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1.
Using the authors’ data obtained during expeditions to the Sea of Okhotsk during the last decade, the primary phytoplankton production and the distribution of organic carbon and chlorophyll a degradation products (chlorin) in the bottom sediments were studied. Using the authors’ and published data, the spatial distribution of the production and paleoproduction indicators was plotted. The ratios of the chlorin and Corg content in the sediments was considered, and the correlation between these parameters was revealed. It was shown that the average annual primary production of phytoplankton and the paleoproduction indices were maximum in the coastal and upwelling zones and decreased towards the sea’s center. A quantitative correlation was found between the distribution of the present primary production in the photic layer and that of the rates of the accumulation of organic matter buried within the surface sediments. As a result, it was shown that the content of chlorin and Corg in the marine bottom sediments may be used to reconstruct the paleoproduction variability of the past.  相似文献   

2.
Data are presented on the content of aliphatic and polycyclic aromatic hydrocarbons (AHC and PAH, respectively) in the interstitial waters and bottom sediments of the Kara Sea compared to the distribution of the particulate matter and organic carbon. It was found that the AHC concentrations within the water mass (16 μg/l on average) are mainly formed by natural processes. The AHC distribution represents the variability of the hydrological and sedimentation processes in different regions of the sea. The widest ranges of the concentrations were registered in the Ob Bay-Kara Sea section: in the water (10–310 μg/l for the AHC and 0.4–7.2 ng/l for the PAH) and in the surface layer of the bottom sediments (8–42 μg/l for the AHC and 9–94 ng/g for the PAH). The differentiation of the hydrocarbons (HC) in the different media follows the marginal filter’s regularities; therefore, no oil and pyrogenic compounds are supplied to the open parts of the sea. In the sediment mass, the HC content is determined by the variations in the oxidative conditions in the sediment and its material’s composition.  相似文献   

3.
In the summer 2006, integrated geological, geochemical, hydrological, and hydrochemical studies were performed on the relict anoxic Lake Mogil’noe (down to 16 m depths) located on Kil’din Island in the Barents Sea. The chemical and grain-size composition of the bottom sediments were compared for the lake (a permanently anoxic basin) and the Baltic Sea Deeps (periodically anoxic basins). The vertical location of the hydrogen sulfide layer boundary in the lake (9–11 m depths) was practically the same from 1974 up to now. The concentrations of suspended particulate matter in the lake in June and July 2006 appeared to be close to its summer concentrations in the seawaters of the open part of the Baltic Sea. The mud from Lake Mogil’noe compared to those of the Baltic Sea Deeps are characterized by fluid and flake consistency and by pronounced admixtures of sandy and silty fractions probably of eolic origin. The lacustrine mud contain much plant remains; iron sulfides and vivanite were also found in ooze. The concentrations of 22 elements determined in the lacustrine bottom sediments were of the same levels as those found here 33 years ago. The concentrations also appeared to be close to those in the corresponding grain-size types of the bottom sediments in the Baltic Sea. The low Corg/N value (5% on average) in the mud of Mogil’noe Lake compared to the values for the mud of the Baltic Sea Deeps (10% on average) points to the considerable planktogenic component in the organic matter composition of the lacustrine mud. No indications were reveled for anthropogenic contaminations of the lacustrine bottom sediments with toxic metals.  相似文献   

4.
Comparative studies of the composition and distribution of the dispersed organic matter (DOM) were performed for the bottom sediments from active areas of the Ashadze hydrothermal field (the Mid-Atlantic Ridge, 13° N) and for background sediments from the area treated (sampled during the cruises of R/V Professor Logachev in 2003 and 2007). The content of hydrocarbons (HCs) in the hydrothermal samples is about 20 times as high as the background values. The HCs composition includes both low-transformed (isoprenoids, hopenes, ββ-hopanes, and ααα27R-steranes) and geologically mature chemofossils (C16-C35 n-alkanes, geohopanes, moretanes, and polyaromatic hydrocarbons). The polyaromatic hydrocarbons (PAHs) are mainly represented by phenanthrene and its alkyl homologues, i.e., by possible products of the diagenetic transformation of biogenic precursors. The results obtained point to the mixed genesis of the hydrothermal DOM, which is caused first by the diversity of the biota composition in the considered region, as well as by the specificity of the processes of the DOM’s maturing under the extreme environmental conditions.  相似文献   

5.
The quantitative distribution and grain-size composition of the suspended particulate matter (SPM) in the marginal filter of the Severnaya Dvina River during the summer low-water periods of 2001–2005 were first analyzed in seawater on board of the vessel immediately after its sampling (without preliminary treatment) using a Coulter counter. This analysis revealed the main regularities in the transformation of the grain-size spectra at successive salinity steps of the marginal filter as well as the boundaries between these steps based on the data obtained by direct complex studies of the SPM dispersion. It is established that the water salinity is the main factor that controls the changes in the grain-size distribution and the composition of the particulate matter in the marginal filter. The concentrations of the pelitic fraction and the salinity demonstrate negative correlations between each other. It is shown that the areas characterized by the mass development of phytoplankton are located along the outer boundary of the marginal filter (at the biological step), where the salinity amounts to 23–24 psu. The content of the suspended forms of some chemical (lithogenic) elements and the Corg indicating the SPM’s genetic composition and their relations with the grain-size composition of the latter and the environments are studied.  相似文献   

6.
The results of the analysis of samples of the Northern Dvina River’s suspended particulate matter obtained by the sedimentation method from large water volumes in the periods of the spring high water and summer low water are presented. By the method of sequential leaching using different reagents, four fractions have been separated: the F1 is the sorbed complex and carbonates, the F2 is the amorphous hydroxides of Fe and Mn, the F3 is the form connected with the organic matter, and the F4 is the residual or silicate-detrital (inert) form. The data have shown that all ten elements determined were grouped with respect to the ratio of the distinguished forms: F4 is the predominant form for Al and Fe (73–88% of all the forms; however, the summer sample contains only 38% of this form of iron, and F2 is the predominant form for this period with 46.6%). As to Mn, the F1, F2, and F4 are nearly equally distributed in the spring high water samples, and only the F3 form is less important (5.4%). In the summer sample, the manganese sorbed complex is predominant (53.5%); for Cu, Ni, Cr, and Co, the inert F4 form is predominant (60–70%) in the sample of the spring suspended matter. The summer low water suspended matter has a lower F4 contribution (25–45%); for Zn, Pb, and Cd, the equal distribution of the forms in the spring samples is typical, while the summer suspended matter differs by the F2 form’s predominance (53–61% for Zn and Pb). The main conclusion from the acquired data is that the geochemical mobility of all the studied elements, except for cadmium, in the summer low water suspended matter is higher than in the spring suspended matter. The more intensive biogeochemical processes in August, the high level of organic matter, and the higher contribution of phytoplankton lead to the intensification of the metals’ geochemical activity in the Northern Dvina suspended matter in the end of the summer compared to the spring high water period when the physical processes are predominant over the biogeochemical ones due to the high speeds of the freshened waters flow.  相似文献   

7.
The considered area of the Russian sector of the Arctic Basin was characterized in August–September of 2008 by the wide horizontal and vertical variability of the concentrations of dissolved and particulate organic matter (OM), as well as of its elemental and biochemical composition. The concentration ranges amounted to 51.6–434 and 2.2–18.6 μM, respectively, for the dissolved and particulate Corg; up to 1.9–30.2 μM for Norg; and up to 0.08–1.53 μM for Porg. The maximum values were characteristic for the Russian Arctic shelf. The analysis of the authors’ and published data showed that a pronounced accumulation of OM, mainly in the dissolved form, took place in the Arctic Basin within the past 12 years. The concentrations of dissolved OM were higher in the western sector of the Russian Arctic than those in the eastern sector. The main biochemical components in all the waters constituting the Arctic Ocean are carbohydrates and lipids for dissolved OM and proteins and carbohydrates for particulate matter.  相似文献   

8.
The distribution and geochemical composition of suspended-particulate matter (SPM) in the East China Sea (ECS) were investigated during the summer period of high continental runoff to elucidate SPM sources, distribution and cross-shelf transport. The spatial variability of SPM distribution (0.3–6.5 mg l−1) and geochemical composition (POC, Al, Si, Fe, Mn, Ca, Mg and K) in the ECS was pronounced during summer when the continental fluxes of freshwater and terrestrial materials were highest during the year. Under the influences of Changjiang runoff, Kuroshio intrusion, surface production and bottom resuspension, the distribution generally showed strong gradients decreasing seaward for both biogenic and lithogenic materials. Particulate organic carbon was enriched in surface water (mean ∼18%) due to the influence of biological productivity, and was diluted by resuspended and/or laterally-transported materials in bottom water (mean 9.4%). The abundance of lithogenic elements (Al, Si, Fe, Mn) increased toward the bottom, and the distribution correlations were highly significant. Particulate CaCO3 distribution provided evidence that the SPM of the bottom water in the northern part of the study area was likely mixed with sediments originally derived from Huanghe. A distinct benthic nepheloid layer (BNL) was present in all seaward transects of the ECS shelf. Sediment resuspension may be caused by tidal fluctuation and other forcing and be regarded as the principal agent in the formation of BNL. This BNL was likely responsible for the transport of biogenic and lithogenic particles across or along the ECS shelf. Total inventories of SPM, POC and PN are 46, 2.8 and 0.4 Tg, respectively, measured over the total area of 0.45 × 106 km2 of the ECS shelf. Their mean residence times are about 27, 13 and 11 days, respectively. The inventory of SPM in the water column was higher in the northernmost and southernmost transects and lower in the middle transects, reflecting the influences of terrestrial inputs from Changjiang and/or resuspended materials from Huanghe deposits in the north and perhaps from Minjiang and/or Taiwan’s rivers in the south. The distribution and transport patterns of SPM and geochemical elements strongly indicate that continental sources and cross-shelf transport modulate ECS particulate matter in summer.  相似文献   

9.
In three sections in the Kara Sea, the contents of the dissolved and particulate organic carbon (the DOC and POC, respectively), as well as of the organic carbon of the bottom sediments (Corg) were determined. The contents of varied from 6.3 to 2400 μg/l for the DOC and from 0.84 to 12.2 mg of C/l for the POC. The average concentrations for all the samples tested amounted to 200 μg/l for the DOC (n = 78, σ = 368) and 2.7 mg/l for the POC (n = 92, σ = 2.7). The concentrations of Corg in the samples of the upper layer of the bottom sediments of the area treated varied from 0.13 to 2.10% of the dry substance at an average value of 0.9% (n = 21, σ= 0.49%). It is shown that the distribution of the different forms of organic matter (OM) is an indicator of the supply and spreading of the particulate matter in the Kara Sea and that the DOC and POC of the Kara Sea are formed under the impact of the runoff of the Ob and Yenisei river waters. It is found that the distribution of the OM of the bottom sediments in the surveyed area of the Kara Sea is closely related to their grain-size composition and to the structure of the currents in the area studied. The variations in the Corg content in the bottom sediment cores from the zone of riverine and marine water mixing represent the variability of the OM burial.  相似文献   

10.
中性糖作为有机质的重要组分,其丰度和组成对于沉积物中有机质的来源和降解等生物地球化学过程具有重要的指示意义。本文在对2009年和2010年采集自东海的24个表层沉积物中有机质和中性糖组成以及分布特征进行分析的基础上,探讨了中性糖及其组分在指示东海表层沉积物有机质来源和降解程度中的作用。结果表明:东海表层沉积物中有机碳(TOC)和中性糖(NS)含量较高,分别为66.8—1441.7?mol/g和0.40—4.87?mol/g,平均浓度分别为(409.4?55.2)?mol/g和(3.07?0.31)?mol/g,NS占有机碳的碳摩尔百分数为1.88%—8.93%;随着沉积物粒径增大,TOC、NS含量降低,NS中的葡萄糖组分摩尔百分数增大,而半乳糖、甘露糖和木糖组分摩尔百分比减小,表明沉积物中有机质降解程度增大。同时发现,葡萄糖和海藻糖的摩尔分数之和与半乳糖和阿拉伯糖的摩尔分数之和的比值可作为判断沉积有机物降解程度的指标,其值越大,说明沉积有机物的生物降解程度越小。  相似文献   

11.
Diatoms play a significant role in the global carbon cycle through their role in biogenic silica production and the transport of organic matter to the seafloor. Recent work has shown that silicified diatom frustules contain a significant amount of organic matter, and that the proportion of diatom-bound organic matter increases with depth in the water column and sediments. Here, we investigate the association between organic matter and the mineral phase. We used a combination of scanning transmission X-ray microscopy (STXM) and carbon X-ray absorption near-edge structure (XANES) spectroscopy to characterize the distribution and composition of organic matter in frustules of the diatom Cylindrotheca closterium and a biomimetic silica gel. To our knowledge, this study represents the first successful attempt to simultaneously image and obtain chemical information about the organic matter within a diatom frustule using X-ray spectromicroscopy near the carbon edge. Organic carbon, most likely protein, was distributed throughout the frustules and was not removed by harsh chemical treatment. The physical structure of the frustules appeared to be related to the chemical composition of this organic matter, with aromatic or unsaturated carbon being concentrated in the most intricately patterned regions of the frustule. A similar physical and chemical structure was observed in a biomimetic silica gel precipitated spontaneously with polylysine. These results are consistent with the theory that organic constituents of diatom frustules direct silica precipitation and become incorporated within the silica matrix as it forms. The relationship between organic matter composition and silica morphology, the failure of harsh chemical treatments to remove this organic matter, and the spontaneous nature of the co-precipitation of silica and organic matter indicate some chemical interaction between the siliceous and organic components of diatom frustules. Frustule-bound organic matter should therefore be protected from decomposition in the water column or diagenetic alteration in sediments unless the frustule dissolves.  相似文献   

12.
The data for the present study were collected at 20 sampling stations in the Kara Sea along the transect from the Ob estuary to the deep sea St. Anna Trough in September 2007. Based on the hydrophysical features, the distribution of the Chl a, and the primary production, we distinguished six habitats: the river, estuary, inner and outer shelf, continental slope, and trough. The impact of the small-size (<0.5 mm) and large-size (>0.5 mm) fractions of the zooplankton on the phytoplankton’s organic carbon in the different regions of the Kara Sea was estimated. The ingestion rate was assessed using the analysis of the gut fluorescence content and the gut evacuation rate. The zooplankton grazed 1–2% of the phytoplankton biomass in the river and estuary; 3.5% over the shelf; and 6 and 10% in the regions of the trough and slope, respectively. The grazing impact of the small-sized zooplankton increased from the river zone to the deep regions (from 1 to 90%) along with their share in the total zooplankton abundance (from 18 to 95%). From 72 to 86% of the primary production was grazed over the shelf and slope. The primary production did not cover the feeding requirements of the zooplankton in the estuarine regions and St. Anna Trough in the autumn. In the estuarine regions, the major portion of the organic matter settles on the bottom due to the strong inflow of the allochthonous matter and the relatively low zooplankton grazing.  相似文献   

13.
The annual (2004–2006) series of probing using a multichannel filter-fluorimeter from the water’s surface to the bottom at fixed sites in Kaliningrad Bay and the adjacent areas were carried out. The following parameters were recorded: the water turbidity and temperature, the intensity of the fluorescence of the photosynthetic pigment (excitation at 450 nm, detection band 675–820 nm), and the intensity of the background fluorescence of the dissolved organic matter. The high levels of “red fluorescence” presumably related to the presence of photosynthetic bacterioplankton, live phytoplankton, or their mixture (which demands further biological identification) annually registered in the aphotic zone of the water column represent specific feature of the obtained data.  相似文献   

14.
《Oceanologica Acta》2002,25(1):1-12
Temporal variations and spatial distribution of sedimentary organic matter composition were investigated over a one year period in an intertidal flat of the NW Spain. Sediment samples were collected from 0 to 25 cm depth, every three months, from January 1997 to January 1998 at three tidal levels (high, medium and low). Changes in the elemental and biochemical composition were assessed to gather information on temporal and spatial fluctuations in quantity and quality of sedimentary organic matter potentially available to benthic deposit-feeder nutrition. Organic matter content was significantly higher at the medium tidal level, while minimum values were found at the high tidal level. The different biochemical classes of organic compounds exhibited different temporal patterns. Carbohydrate and lipid concentrations decreased with sediment depth. The biopolymeric fraction of organic carbon (i.e. the sum of lipid, carbohydrate and protein carbon) was dominated by proteins (61%), followed by lipids (26%) and carbohydrates (14%). Biopolymeric carbon accounted for only a small fraction (37% on average) of the total organic carbon. Refractory organic carbon (i.e. non biopolymeric) accounted for 50 to 80% of the total organic carbon and it tended to be buried into deeper sediment layers. The nutritional quality of the sedimentary organic matter, expressed as the biopolymeric carbon to total organic carbon ratio, was higher in January 1997, when also the higher protein to carbohydrate ratio values were observed and related to the presence of newly-produced organic matter. Low biopolymeric carbon to total organic carbon ratio and protein to carbohydrate ratio were recorded during the rest of the year, indicating a low-quality and aged organic matter. Results of the present study revealed an inverse relationship between the overall amount of organic matter and its potential availability to consumers.  相似文献   

15.
Continental shelves play a major role as transition zone during transport of multiply-sourced organic matter into the deep sea. In order to obtain a comprehensive understanding of the origin and fractionation processes of organic matter at the NW Iberian margin, 40 surface sediment samples were analyzed for a structurally diverse range of lipid biomarkers, lignin phenols, grain size distribution, organic carbon content (TOC), its stable carbon isotopic composition (δ13CTOC), and the organic carbon to nitrogen ratio (TOC/TN). The biomarker inventory reflected a heterogeneous mixture of organic matter from various marine and terrestrial sources. Soil- and vascular plant-derived continental organic matter, indicated by lignin phenols and plant-derived triterpenoids, was primarily associated with the silt fraction and transported by river run-off. The spatial distribution patterns of higher plant-derived waxes, long-chain n-alkanes, n-alcohols, and n-fatty acids suggested distinct different transport mechanisms and/or sources. The branched tetraether index, a molecular proxy expressing the relative abundance of branched dialkyl tetraethers vs. crenarchaeol and considered to signal soil-derived organic matter, was not as sensitive as the other molecular indicators in detecting continental organic matter. Hydrodynamic sorting processes on the shelf resulted in a separation of different types of terrestrial organic matter; grass and leaf fragments and soil organic matter were preferentially transported offshore and deposited in areas of lower hydrodynamic energy. Algal lipid biomarker distributions indicated a complex community of marine plankton contributing to organic matter. Spatial and seasonal patterns of phytoplankton growth primarily controlled the distribution of algal organic matter components. The interplay of all of these processes controls production, distribution, and deposition of organic matter and results in three distinct provinces at the Galicia–Minho shelf: (I) fresh marine organic matter dominated the inner shelf region; (II) high inputs of terrestrial organic matter and high TOC content characterized the mid-shelf deposited mudbelt; (III) lower concentrations of relatively degraded organic matter with increased proportions of refractory terrestrial components dominated the outer shelf and continental slope.  相似文献   

16.
Organic matter in a tropical mangrove ecosystem was characterized by stable carbon and nitrogen isotopic analyze, conducted on various organic samples, including land and mangrove plants, soils, particulate organic matter (POM), and sea and river sediments along the southwestern coast of Thailand. The δ13C values of land plants and POM in river water can be explained in terms of a greater influence of C3 plants than C4 plants in this area. The POM and sediments from the Trang River and Ko Talibong area showed systematically higher δ15N values than those from Ko Muk and other coastal areas. Organic matter in the Trang River might be influenced by nitrogen released from agricultural or human waste, which could affect the isotopic composition of POM and sediments in the Trang River estuary and along the coast near the river mouth. We used a stochastic method to estimate the contributions of four organic end-members, identifiable by their δ13C and δ15N values. The results implied that seagrasses were a major source of sedimentary organic matter, contributing 42 ± 5% in the Ko Muk area and 36 ± 5% in the Ko Talibong area. The contribution of coastal POM to sediments was estimated to be only 13% in Ko Muk and 19% in Ko Talibong. Mangrove plants contributed approximately 23% in both areas. It was concluded that seagrasses are an important source of sedimentary organic matter in this coastal region of southwestern Thailand. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

17.
Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable organic matter inputs, and to assess the sediment record for possible evidence of hypoxic events. Sediment from site MRJ03-3, which is located close to the Mississippi Canyon and generally not influenced by summer-time hypoxia, is typical of marine sediment in that it contains mostly marine algae and fine-grained material from the erosion of terrestrial C4 plants. Sediment from site MRJ03-2, located closer to the mouth of the Mississippi River and at the periphery of the hypoxic zone (annual recurrence of summer-time hypoxia >50%), is similar in composition to core MRJ03-3, but exhibits more isotopic and elemental variability down-core, suggesting that this site is more directly influenced by river discharge. Site MRJ03-5 is located in an area of recurring hypoxia (annual recurrence >75%), and is isotopically and elementally distinct from the other two cores. The carbon and nitrogen isotopic composition of this core prior to 1960 is similar to average particulate organic matter from the lower Mississippi River, and approaches the composition of C3 plants. This site likely receives a greater input of local terrestrial organic matter to the sediment. After 1960 and to the present, a gradual shift to higher values of δ13C and δ15N and lower C:N ratios suggests that algal input to these shelf sediments increased as a result of increased productivity and hypoxia. The values of C:S and δ34S reflect site-specific processes that may be influenced by the higher likelihood of recurring seasonal hypoxia. In particular, the temporal variations in the C:S and δ34S down-core are likely caused by changes in the rate of sulfate reduction, and hence the degree of hypoxia in the overlying water column. Based principally on the down-core C:N and C:S ratios and δ13C and δ34S profiles, sites MRJ03-3 and MRJ03-2 generally reflect more marine organic matter inputs, while site MRJ03-5 appears to be more influenced by terrestrial deposition.  相似文献   

18.
The Late Cretaceous sedimentary record of the North American Western Interior Seaway is characterized by cyclic deposition of organic carbon-rich sediments. One notable interval during the late Coniacian-Santonian is recorded by the Niobrara Formation. The organic carbon-rich interval within the Niobrara Formation has been identified as Oceanic Anoxic Event (OAE) 3. Understanding the reason for this distribution of organic carbon within the Niobrara Formation requires a refined understanding of the source and maturity of the organic matter. In this study, we present lipid biomarker records from the USGS Portland #1 core (Cañon City, CO) to constrain the thermal maturity of the organic matter and the differing contributions of organic matter sources. Sterane and hopane thermal maturity indices indicate that the samples are somewhat immature with respect to oil formation and that there is strong agreement between different proxies for thermal maturity. Based on the distribution of n-alkanes, steranes, and hopanes, there is a significant increase in the contribution of algal organic matter during and after OAE 3, coeval with increased organic carbon accumulation. Although a consistent terrestrial contribution is observed, it is only a minor source of organic matter at the Portland core location and does not drive increased organic matter accumulation during OAE 3. Of particular note is the consistent influence of even-over-odd predominantly mid-chain length (C21 to C25) organic matter. This observation within the brackish to marine, not methanogenic WIS represents an expansion of the depositional settings in which even-over-odd predominance has been observed in mid-chain length n-alkanes. Pristane (Pr) and phytane (Ph) abundances are inconsistent with a redox control on Pr/Ph ratios and suggest an increase in the delivery and/or preservation of phototrophic organic matter as the source for pristane and phytane in the Portland core.  相似文献   

19.
Spatial distribution of the carbon and nitrogen content and their isotopic enrichment in suspended matter and sediments were measured in the Godavari estuary to identify the sources and transformation mechanism of organic matter. Significant variability in isotopic distribution was found over the entire length of the Godavari estuary, suggesting multiple sources of organic matter. The mean isotopic ratios (δ13Csed −25.1 ± 0.9, δ13Csus −24.9 ± 1, δ15Nsed 8.0 ± 2 and δ15Nsus 6.5 ± 0.9‰) and elemental concentrations (Csed 0.45 ± 0.2%, Csus 0.9 ± 0.7%, Nsed 0.07 ± 0.05% and Nsus 0.16 ± 0.1%) support a predominantly terrigenous source. Significant enrichment in the isotopic ratios of δ13C from the upper to lower estuary in both suspended (−27.5 and −24.3‰, respectively) and sedimentary (−26.2 and −24.9‰, respectively) phases indicates a decrease in the influence of terrigeneous material toward the mouth of the estuary. A significant positive relationship exists between the δ13C of suspended and sediment, which indicates that these two organic carbon pools are likely coupled in the form of a significant exchange between the two phases. A positive relationship exists between chlorophyll a and suspended organic matter, which may mean that a significant source of organic carbon is the in situ produced phytoplankton. But, applying a simple mixing model to our isotopes, data yielded about 46% as the contribution of the terrestrial source to suspended matter, which may support the excessive heterotrophic activity in the Godavari estuary reported earlier.  相似文献   

20.
Dissolved Organic Matter in Oceanic Waters   总被引：13，自引：0，他引：13  
The amount of information on oceanic dissolved organic matter (DOM) has increased dramatically in the last decade thanks to the advances in chemical characterization. This information has supported the development of some novel and important ideas for DOM dynamics in the ocean. Consequently, we have a better understanding of the importance of DOM in oceanic biogeochemical cycles. Here we review studies published mainly during 1995–2001, synthesize them and discuss unsolved problems and future challenges. The measurement, distribution and turnover of dissolved organic carbon (DOC) are presented as the bulk dynamics of the oceanic DOM. The size spectrum, elemental composition, and chemical compositions at molecular and functional group levels are described. The mechanisms proposed for the survival of biomolecules in DOM are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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