海洋有机质的光谱分析方法评述

海洋有机质的光谱分析已成为海洋碳循环的研究热点之一。本文从天然有机质吸收光谱和荧光光谱分析的基本原理入手,系统梳理了有机质光谱分析中容易被忽视的基本概念,讨论了过滤与保存方式、p H值、荧光内滤效应等对有机质光谱分析的影响。结合色氨酸、酪氨酸、腐殖酸及大量现场样品的实验结果,对吸收光谱和三维荧光光谱的不同解析方法进行了系统的分析与对比。基于在南海、西菲律宾海获取的现场调查数据,对于文献中常用的荧光指数(FI)、腐殖化指数(HIX)、自生源指数(BIX)等光谱参数的内在含义及其在海洋环境中的适用性进行了评述。此外,还归纳和总结了胶体有机质和颗粒有机质荧光分析的最新进展,并对今后在光谱分析与观测领域有待完善和突破的一些关键领域进行了展望。     

Abundance, size distribution, and stable carbon and nitrogen isotopic compositions of marine organic matter isolated by tangential-flow ultrafiltration

Tangential-flow ultrafiltration was used to isolate particulate and high-molecular-weight dissolved material from seawater collected at various depths and geographic regions of the Pacific and Atlantic Oceans. Ultrafiltration proved to be a relatively fast and efficient method for the isolation of hundreds of milligrams of material. Optical and electron microscopy of the isolated materials revealed that relatively fragile materials were recovered intact. Depth-weighted results of the size distribution of organic matter in seawater indicated that ˜ 75% of marine organic carbon was low-molecular-weight (LMW) dissolved organic carbon (< 1 nm), ˜ 24% was high-molecular-weight (HMW) dissolved organic carbon (1–100 nm), and ˜ 1% was particulate organic carbon (> 100 nm). The distribution of carbon in surface water was shifted to greater relative abundances of larger size fractions, suggesting a diagenetic sequence from macromolecular material to small refractory molecules. The average C:N ratios of particulate organic matter (POM) and HMW dissolved organic matter (DOM) were 7.7 and 16.7, respectively. Differences in C:N ratios between POM and HMW DOM were large and invariant with depth and geographic region, indicating that the aggregation of HMW DOM to form POM must be of minor significance to overall carbon dynamics. The stable carbon isotope composition (δ¹³C) of POM averaged −22.7%. in surface water and −25.2%. in subsurface water. Several possible explanations for the observed isotopic shift with depth were explored, but we were unable to discern the cause. The δ¹³C of HMW DOM samples was relatively constant and averaged −21.7%., indicating a predominantly marine origin for this material. The δ¹⁵N values of POM were highly variable (5.8–15.4%.), and the availability of nitrate in surface waters appeared to be the major factor influencing δ¹⁵N values in the equatorial Pacific. In the upwelling region nitrate concentrations were relatively high and δ¹⁵N values of POM were low, whereas to the north and south of the upwelling nitrate concentrations were low and δ¹⁵N values were high. The δ¹⁵N values of HMW DOM reflected the same trends observed in the POM fraction and provided the first such evidence for biological cycling of dissolved organic nitrogen (DON). Using the observed δ¹⁵N values and an estimate of meridional advection velocity, we estimated a turnover time of 0.3 to 0.5% day⁻¹ for HMW DON. These results suggest a major role for DON in the upper ocean nitrogen cycle.     

The origin of the suspended particulate matter in the seagrass meadow of tropical waters, an evidence of the stable isotope signatures

Suspended particulate matter (SPM) has been known as an important variable in the organic matter flow of coastal ecosystem. Half of burial carbon in seagrass meadows is contributed by allochthonous sources that compose the SPM such as phytoplankton, seagrass detritus, marine snow aggregates and terrestrially derived particles. Each composition of the SPM contributes different roles and is important to be identified, for instance, the exact contribution of seagrass detritus will be useful for determination of carbon export through the detritus form in seagrass meadows. Here, the SPM of seagrass meadows is studied in Bintan Island and the Selayar Archipelago. The aim of this research is to determine the source origin of the SPM using a stable isotope signature. In order to fulfill this aim, the objectives are defined as: (1) to specify the stable isotope signature (δ¹³C and δ¹⁵N) of the SPM, and (2) to determine the proportional distribution of the SPM''s prospectus sources. The result shows that the possibility of the source origin of the SPM includes a seagrass fraction (Enhalus acoroides and Thalassia hemprichii), terrestrial C4 plant, macroalgae, and terrestrial C3 plant. The SPM lies between the marine- and terrigenous-end members. However, it seems that the SPM is more to be terrigenous-end and allochthonous. According to a Bayesian mixing model, the terrestrial C4 has the highest contribution of the SPM at all sites except Barugaia and Pasi Island in Selayar (i.e., the highest contribution of the SPM is from the detritus of E. acoroides). The second contribution has been contributed by either seagrass detritus (E. acoroides or Th. hemprichii) or terrestrial C3 plant. The finding of this study indicates that there is a strong influence of the terrigenous sources in the SPM of the seagrass meadows.     

Water, organic matter, nitrogen and phosphorus contents in sediment of a large-scale mariculture area in the Zhelin Bay of eastern Guangdong Province, China

The Zhelin Bay is one of the most important bays for large-scale mariculture in Guangdong Province, China. Owing to the increasing human population and the expanding mariculture in the last two decades, the ecological environment has greatly changed with frequent harmful algal blooms. A monthly survey of water content, organic matter （TOM）, and various forms of nitrogen and phosphorous in sediment from July 2002 to July 2003 in the bay was conducted. The results showed that the water content was correlated significantly with TOM and various forms of nitrogen and phosphorus and can be used as proxy for quick and rough estimate of these factors in the future surveys. TOM was also correlated significantly with various forms of nitrogen and phosphorus, indicating that it was one of the key factors affecting the concentrations and distributions of nitrogen and phosphorus in the investigated waters. Average total Kjeldhal nitrogen （TkN） content was（ 1 113.1 ± 382.5）μg/g and average total phosphorus （TP） content was（567.2± 223.3）μg/g, and both were much higher than those of similar estuaries in China and elsewhere. Average nitrogen and phosphorus tended to be higher inside than outside the bay, higher at aquaculture than non-aquaculture areas, and higher at fish-cage culture than oyster culture areas, suggesting that large-scale mariculture inside the bay played an important role in the eutrophication of the Zhelin Bay. Various forms of nitrogen and phosphorus concentrations were higher during the warm season （July--September）, which was due to the increased decomposition and concentration of organic matter resulted from the fast growth and high mortality of the cultured species. Compared with July 2002, TkN and TP contents were much higher in July 2003, in consonance with the eutrophication of the Zhelin Bay. Because exchangeable phosphorus （Ex-P）, iron-bounded phos- phorus （Fe-P） and organic phosphorus （OP） combined accounted for 34.3% of the TP and authigenic phosphorus （Au-P     

Sources and distribution of organic matter in a river-dominated estuary (Winyah Bay, SC, USA)

The sources and distribution of organic matter (OM) in surface waters and sediments from Winyah Bay (South Carolina, USA) were investigated using a variety of analytical techniques, including elemental, stable isotope and organic biomarker analyses. Several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range. The dissolved organic carbon (DOC) concentrations of surface waters ranged from 7 mg l⁻¹ in the lower bay stations closest to the ocean to 20 mg l⁻¹ in the river and upper bay samples. There was a general linear relationship between DOC concentrations and salinity in three of the four sampling periods. In contrast, particulate organic carbon (POC) concentrations were significantly lower (0.1–3 mg l⁻¹) and showed no relationship with salinity. The high molecular weight dissolved OM (HMW DOM) isolated from selected water samples collected along the bay displayed atomic carbon:nitrogen ratios ([C/N]a) and stable carbon isotopic compositions of organic carbon (δ¹³C_OC) that ranged from 10 to 30 and from −28 to −25‰, respectively. Combined, such compositions indicate that in most HMW DOM samples, the majority of the OM originates from terrigenous sources, with smaller contributions from riverine and estuarine phytoplankton. In contrast, the [C/N]a ratios of particulate OM (POM) samples varied significantly among the collection periods, ranging from low values of 5 to high values of >20. Overall, the trends in [C/N]a ratios indicated that algal sources of POM were most important during the early and late summer, whereas terrigenous sources dominated in the winter and early spring.In Winyah Bay bottom sediments, the concentrations of the mineral-associated OM were positively correlated with sediment surface area. The [C/N]a ratios and δ¹³C_OC compositions of the bulk sedimentary OM ranged from 5 to 45 and from −28 to −23‰, respectively. These compositions were consistent with predominant contributions of terrigenous sources and lesser (but significant) inputs of freshwater, estuarine and marine phytoplankton. The highest terrigenous contents were found in sediments from the river and upper bay sites, with smaller contributions to the lower parts of the estuary. The yields of lignin-derived CuO oxidation products from Winyah Bay sediments indicated that the terrigenous OM in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil OM. Based on the lignin phenol compositions, most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region. A few samples displayed lignin compositions that suggested a more significant contribution from marsh C₃ grasses. However, there was no evidence of inputs of Spartina alterniflora (a C₄ grass) remains from the salt marshes that surround the lower sections of Winyah Bay.     

Degradation of phytoplankton-derived organic matter: Implications for carbon and nitrogen biogeochemistry in coastal ecosystems

Experiments were conducted using seawater from the Oregon continental shelf to determine: (1) rates of phytoplankton-derived particulate organic matter (POM) and dissolved organic matter (DOM) degradation by natural microbial communities, and (2) whether inorganic nutrients or flagellate grazing limit the bacterial response to, and subsequent degradation of, the DOM. In the initial seawater samples, nutrients were depleted and organic matter concentrations were elevated above concentrations found in upwelled water, indicative of recent bloom conditions. In whole water treatments incubated for 3 d, an average of 24% of the total organic C and 33% of the POC was degraded, with some portion of the POC being converted to DOC. In treatments incubated after POM was removed by filtration, DOC degradation was initially rapid and then proceeded at a slower rate. After 3 d, an average of 41% of the DOC was degraded. Selective degradation of the C-component of both the POM and DOM relative to the N-component was observed. Reductions in flagellate grazing resulted in increases in bacterial abundance and enhanced DOC degradation, while inorganic nutrient amendments had little effect. Overall, these results suggest that a fraction of the phytoplankton-derived POM and DOM can be rapidly degraded, contributing to oxygen consumption on the continental shelf. The long degradation time of a less labile DOC fraction relative to potential offshelf transport mechanisms suggests that Oregon's coastal waters may be a source of DOC to adjacent offshore waters of the North Pacific.     

Effects of organic matter input from a fish farming facility on a Posidonia oceanica meadow

In the Mediterranean, the development of aquaculture along the coasts appears as a source of disturbance to the littoral ecosystems, and in particular to Posidonia oceanica seagrass meadows. Although the impact of fish farms in Northern Europe has been studied over the last few years, the data are more scarce in the Mediterranean. Thus, a number of physico-chemical and biological parameters have been examined here in order to evaluate the impact of a fish farm in a littoral bay of Corsica. The following values that were recorded in the vicinity of the fish farm are much higher than those at the reference station: organic content of the sediment (24–21 versus 2%), nitrogen concentrations (ammonium: 19.5–8.4 versus 1.8 μM) and phosphorous levels in the pore water (orthophosphates: 5.2–1.3 versus 1.7 μM). The seagrass meadow vitality also seems to be affected in the vicinity of cages, with densities that drop from 466 (reference station) to 108 shoots m⁻² (20 m from cages). Total primary production also varies from 1070.6 to 87.9 g m⁻² year⁻¹. The main impact factors seem to be the input of organic matter originating from the cages and the high epiphyte biomass caused by the nutrient enrichment. The high level of organic matter and the presence of mud seem to alter the physico-chemical characteristics of the bottom sediment; moreover, the plant/epiphyte competition seems to lead to a leaf fragility and, more importantly, to a decrease in available light.     

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.     

浙江近岸海域悬浮颗粒物中磷的赋存形态及分布特征研究

磷元素是海洋基础营养盐之一,其赋存形态及分布直接影响海区的初级生产力,是海洋生物地球化学循环的重要驱动力。但大河河口与近海等重要的水生关键带水动力循环过程复杂,导致悬浮颗粒物(SPM )中磷元素的赋存形态和分布特征变化多端,亟须深入研究。根据2016年春季(4−5月)、夏季(7月)和秋季(9−10月)对浙江近岸海域的调查结果,本研究分析了浙江近岸海域SPM中总磷(TPP)、无机磷(PIP)和有机磷(POP)的含量水平、空间分布特征和影响因素。结果表明,浙江近岸海域SPM中TPP含量范围为0.13～66.13 μmol/L,均值为3.35 μmol/L;PIP含量范围为0.03～34.19 μmol/L,均值为1.97 μmol/L;POP含量范围为0.06～31.94 μmol/L,均值为1.39 μmol/L。PIP是浙江近岸海域水体中TPP的主要存在形式,占52.3%。春季浙江近岸海域表层TPP含量占总磷(TP)含量的19.3%～97.7%。春、秋季的SPM中,TPP、PIP和POP含量空间分布相似,均呈现由内湾向外海逐渐降低的变化趋势。PIP、POP与SPM呈显著的正相关性,表现出高SPM含量的海区有着较高的颗粒态磷含量,说明其受陆源输入的影响。春季盐度大于28且SPM含量小于20 mg/L的外侧远海海域,POP与Chl a的相关系数和斜率均明显高于PIP与Chl a的相关系数和斜率,说明该区域浮游植物是POP的主要贡献来源。     

宁波—舟山深水港海域水体有机物分布特征初探

本文根据1987年5月宁波—舟山深水港海域水体中有机物分布,初步讨论了有机物在水体中的行为。海水中溶解态的有机物与有机物总量存在如下关系:[DOM]/[TOM]=0.611[TOM]~(-0.899)。并且在通常状况下,调查海区水体中的有机物随悬浮颗粒物的增加而增高,其关系式为:[TOM]=0.65e~(0.0011〔SS〕)。认为该海区的悬浮物是制约有机物行为的主要因素之一。     

夏季大亚湾悬浮颗粒有机物碳、氮同位素组成及其物源指示

2015年夏季开展了大亚湾悬浮颗粒有机物碳（POC）、氮含量（PN）及其同位素组成的研究,结果表明,δ13C_POC和δ15N_PN的变化范围分别为-25.7‰~-17.4‰和-6.3‰~10.4‰,平均值分别为-20.2‰和8.2‰。大亚湾悬浮颗粒有机物含量及其碳氮同位素组成的空间变化反映了不同有机质来源的影响:喜洲岛附近海域表现出高POC、PN、δ13C_POC和δ15N_PN的特征,指征着浮游植物水华的主导贡献;东北部范和港附近海域具有高POC、PN、低δ13C_POC和高δ15N_PN的特征,反映了河流/河口水生有机物的影响;湾顶白寿湾附近海域的δ13C_POC和δ15N_PN出现低值,体现了陆源有机质和人类污水排放的影响。借助δ13C_POC和δ15N_PN的三端元混合模型,定量出海洋自生有机质、陆源有机质、河流/河口水生有机质等3个来源的贡献平均分别为70%、13%和17%,其中海洋自生有机质是夏季大亚湾悬浮颗粒有机物的最主要来源。从这3种来源颗粒有机物含量的空间变化看,海洋自生有机质含量由湾内向湾外减少,与初级生产力的空间变化相对应;河流/河口水生有机质含量在大亚湾东北部出现高值;陆源有机质含量在表、底层出现不同态势,表层陆源有机物含量在湾中部海域最低,而底层则呈现出自湾内向湾口增加的趋势,主要受控于离岸距离和珠江冲淡水、粤东沿岸上升流输送的影响。     

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。     

温度与溶解态有机磷源对中肋骨条藻生长的影响

为探讨温度与溶解态有机磷(Dissolved organic phosphorus,DOP)对浮游植物生长的共同影响,本文以中肋骨条藻为研究对象,选取含有C-O-P键的三磷酸腺苷(Adenosine triphosphate,ATP)、甘油磷酸钠(Sodium glycerophosphate,SG-P)、6-磷酸葡萄糖(Glucose 6-phosphate,G-6-P)和含有C-P键的草甘膦(Glyphosate,G-P)为不同类型的DOP,检测了4种温度条件下(20、23、26、29℃)藻细胞的生长状况以及培养液中总溶解态磷(Total dissolved phosphorus,TDP)、溶解态无机磷(Dissolved inorganic phosphorus,DIP)浓度与藻细胞内碱性磷酸酶(Alkaline phosphatase,AP)的变化。研究结果表明:含有C-O-P键的ATP、SG-P和G-6-P均能较好地维持中肋骨条藻的生长,并且升温可进一步促进各组藻细胞的生长,最大藻细胞密度分别达到176.7×10⁴、218.8×10⁴     

The decomposition rate of the organic carbon content of suspended particulate matter in the tropical seagrass meadows

In terms of downward transport, suspended particulate matter(SPM) from marine or terrigenous sources is an essential contributor to the carbon cycle. Within mesoscale environments such as seagrass ecosystems, SPM flux is an essential part of the total carbon budget that is transported within the ecosystem. By assessing the total SPM transport from water column to sediment, potential carbon burial can be estimated. However, SPM may decompose or reforming aggregate during transport, so estimating the vertical flux without knowing the decomposition rate will lead to over-or underestimation of the total carbon budget. Here this paper presents the potential decomposition rate of the SPM in seagrass ecosystems in an attempt to elucidate the carbon dynamics of SPM. SPM was collected from the seagrass ecosystems located at Sikka and Sorong in Indonesia. In situ experiments using SPM traps were conducted to assess the vertical downward flux and decomposition rate of SPM. The isotopic profile of SPM was measured together with organic carbon and total nitrogen content. The results show that SPM was transported to the bottom of the seagrass ecosystem at a rate of up to(129.45±53.79)mg/(m~2·h)(according to carbon). Considering the whole period of inundation of seagrass meadows, SPM downward flux reached a maximum of 3 096 mg/(m~2·d)(according to carbon). The decomposition rate was estimated at from 5.9 μg/(mg·d)(according to carbon) to 26.6 μg/(mg·d)(according to carbon). Considering the total downward flux of SPM in the study site, the maximum decomposed SPM was estimated 39.9 mg/(m~2·d)(according to carbon) and 82.6 mg/(m~2·d)(according to carbon) for study site at Sorong and Sikka, respectively.The decomposed SPM can be 0.6%–2.7% of the total SPM flux, indicating that it is a small proportion of the total flux. The seagrass ecosystems of Sorong and Sikka SPM show an autochthonous tendency with the primary composition of marine-end materials.     

春季长江口及其邻近海域溶解有机物的分布、组成及降解行为研究

2021年3月对长江口及其邻近海域9个断面溶解氨基酸(THAA)、溶解有机碳(DOC)和溶解有机氮(DON)的分布和组成进行了调查研究。结果表明:THAA的浓度范围为1.24~4.71μmol/L,平均浓度为(2.61±0.85)μmol/L;DOC的浓度范围为118.17~450.58μmol/L,平均浓度为(149.73±33.34)μmol/L;DON的浓度范围为10.48~24.45μmol/L,平均浓度为(13.80±1.81)μmol/L。THAA、DOC和DON的水平分布表现出近岸高于远岸的特点,表明陆源输入对调查区域的THAA等分布有重要影响。而THAA与D-天门冬氨酸、D-谷氨酸、D-丝氨酸和D-丙氨酸的D/L比均呈显著负相关,与天门冬氨酸/β-丙氨酸(Asp/β-Ala)呈正相关,表明细菌活动是影响THAA浓度变化的重要因素。长江口及邻近海域的优势氨基酸为L型氨基酸,D型氨基酸和非蛋白型氨基酸的占比仅为7.34%。基于C/N比值分析,长江口及其邻近海域溶解有机物(DOM)的来源受到长江冲淡水和台湾暖流的共同影响。THAA-C%、THAA-N%、降解因子和反应活性指数表明:水平方向上盐度接近于0的淡水区域和盐度高于34的远海区域降解程度较高;垂直方向上随着深度的增加,有机物的降解程度逐渐升高。调查区域有机物的降解程度主要受到陆源输入和细菌活动的影响。     

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。     

粤东大规模海水增养殖区柘林湾表层沉积物中的含水量、有机质、氮和磷

柘林湾是粤东地区规模最大的海水增养殖区,近20年来水体富营养化情况日益加重,赤潮频繁发生。2002年7月至2003年7月对该湾9个站位表层沉积物中的含水量(W)、有机质(TOM)和不同形态的氮(TkN,NH₄+)与磷(Ex-P,Fe-P,Au-P,De-P,OP)进行每月一次的周年调查。结果显示,表层沉积物中的含水量和有机质及不同形态的氮、磷均呈现极显著意义的正相关关系,今后可用含水量直接对这些指标进行粗略估算。有机质与氮、磷呈显著意义的正相关关系,表明有机质是影响氮、磷含量和分布的重要因素之一。凯氏氮(TkN)和总磷(TP)的总平均值分别为(1113.1±382.5)μg/g和(567.2±223.3)μg/g,显著高于国内外许多同类型的海湾。各形态氮、磷含量年均值的平面分布呈现湾内(除S1,S7站外)高于湾外、养殖区高于非养殖区、网箱渔排养殖区高于牡蛎养殖区的总体趋势,说明湾内大规模增养殖业对海湾富营养化进程起着重要的作用。各形态氮、磷含量均于盛夏至初秋的高温季节(7-9月)处于年度峰值,这与该季节养殖动物处于生长旺期与高死亡率所造成的生物碎屑增多和有机质分解加速有关。与2002年7月相比,2003年7月的TkN和TP均出现大幅升高,与水体富营养化程度不断加重的趋势相符。此外,自生磷(Au-P)年平均占TP的49.2%,是该湾沉积物中最主要的磷形态。由于水体富营养化能导致沉积物的pH降低,继而促进Au-P中的自生钙氟磷灰石和碳酸钙所结合的磷释放进入水体,因而表层沉积物中高浓度的Au-P可能成为此类海湾富营养化水平加剧和赤潮大规模暴发加剧的隐患。     

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.     

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。     

Tracing dissolved organic matter in aquatic environments using a new approach to fluorescence spectroscopy

Dissolved organic matter (DOM) is a complex and poorly understood mixture of organic polymers that plays an influential role in aquatic ecosystems. In this study we have successfully characterised the fluorescent fraction of DOM in the catchment of a Danish estuary using fluorescence excitation–emission spectroscopy and parallel factor analysis (PARAFAC). PARAFAC aids the characterisation of fluorescent DOM by decomposing the fluorescence matrices into different independent fluorescent components. The results reveal that at least five different fluorescent DOM fractions present (in significant amounts) in the catchment and that the relative composition is dependent on the source (e.g. agricultural runoff, forest soil, aquatic production). Four different allochthonous fluorescent groups and one autochthonous fluorescent group were identified. The ability to trace the different fractions of the DOM pool using this relatively cheap and fast technique represents a significant advance within the fields of aquatic ecology and chemistry, and will prove to be useful for catchment management.