Biochemical composition of marine sediment from the eastern Weddell Sea (Antarctica): High nutritive value in a high benthic-biomass environment

Within the SCAR's international EASIZ programme, as part of the benthic–pelagic coupling experiment, grain size and organic matter contents in marine surface sediment were measured. Samples were taken during the austral autumn of 2000 from 3 regions in the eastern Weddell Sea: Kapp Norvegia, Four Seasons Bank, and Austasen.In general, sediments were fine sand with a grain size fraction < 200 μm representing more than 40% of the total weight. The sediments from Four Seasons Bank (64 to 107 m depth) were coarser than those from Austasen and Kapp Norvegia (209 to 480 m depth), presumably due to winnowing of fine sediment at shallow depths. Organic carbon (OC) content ranged from 0.25% to 1.2% and constituted 10% to 97% of the total carbon. The samples from Kapp Norvegia presented the highest OC values. Overall, protein (PRT), lipid (LPD), and carbohydrate (CHO) contents were similar to those in sediment from cold regions (e.g., the North Atlantic and the Ross Sea) but higher than those in sediment from other Antarctic and more septentrional regions (e.g., the Ross Sea and the Mediterranean). The difference within the Antarctic is explained through the local conditions in Terra Nova Bay and Kapp Norvegia. In the Antarctic, PRT and LPD carbon were the main contributors to the biopolymeric carbon (BPC). In the eastern Weddell Sea shelf, the BPC accounted for more than 90% of the OC in most of the samples. More than 82% of the total PRT, LPD, and CHO were present in the fraction < 200 μm. This work remarks the existence of sediments with a high nutritional value persistent several weeks after the spring–summer pulse of fresh organic matter. It is also highlighted the high potential availability of these sediments (due to its grain size) for the benthic communities inhabiting this high-latitude continental shelf.     

Tectonically active sediment dispersal system in SW Taiwan margin with emphasis on the Gaoping (Kaoping) Submarine Canyon

The sediment dispersal system in southwestern Taiwan margin consists of two main parts: the subaerial drainage basin and the offshore receiving marine basin. In plan view, this sediment dispersal system can be further divided into five geomorphic units: (1) the Gaoping (formerly spelled Kaoping) River drainage basin, (2) the Gaoping (Kaoping) Shelf, (3) the Gaoping (Kaoping) Slope, (4) the Gaoping (Kaoping) Submarine Canyon and (5) the Manila Trench in the northernmost South China Sea. The Gaoping River drainage basin is a small (3250 km²), tectonically active and overfilled foreland basin, receiving sediments derived from the uprising Central Range of Taiwan with a maximum elevation of 3952 m. The Gaoping Submarine Canyon begins at the mouth of the Gaoping River, crosses the narrow Gaoping Shelf (~ 10 km) and the Gaoping Slope, and finally merges into the northern termination of the Manila Trench over a distance of ~ 260 km. The SW Taiwan margin dispersal system is characterized by a direct river-canyon connection with a narrow shelf and frequent episodic sediment discharge events in the canyon head.In a regional source to sink scheme, the Gaoping River drainage basin is the primary source area, the Gaoping Shelf being the sediment bypass zone and the Gaoping Slope being the temporary sink and the Manila Trench being the ultimate sink of the sediment from the Taiwan orogen. It is inferred from seismic data that the outer shelf and upper slope region can be considered as a line source for mass wasting deposits delivered to the lower Gaoping Slope where small depressions between diapiric ridges are partially filled with sediment or are empty.At present, recurrent hyperpycnal flows during the flood seasons are temporarily depositing sediments mainly derived from the Gaoping River in the head of the Gaoping Submarine Canyon. On the decadal and century timescales, sediments temporarily stored in the upper reach are removed over longer timescales probably by downslope-eroding sediment flows within the canyon. Presently, the Gaoping Submarine Canyon serves as the major conduit for transporting terrestrial sediment from the Taiwan orogen to the marine sink of the Manila Trench. Seismic data indicate that the Gaoping Submarine Canyon has been eroding the Gaoping Slope intensely by presumed hyperpycnal flows and transporting sediments from the canyon head to the middle and lower reaches of the canyon. The middle reach is a sediment bypass zone whereas the lower reach serves as either a temporary sediment sink or a sediment conduit, depending on relative prevalence to deposition or erosion during canyon evolution. Contrast differences in channel gradient and travel length between the Gaoping and Amazon sediment dispersal systems suggest that the Gaoping (Kaoping) River-Canyon system is an active sediment dispersal system for transporting terrestrial materials to the deep sea. The fate of the Gaoping River sediment is the northern Manila Trench.     

细颗粒泥沙絮凝现象研究综述

概述了河口泥沙絮凝研究工作中有关絮凝机理、絮凝特性、影响河口细颗粒泥沙絮凝的若干因子。一般研究表明,泥沙颗粒越细,絮凝现象就越明显。絮团的沉降速度主要取决于絮团密度和絮团大小。水流一方面能加强细颗粒泥沙的相互碰撞,促进絮凝作用的发生,另一方面水流又具有剪切破坏作用,因此水流对细颗粒泥沙絮凝沉降的影响表现为在低流速时的促进絮凝作用和高流速时的阻滞絮凝作用。     

滨州港海域沉积物特性分析

依据2008年1月、2006年3月和7月的黄骅港、滨州港海区沉积物取样资料,对海床泥沙中值粒径、细颗粒泥沙含量、分选程度等平面分布特征进行了分析,并与黄骅港海域的泥沙底质进行了比较,结果表明滨州港的兴建阻挡了港岛以南床面泥沙的北移,部分遏制了泥沙来源,同时滨州港外航道成为从南到北泥沙输移的沉沙池,对减少黄骅港外航道泥沙淤积有利。     

Distribution of suspended sediment in the coastal sea off the Ganges–Brahmaputra River mouth: observation from TM data

Remote sensing technique was applied to estimate suspended sediment concentration (SSC) and to understand transportation, distribution and deposition of suspended sediment in the estuary and throughout the coastal sea, off the Ganges–Brahmaputra River mouth. During low river discharge period, zone of turbidity maximum is inferred in the estuary near the shore. SSC map shows that maximum SSC reaches 1050 mg/l in this period. Magnitude of SSC is mainly owing to resuspension of the bottom surface sediments induced by tidal currents flowing over shallow water depths. The influence of depth on resuspension is farther revealed from the distribution and magnitude of SSC along the head of Swatch of No Ground (SNG) submarine canyon. During high river discharge period, huge river outflow pushed the salt wedge and flashes away the suspended sediments in the coastal sea off the river mouth. Zone of turbidity maximum is inferred in the coastal water approximately within 5–10 m depth of water, where the maximum SSC reaches 1700 mg/l. In this period, huge fluvial input of the suspended sediments including the resuspended bottom sediments and the particles remaining in suspension for longer period of time since their initial entry control mainly the magnitude of SSC. In the estuary near the shore, seasonal variation in the magnitude of SSC is not evident. In the coastal sea (>5 m water depth), seasonal influence in the magnitude of SSC could be concluded from the discrepancy between SSC values of two different seasons. Transportation and deposition of suspended sediments also experiences seasonal variations. At present, suspended sediments are being accumulated on the shallow shelf (between 5 and 10 m water depth) in low discharge period and on the mid-shelf (between 10 and 75 m water depth) during high discharge period. An empirical (exponential) relationship was found between gradual settle down of suspended sediments in the coastal sea and its lateral distance from the turbidity maximum.     

Spatial distribution patterns of demersal and epibenthic communities on the Galician continental shelf (NW Spain)

Spatial distribution patterns of epibenthic communities on the Galician continental shelf were studied using multivariate methods. Data came from 5 surveys carried out in 2002, 2003 and 2004. Beam trawls and otter trawls were used to study epibenthic communities along 8 transects perpendicular to the coastline. The role of depth, season, latitude and sediment characteristics was examined. Seven habitats were described according to bathymetry and sediment characteristics. There were weak linear relationships between environmental variables and species richness, biomass and species diversity. However, the canonical analysis showed that depth and sediment characteristics greatly influence smaller epibenthic communities sampled by beam trawl. Six assemblages were obtained for beam trawls: inner shelf mud, very fine sands, and fine sands, middle shelf sands, and outer shelf very fine sands, and fine sands. Five assemblages were identified for larger-sized and swimming epibenthos sampled with otter trawls. These assemblages were also determined according to depth and sediment type but sediment characteristics were less important. Otter trawl assemblages were the same as the beam trawl ones, except for on the outer shelf where no differences between sediment type were detected. For both gears, inner and outer shelf assemblages displayed a higher biotic variability than the middle shelf, as a consequence of a higher environmental heterogeneity. Typifying species were mainly eurytopic in the middle shelf, whereas eurytopic and stenotopic species characterised the inner and outer shelves.     

Methane release and coastal environment in the East Siberian Arctic shelf

In this paper we present 2 years of data obtained during the late summer period (September 2003 and September 2004) for the East Siberian Arctic shelf (ESAS). According to our data, the surface layer of shelf water was supersaturated up to 2500% relative to the present average atmospheric methane content of 1.85 ppm, pointing to the rivers as a strong source of dissolved methane which comes from watersheds which are underlain with permafrost. Anomalously high concentrations (up to 154 nM or 4400% supersaturation) of dissolved methane in the bottom layer of shelf water at a few sites suggest that the bottom layer is somehow affected by near-bottom sources. The net flux of methane from this area of the East Siberian Arctic shelf can reach up to 13.7 × 10⁴ g CH₄ km^− 2 from plume areas during the period of ice free water, and thus is in the upper range of the estimated global marine methane release. Ongoing environmental change might affect the methane marine cycle since significant changes in the thermal regime of bottom sediments within a few sites were registered. Correlation between calculated methane storage within the water column and both integrated salinity values (r = 0.61) and integrated values of dissolved inorganic carbon (DIC) (r = 0.62) suggest that higher concentrations of dissolved methane were mostly derived from the marine environment, likely due to in-situ production or release from decaying submarine gas hydrates deposits. The calculated late summer potential methane emissions tend to vary from year to year, reflecting most likely the effect of changing hydrological and meteorological conditions (temperature, wind) on the ESAS rather than riverine export of dissolved methane. We point out additional sources of methane in this region such as submarine taliks, ice complex retreat, submarine permafrost itself and decaying gas hydrates deposits.     

丁坝群坝田与主流水沙交换与冲淤机理综述

丁坝群不同平面布置方案下坝田与主流间的泥沙交换和地形变化是长江口深水航道回淤机理及减淤措施研究的重要内容,但以往研究不多。坝田与主流的泥沙交换及地形变化与紊流结构及时均流场有关,即与坝田-主流主界面混合层的大尺度相干结构和坝田内时均大尺度环流有关。在出水丁坝和淹没丁坝情况下坝田与主流的质量交换系数变化不大,约为0. 02左右。坝田不存在悬沙的平衡剖面(Rouse分布),悬沙和底沙均存在指向坝田的净输沙。坝田淤积达到准平衡状态需要5～6 a,但基本上在前2 a就达到了平衡。     

Response of benthic infauna and epifauna to ocean disposal of red clay dredged material in the New York Bight: A study using sediment-profile imaging, surface imaging and traditional methods

In 1997, approximately 1 million cubic yards of consolidated red clay was dredged from Newark Bay in New Jersey and deposited on the seafloor at an open-water dredged material disposal site located on the inner continental shelf of the New York Bight. To address concerns about the ability of benthic organisms to colonize the seafloor deposits of this compact, organic-poor red clay, monitoring surveys were conducted in 1998 (1 year after disposal) and 2002 (5 years after disposal). The surveys used a combination of sediment imaging and traditional grab sampling methods to characterize physical and biological conditions over the surface of the red clay deposits in comparison to nearby reference areas consisting of either naturally-occurring, sandy surface sediments or deposits of unconsolidated, muddy dredged material. Sediment-surface and sediment-profile images (SPI) collected in summer 2002 indicated that the surface of the red clay deposits had become much smoother and more heterogeneous in texture compared to images collected in 1998. The images also indicated that these deposits had become colonized to a much greater degree by relatively abundant and diverse infaunal and epifaunal communities compared to 1998. Taxonomic analysis of benthic grab samples confirmed the imaging results and indicated relatively high infaunal organism abundance and diversity over the red clay deposits in 2002 compared to the reference areas. However, the structure of the benthic community inhabiting the red clay was fundamentally different from the communities in the reference areas, due to the differences in sediment texture and composition. The combination of imaging and traditional taxonomic approaches used in this study provided much greater insight on the red clay colonization process than either approach by itself.     

基于颗粒流理论的深海沉积物土力学特性研究

深海沉积物剪切与承载特性是决定深海采矿车行走稳定性重要参数。分析深海沉积物的物理力学性质, 基于颗粒流理论，建立了具有高孔隙比、高含水率和长条状等特性的深海沉积物颗粒流模型。开展不同深度下的十字板剪切和静力触探的数值模拟，获得了深海沉积物剪切应力-转角及贯入阻力-深度曲线，初步阐明深海沉积物剪切与贯入细观破坏机理。研究表明，深海沉积物的剪切应力-转角及贯入阻力-深度的模拟曲线与原位测试曲线吻合，验证了深海沉积物颗粒流模型及数值模拟方法的正确性。深海沉积物的剪切与贯入破坏形式主要为沉积物颗粒的挤压破坏，且应力集中于触地边缘。     

深水航道的河势控制和航道回淤问题

长江口深水航道的整治为检验和深化潮汐河口汊道整治理论及方法提供了依据。河势的宏观控制要求北槽维持落潮流输沙优势。分析表明,工程后北槽分流比下降,已接近河槽性质转变的阈值。一、二期整治工程使河槽断面由宽浅向相对窄深转变,形成了覆盖航槽的连续深泓,为航道维护提供了重要保证,但三期减淤工程使-8 m以下河槽断面向相对宽浅逆转,加上北槽中段过高的流速造成该河段的高含沙量和高输沙率以及该河段近底净输沙方向指向航槽内,使回淤量进一步增大。通过现场观测进一步揭示了近底高含沙量及浮泥形成的机制。进一步的减淤措施应注意恢复合理的导治线放宽率以使输沙率的沿程分布较为均匀。     

A three-dimensional, wave-current coupled, sediment transport model for POM

In the high-energy environment of coastal seas and estuaries,strong sediment resuspension/ deposition events are driven by surface waves,tides,winds and buoyancy driven currents.In recent years,A POM based three-dimensional,wave-current coupled,sediment transport model has been developed by the University of New South Wales.This paper presents several examples of the model applications to study sediment dynamics in the environments where forcings such as waves,tides,and winds are equally important to affect sediment fluxes and distributions.Firstly,the sediment transport model coupled to the Yellow Sea general circulation model and a third generation wave model SWAN was implemented in the Yellow Sea to study the dynamics of the sediment transport and resuspension in the northern Jiangsu shoal-wate(rNJSW).The sediment distributions and fluxes and their inter-annual variability were studied by realistic numerical simulations.The study found that the surface waves played a dominant role over the tides to form the turbidity maxima along the muddy coast of NJSW. Secondly,the sediment transport model was used to explore the effect of suspended sediment-induced stratification in the bottom boundary laye(rBBL).The model uses a re-parameterized bottom drag coefficient Cd that incorporates a linear stability function of flux Richardson number Rf.The study has shown that the sediment induced stratification in the BBL reduces the vertical eddy viscosity and bottom shear stress in comparison with the model prediction in a neutrally stratified BBL.In response to these apparent reductions,the tidal current shear is increased and sediments are abnormally concentrated within a thin wall layer that is overlain by a thicker layer with much smaller concentration.The formation of this fluid-mud layer near the seabed has led to a significant reduction in the total sediment transport.This study contributes to the understanding of formations of tidal flats along the coasts of turbid seas and estuaries.     

南汇嘴潮滩沉积物粒度特征研究

文中以实测底质采样资料为基础,对南汇嘴沉积物粒度特征进行了分析,并利用Gao&Collins沉积物趋势分析法探讨边滩的沉积物输运趋势。总体上看,样品粒级变化不大,主要以粘土质粉砂、粉砂为主。没冒沙区域由于受到特殊地形以及水流的影响,沉积物以细砂为主;南汇东滩在横向分布上,沉积物粒径逐渐变粗再逐渐变细;南滩受风浪影响,近岸浅滩沉积物颗粒组成较粗,而远岸区域海床颗粒较细。沉积物中值粒径、分选系数和偏度的分布具有一致性,三者相关性较强;浅滩的沉积物粒度特征表现为正偏,分选性较差,分选系数值集中在2左右;南汇嘴区域沉积物运移方向主要是从口外向西输移,汇聚在南汇嘴附近;杭州湾北岸沉积物主要是向东输运,达到芦潮港西侧水域后逐渐转为向南或向南偏东离岸方向运动,对芦潮港附近水下岸坡的冲刷后退起到了一定的影响。     

潍坊港沉积物特征及岸滩稳定性研究

通过潍坊港海岸动力地貌调查,分析研究了潍坊港各港区的水下沉积物分布特征。近岸沉积物质主要表现为极细砂与砂质粉砂,源于历史上黄河及附近河流的泥沙,中值粒径大致在0.01～0.4 mm,分选程度为分选好-中常。通过不同历史时期海图的等深线和断面海床冲淤变化对比,分析认为,潍坊中港区以西,受黄河口泥沙扩散、沉积影响,海床一直处于持续淤涨之中,这种趋势还将持续,潍坊中港区以东海床则基本保持稳定。从黄河口流路变迁这一角度来看,该海区岸线将在长期内保持稳定。     

新型箱式采泥器研制及在长江口航道回淤研究中的应用

为获取河床沉积物原状样品,研制一种新型箱式采泥器,并在长江口12.5 m深水航道回淤研究中开展应用。结果表明:新型箱式采泥器密封性好、适应性强、成功率高、样品量多且保持原状。新型箱式采泥器采集的原状样品揭示出长江口南港北槽河床沉积物包括沙、泥、沙泥混合、沙泥分层4类,沉积物类型及变化特征反映了泥沙来源和沉积过程。基于沉积物原状样品粒度参数,开展南港底沙输运趋势研究及底沙对深水航道淤积影响的定量估算。     

Hydrology, sediment yield, erosion and sedimentation rates in the estuarine environment of the Ria de Vigo, Galicia, Spain

The aim of this study is to provide a budget study with calculated erosion rates. Three methods have been used to calculate sediment yield and denudation rates in the Ria de Vigo: (1) measurements of sediment loads, (2) measurements of sediment accumulation rates at the coast, (3) theoretical calculations of potential denudation. Sediment loads and water discharge were measured over a period of 14 months from May 1997 to July 1998. Two of the tributaries entering the Ria de Vigo were monitored for 12 more months, from May 2000 to May 2001, to observe changes in discharge and sediment loads. This period corresponded with atypical precipitation, with peak monthly values (600 mm) three times higher than those on record.Water rating curves are typically exponential. Suspended and dissolved loads vary for different rivers, showing values of 1.5 to 130 mg/l during 1997/1998. For 2000/2001, these values are twice as high. Suspended load versus discharge relationships for 1997/1998 were logarithmic, but data from 2000/2001 does not fit the same equation. Dissolved loads are several times higher than suspended loads in almost all cases. Dissolved load concentrations vary more widely with discharge than suspended loads. This is probably due to local pollution and contamination from marine spray in areas closer to the sea.Second, erosion rates and bed load sediment yields were calculated from accumulation rates at the Ramallosa Complex. Well-preserved estuarine and tidal sediments, associated with the Minor River, have accumulated in this area during the Holocene. ¹⁴C ages allow calculation of sedimentation rates (SR) for two intervals. The lower interval extends from 2001 to 484 years BP and yields an SR of 1.12 mm/a. The upper interval extends from 484 years BP to the present and has an SR of 3.3–4.4 mm/a. These differences may be explained by basin dynamics as the beach progressively encloses the area and also by human interference. From sedimentary facies analysis it is concluded that 90% to 95% of the accumulated deposits were transferred to the basin as bed load. Muddy deposits (mostly marshes) are better developed at the upper part of the sediment pile, and inner areas, indicating a progressive shallowing and filling up of the basin. Most of suspended load is exported to the ria, whereas the Ramallosa Complex acts as a sediment sink for bed load derived material.Calculated potential erosion rates using Ahnert's [Am. J. Sci. 268 (1970) 243] equation show lower values than those estimated from river load concentrations. Potential erosion rates for the Minor River are higher than for the Lagares River which contrast with mechanical denudation rate values from river loads during 1997/1998 which are higher for the Lagares River. During 2000/2001 MDR values were higher than those of the potential erosion rates for both rivers, in line with the extremely high precipitation. Higher values in the Lagares could be in part due to human interference.     

Food supply mechanisms for cold-water corals along a continental shelf edge

In recent years it has been documented that deep-water coral reefs of the species Lophelia pertusa are a major benthic habitat in Norwegian waters. However, basic information about the biology and ecology of this species is still unknown. Lophelia live and thrive under special environmental conditions of which factors such as temperature, water depth, water movement and food supply are important. The present work explores the hypothesis that Lophelia forms reefs in places where the encounter rate of food particles is sufficiently high and stable over long periods of time for continuous growth. This is done by relating the distribution of reefs with the results of numerical ocean modelling.Numerical simulations have been performed with an idealized bottom topography similar to what is found outside parts of the Norwegian coast. In the simulations the model is first forced with an along slope jet and then with an idealized atmospheric low pressure. The model results show that the encounter rates between the particles and the water layer near the seabed are particularly high close to the shelf break. This may indicate that many Lophelia reefs are located along the shelf edges because the supply of food is particularly good in these areas.A sensitivity study of the particle supply in the area close to the seabed for increasing latitude has also been done. This shows that the Ekman transport in the benthic layer tends to create a steady supply of food for benthic organisms near the shelf edge away from the equator.