Fatty-acid methyl esters dissolved in seawater and associated with suspended particulate material

Methyl esters of saturated and unsaturated fatty acids were isolated as trace components from organic material suspended in seawater. Methyl palmitate and methyl stearate were accumulated from the filtrate by adsorption onto Amberlite XAD-2 resin. Identification of most methyl esters is based on the comparison of gas chromatographic retention indices and mass spectrometric fragmentation with those of authentic standard compounds. In cases where reference substances were not available, identification is based on mass spectrometric and gas chromatographic properties of the unknown compounds.     

A new method of evaluating the mineralization of particulate and dissolved photoassimilated organic matter

A new method of evaluating the rate of mineralization of photoassimilated organic matter is described. This method enables us to compare the rate of direct mineralization of particulate organic carbon (POC) to CO₂ with the rate of solubilization of photoassimilated organic carbon followed by the mineralization of the resultant dissolved organic carbon (DOC) under the same conditions. The direct mineralization of photoassimilated carbon from POC to CO₂ is a more significant process compared with the mineralization of extracellular released organic carbon. The first-order rate coefficients range from 0.132 to 0.434 day^–1 for direct mineralization and 0.034 to 0.189 day^–1 for solubilization.     

Mineral composition of the suspended particulate matter in the White Sea

The mineral composition of the suspended particulate matter (SPM) was studied for the White Sea area. The comparative analysis of the composition of the marine SMP and the SPM of the rivers of the White Sea catchment area was performed, including the Severnaya Dvina River, one of the major sources of the terrigenous suspended matter to the sea. The research of such kind is faced with numerous methodological difficulties, which slows down the study process. Data on the mineral composition of the SPM are scarce. Applying the method of X-ray powder diffractometry, we assessed the bulk mineral composition of the SPM with special regard to its clay fraction.     

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.     

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.     

Distributions of particulate and dissolved organic and inorganic phosphorus in North Pacific surface waters

Several operationally defined fractions of phosphorus (P) were measured along a surface water transect in the North Pacific. The P content in all fractions was found to increase northward from the edge of the subtropical to the subarctic region. Particulate organic P (POP) concentrations increased from 9 to 110 nmol L^− 1, whereas the particulate inorganic P (PIP) concentrations increased from 1 to 13 nmol L^− 1. A significant correlation between POP, PIP and chlorophyll a suggested that these P pools are associated directly or indirectly with phytoplankton cells. PIP comprised 10–20% of the total particulate P pool across the transect, indicating it is an important component of the marine P cycle in this region. Dissolved non-reactive P (assumed to consist predominantly of non-reactive organic P compounds, thus referred to as DOP) concentration increased from 0.10 to 0.22 μmol L^− 1, whereas soluble reactive P (SRP) concentration increased from 0.01 to 1.42 μmol L^− 1 along the transect. The proportion of DOP and SRP varied widely, with a large proportion of DOP in areas with low total dissolved P concentrations in lower latitudes and a large proportion of SRP in areas with high total dissolved P concentrations in higher latitudes. High demand for DOP in the lower latitudinal region would diminish the concentration of this pool relative to higher latitudinal regions where SRP is more abundant and would be preferentially utilized. The availability of SRP could have a significant impact on the concentration and probably on the composition of DOP. We show that P fractionation provides an important insight for discussing the marine P cycle.     

Variations in the composition of particulate organic matter in a time-series sediment trap

A time-series sediment trap was used to collect material for organic geochemical analyses as part of the Sediment Trap Intercomparison Experiment. The flux of particulate matter was more likely related to a change in current direction during the course of the experiment than to small-scale changes in surface productivity. Of the compounds measured, the n-alkanes reflected this change most dramatically, decreasing with the change in current direction.Amino acid and lipid components were measured in the samples. Amino acids made up 15–35% of the total organic carbon flux and 35–75% of the total organic nitrogen flux collected in the traps. Specific amino acids indicative of bacterial biomass or activity suggested that microbial growth occurred in the traps, probably as a result of incomplete poisoning by NaN₃. However, the effect of this growth on the bulk composition of particulate matter appeared to be minimal.The amino acid distribution of particulate organic material collected by large volume filtration (LVF) was not significantly different from the sediment trap material, except that the LVF material did not appear to be affected by bacterial growth.     

南海颗粒物的氨基酸通量与组成

本文对在南海中部布设的两个层次（１１９１ｍ和３６９６ｍ）沉积物捕集器的沉降粒子进行了颗粒沉降通量和氨基酸组成的研究。南海的物质通量呈现季节性变化，深层样变动范围在６９．６～１４１．７ｍｇ／（ｍ２·ｄ）；但火山灰侵入后，其物质通量（按每月平均）高出１～２个数量级，氨基酸和氨基糖含量亦由原来的１０×１０－３和０．９×１０－３减少为０．０９×１０－３和０．０２×１０－３。氨基酸组分中以天门冬氨酸占优势，其次为甘氨酸与谷氨酸。在火山灰影响下，其丰度顺序为：谷氨酸＞天门冬氨酸＞甘氨酸。     

Chemical forms and dynamics of amino acid-containing particulate organic matter in Pacific surface waters

Particulate combined amino acids (PCAA) are the most abundant identified constituents of particulate organic matter (POM) in Pacific Ocean surface waters, but their chemical forms are unclear. In the present study, chemical characterization of amino acid-containing materials in surface POM from subarctic to subtropical waters along 165 °E in the Pacific was carried out by one- and two-dimensional gel electrophoresis. At least four chemical forms of amino acid-containing POM were distinguished: proteins, acidic materials containing peptides, protein/peptide-specific dye-stainable low-molecular-mass materials (stainable materials) and non-stainable materials, all of which were considered to be major components of detrital POM. Seventeen distinct protein containing components were distinguished in samples across the transect. A majority of stainable materials was estimated to comprise 6–8 amino acid residues, while less than six amino acid residues made up the non-stainable materials. Among the four chemical forms, acidic materials and non-stainable materials were major components, accounting for 31–42% and 49–63% of PCAA, respectively, along the transect. Proteins were common, but they were quantitatively less than 2% of PCAA. Stainable materials were regionally variable and more abundant in subarctic waters than in subtropical waters. The mechanistic processes by which such amino acid-containing POM occurs as detrital POM are discussed.     

Potential source and diagenetic signatures of oceanic dissolved and particulate organic matter as distinguished by lipid biomarker distributions

Potential biogenic sources of ultrafiltered dissolved and suspended particulate organic matter (UDOM and POM, respectively) from the Sargasso Sea (SS) and North Central Pacific (NCP) Ocean were investigated using lipid biomarker compounds. Organic carbon (OC) concentrations were ~ 20–40 times greater in UDOM than POM and decreased with depth. However, total OC-normalized lipid concentrations were 2–3 orders of magnitude higher in POM than in UDOM. Particulate total lipids decreased 3–10-fold with depth, compared to 10–20% for dissolved total lipids. Total fatty acids (FA), the most abundant lipids, showed similar patterns as total lipids, comprising ~ 62–88% of the total lipids analyzed in UDOM and ~ 57–84% in POM.FA were dominated by straight-chain saturated compounds followed by monounsaturated, polyunsaturated, and branched FA. Polyunsaturated FA were enriched in POM vs. UDOM and in surface vs. deep waters for both UDOM and POM, likely reflecting the algal origins and greater reactivity of surface-derived materials. In both UDOM and POM, sterols of planktonic origin dominated, including cholest-5-en-3β-ol (C₂₇Δ⁵), 24-methylcholesta-5,24(28)E-dien-3β-ol (C₂₈Δ^5,24(28)) and 24-ethylcholest-5-3β-ol (C₂₉Δ⁵), with varying contributions from cholesta-5,22E-3β-ol (C₂₇Δ^5,22), 24-methylcholesta-5,22E-3β-ol (C₂₈Δ^5,22) and 24-ethylcholesta-5,22E-3β-ol (C₂₉Δ^5,22).Factor analysis of lipid biomarkers showed major differences between the UDOM and POM pools and for each pool as a function of depth, but not between the SS and NCP. While UDOM and POM biomarkers were both dominated by autochthonous sources, differences between the two pools suggest potential effects from some combination of source and diagenetic factors. The lipid biomarker data are further evaluated relative to previous studies of radiocarbon (¹⁴C) and elemental (C:N:P) characteristics of UDOM and POM in the SS and NCP.     

Chromophoric dissolved organic matter and dissolved organic carbon in Chesapeake Bay

Chromophoric dissolved organic matter (CDOM) is the light absorbing fraction of dissolved organic carbon (DOC). The optical properties of CDOM potentially permit remote sensing of DOC and CDOM, and correction for CDOM absorption is essential for remote sensing of chlorophyll a (chl a) in coastal and estuarine waters. To provide data for this purpose, we report the distributions of CDOM, DOC, and chl a from seven cruises in Chesapeake Bay in 1994–1997. We observed non-conservative distributions of chl a and DOC in half of the cruises, indicating net accumulations within the estuary; however, there were no net accumulations or losses of CDOM, measured as absorption at 355 nm or as fluorescence. Freshwater end member CDOM absorption varied from 2.2 to 4.1 m⁻¹. Coastal end member CDOM absorption was considerably lower, ranging over 0.4–1.1 m⁻¹. The fluorescence/absorption ratio was similar to those reported elsewhere for estuarine and coastal waters; however, in the lower salinity/high CDOM region of the Bay, the relationship was not constant, suggestive of the mixing of two or more CDOM sources. Chl a was not correlated with the absorption for most of the cruises nor for the data set as a whole; however, CDOM and DOC were significantly correlated, with two groups evident in the data. The first group had high CDOM concentrations per unit DOC and corresponded to the conservative DOC values observed in the transects. The second group had lower CDOM concentrations per unit DOC and corresponded to the non-conservative DOC values associated with net DOC accumulation near the chl a maximum on the salinity gradient. This indicates the production of non-chromophoric DOC in the region of the chl a maximum of Chesapeake Bay. In terms of remote sensing, these data show that (1) the retrieval of the absorption coefficient of CDOM from fluorescence measurements in the Bay must consider the variability of the fluorescence/absorption relationship, and (2) estimates of DOC acquired from CDOM absorption will underestimate DOC in regions with recent, net accumulations of DOC.     

Stability and composition of terrestrially derived dissolved organic nitrogen in continental shelf surface waters

A linear decrease in dissolved organic carbon and nitrogen with increasing salinity offshore from the Georgia coast suggests that organic nitrogen compounds contributed to coastal waters by rivers are stable during the period (2–3 months) of their transfer over the continental shelf. While the C/N ratio decreased with distance from shore, total dissolved organic nitrogen (DON), total amino nitrogen, and primary amino nitrogen showed similar relative decreases, suggesting that nitrogen is associated with refractory organic compounds. Measured amino nitrogen accounted for about 20% of the total DON, leaving about 80% of the organic nitrogen undefined.     

秋季东海溶解态和颗粒态氨基酸的分布与组成*

本文对2012年秋季中国东海31个站位的海水样品中溶解态氨基酸（THAA）和颗粒态氨基酸（PAA）的分布与组成进行了研究。结果表明：表层海水中溶解游离氨基酸(DFAA)的平均浓度为0.12±0.04 μmol/L (0.06~0.19 μmol/L),溶解结合氨基酸(DCAA)的平均浓度为0.61±0.51 μmol/L (0.15~1.79 μmol/L),PAA的平均浓度为0.11±0.06 μmol/L (0.02~0.27 μmol/L)。THAA的水平分布特点大致为近岸高、远岸低;PAA的水平分布特点是近岸海域向远海海域分布呈现逐渐减小的趋势。THAA的垂直分布特点是由表层向底层逐渐降低。DCAA、PAA与Chl-a有很好的相关性,而DFAA与Chl-a的相关性不明显。东海表层海水中THAA的主要组分是天门冬氨酸、谷氨酸、丝氨酸、甘氨酸、苏氨酸及丙氨酸,PAA的主要组分是天门冬氨酸、谷氨酸、丝氨酸、甘氨酸、丙氨酸及亮氨酸。在表层海水中氨基酸是作为一个整体而对海洋生物地球化学过程产生影响的。     

珠江口表层水体颗粒物中古菌四醚类脂物的分布特征

类异戊二烯甘油二烷基甘油四醚类化合物（isoGDGTs）是古菌微生物的特征脂类标志物,由这组化合物构造出的TEX₈₆温标在海水古温度重建中得到了广泛应用。本文调查了珠江口及近岸海域（水深小于30 m）4个季节水体悬浮颗粒物（SPM）的isoGDGTs分布情况。结果显示:虎门上游河流水体中的isoGDGTs主要来自原地生产的甲烷古菌输入,进入河口水体后,主要来自原地奇古菌和广古菌的输入。陆源古菌的输入在5月份和8月份,对河流水体产生一定的影响,但对河口水体的影响相对较小。珠江口水体isoGDGTs中的GDGT-2与GDGT-3比值（GDGT-[2]/[3]）和GDGT-Cren'的丰度百分比（Cren'%）分别小于4和4%,与南海深水沉积物明显不同,表明珠江口与南海深水沉积物中isoGDGTs的古菌来源存在差异,这也可能是引起珠江口水体TEX₈₆温度（基于全球标定公式）偏离水体实际温度的原因。珠江口表层水体isoGDGTs中的GDGT-2和GDGT-3的丰度百分比与南海表层水体存在差异,这可能与GroupⅠ奇古菌和GroupⅡ广古菌相对比例空间变化有关。珠江口表层水体isoGDGTs的TEX₈₆温度在2月份明显高于原地表层水体温,而其他月份都低于原地表层水体温度,可能与Group Ⅰ奇古菌和Group Ⅱ广古菌相对比例的季节变化有关。几个月份中11月份isoGDGTs绝对含量最高,8月份较低,表明11月份和8月份分别是原地古菌生产量较大和较小时期。统计分析的结果显示,水体铵根离子含量、水体温度,以及溶解氧水平可能是控制珠江口水体isoGDGTs分布的主要环境因素。     

白令海颗粒有机物碳、氮同位素组成及其生物地球化学意义

Stable carbon and nitrogen isotopic composition of particulate organic matter(POM) were measured for samples collected from the Bering Sea in 2010 summer. Particulate organic carbon(POC) and particulate nitrogen(PN) showed high concentrations in the shelf and slope regions and decreased with depth in the slope and basin, indicating that biological processes play an important role on POM distribution. The low C/N ratio and heavy isotopic composition of POM, compared to those from the Alaska River, suggested a predominant contribution of marine biogenic organic matter in the Bering Sea. The fact that δ13C and δ15N generally increased with depth in the Bering Sea basin demonstrated that organic components with light carbon or nitrogen were decomposed preferentially during their transport to deep water. However, the high δ13C and δ15N observed in shelf bottom water were mostly resulted from sediment resuspension.     

Temporal changes in the biochemical composition of particulate organic matter sedimentation in the Bay of Banyuls-sur-Mer

Gross sedimentation rates (GSRs) were monitored together with meteorological data and the main biochemical characteristics of the collected material (i.e. organic content, C, N, total proteins, carbohydrates, lipids and available proteins) over a three year cycle at a shallow station (18 m) of the Bay of Banyuls, France. GSRs were between 0.26 (l 1/04/ 92) and 317.75 gDW m⁻² d⁻¹ (18/02/94). They followed an annual cycle with low and relatively constant values during spring and summer and high, variable values during fall and winter. During the study GSRs correlated poorly (state of the sea, precipitation) or even non-significantly (wind speed) with the main meteorological parameters. GSRs correlated negatively with the organic content of the material collected within the sediment traps suggesting the importance of resuspension in controlling GSRs. This hypothesis is consistent with the fact that, among all the measured biochemical parameters, available proteins (i.e. enzymatically hydrolizable proteins) are the most negatively correlated with GSRs. Available proteins showed important temporal changes that are only partly described by changes in carbon and nitrogen contents. These results are discussed in relation to the conceptualisation and the modelling of benthic trophic networks. The major objectives of our research group within the framework of the second phase of the French “Programme National d'Océanographie Côtière” are briefly discussed.     

南极普里兹湾及其邻近海域悬浮颗粒有机物的碳同位素组成及其影响因素

依托中国第29次南极科学考察航次开展了南大洋普里兹湾及其邻近海域悬浮颗粒有机物碳同位素组成(δ13CPOC)的研究,结合温度、盐度、营养盐和溶解CO_2的数据,揭示了影响研究海域颗粒有机物碳同位素组成的主控因素,计算出混合层中浮游植物吸收无机碳过程的碳同位素分馏因子。结果表明,普里兹湾及其邻近海域的δ13CPOC介于-28.5‰~-21.1‰,平均值为-24.6‰,表现出湾内大于湾外的特征。浮游植物同化吸收CO_2过程的碳同位素分馏是影响研究海域混合层δ13 CPOC的主要因素,根据δ13CPOC和1/[CO_2(aq)]的线性拟合关系,计算出浮游植物同化吸收CO2过程的碳同位素分馏因子εp为23.4‰。δ13CPOC的垂直分布随深度增加而增大,反映出颗粒有机物垂向输送过程中颗粒有机物再矿化过程同位素分馏作用的影响。     

Evidence for the decoupling of dissolved, particulate and surface microlayer hydrocarbons in Northwestern Atlantic continental shelf waters

Detailed sampling of the water column and subsequent high-resolution gas chromatographic analyses of surface film, particulate and dissolved hydrocarbons from the Georges Bank region off the New England coast have revealed large spatial and temporal heterogeneity in the source of hydrocarbons. Dissolved hydrocarbons, largely of a petroleum-related origin, surface film hydrocarbon also of a petroleum-related origin but different from the dissolved fraction, and bulk-water particulate matter of a mixed biogenic and petrogenic origin are all decoupled with respect to source and quantity in the region.Surface film (microlayer) hydrocarbons are found in greater concentrations than the dissolved fraction, which in turn is greater than the particulate hydrocarbon quantities in the water column. Although the microlayer appears enriched in hydrocarbons relative to the bulk water, the nature of the hydrocarbons is quite different, indicating that the use of a microlayer enrichment factor may not be appropriate in these waters.     

Major-element composition of the particulate matter in the near-bottom nepheloid layer of the gulf of Mexico

During cruises 71-A-12 and 73-A-3 of the R/V “Alaminos” eighty-six samples of suspended matter at eleven near-bottom stations in the Gulf of Mexico and northwestern Caribbean Sea were collected, and simultaneously, values for light scattering were measured. Selected samples of the suspended matter were analyzed for particulate aluminum, silicon, iron, calcium, magnesium, organic carbon and inorganic carbon. The results indicate that a permanent but highly variable near-bottom nepheloid layer exists in the Gulf of Mexico but not in the northwestern Caribbean Sea. Average total-suspended loads in the Gulf of Mexico nepheloid layer are two times higher than in the clear water above the nepheloid layer.Since there is a significant increase in the alumino-silicate fraction and a corresponding decrease in the organic fraction of the suspended matter in the nepheloid layer relative to the overlying water, it appears that sediments are the most probable source of the increased concentrations of suspended matter in the nepheloid layer. This hypothesis is supported by X-ray diffraction analyses on the nepheloid material collected at one station which show the same mineral assemblages as the underlying sediments.Time studies over periods of one week and one and one-half years showed large total-suspended-matter variations which indicate that non steady-state processes, primarily vertical eddy diffusion and possibly advection, are controlling the distribution of suspended matter in the nepheloid layer.