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1.
Suspended particulate matter was collected, from the water layer at 10 cm above the sediments, over a period of 13 months in the Golfo Marconi (Ligurian Sea, NW Mediterranean). Measurements of seston concentration as well as the elemental (particulate organic carbon and nitrogen; POC and PON, respectively) and biochemical composition (lipids, proteins, carbohydrates, DNA) of particulate organic matter were carried out to assess quality and quantity of food potentially available to benthic suspension-feeders. Particulate organic matter showed wide qualitative and quantitative variations during the sampling year. Seston concentrations and POC did not reflect the quantity and quality of the food available to benthic suspension-feeders. The biopolymeric fraction of particulate matter (C-BPF, i.e. the sum of lipid, protein and carbohydrate carbon) was mostly composed of phytoplankton (which accounted for about 60% of C-BPF). The ratio of C-BPF to POC was utilized as a measure of the fraction which had the potential to be more readily available to consumers. Suspended organic matter showed higher values of the C-BPF:POC ratio during spring, and lower values in summer and autumn–winter. Quantitative estimates of the energy content of the suspended particulate matter were obtained from its biochemical composition. Bacterial dynamics were significantly related to changes in phytoplankton biomass. Bacteria accounted for a significant fraction of the biopolymeric carbon pool (annual average about 15%) and of the total particulate DNA (21·5%), thus enhancing the nutritional value of the particulate organic matter. The results achieved in this study indicate that the biochemical composition of the particulate matter provides additional information on the origin, quality and characteristics of the seston more readily available to benthic suspension-feeders.  相似文献   

2.
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3.
The seasonal, spatial and bathymetric changes in the distribution of chloroplastic pigments (Chl a, phaeopigments and CPE), TOC, TON, ATP, bottom water nutrient content and the main biochemical classes of organic compounds (lipids, proteins and carbohydrates) were recorded from May 1994 to September 1995 over the continental margin of northern Crete. The concentration of chloroplastic pigment equivalents (CPE) was always low, dropping dramatically along the shelf-slope gradient. Microbial activity (ATP) also dropped sharply beyond the continental shelf following a distribution pattern similar to TOC and TON. Lipid, protein and carbohydrate concentrations, as well as biopolymeric carbon were comparable to those reported for other more productive areas, however, the quality of the organic matter itself was rather poor. Thus, carbohydrates, the dominant biochemical class, were characterised by being highly (80–99%) refractory, as soluble carbohydrates represented (on annual average) only 6% of the total carbohydrate pool. Protein and lipid concentrations strongly decreased with depth, indicating depletion of trophic resources in the bathyal zone. Proteins appeared to be the more degradable compounds and indeed the protein to carbohydrate ratios were found to decrease strongly in the deeper stations. Organic matter content and quality decreased both with increasing distance from the coast and within the sediment. All sedimentary organic compounds were found to vary between sampling periods, with the changes being more pronounced over the continental shelf. The different temporal patterns of the various components suggest a different composition and/or origin of the OM inputs during the different sampling periods. The amount of material reaching the sediments below 540 m is extremely low, suggesting that most of the organic material is decomposed and/or utilised before reaching the sea floor. In conclusion, the continental shelf and bathyal sediments of the Cretan Sea can be considered, from a trophic point of view, as two different subsystems.  相似文献   

4.
Downward fluxes of labile organic matter (lipids, proteins and carbohydrates) at 200 (trap A) and 1515 m depth (trap B), measured during a 12 months sediment trap experiment, are presented, together with estimates of the bacterial and cyanobacterial biomasses associated to the particles. The biochemical composition of the settling particles was determined in order to provide qualitative and quantitative information on the flux of readily available organic carbon supplying the deep-sea benthic communities of the Cretan Sea. Total mass flux and labile carbon fluxes were characterised by a clear seasonality. Higher labile organic fluxes were reported in trap B, indicating the presence of resuspended particles coming from lateral inputs. Particulate carbohydrates were the major component of the flux of labile compounds (on annual average about 66% of the total labile organic flux) followed by lipids (20%) and proteins (13%). The biopolymeric carbon flux was very low (on annual average 0.9 and 1.2 gC m−2 y−1, at trap A and B). Labile carbon accounted for most of the OC flux (on annual average 84% and 74% in trap A and B respectively). In trap A, highest carbohydrate and protein fluxes in April and September, corresponded to high faecal pellet fluxes. The qualitative composition of the organic fluxes indicated a strong protein depletion in trap B and a decrease of the bioavailability of the settling particles as a result of a higher degree of dilution with inorganic material. Quantity and quality of the food supply to the benthos displayed different temporal patterns. Bacterial biomass in the sediment traps (on average 122 and 229 μgC m−2 d−1 in trap A and B, respectively) was significantly correlated to the flux of labile organic carbon, and particularly to the protein and carbohydrate fluxes. Cyanobacterial flux (on average, 1.1 and 0.4 μgC m−2 d−1, in trap A and B, respectively) was significantly correlated with total mass and protein fluxes only in trap A. Bacterial carbon flux, equivalent to 84.2 and 156 mgC m−2 y−1, accounted for 5–6.5% of the labile carbon flux (in trap A and B respectively) and for 22–41% protein pool of the settling particles. These results suggest that in the Cretan Sea, bacteria attached to the settling particles represent a potential food source of primary importance for deep-sea benthic communities.  相似文献   

5.
本研究旨在揭示九龙江口潮滩有机质含量及其来源的时空分异规律,寻找有效识别潮滩沉积环境的有机碳指标,以便更好地将有机碳应用于河口沉积微相识别和古环境研究。在九龙江口潮滩不同地貌单元,于夏季和冬季采集41个表层沉积物,进行粒度、总有机碳(TOC)、总氮(TN)和稳定碳同位素(δ13C)测试。结果显示：从高潮滩至低潮滩,沉积物粒度逐渐变粗,TOC、TN和C/N变小,δ13C值偏正。高潮滩有机质来源以陆源和红树林贡献为主,中潮滩以海源和互花米草贡献为主,低潮滩以海源贡献为主。九龙江口潮滩有机质的分布和来源受控于河口陆海相互作用的季节变化、潮滩沉积动力分异和潮滩植被分布。高潮滩与中–低潮滩之间,TOC存在显著性差异,TN、δ13C存在极显著性差异,因此参数组合TOC、TN和δ13C可作为高潮滩与中–低潮滩的有效判别指标。  相似文献   

6.
The biogeochemistry of particulate organic matter was studied in the Great Ouse estuary draining to the North Sea embayement known as the Wash from March 1990 to January 1991. Eleven locations were sampled monthly on a 50 km transect across the shallow estuary from the tidal weir to the middle of the Wash. Particulate organic carbon (POC) and total carbohydrate, protein and lipid analyses were combined with the determination of stable carbon isotopes. δ13C often increased from −30‰ in the river to −22‰ in the tidal freshwater reach. The mixing zone between fresh and marine tidal waters displayed only a slight increase in δ13C to −19‰. The change in δ13C values in the freshwater tidal reach demonstrated that mixing of riverborne and marine suspended POC was not the only process affecting the carbon stable isotope composition. Complementary sources, interfering considerably with the two end-member sources, may be identified as autocthonous primary production and resuspension of sediment that may be transported upstream. The respective importance of these sources is subject to seasonal variation. From March to August, high concentrations in carbohydrate and protein through the whole estuary indicate that despite turbidity significant primary production occurred. The proportional importance of the uncharacterized fraction of POC, which is considered as complex organic matter, was high from September to January and low from March to August. During most of the year, the biochemical compositions of particulate organic matter in the turbidity maximum and the rest of the estuary were similar. This contradicted the principle that owing to the long residence times of particles degradation processes largely dominate the production processes within the turbidity maximum. The occurence of significant in situ production in such shallow water estuaries may partially compensate for the degradation of suspended particulate organics, resulting in a complex relationship between the biogeochemical cycling and the fate of nutrients.  相似文献   

7.
Quantitative information on the abundance and biomass of metazoan meiofauna was obtained from samples collected at 15 deep-sea stations in the Eastern Mediterranean Sea (533–2400m). Meiofaunal abundance was compared to bacterial biomass and other environmental factors such as the total sedimentary organic matter content, the concentrations of the main biochemical classes of organic compounds (i.e. proteins, carbohydrates and lipids) and to ATP. To estimate the sedimentation potential of primary organic matter, sediment bound chloroplastic pigment equivalents (CPE) were assayed. Meiofaunal density was very low ranging from 4 ind.10cm−2 (Station A4, 1658m depth) to 290 ind.10cm−2 (Station A12, 636m depth). Nematodes were the numerically dominant taxon (68% of total meiofauna) and were usually confined to the top 6cm of the sediments. Total meiofaunal biomass ranged from 2.78μgC 10cm−2 (Station A4) to 598.34μgC 10cm−2 (Station 15A). There was a significant decrease in the density of metazoan meiofauna with water depth. Bacterial biomass largely dominated the total biomass (as the sum of bacterial and meiofaunal biomass) with an average of 73.2% and accounted for 35.8% of the living biomass (as ATP carbon) whereas meiofaunal biomass accounted only for 6.56%. Bacterial biomass was significantly related to the DNA concentrations of the sediment. A significant correlation between ATP concentration and CPE content was also found. No correlations were found between meiofauna, ATP and CPE, or between meiofauna and bacterial parameters. The significant relationship between meiofaunal density and the ratio of labile organic matter/total organic matter indicates that deep-sea meiofauna inhabiting an extremely oligotrophic environment (such as the Eastern Mediterranean) may be more nutritionally dependent upon the quality than on the quantity of sedimentary organic matter.  相似文献   

8.
Estuaries are characterised by highly variable environmental conditions largely driven by tidal and atmospheric forces. This study investigates variation in the physical environment and the composition of the seston on various temporal scales in the Quempillén estuary, southern Chile. The water column was sampled throughout the tidal cycle at various times of the year. Total particulate matter, particulate inorganic matter, particulate organic matter, particle numbers, total particle volume, proximate biochemical composition and energy content of the seston, chlorophyll a and chloropigments were routinely measured. In each of the months in which sampling took place, two or three tidal cycles were examined. The information not only helps to explain the dynamics of the estuary, but is essential for an understanding of the physiology and ecology of the suspension-feeders which exploit the seston as a food source, the most dominant being the gastropod Crepipatella dilatata. Temperature and salinity were generally highest during summer, but seston quality, defined by energy content and biochemical composition (lipid, protein and carbohydrate) was higher at the end of winter and during spring. Chlorophyll a values were greatest in late spring (November). Many of the variables studied changed frequently according to the phase of the tidal cycle, and in several cases significant differences were observed among tidal cycles from the same month of the same year. In general the variables measured did not exhibit consistent patterns linked to the tidal cycle, possibly because any such patterns were masked by atmospheric conditions (wind and rain) that dominate the region and greatly influence the estuary. The quantity and quality of the seston available to suspension-feeders is largely determined by these atmospheric forces, which cause an influx of terrigenous material from adjacent areas and also resuspend bottom sediment. These effects are magnified by the shallowness of the estuary (<2 m depth). The food supply for C. dilatata and other suspension-feeders therefore varies on temporal scales varying from hourly (tidal cycle) to daily/weekly (atmospheric forces) to monthly (seasonal influences), but inhibition of feeding by low salinity sometimes limits the ability of C. dilatata to exploit fully the available organic matter.  相似文献   

9.
The terrigenously-dominated marine shales which were deposited in the lower Eocene Pinghu Formation were thought to be a potential source rock in the Xihu Depression of the East China Sea Shelf Basin. However, the exceptionally high total organic carbon content (TOC, >6% on average) of the tidal sand ridge samples was not compatible with their sedimentary environment, indicating coal-bearing sedimentary debris may have been transferred from the coast to the ocean. In this study, new sights into the origins and supply of organic materials in the coastal environment were proposed in the neritic organic matter of the Eocene Pinghu Formation. A discriminant model was developed using plynofacies analysis data to pinpoint the source of organic materials in marine source rocks. The discrimination results suggested that marine mudstones were associated with tidal flat mudstones rather than deltaic ones. The biomarker characteristics of mudstones deposited in various environments support this assertion, indicating that the supply of plant materials in tidal flats is the primary organic matter source for the marine environment. The organic matter abundance was elevated in tidal flats due to their superior preservation conditions. Additionally, the lithological assemblage of tidal flats suggests that tidal currents can scour marshes and then transport dispersed terrigenous organic materials to neritic areas. These findings indicate that coal-bearing sedimentary debris was likely transferred from the coast to the ocean, and tidal currents are thought to be the dominant mechanism driving organic matter from the tidal to the marine environment.  相似文献   

10.
Naturally existing stable carbon and nitrogen isotopes are important in the study of sedimentary organic matter sources. To identify the sources of sedimentary organic matter in Sanggou Bay and its adjacent areas, which is characterized by high-density shellfish and seaweed aquaculture, the grain size, organic carbon(OC), total nitrogen(TN), carbon and nitrogen isotopic composition(δ13C and δ15N) of organic matter in the surface sediment were determined. The results showed that, in August, sedimentary OC and TN ranged from 0.17% to 0.76% and 0.04% to 0.14%, respectively. In November, OC and TN ranged from 0.23% to 0.87% and 0.05% to 0.14%, respectively. There was a significant positive correlation between OC and TN(R=0.98, P0.0001), indicating that OC and TN were homologous. In August, the δ13C and δ15N of organic matter varied from-23.06‰ to-21.59‰ and 5.10‰ to 6.31‰, respectively. In November, δ13C and δ15N ranged from-22.87‰ to-21.34‰ and 5.13‰ to 7.31‰, respectively. This study found that the major sources of sedimentary organic matter were marine shellfish biodeposition, seaweed farming, and soil organic matter. Using a three-end-member mixed model, we estimated that the dominant source of sedimentary organic matter was shellfish biodeposition, with an average contribution rate of 65.53% in August and 43.00% in November. Thus, shellfish farming had a significant influence on the coastal carbon cycle.  相似文献   

11.
A cross-system analysis of bulk sediment composition, total organic carbon (TOC), atomic C/N ratio, and carbon isotope composition (δ13C) in 82 surface sediment samples from natural and planted mangrove forests, bank and bottom of tidal creeks, tidal flat, and the subtidal habitat was conducted to examine the roles of mangroves in sedimentation and organic carbon (OC) accumulation processes, and to characterize sources of sedimentary OC of the mangrove ecosystem of Xuan Thuy National Park, Vietnam. Sediment grain sizes varied widely from 5.4 to 170.2 μm (mean 71.5 μm), with the fine sediment grain size fraction (< 63 μm) ranging from 11 to 99.3% (mean 72.5%). Bulk sediment composition suggested that mangroves play an important role in trapping fine sediments from river outflows and tidal water by the mechanisms of tidal current attenuation by vegetation and the ability of fine roots to bind sediments. The TOC content ranged from 0.08 to 2.18% (mean 0.78%), and was higher within mangrove forests compared to those of banks and bottoms of tidal creeks, tidal flat, and subtidal sediments. The sedimentary δ13C ranged from − 27.7 to − 20.4‰ (mean − 24.1‰), and mirrored the trend observed in TOC variation. The TOC and δ13C relationship showed that the factors of microbial remineralization and OC sources controlled the TOC pool of mangrove sediments. The comparison of δ13C and C/N ratio of sedimentary OC with those of mangrove and marine phytoplankton sources indicated that the sedimentary OC within mangrove forests and the subtidal habitat was mainly composed of mangrove and marine phytoplankton sources, respectively. The application of a simple mixing model showed that the mangrove contribution to sedimentary OC decreased as follows: natural mangrove forest > planted mangrove forest > tidal flat > creek bank > creek bottom > subtidal habitat.  相似文献   

12.
环雷州半岛近海表层沉积物有机碳分布及其控制因素分析   总被引：1，自引：0，他引：1  
对环雷州半岛近海43个海底表层沉积物的总有机碳(TOC)、总氮(TN)、沉积介质条件(包括沉积物粒度)进行了分析,探讨了沉积物TOC、TN的区域分布特征以及影响有机碳分布的主要因素。结果表明,环雷州半岛近海海域海底表层沉积物有机碳含量在0~0.79%之间,平均值为0.26%。与中国其它近海海域相比,环雷州半岛大部分近海区域海底表层沉积物有机碳含量明显偏低,为有机质贫乏区,仅雷州半岛西南部流沙湾近海海域为TOC相对高值区。总氮含量也不高,在0.011%到0.100%之间,TOC与TN存在较强的正相关性,且平面上TOC与TN分布高度重合,显示氮元素主要以有机化合物形式存在。TOC/TN比值在5.1~14.3之间,表明沉积有机质具有陆源输入和海洋自生来源的混合特征,但以雷州半岛西侧北部及东侧中部海域受陆源有机质输入影响更大。大多数站位海底沉积物粒度构成以粉砂为主、粘土次之,少数站位以砂质沉积为主。沉积物有机碳含量与粘土及粉砂含量呈弱正相关性,与沉积物pH值、Eh值及砂含量呈弱负相关性,这表明海底沉积物有机质丰度受有机质来源输入、海底氧化还原状态和沉积水动力条件(沉积物粒度)等因素综合控制。  相似文献   

13.
Salt marsh formation can be initiated by the colonization of bare tidal flats by pioneer halophytes such asSpartina anglica. In the present study, growth ofS. anglicain the edge and centre zones of pioneer patches colonizing a tidal flat in a marine bay in the south-west Netherlands was investigated. Average biomass and shoot length was significantly lower in centre zones than in edge zones of the patches. Multiple linear regression showed that 84% of the variance in aboveground biomass in the centre zones could be explained by sediment phosphorus and nitrogen concentrations. No such relationship existed in the edge zone. This suggests that biomass production in the centre zones of the patches is nutrient limited, but that factors other than sediment nitrogen and phosphorus content determine growth ofSpartinain the edge zones.The sediment nitrogen and phosphorus concentrations in the centre zones of the patches were significantly related with sediment carbon concentrations, indicating that the pool of particle-bound nutrients in the sediment to an important extent is associated with organic particles. Determination of stable carbon isotope signatures of the sedimentary organic matter showed that an increasing carbon content of the sediment in the centre zone of the patches (and a rise in plant biomass) coincides with a higher contribution of non-Spartinaderived carbon to the sedimentary organic matter pool. Sustained biomass production in the centre zones of the patches, thus, probably depends on deposition of allochthonous organic particles and the nutrient inputs inherent in this process. Due to the construction of large-scale hydro-engineering works, however, conditions for deposition of waterborne particles are currently unfavourable. The consequences of reduced carbon and nutrient inputs into the patches will be particularly in the (older) centre zones, where the nutrient pools in non-refractory organic matter have been drained in the years of previous growth. Accordingly, it is hypothesized that the canopy-enhanced sedimentation for whichSpartinais well- known, via positive feed-back effects on plant growth can be crucial for plant vitality, and, hence, for successful colonization of unvegetated areas.  相似文献   

14.
The biochemical composition of particulate organic matter (POM) is very important to understand in relation to the trophic conditions of marine ecosystems since it forms the primary trophic base. The present study investigated the biochemical compositions (i.e., carbohydrates, proteins, and lipids) of POM monthly from January to December 2015 in Geoje-Hansan Bay to determine if the macromolecular composition of POM is coupled between the water columns and sediment. A spatial difference in the macromolecular compositions was observed in the water columns between the inner and outer bays, which may be caused by the different physiological conditions of phytoplankton growth that are due to the water circulation pattern in the bay. In contrast, no distinctive spatial difference in the macromolecular compositions was found in the sedimentary organic matter. Overall, while carbohydrates were the dominant (45.7%) macromolecules of the POM in the water columns, proteins were dominant (47.9%) in the sedimentary organic matter during our observation period. Decoupling of the macromolecular compositions between the water columns and underneath the sediment in Geoje-Hansan Bay appears to be a result of the various effects of selective filter feeding by oysters and protein-dominant benthic microalgae and fouling organisms.  相似文献   

15.
采用气相色谱-质谱技术对南极半岛东北海域海底表层沉积物的总有机碳、有机质碳同位素(δ13 Corg)和生物标志化合物等进行了测试分析。研究区表层沉积物总有机碳TOC平均值高于现代深海沉积物中的平均含量。δ13 Corg的变化说明该海域有机碳来源呈海洋水生生物来源和陆源混合的特征。正构烷烃的峰型分布、主峰碳、饱和烃轻重比C-21/C+22和(C21+C22)/(C28+C29)、甾烷组合和藿烷组合证实研究区西部表层沉积物有机质来源以陆源高等植物为主,其陆源可能来自于附近的南极半岛和南舍得兰群岛;研究区东部表层沉积物有机质来源偏以海源为主,且以低等浮游生物、藻类及细菌生物等海源输入为主。碳优势指数(Carbon preference index,CPI)、奇偶优势指数(Odd-even Predominance,OEP)和甾烷C29ααα20S/(20S+20R)比值显示研究区D1-7站位和D5-9沉积物有机质演化程度较高,D5-2和D2-4站位的有机质演化程度低,其他站位介于中间状态。饱和烃中姥鲛烷、植烷及其比值(Pr/Ph)等组合显示研究区西部以氧化-弱还原的沉积环境为主,其可能是受高温低盐别林斯高晋海水流和附近火山喷发的影响所致;研究区东部以还原—强还原沉积环境为主,可能是受低温高盐的威德尔底层水(WSBW)和威德尔海深层水(WSDW)影响所致。  相似文献   

16.
Sedimentary samples were collected from a site (57°02.9N, 176°57.4W: 3,650 m) in the Aleutian Basin of the Bering Sea and analyzed for organic carbon, total nitrogen and various organic materials. Organic carbon and total nitrogen were measured in the range of 0.1–1.9% and 0.01–0.2% of the dry weight of the sediment, these values tended to decrease with depth, but considerably lower values were obtained in the volcanogenic sediment layers. Carbohydrate, amino acid and protein and lipid carbons accounted for 40% of the total organic carbon on the surface of the sediment, and this value tended to decrease with depth to 20% at 10m depth from the top of the core sample. The carbon to nitrogen (C/N) ratios ranged from 6.3 to 9.0. Vertical change in the values of the ratios can be understood in terms of a higher decay rate of amino acids and proteins.Radiocarbon age determinations on five sedimentary samples yielded sedimentation rates ranging from 37 to 90cm/1,000y.  相似文献   

17.
The sediments of the Bay of Concepción and the adjacent shelf underlie one of the most productive upwelling areas in the SE Pacific margin. Reports on factors controlling meiofaunal community structure in these kinds of organic‐rich and oxygen‐deficient habitats are scarce in the literature. In this study, five sites along a transect from the mid‐Bay of Concepción (27 m) to the outer shelf (120 m) were studied on fives dates (May, August, November 1997, and March and May 1998) in order to assess the dynamic relationships between sedimentary organic matter and metazoan meiofauna. The sampling period coincided with the 1997–1998 El Niño event. Sediment parameters investigated were the redox potential discontinuity depth, photosynthetic pigment concentrations (chlorophyll a and phaeopigments), organic carbon, nitrogen, total lipids, carbohydrates, and proteins. In general, lowest values of meiofauna abundance and biomass were found within the naturally eutrophic Bay of Concepción and towards the shelf break, while maximum values occurred at intermediate depths. During the whole period, the meiofaunal abundance was negatively correlated with the concentration of most of the biochemical components of organic matter, as well as with the sediment phaeopigment content. However, positive correlations were found with chlorophyll a derived indices and with bottom‐water oxygen content. Most of the sediment parameters displayed a seasonal cycle, but towards the beginning of 1998, an effect of the 1997–1998 El Niño was evident. Typical austral‐summer (i.e. oxygen‐deficient) conditions did not develop, and sedimentary parameters reflected a decreased input of phytodetritus. Along the transect, the magnitude of this effect on meiofauna varied among sites. An overall positive response, in terms of meiofaunal abundance was observed, probably due to the amelioration of low oxygen conditions in the sediment.  相似文献   

18.
We describe the quantitative and compositional (phytopigment, protein, carbohydrate and lipid) patterns of sedimentary organic matter along bathymetric gradients in seven submarine canyons and adjacent open slopes located at four European regions: one along the NE Atlantic and three along the Mediterranean continental margins. The investigated areas are distributed along a putative longitudinal gradient of decreasing primary production from the Portuguese (northeastern Atlantic Ocean), to the Catalan (western Mediterranean Sea), Southern Adriatic (central Mediterranean Sea) and Southern Cretan (eastern Mediterranean Sea) margins. Sediment concentrations of organic matter differed significantly between the Portuguese margin and the Mediterranean regions and also from one study area to the other within the Mediterranean Sea. Differences in quantity and composition of sediment organic matter between canyons and open slopes were limited and significant only in the eutrophic Portuguese margin, where the differences were as large as those observed between regions (i.e. at the mesoscale). These results suggest that the overall trophic status of deep margin sediments is controlled mostly by the primary productivity of the overlying waters rather than by the local topography. Moreover, we also report that the quantity and nutritional quality of sediment organic matter in canyons and adjacent open slopes do not show any consistent depth-related pattern. Only the Nazaré and Cascais canyons in the Portuguese margin, at depths deeper than 500 m, displayed a significant accumulation of labile organic matter. The results of our study underline the need of further investigations of deep margins through sampling strategies accounting for adequate temporal and spatial scales of variability.  相似文献   

19.
曲宝晓  宋金明  袁华茂 《海洋学报》2018,40(10):119-130
通过对沉积物中粒度组成、总有机碳（TOC）、总氮（TN）、碳氮比（TOC/TN）和碳、氮稳定同位素丰度（δ13C、δ15N）等的分析，结合沉积年代学信息与端元混合模型结果，解析了百年尺度下大亚湾沉积物中不同来源有机质的演变过程及控制因素。结果表明，大亚湾沉积物特性在20世纪70年代末至80年代初发生了显著改变:在此之前，TOC、TN、δ13C和δ15N表现稳定，陆源与海源有机碳的比例维持在3∶7，而自此之后，TOC与TN含量显著升高，TOC/TN持续下降，在1980—2000年和2010年至今都出现了陆源有机碳比例升高，海源有机碳比例降低的现象。上述显著变化表明大亚湾海洋环境自20世纪70年代末至80年代初已经发生了重大变化。近20年来GDP与沉积柱中TN和δ15N呈现出的显著正相关，与TOC/TN呈现出的显著负相关，表明沿岸经济的迅猛增长，水产养殖业的快速发展，周边人口的急速增加等人为活动，是造成大亚湾生态环境变化的重要原因。未来的研究应更密切关注人为活动对海湾生态环境的影响，通过法律法规约束行为，加强海湾生态环境保护与修复治理工作。  相似文献   

20.
Sediment and water column data from four sites in North, Central and South San Francisco Bays were collected monthly from November 1999 through November 2001 to investigate the seasonal variation of benthic organic matter and chlorophyll in channel sediments, the composition and quality of sediment organic matter (SOM), and the relationship between seasonal patterns in benthic organic matter and patterns in water column chlorophyll. Water column chlorophyll peaked in the spring of 2000 and 2001, characteristic of other studies of San Francisco Bay phytoplankton dynamics, however an unusual chlorophyll peak occurred in fall 2000. Cross-correlation analysis revealed that water column chlorophyll at these four channel sites lead sediment parameters by an average of 2 to 3 months. Sediment organic matter levels in the San Francisco Bay channel showed seasonal cycles that followed patterns of water column production: peaks in water column chlorophyll were followed by later peaks in sediment chlorophyll and organic matter. Cyclical, seasonal variations also occurred in sediment organic matter parameters with sediment total organic carbon (TOC) and total nitrogen (TN) being highest in spring and lowest in winter, and sediment amino acids being highest in spring and summer and lowest in winter. Sediment chlorophyll, total organic carbon, and nitrogen were generally positively correlated with each other. Sediment organic matter levels were lowest in North Bay, intermediate in Central Bay, and highest in South Bay. C:N ratio and the ratio of enzyme hydrolyzable amino acids to TOC (EHAA:TOC) data suggest that SOM quality is more labile in Central and northern South Bay, and more refractory in North Bay and southern South Bay.  相似文献   

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