Distribution of benthic macrofaunal communities in intertidal flat under hydrodynamic influence:a case study of Jiangsu coast,East China

To identify the distribution pattern of macrofaunal assemblages of the Dafeng intertidal flats in response to hydrodynamic and sediment dynamic processes in the northern Jiangsu coast,East China,macrofauna sampling and hydrodynamic observations were carried out simultaneously across the mud flat,mixed mud-sand flat,and silt-sand flat of the intertidal zone in June 2018.Results show that there was a clear zonal distribution pattern of the macrofaunal communities,as is controlled by local hydrological and sedimentary environments.Principal component analysis(PCA)revealed three types of intertidal area in terms of hydrological and surficial sediment parameters.Similarly,three distinct groups of the macrofaunal communities,i.e.,mud flat,mix mud-sand,and silt-sand groups,were recognized at similarity level of 24%based on the CLUSTER analysis in similarity profile(SIMPROF)test.Correlation analysis upon best variables stepwise search(BVSTEP)indicated the importance of the hydrodynamics(e.g.,water temperature and salinity,tidal duration,flow speed,suspended sediment concentration,and wave height)in the differentiation of macrofaunal communities with different taxonomic classes over the intertidal zone.Therefore,macrofaunal assemblages,similar to hydrology and surficial sediment,have a unique zonation pattern.Small-sized deposit feeders adapt better to low energy environments,thus dominated the upper part of the intertidal flat,whilst the heavy and large-sized filter feeders and deposit feeders were dominant over the middle and lower parts.The hydrodynamic and sediment processes cause biota-niche separation,which affected the biological processes across the intertidal flat.

Impact of the cord-grass Spartina alterniflora on sedimentary and morphological evolution of tidal salt marshes on the Jiangsu coast,China

The tidal flats of the Wanggang area, on the Jiangsu coast, represent the largest continuously distributed coastal wetland in terms of area coverage in China, and the dynamics of tidal flat accretion and erosion is highly complicated. The cord-grass Spartina alterniflora, which was introduced artificially into the Jiangsu coast, has significant influences on the regional tidal flat evolution in terms of deposition rate, spacial sediment distribution patterns and tidal creek morphology. On the basis of the data set of bed elevation and accumulation rate for different periods of time, the applicability of the Pethick - Allen model to the Jiangsu tidal salt marshes is discussed. In addition, caesium-137 dating was carried out for sediment samples collected from the salt marsh of the Wangang area. In combination with the caesium-137 analysis and the data collected from literature, the Pethick - Allen model was used to derive the accumulation rate in the Wanggang tidal flat for the various periods. The results show that the pattern of tidal flat accretion has been modified, due to more rapid accretion following the iatroduction of S. alterniflora to the region. Surficial sediment samples were collected from representative profiles and analyzed for grain size with a laser particle analyzer. The result shows that fine-grained sediment has been trapped by the plant, with most of the sediment deposited on the Suaeda salsa and Spartina angelica flats being derived from drainage creeks rather than the from gently sloping tidal flats. Remote sensing analysis and in situ observations indicate that the creeks formed in the S. alterniflora flat have a relatively small ratio of width to depth, a relatively high density, and are more stable than the other tidal flat creek systems in the study area.

Invading cord grass vegetation changes analyzed from Landsat-TM imageries: a case study from the Wanggang area, Jiangsu coast, eastern China

Cord grass colonization on the Jiangsu coast, eastern China, modifies the native salt marshes in terms of ecosystem structure. The Landsat TM images from 1992 to 2003 were analyzed to identify salt-marsh vegetation distribution patterns and their changes over this coastal region, in order to evaluate the effects of the spreading of the artificially introduced halophyte Spartina. Supervised classification was performed using Bands 3, 4 and 5 in conjunction with in situ training samples, to derive the distribution pattern of the vegetation in the study area. Further, in order to identify the intertidal areas with different tidal elevations, a data treatment procedure was designed to combine regional water level data using harmonic analysis with the waterlines on the TM images extracted by density slice. The results show that： （1） the Spartina alterniflora area has been expanding towards the sea rapidly since it was introduced, especially at initial stages; （2） in the upper part of the inter-tidal zone, the local marsh plant Suaeda salsa and the exotic species Spartina anglica were present only near the sea dyke, occupying only a small part of the entire salt marsh, and the area of these two species has been reduced by land reclamation; （3） there has been a trend for Spartina alterniflora to become the dominant species in the salt marshes in the study area; and （4） the elevation of Spartina alterniflora’s seaward fringe was close to mean high water on neaps, and its landward boundary was slightly higher than mean high water. The salt marsh environment of the study area has been modified rapidly by the Spartina vegetation for the last 12 years.

Numerical simulation of typhoon-induced storm surge along Jiangsu coast,PartⅠ:Analysis of tropical cyclone

The Tropical Cyclone Best Track Dataset issued by the Shanghai Typhoon Institute of the China Meteorological Administration, for the period from 1949 to 2013, was analyzed, and the typhoons threatening the Jiangsu coast were categorized into three different classes in terms of track, including typhoons making straight landfall, typhoons active in offshore areas, and typhoons moving northward after landfall. On the basis of the 65-year dataset, the typhoon parameters of these three categories, including the central pressure and the maximum wind speed, were investigated. Statistical analysis suggested that the minimum central pressure increased northward and shoreward gradually. The relationship between the maximum wind speed and the minimum central pressure was established through second-order polynomial fitting. Considering typhoons No. 1210, No. 0012, and No. 9711 as the basic typhoons, ten hypothetical cyclones with typical tracks and minimum central pressure occurring during the period from 1949 to 2013 were designed, providing the driving conditions for numerical simulation of typhoon-induced storm surges along the Jiangsu coast.

Spatial variations of tidal water level and their impact on the exposure patterns of tidal land on the central Jiangsu coast

The exposed area of intertidal zone varies with tidal water level changes, If intercomparisons of satellite images are adopted as a method to determine geomorphological changes of the intertidal zone in response to accretion or erosion processes, then the effect of water level variations must be evaluated. In this study, two Landsat TM images overpassing the central Jiangsu coastal waters on 2 January and 7 March 2002, respectively, were treated by the changing detection analysis using Image Differencing and Post-classification Comparison. The simultaneous tide level data from four tide gauge stations along the coast were used for displaying the spatial variations of water levels and determining the elevations of waterlines. The results show that the spatial variations of water levels are highly significant in the central Jiangsu coastal waters. The huge differences of tidal land exposure patterns between the two imaging times are related mainly to the spatial variations of tidal water levels, which are controlled by the differences in tidal phases for different imaging times and the spatial variations of water level over the study area at each imaging time. Under complex tidal conditions, e.g., those of the central Jiangsu coastal waters, the tide-surge model should be used to eliminate effectively the effects of water level variations on remote sensing interpretation of geomorphological changes in the intertidal zone.

Numerical simulation of typhoon-induced storm surge along Jiangsu coast,PartⅡ:Calculation of storm surge

The Jiangsu coastal area is located in central-eastern China and is well known for complicated dynamics with large-scale radial sand ridge systems. It is therefore a challenge to simulate typhoon-induced storm surges in this area. In this study, a two-dimensional astronomical tide and storm surge coupling model was established to simulate three typical types of typhoons in the area. The Holland parameter model was used to simulate the wind field and wind pressure of the typhoon and the Japanese 55-year reanalysis data were added as the background wind field. The offshore boundary information was provided by an improved Northwest Pacific Ocean Tide Model. Typhoon-induced storm surges along the Jiangsu coast were calculated based on analysis of wind data from 1949 to 2013 and the spatial distribution of the maximum storm surge levels with different types of typhoons, providing references for the design of sea dikes and planning for control of coastal disasters.

Characteristics analysis for cold water patches off the Jiangsu coast in the last 35a

The daily and monthly-mean characteristics of cold water patches （CWPs） off the Jiangsu coast in 35 a of 1982-2016 are examined based on advanced very high resolution radiometer （AVHRR） data. Most of the CWPs are found to occur in the warm and hot months （May-September）, with some CWPs in the cool and cold months （October-April）. The average radius and intensity of the monthly-mean CWPs are about 81 km and 0.6℃, respectively. The average difference in the sea surface temperature （SST） between the centers of the CWPs and the nearshore is about 2.0℃. The correlation analysis between the CWPs, winds and tides indicates that most of the CWPs occurred during the southerly winds, with some CWPs occurring during the northerly winds. The average intensity of the CWPs during spring tides is slightly stronger than that during neap tides in the warm and hot months, and the difference is very small in the cool and cold months.

Effects of Climatic Suitability on Clamworm Breeding along Jiangsu Coast of China

Data were collected by clamworm breeding and investigation and then analyzed to understand the changes in salinity and pH value caused by rainfall as well as climatic suitability along Jiangsu coast of China. The main climatic factors affecting clamworm breeding included water temperature, strong wind and heavy rainfall. The period with air temperature stable above 14 ℃ was suitable for clamworm breeding, and it was from eady Apr. to mid-Nov, along Jiangsu coast. The period with air temperature stable above 30 ℃ in summer was unsuitable for clamworm breeding, and it was from mid-Jul, to late Jul. along Jiangsu coast. During the suitable period for clamworm breeding, the annual days of strong wind and those of heavy rainfall were 4.3 - 39.2 and 2.9 - 4.0 d, respectively. The effects of rainfall （or water exchange） on pH values were determined by the proportion of rainfall （or water exchange） in total pond water and the difference between their pH values. The climate along Jiangsu coast was suitable for clamworm breeding, and the climatic suitability decreased successively in Qidong, Lusi, Ganyu, Rudong, Dafeng, Sheyang, Yanweigang, and Western Liandao. Therefore, it is important to evaluate the effects of severe weather, forecast disastrous weather and formulate rational measurements for flood control and disaster relief.

Evolution of sedimentary environments of the middle Jiangsu coast, South Yellow Sea since late MIS 3

An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 （late MIS 3, i.e., ca. 39 cal ka BP） along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea （SYS）, and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments （Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel）. This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial （Para-Sq2）, including the highstand and forced regressive wedge system tracts （HST and FRWST）, and the parasequence of the postglacial period （Para-Sql）, including the transgressive and highstand system tracts （TST and HST）. The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities.

Detrital Zircon Geochronology of the Radial Sand Ridge System of Jiangsu Coast, East China: Implication for Sediment Provenance

The radial sand ridge system （RSRS） located at Jiangsu coast of China attracts much attention on its origin and mechanic of formation for its special structure and potential land resource. Due to complicated hydrodynamic condition, the Jiangsu RSRS is a hot debated on its potential sources, Yangtze River or Yellow River？ We collected ten sand samples from surface sediments along the west coast of Bohai Sea and Yellow Sea from the modern Yellow River estuary to Yangtze River estuary in summer, 2013. The samples are analyzed by method of detrital zircon age for source identification of the RSRS sediments. The U-Pb age spectra of detrital zircon grains of the samples show a wide range from Cenozoic to Late Archean with several age peaks. Comparing the age spectra between the Yangtze River and the Yellow River, the detrital zircons have younger age （〈100 Ma） group in the Yangtze River. These age distribution of the Jiangsu coastal RSRS sediments are similar to that of the Yangtze River, but different from the Yellow River. The samples located adjacent to the old Yellow River Delta show more wide-range age distribution, implying a compounded origination from the both rivers. Based on these findings it is proposed that, contrary to common opinion, the main sediment source of the Jiangsu RSRS is the Yangtze River, rather than the Yellow River. By implication, there should be evidence of hydrodynamic mechanics of oceanic currents and tidal motion. This aspect awaits confirmation in future research.

Numerical simulation of typhoon- induced storm surge on the coast of Jiangsu Province,China,based on coupled hydrodynamic and wave models

In order to facilitate engineering design and coastal flooding protection, the potential storm surge induced by a typhoon is studied.Using an unstructured mesh, a coupled model which combines the advanced circulation （ ADCIRC ） hydrodynamic model and simulating waves nearshore （ SWAN ） model is applied to analyze the storm surge and waves on the coast of Jiangsu Province.The verifications of wind velocity, tidal levels and wave height show that this coupling model performs well to reflect the characteristics of the water levels and waves in the studied region.Results show that the effect of radiation stress on storm surge is significant, especially in shallow areas such as the coast of Jiangsu Province and the Yangtze estuary.By running the coupled model, the simulated potential flooding results can be employed in coastal engineering applications in the Jiangsu coastal area, such as storm surge warnings and extreme water level predictions.

Research on Environmental Impact Assessment Methods of Farmland Improvement along Coastal Areas of Jiangsu Province

[ Objective] The study aimed to assess the impact of farmland improvement on ecological environment along coastal areas of Jiangsu Province. [ Method] Taking the coastal farmland improvement of Sheyang County, Jiangsu Province as an example, an indicator system of environ- mental impact assessment （EIA） for coastal farmland improvement was established based on data collection, field survey and monitoring results, expert consultation, literature study and other methods, including four subsystems （biological resource, soil, vegetation and water environment） and 12 indicators. [ Result] The weights of soil, biological resource, vegetation and water environment were 0.614, 0.219, 0.118 and 0.049, and the top weight of soil showed that farmland improvement had a great influence on soil. Among the 12 indicators, the most important indicators with higher weights were reclamation rate of the land （weight 0.389）, population density （weight 0.164） and the content of soil organic matter （weight 0.088）. Therefore, in EIA of such kind of projects in the future, we should give prominence to the identification, evaluation and monitoring of the main characteristic factor above. [ Conclusion] The research could provide scientific references for the sustainable utilization of resources and estab- lishment of environmental management policies along costal areas of Jiangsu Province.

Interpreting grain-size trends associated with bedload transport on the intertidal fiats at Dafeng，central Jiangsu coast

A MIDAS-400 customized data acquisi- tion system has been used for the high-resolution sediment dynamic measurements over the Dafeng intertidal flats of northern Jiangsu during 6 tidal cy- cles from July 3 to July 10, 2003. The bed shear stress and bedload transport rates, in response to wave-current interactions, are calculated, which in- dicate that wind waves enhance the bottom shear stress and bedload transport rates. At the station for measurements, bedload transport was directed to seaward, with a sediment discharge of 30—150 kg·m?1 per tidal cycle. The surficial sediment samples were collected from a grid with 10 m spatial intervals over a rectangle 2×104 m2 experimental area, near the MIDAS-400 during the spring tide of July 4, 2003, and the neap tide of July 9, 2003. In addition, leveling survey was undertaken to obtain the detailed topog- raphy of the sampling area. Grain-size trend analysis of the sediment samples shows that the bedload transport patterns are complex, mainly controlled by the hydrodynamics and local geomorphology (e.g. tidal creeks) over the intertidal flats. Furthermore, the grain-size trends pattern during the neap tide rather than during the spring tide is consistent with the cal- culated bedload transport, and the grain-size trend vectors for the spring tide are larger than those forthe neap tide, indicating that the sampling thickness of surficial sediment during the neap tide may contain the information on the geomorphological evolution (or sediment deposition/erosion) from the spring to the neap tide.

Processes of small-scale tidal flat accretion and salt marsh changes on the plain coast of Jiangsu Province,China

Large-scaled reclamation modifies the coastal environment dramatically while accelerating the disappearance of salt marshes,which causes the degradation of the coastal ecosystem and the biodiversity function.In this study,we explored the changes of tidal flat and salt marsh coverage in a small-scale tidal flat with an area of ~160 000 m^2 in the plain coast of Jiangsu Province,China.Human activities（e.g.,the construction of dikes） are a crucial contributor that benefits for the tidal flat accretions and the following changes of salt marsh coverage.Located in the front of the man-made ＂concave coastline＂,the study area is suitable for sediment accretion after the dike construction in the end of 2006.On the basis of the annual tidal surface elevation survey from 2007 to 2012,the sedimentation rates in the human influenced tidal flat varied from a few centimeters per year to 23 cm/a.The study area experienced a rapid accretion in the tidal flat and the expansion of the salt marsh,with the formation of a longshore bar,and a subsequent decline of the salt marsh.Breaking waves during the flooding tide brought much sediment from the adjacent tidal flat to the study area,which caused burial and degeneration of the salt marsh.The vertical grain size changes within a 66 cm long core in the study area also demonstrated the above changes in the tidal environment.This study indicates that the responses of small-scale tidal flat changes to reclamation are significant,and the rational reclamation would benefit for the new salt marsh formation in front of the dikes.Further research about the evolution of small scale tidal flat as well as the spatial planning of the polder dike should be strengthened for the purpose to maintain a healthier coastal environment.

江苏沿海沙脊群表层沉积物Pb同位素特征及对物源的指示

为进一步查明江苏沿海沙脊群沉积物的来源,分析了该区域沉积物酸不溶组分Pb同位素特征。结果表明,远岸沙脊群陆向区域沉积物Pb同位素比值与近岸沙脊群相似,暗示其在潮波作用下有向岸运移的趋势。铅钕同位素分析揭示长江及周边河流沉积物在长江冲淡水和东海沿岸流作用下输移至远岸沙脊群海向区域。在苏北沿岸流作用下,老黄河三角洲沉积物输入对近岸沙脊群及远岸沙脊群陆向区域有影响;相反,诸如现代黄河口、济州岛和韩国河流等地沉积物输入对江苏沿海沙脊群的影响较弱。

江苏海岸侵蚀及其防护工程研究进展

在分析江苏淤泥质海岸侵蚀特征的基础上,对江苏海岸防护工程发展历程进行了梳理。随着冲淤转换节点南移,江苏海岸侵蚀岸段范围逐渐扩大,滩面下蚀且海岸盐沼大面积消失;传统的局部海岸防护形式已显被动,迫切需要一种局部与宏观相结合、自然与工程相结合的可持续性侵蚀海岸管理策略。指出应将废黄河三角洲沿岸作为一个整体,建立宏观的“大型丁坝+离岸潜堤”相结合的整体海岸防护体系。在纵向上,构建以人工岬角为节点的岬湾相间海岸;在横向上,通过离岸潜堤消浪促淤来进行盐沼生态系统的修复与重建。

江苏沿海台风风暴潮特征分析

收集了1950—2022年影响江苏沿海的历史台风风暴潮过程资料,对引起江苏沿海台风风暴潮的台风路径进行了分类和分析,开展了江苏沿海台风风暴潮的月际分布和年际变化研究,提出了不同路径台风风暴潮的预报要点。结果表明:引起江苏沿海台风风暴潮次数最多的是外海转向型台风,占比高达44.3%,而正面登陆型台风最少,占比只有5.4%,但引起的增水量值最大;江苏沿海台风风暴潮在6—10月均有出现,8月出现次数最多;风暴潮强度等级为Ⅴ级(增水50~100 cm)的过程占比最多,为42.7%,而高潮位超警戒程度等级为Ⅳ级(超警戒30 cm之内或达到黄色警戒潮位值)的占比最多,为45.0%;风暴潮发生次数在近几年呈上升趋势,尤其是增水为50~100 cm的过程,高潮位超警戒或达到黄色警戒潮位值以上的过程在近20年只出现3次;在江苏沿海台风风暴潮的预报和应对中,需要重视可能正面登陆的和9—10月的外海转向型台风;8月和9月是江苏沿海出现风暴潮灾害可能性较高的月份,若这两个月的天文高潮与风暴增水叠加合适,极有可能出现达到黄色警戒潮位以上的高潮位。

Observations of boundary layer parameters and suspended sediment transport over the intertidal flats of northern Jiangsu, China

A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.

Invasive Spartina alterniflora-induced factors affecting epibenthos distribution in coastal salt marsh, China

Artificially introduced cordgrass, Spartina alterniflora, rapidly colonized the intertidal flats of the Jiangsu coast, eastern China. The epibenthos on an intertidal flat invaded by S. alterniflorawere studied, to identify how local epibenthos species react to an altered environment. Epibenthic samples and surficial sediment samples were collected along a shore-normal profile in 50 quadrats at ten stations across the Spartina salt marsh; and five control quadrats for a station located on the barren sandy-mud flat. The grain size param- eters of the surficial sediments show that S. alterniflora altered the grain size gradient along the profile of the intertidal zone by trapping fine-grained sediments. Spartina alterniflora could inhabit lower elevation- s than indigenous salt marsh vegetation, thus creating larger areas of finer surficial sediments, which was suitable for not only native epibenthic species but also species which do not exist on the barren sandy-mud flat. Correlation analyses show that the epibenthos were sensitive to sediment grain size and type, on the invaded S. alterniflora salt marsh. Further, there was an interspecific relationship affecting the distribution of epibenthos. The results show that epibenthos preferred ecological niches, within the Spartina salt marsh, even in the same sampling station.

Analysis of Jiangsu Tidal Flats Reclamation from 1974 to 2012 Using Remote Sensing

Jiangsu has the most abundant tidal flat resources among China＇s coastal provinces. To ease the conflict between the growing population and shrinking usable land and to promote regional sustainable development, large-scale coastal reclamation development activities have been performed in Jiangsu Province since 1949. The present study has integrated multi-source remote sensing images during 1974 to 2012 by using a Multi-point Fast Marching Method （MFMM） to extract the Jiangsu coastal reclamation areas for different time periods. The temporal and spatial patterns of the extent and elevation of the reclamation areas were analysed in order to determine the unused potential for future reclamation. It will provide information necessary to support the development and construction of tidal flats in Jiangsu. Results show that： （1） the reclaimed tidal fiats along the Jiangsu coast cover more than 19.86×10^4 hm^2, of which 13.97×10^4 hm^2 is located in Yancheng, 4.84×10^4 hm^2 in Nantong, and 1.05×10^4 hm^2 in Lianyungang; （2） the average elevation of the reclaimed Jiangsu tidal flats has gradually decreased over the last 40 years, while those in Dongtai and Rudong have showed particularly accelerated decrease since the 1990s; and （3） in 2012, very few unused tidal flats two meters above the sea level are left along the Jiangsu coast, and mainly concentrated in Yancheng. As there are still reserving some coastal land resources between 0-2 m, providing us with a potential for future development. All of these findings may be useful for researchers and local authorities for the development and utilization of tidal flat resources in Jiangsu.