Zhejiang Coast Research Articles

Identification of Main Oyster Species and Comparison of Their Genetic Diversity in Zhejiang Coast, South of Yangtze River Estuary

Oysters are an important aquaculture species distributed worldwide, including in Zhejiang Province, located on the east coast of China. Because of the high diversity and complicated introduction history of oysters and their seedlings, there has been much disagreement regarding the origin of each species, and the dominant and indigenous species remain unclear. We sampled 16 batches of oysters from seven sites in three aquaculture bays and found two main oyster species, Crassostrea sikamea and Crassostrea angulata. The former occupied the higher intertidal zone and comprised more than 70% of the cultured oysters. Based on the cytochrome oxidase C subunit I (COI) and mitochondrial noncoding region (MNR), C. sikamea showed higher genetic diversity than C. angulata. The analysis of molecular variance among COI sequences of these species from the Xiangshan Bay populations were comparable to those of other populations and showed that most of the molecular variance was within groups, which was consistent with the low pairwise fixation index FST values. The neutrality test revealed that C. sikamea experienced population expansion events, whereas for C. angulata, the significant Fu’s Fs and non-significant Tajima’s D test results may indicate a possible population expansion event, implying that C. sikamea is likely an indigenous species. The method established based on internal transcribed spacer 1 digestion by the HindIII restriction enzyme is useful for identifying C. sikamea and C. angulata in the local region. The specific primers on the MNR sequence show potential for distinguishing C. sikamea from four other important Crassostrea oysters. These results highlight the abundance of C. sikamea on the Zhejiang coast and lay the foundation for protecting and utilizing the local oyster germplasm resources and for the sustainable development of the oyster industry.

Analysis of the influence about back side sand pile on the stability and deformation of the Pile foundation frame Seawall

The article analyzes the influence about backwater side sand piling of a Pile-based frame Seawall along the east coast of Zhejiang on the stability and deformation. When sand is not piled on the backwater side of the Seawall, the overall safety factor of the Seawall is 1.619∼2.941, which meets the specifications and design requirements; when the backwater side is piled with sand or sand piling+vehicle driving, the overall safety factor of the Seawall is respectively 1.119∼1.617, 1.107∼1.599, and the safety factor of some working conditions is less than required 1.20, which does not meet the specifications and design requirements. According to the simulation results of the MIDAS finite element software, the settlement of the Seawall within 3 months of sand piling is 22.0mm, and the horizontal displacement is 7.9mm, indicating that the sand piling on the back side has a great influence on the deformation of the Seawall. The settlement and horizontal displacement of the Seawall are too large, resulting in a large reduction in the vertical and horizontal bearing capacity of the pile foundation, which has a huge impact on the overall stability and safe operation, severely disrupting the stress balance of the Seawall structure, and causing landslides on the water-facing side risk.

A Spatially Weighted Neural Network Based Water Quality Assessment Method for Large-Scale Coastal Areas.

The accurate assessment of large-scale and complex coastal waters is a grand challenge due to the spatial nonstationarity and complex nonlinearity involved in integrating remote sensing and in situ data. We developed a water quality assessment method based on a newly proposed geographically neural network weighted regression (GNNWR) model to address that challenge and obtained a highly accurate and realistic water quality distribution on the basis of the comprehensive index of Chinese Water Quality Classification Standards. Using geostationary ocean color imager (GOCI) data and observations from 1240 water quality sampling sites, we conducted experiments for a typical large-scale coastal area of the Zhejiang Coastal Sea (ZCS), People's Republic of China. The GNNWR model achieved higher prediction performance (average R2 = 84%) in comparison to the widely used models, and the obtained water quality classification (WQC) maps in May of 2015-2017 and August 2015 can depict intuitively reasonable spatiotemporal patterns of water quality in the ZCS. Furthermore, an analysis of WQC maps successfully illustrated how terrestrial discharges, anthropogenic activities, and seasonal changes influenced the coastal environment in the ZCS. Finally, we identified essential regions and provided targeted regulatory interventions for them to facilitate the management and restoration of large-scale and complex coastal environments.

Marine embankment slide and reinforcement simulation based on discrete numerical method

Hybird discrete numerical methods inclusive of DEM and XFEM were developed in the study to simulate the marine embankment slide in Zhejiang coast. The study derived the comprehensive fields that included the displacement, stress, internal forces and reliality factor. Therefore, the typical marine embankment slide simulation and reinforcement effect evaluation were completed. The methods and results were helpful for the marine embankment cases.

Characteristics of Sedimentary Organic Matter and Phosphorus in Minor Rivers Discharging into Zhejiang Coast, China

In this study, the spatial distribution of lignin-derived phenols, bulk elemental composition and different phosphorus (P) species in surface sediments along six rivers discharging into Zhejiang coast, Southeast China, were investigated to improve the understanding of the carbon and P dynamics in these small river systems. The Shuang, Jiao, Ximen, Feiyun and Ao Rivers have total organic carbon (TOC) ranging from 0.29% to 2.77% and Λ (total lignin in mg/100 mg TOC) ranging from 0.24 to 4.24; Qiantang River has the lowest Λ (0.08–0.19) but the highest TOC (1.05%–6.46%). Jiao, Ximen, Feiyun and Ao Rivers have mean the total P (TP) and bioavailable P (BAP) of 34 to 124 mg/kg and 29 to 89 mg P/kg, and mean OC/OP molar ratio of 397–917. Qiantang River has the lowest mean TP and BAP of 13 mg P/kg and 7 mg P/kg, and highest OC/OP of 18,753; whereas Shuang River has the highest mean TP and BAP of 645 mg P/kg and 559 mg P/kg, and lowest mean OC/OP of 90. The lowest Λ, TP and BAP, but highest OC/OP, in the Qiantang River could be due to tidal bore causing rapid cycling of carbon and P. Trends of slight decrease in abundance of OC, Λ, TP and BAP, but increasing ratios of vanillic acid to vanillin [(Ad/Al)v], syringic acid to syringaldehyde [(Ad/Al)s] and OC/OP farther downstream of the rivers indicate a continuous decomposition of organic matter during transport along the rivers.

Typhoon Haikui Induced Sea Surface Temperature Cooling and Rainfall Influence over Zhejiang Coastal Waters

Strong winds in typhoons cause upwelling/mixing of seawater and hence a reduction in sea surface temperature (SST). The SST cooling depends on the intensity and translation speed of the typhoon. In this paper, typhoon Haikui’s induced SST cooling was analyzed with satellite-derived data. Haikui produced SST cooling on both sides of the track: the right-side cooling was due to upwelling/mixing (which depend upon the intensity of the typhoon), and rainfall induced SST cooling on the left side. Typhoon Haikui induced SST cooling over the coastal region was found to be about 1.9 oC due to lower translation speed leading to upwelling, and also due to rainfall. The spatial extent of the cooler SST increased after the typhoon made landfall, especially over coastal regions. SST cooling over the study area has an inverse relation both to the typhoon’s translation speed and to rainfall. Due to heavy rainfall and air-sea interaction processes, SST cooling was higher on coastal waters, and cool waters persisted for a few days after the typhoon landfall.

Environmental magnetic properties used to assess sediment sources and transport patterns in the muddy area along the Zhejiang coast, China

The muddy area along the Zhejiang coast contains a record of historical environmental conditions and can facilitate a better understanding of the linkages among terrestrial sediment fluxes, littoral sediment dynamics, and climate change. However, the origin and transport of the sediments in this muddy area has been open to debate. We present a detailed environmental magnetic study with high-density sampling to provide magnetic evidence for the input and transport of the materials in this region. Our results show that magnetic minerals in the sediments are generally dominated by magnetite and titanomagnetite with minor amounts of maghemite and hematite. The magnetic minerals are mainly pseudo-single domain (PSD) particles, and decrease in concentration seawards. Based on the coastal current flow and magnetic characteristics, we argue that the sediments in this area are mainly derived from the Changjiang River, the mountainous rivers in the surrounding islands, and erosion by coastal currents. Notably, the increase in sediment input from small mountainous rivers and coastal erosion in the Zhejiang coastal area is primarily associated with decreased sediment discharge from the Changjiang River. However, there is no evidence of the accumulation of Taiwan-derived sediment in this area.

Correlation between the Construction of Zhejiang Coastal Military Settlements in the Ming Dynasty and the Natural Terrain

Tan, L.; Zhou, J.; Zhang, Y.; Liu, J., and Liu, H., 2020. Correlation between the construction of Zhejiang coastal military settlements in the Ming Dynasty and the natural terrain. In: Gong, D.; Zhang, M., and Liu, R. (eds.), Advances in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 106, pp. 381–387. Coconut Creek (Florida), ISSN 0749-0208.The military settlement for the coastal defense of Zhejiang Province in the Ming Dynasty (1368–1644) is representative of military settlements throughout ancient China. The distribution of military power was closely related to the natural terrain, and its military hierarchical structure conformed to fractal systems. Based on fractal theory, the box dimension method, which has been widely used in geography, was selected to calculate the geomorphic fractal dimension of coastal-defense settlements within a certain range. The traditional box-counting method was optimized by ArcGIS to obtain the geomorphic-complexity index. By analyzing the correlation between this index and the military-force scale data extracted from historical books, this article breaks through the qualitative conclusions of general studies and obtains the quantitative influence of the complexity of the natural terrain on military construction, especially on the distribution of the size of garrison troops. This method quantifies complex concepts through fractal dimensions and provides a new idea for research on the influence of the natural environment on the formation of traditional settlements.

Wave characteristics in the nearshore waters of Sanmen bay

The wave characteristics in the bay of central coast of Zhejiang are studied based on the AWAC-measured data for 1 year off Sanmen at 7.5 m water depth. The observed wave parameters are analyzed by statistical analysis and linear regression analysis, and moreover the variations of wave parameters and wave spectra in Sanmen Bay under the influence of typhoon are discussed. The results show that: The dominant wave direction and the strong wave direction are both E due to the topography of Sanmen Bay, while the one-tenth wave height (H1/10) is mainly under 0.8 m with a typical Rayleigh distribution of wave height. Due to the influence of typhoon Talim, the maximum wave height (Hmax) of 2.71 m was observed on 14 September 2017. The wave spectra estimated during typhoon Talim are mainly double-peaked, and the sea waves are mixed waves consisting of swells and wind-seas, when the low frequency swells about 0.08 Hz are in a dominant position and the high frequency wind-seas about 0.3 Hz are relatively weak. This study will be important as reference in the design of offshore structures as well as for disaster prevention and mitigation.

Spatial distribution, source identification, and risk assessment of heavy metals in seawater and sediments from Meishan Bay, Zhejiang coast, China

The aim of this study is to determine the spatial distribution, potential sources, and ecological risks of 8 heavy metals (Zn, Cu, Cr, Ni, As, Cd, Hg, and Pb) in Meishan Bay, Zhejiang coast, China. Surface water (n = 31), bottom water (n = 31), and surface sediments (n = 31) were collected. Water physicochemical properties and sediment resuspension were important factors affecting spatial distributions of heavy metals. The spatial distributions of Cr, Ni, Pb, As, Cu, and Zn were consistent with the clay distribution. Atmospheric deposition was the main source of Cd and Pb, mainly from industrial and transportation exhausts, while Zn was mainly from ship transportation. Agriculture pesticides and sewage wastewater were considered as the main sources for Hg. The geo-accumulation index results indicated that there was limited pollution of Cu, Zn, Cr, Pb, and As, and mild to moderate pollution of Cd and Hg. The potential ecological risk assessment suggested a high ecological risk of Hg in Meishan Bay.

Analysis of Heterogeneous Settlement of Connecting Sections of Embankment on Deep Soft Ground Based on PLAXIS

The article analyzes the uneven settlement of the dam gate connection section of a reclamation project along the coast of eastern Zhejiang by PLAXIS finite element software, and compares and analyzes the in-situ monitoring results to understand the settlement development law of the dam gate connection section during operation and the location of the largest uneven settlement. Through analysis, after the sluice and the seawall are connected, the sluice settlement in the first year of the operation period is 5.51 mm, the settlement at the seawall is 105.30 mm, and the settlement difference is 99.79 mm; the cumulative settlement of the sluice is 9.01 mm, and the cumulative settlement at the seawall is 214.00 mm and the settlement difference is 204.99 mm. The uneven settlement of the connecting section of the dyke is mainly manifested at the junction of the empty box of the sluice and the riprap area of the seawall. When the uneven settlement is large, it will cause road cracks.

The impact of different historical typhoon tracks on storm surge: A case study of Zhejiang, China

Abstract A typhoon-induced storm surge simulation system was developed for the Zhejiang coast consisting of an assimilation wind-pressure model and the ADCIRC+SWAN model. The simulated peak and phase of the storm surge were found to match the observed data very well. We discussed the sensitivity of the modeled storm surge to changes in the computational domain, and compared the simulation results from the assimilation wind-pressure model and the symmetric Holland model. The sensitivity of 23 newly-constructed typhoon tracks to the Wenzhou City storm surge was investigated using the validated storm surge simulation system. The storm surges vary significantly when the typhoon tracks are at different positions relative to the station. Given this, the impacts of 55 historical tracks from 1951 to 2017 on the coast of Zhejiang Province were simulated and analyzed. Although the typhoon tracks with no landfall on China's eastern mainland posed a threat to the entire Zhejiang coast, the tracks making landfall at Fujian were most likely to cause a storm surge in Wenzhou City, Zhejiang Province. The results of this study will help to increase the understanding of typhoon storm surge along China's coastal areas and may serve as reference material in studies of disaster reduction and prevention techniques in the Zhejiang region.

Analysis of spatio-temporal distribution characteristics and fog forming conditions of Zhejiang coast in recent ten years

Based on the hydrometeorological observation data of Zhejiang coastal observation station from 2009 to 2018, the temporal and spatial distribution characteristics and fogging conditions of sea fog along the coast of Zhejiang Province were analyzed in this paper. The result shows that the average annual fog day along the coast of Zhejiang Province is 112 days according to the situation that the sea fog occurs as long as there is one station along the coast of Zhejiang Province. The fog season is from March to June and the sea fog occurs in the middle of the night and early in the morning. The spatial distribution of sea fog along the coast of Zhejiang Province is more in the middle of the two ends and the average annual fog days of each station are in the range of 19.2-82.0 days. Under the condition of fog, most of the relative humidity in Zhejiang coastal area is greater than or equal to 90%, the average temperature difference between gas and water is-0.5 - 2.1°C, and the direction of fog wind is mainly eastward. More than 93.6% of the sea fog occurs under the condition that the wind force is less than or equal to level 5. There are four main types of weather situation affecting the occurrence of sea fog in coastal areas of Zhejiang Province, including inverted trough type, low pressure sea exit type, weak cold air type and high-pressure sea entry type. When the continuous sea fog process occurs, the weather situation usually goes through the high-pressure sea entry type, the inverted trough type and the low pressure sea exit type. The wind direction will change with the variation of weather situation and the wind force will be less than or equal to 4 levels. When the wind is greater than level 5, the wind changes from west to southwest, and the sea fog tends to dissipate. Thick fog or strong fog occurs mainly in the middle of the night, early in the morning and around the evening.

Distribution and source of heavy metals in the sediments of the coastal East China sea: Geochemical controls and typhoon impact

The present study conducted a comprehensive study on the distribution and source of heavy metals (Cu, Zn, Ni, Pb, Cd) in the sediments of the coastal East China Sea (ECS), one of the most developed regions in China with very active land-sea interactions, using 119 surface sediment samples and a 2-m sediment core collected after super Typhoon Chan-hom in 2015. Heavy metals in the surface sediments exhibited metal-dependent and regional distribution patterns, showing higher levels in the southern inner shelf (SIS) than the Yangtze River estuary (YRE), and generally being evaluated as unpolluted to moderately polluted in the coastal ECS (except few sites adjacent to Xiangshan Harbor were strongly polluted by Cd). Based on the organic carbon isotope compositions (δ13C) data as well as the strong correlations between heavy metals and natural major elemental contents (Al2O3, Fe2O3, and SiO2), we suggest natural weathering detritus as the major source of heavy metals in the YRE region and the spatial distributions were highly controlled by sediment grain size and organic matter. In contrast, the spatial distributions of heavy metals in the SIS region were less correlated with sediment properties, due to more complex sources and stronger hydrodynamic impacts. The vertical distribution of heavy metals in the sediment core indicated significant enrichments since 1950s, but showed unusual gradually decreasing trends in top layer (30 cm–0.5 cm), attributing to the strong disturbance of super Typhoon Chan-hom on sediment transportation and metal partitioning. Besides, we also observed that heavy metal levels in shallow water regions of Zhejiang coast were reduced due to the passage of typhoon. Such strong impacts of super Typhoon Chan-hom on heavy metal distributions in the ECS indicates that the impacts of extreme hydrodynamic events should raise more concern when assessing the distribution and potential risks of contaminants in coastal regions.

Species identification of small fish in Xixuan Island coastal waters of Zhoushan using DNA barcoding

This study aimed to assess the fish species composition in Xixuan Island coastal waters and confirm the applicability of DNA barcoding in fish identification. Fish samples were caught with a gill net in December 2016 and in January, February, April, May and June 2017, and the fish species in these samples were analyzed and identified via both traditional morphological methods and DNA barcoding (mitochondrial 12S rRNA). The sample contained 1,357 individuals, the majority of which were Tridentiger barbatus (829 individuals). A total of 154 individuals were selected for DNA barcode analysis, and 147 sequences were obtained. A total of 35 species, which belonged to six orders and 16 families, were accurately identified. One species was identified to the genus level (Repomucenus), and only one was identified to the family level (Moridae). Most of the species belonged to Gobiidae (12 species). With the exception of those in Moridae, the identified species were commonly detected on the Zhejiang coast. The average Kimura two-parameter (K2P) distances within species, genera, families, and order and between orders were 0.15%, 4.44%, 14.96%, 20.37%, and 26.20%, respectively. The intraspecific K2P distance was markedly greater than the interspecific distance. The A + T content (55.41%) was higher than the G + C content (44.58%). Phylogenetic tree analysis showed that individuals belonging to the same species were clustered together and could be clearly distinguished. Mitochondrial 12S rRNA can be effectively used for juvenile and adult fish identification and has good application prospects in fish species identification. The investigation and species identification of small fish collected monthly from Xixuan Island coastal waters are conducive to understanding the distribution characteristics and species composition of fish in the Zhoushan coastal area.

Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study

Abstract. An airborne cloud seeding experiment was conducted over the eastern coast of Zhejiang, China, on 4 September 2016 during a major international event held in Hangzhou. In an attempt to reduce the likelihood of rainfall onset, a major airborne experiment for weather modification took place by seeding hygroscopic agents to warm clouds to reduce cloud droplet size. The effectiveness of seeding is examined, mainly for stratiform clouds with patchy small convective cells. A radar-domain-index (RDI) algorithm was proposed to analyze the seeding effect. The threshold strategy and the tracking radar echo by correlation (TREC) technique was applied in the domain selection. Factors analyzed include echo reflectivity parameters such as the mean and maximum echo intensity, the anomaly percentage of the grid number of effective echoes, the fractional contribution to the total reflectivities, and the vertically integrated liquid (VIL) water content during and after the seeding process. About 12 min after seeding ended, the composite reflectivity of seeded clouds decreased to a minimum (< 10 dBz) and the VIL of seeded clouds was ∼0.2 kg m−3. The echo top height dropped to ∼3.5 km, and the surface echoes were also weakened. By contrast, there was no significant variation in these echo parameters for the surrounding non-seeded clouds. The seeded cell appeared to have the shortest life cycle, as revealed by applying the cloud-cluster tracking method. The airborne Cloud Droplet Probe (CDP) measured cloud number concentration, effective diameter, and liquid water content, which gradually increased after the start of cloud seeding. This is probably caused by the hygroscopic growth of agent particles and collision–coalescence of small cloud droplets. However, these parameters sampled at ∼40 min after seeding decreased significantly, which is probably due to the excessive seeding agents generating a competition for cloud water and thus suppressing cloud development and precipitation. Overall, the physical phenomenon was captured in this study, but a more quantitative in-depth analysis of the underlying principle is needed.

Sedimentary signals of the upwelling along the Zhejiang coast, China

The muddy deposits of the Zhe–Min coastal area have attracted much recent research interest. However, the sedimentary processes that dominate along the Zhejiang coast remain controversial. Determining sedimentation rates is important for understanding sedimentary processes and depositional patterns. In the present study, 23 vibrocores were collected from the muddy area along the Zhejiang coast to analyse their sediment accumulation rates over the past 100 years using 210Pb geochronology. Three types of typical excess 210Pb profiles were identified in the sediment vibrocores. The spatial distribution of the sedimentation rates derived from the 23 vibrocores, as well as previously published data, demonstrated that the middle part of the study area around 29°N experienced relatively high sedimentation rates, and that the rate of deposition gradually decreased landwards and seawards. The location of high sedimentation rates is approximately consistent with that of the Holocene maximum thickness deposition, finest surface sediments and high concentration of chlorophyll, resulting from the existence of upwelling along the Zhejiang coast besides the fluvial inputs.

Safety Problems in Typhoon Weather of Anchored Fishing Vessels in Zhejiang Coast

Coastal fishing boats play an important role in the development of our economy. Typhoons have always had an important impact on the safety of fishing boats along the coast. Coastal mooring fishing boats are smaller in size and weaker in typhoon resistance than bulk carriers and container ships. This paper studies the safety guarantee of fishing boats in zhejiang coastal areas in typhoon weather. By consulting and studying relevant literatures, the influences of external conditions and ship conditions on the safety of fishing boats are discussed respectively. Finally, this paper summarizes the measures to cope with the typhoon weather, by analyzing the impact of various aspects.

Genetic diversity and metapopulation structures of two intertidal species along the coast of Zhejiang, China: implications for conservation

To priority areas for conservation in the coast of Zhejiang, this study attempts to map the spatial patterns of the intra-specific genetic diversity of two intertidal species, Septifer virgatus and Tetraclita japonica, using the sequences of mitochondrial DNA cytochrome oxidase subunit I (COI) and large subunit ribosomal RNA (16S rRNA) genes. In total, 129 and 112 specimens were collected from 12 and 11 populations for S. virgatus and T. japonica, respectively. These two species revealed congruent population historical signals, including (1) high levels of haplotype diversity and low values of nucleotide diversity, (2) post-LGM expansion, (3) the lack of population genetic structure, sharing haplotypes over all sampling populations, (4) gene flow connections, and (5) migration directions. Largely, all results supported that all sampling populations could be divided into two main metapopulations, exhibiting a northern and southern distribution. The north metapopulation could be considered as a marine protected area. The genetic patterns of the two species should be considered in the management and conservation in the islands along the Zhejiang, China.

Study on the drift caused by ship leaving out of control with dragging anchor in Zhejiang Coastal

The ship anchored in bad weather, and when dragging anchor, emergency manipulation is the key to ensure the safety of the ship’s runaway drift. This paper analyses the preventive measures of ship out of control from several aspects, such as the reason of dragging anchor, the accident of dragging anchor and the emergency plan after dragging anchor.