea. The cruises were conducted during late austral winter to autumn from 1994 to 1997 and included coverage of various stages of the seasonal phytoplankton bloom. The data from the various years are compiled into a representative seasonal cycle in order to assess general patterns of dissolved organic matter (DOM) and particulate organic matter (POM) dynamics in the southern Ross Sea. Dissolved organic carbon (DOC) and particulate organic carbon (POC) were at background concentrations of approximately 42 and 3 μM C, respectively, during the late winter conditions in October. As the spring phytoplankton bloom progressed, organic matter increased, and by January DOC and POC reached as high as 30 and 107 μM C, respectively, in excess of initial wintertime conditions. Stocks and concentrations of DOC and POC returned to near background values by autumn (April). Approximately 90% of the accumulated organic matter was partitioned into POM, with modest net accumulation of DOM stocks despite large net organic matter production and the dominance of Phaeocystis antarctica. Changes in NO₃ concentration from wintertime values were used to calculate the equivalent biological drawdown of dissolved inorganic carbon (DIC_equiv). The fraction of DIC_equiv drawdown resulting in net DOC production was relatively constant (ca. 11%), despite large temporal and spatial variability in DIC_equiv drawdown. The C : N (molar ratio) of the seasonally produced DOM had a geometric mean of 6.2 and was nitrogen-rich compared to background DOM. The DOM stocks that accumulate in excess of deep refractory background stocks are often referred to as “semi-labile” DOM. The “semi-labile” pool in the Ross Sea turns over on timescales of about 6 months. As a result of the modest net DOM production and its lability, the role DOM plays in export to the deep sea is small in this region.     

Wet-oxidation and automated colorimetry for simultaneous determination of organic carbon, nitrogen and phosphorus dissolved in seawater

We developed a simple and reliable method which allows simultaneous determination of organic forms of carbon (DOC), nitrogen (DON) and phosphorus (DOP) dissolved in seawater. Conversion of dissolved organic matter (DOM) to inorganic products (carbon dioxide, nitrate+nitrite and soluble reactive phosphate) is performed by a persulfate wet-oxidation in low alkaline condition. After oxidation, the concentration of the inorganic products dissolved in the sample was measured automatically by colorimetry using a 3-channel Technicon AutoAnalyzer system. A number of pure organic compounds were tested in the concentration range encountered in coastal and open ocean, indicating a high efficiency of the digestion procedure. The recovery range is similar to that obtained by other wet-oxidation procedures and by high-temperature catalytic oxidation techniques. Direct comparisons with usual methods used for separate determination of DOC, DON and DOP indicated a high efficiency of the procedure. Reproducibility tests demonstrated a very good precision (around 5%) for lagoonal and coastal waters, while precision was sometimes around 10–25% in oligotrophic oceanic waters, especially for DOP where values approached limits of detection for measuring phosphate. This method is highly suitable for routine analysis and especially appropriate for shipboard work.     

厦门湾有色溶解有机物的光吸收特性研究

研究了厦门湾九龙江河口区、西海域、同安湾及东侧水道海水中有色溶解有机物(CDOM)的光吸收特性,分析了CDOM的河口行为,并讨论了CDOM光吸收特性与其荧光性质之间的关系。结果表明,厦门湾表层海水CDOM光吸收系数a(355)的水平分布表现为河口区最高、东侧水道最低、西海域和同安湾介于两者之间,底层水a(355)的分布与表层基本相似,表明陆源河流输入是厦门湾CDOM的主要来源;a(355)的垂直分布为表层高于底层,主要受水文和生物因素控制。厦门湾表层水CDOM光谱斜率S的平均值介于0.014—0.018nm-1,但河口低盐度区S值较小,反映陆源腐殖质的影响。a(355)在河口混合中呈保守行为,表明CDOM具有良好的保守性质。CDOM的吸收系数a(355)与其荧光强度之间表现为较好的相关关系,指示可以用灵敏度更高的荧光方法来研究CDOM的分布和行为。     

The satellite reversion of dissolved organic carbon (DOC) based on the analysis of the mixing behavior of DOC and colored dissolved organic matter: the East China Sea as an example

The retrieval of dissolved organic carbon (DOC) distribution by remote sensing is mainly based on the empirical relationship of DOC concentration and colored dissolved organic matter (CDOM) concentration in many literatures. To investigate the nature of this relationship, the distributions and mixing behaviors of DOC and CDOM are reviewed in the world’s major estuaries and bays. It is found that, generally, the CDOM concentration is well correlated with the salinity in most estuaries, while DOC usually shows a nonconservative behavior which leads to a weak correlation between the DOC concentration and the CDOM concentration. To establish a good satellite reversion of the DOC concentration, the East China Sea(ECS) was taken as an example, and the mixing behavior of DOC and CDOM as well as the influence of biogeochemical processes were analyzed except for the physical mixing process with the data from late autumn (November, 2010) and winter (December, 2009) cruises. In the two ECS cruises, the CDOM concentration was found to be tightly correlated with the salinity, influenced little by the photochemical or biological processes. The data from the winter cruise show that DOC followed a conservative mixing along the salinity gradient, while in the late autumn cruise it was significantly affected by the biological activities, resulting in a poor correlation between the DOC and the CDOM. Accordingly, an improved DOC algorithm (CSDM) was proposed: when the biological influence was significant (Chl a greater than 0.8 μg/dm3 ), DOC was retrieved by the conservative and biological model, and if the conservative mixing was dominant (Chl a less than 0.8 μg/dm3 ), the direct DOC concentration and CDOM concentration relationship was used. Based on the proposed algorithm, a reasonable DOC distribution for the ECS from satellite was obtained in this study, and the proposed method can be applied to the other large river-dominant marginal sea.     

Seasonal trends in the abundance, composition and bioavailability of particulate and dissolved organic matter in the Chukchi/Beaufort Seas and western Canada Basin

The objectives of this study were to investigate the seasonality, abundance, sources and bioreactivity of organic matter in the water column of the western Arctic Ocean. The concentrations of particulate and dissolved amino acids and amino sugars, as well as bulk properties of particulate and dissolved organic matter (DOM), were measured in shelf, slope and basin waters collected during the spring and summer of 2002. Particulate organic matter concentrations in shelf waters increased by a factor of 10 between spring and summer. Dissolved organic carbon (DOC) and nitrogen (DON) concentrations exhibited only minor seasonal variations, whereas dissolved amino acid concentrations doubled between spring and summer, and dissolved amino sugars increased by 31% in shelf waters of the Chukchi and Beaufort Seas. Concentrations of DOC did not exhibit a significant seasonal change in surface waters of the Canada Basin, but dissolved amino acid concentrations increased by 45% between spring and summer. No significant seasonal differences were detected in the concentration or composition of DOM in waters below 100 m in depth. Concentrations of particulate and dissolved amino acids and amino sugars were strongly correlated with chlorophyll-a, indicating a plankton source of freshly produced organic matter. The amino acid and amino sugar compositions of freshly produced DOM indicated that a large portion of this material is bioavailable. While freshly produced DOM was found to be relatively bioreactive, preformed DOM in the Arctic appears to be less bioreactive but similar in degradation state to average DOM in the Atlantic and Pacific. These data demonstrate substantial summer production of POM and DOM on the Chukchi and Beaufort shelves that is available for utilization in shelf waters and export to the Canada Basin.