Yellow Sea Of China Research Articles

Estimating structure and geoacoustic parameters of sub-bottom by using spatial characteristics of ocean ambient noise in shallow water

The field of ocean ambient noise contains numerous information about the water column, especially the information about the sub-bottom. The geoacoustics parameters of sub-bottom are very important factors influencing the spatial characteristics of ocean ambient noise field. For different layered structures of the sub-bottom, the bottom-loss shows different critical angles according to sound speed of each layer, while the structure of interference fringe is dependent on the thickness of the sediment. Flux theory of ocean ambient noise proposed by Harrison is used in this paper. Using this theory, the curve of bottom-loss can be extracted by computing the ratio between the energy of the upward wave and the downward wave. From the ideal reflection coefficient, the influence of sound speed, density and attenuation coefficient on reflection coefficient are discussed in the situation of the sub-bottom of acoustic half space, while the reflection coefficient of 1 layer of sediment is simplified. Initially, the reflection coefficient is the sum of sound waves reflect from the sub-bottom transmitted from the same source at the same angle. Only the first two terms are reserved, so that the mechanism of the interference fringe can be easily discussed. The structure of interference fringe can be explained which is affected by the thickness of the sediment. The curve of bottom-loss oscillates periodically with the increase of the thickness of the sub-bottom. Also by the reciprocity principle, the interference fringe of the reflection coefficient can be explained by considering the sound transmitted from two point sources at the surface of the sea. In this way the same result can be obtained as that from the method of simplification. The result of the experiment in China Yellow Sea shows that the information about the reflection coefficient of the sub-bottom can be extracted by the vertical azimuth spectrum of ocean ambient noise. In this way, the critical angle can be obtained, so that the sound speed of the sub-bottom can be estimated by using Snell law. The structure of the interference fringe is also contained in the bottom-loss curve estimated by ocean ambient noise. Therefore the layered structure, sound speed and the thickness of the layer of the sub-bottom can be estimated.

Microplastic ingestion by the farmed sea cucumber Apostichopus japonicus in China

Microplastic ingestion by the farmed sea cucumber is undocumented. Microplastics were isolated from the sea cucumber Apostichopus japonicus that was collected from eight farms along the Bohai Sea and the Yellow Sea in China. To examine microplastic ingestion, the intestines were isolated, digested and then subjected to the floatation test. The microplastic abundance in the sediment ranged from 20 to 1040 particles kg−1 of dry sediment, while the ingested microplastics ranged from 0 to 30 particles intestine−1. After filtering the coelomic fluid, the extracted microplastics from the coelomic fluid ranged from 0 to 19 particles animal−1. Thus, we speculated that microplastics may transfer to the coelomic fluid of sea cucumber. The ingested microplastics did not correlate with the animal body weight but was site dependent, suggesting that sea cucumber may serve as sentinel for microplastic pollution monitoring in the sediment. The microplastics were identified by Fourier transform infrared micro spectroscopy, and the polymer types were mainly cellophane, polyester, and polyethylene terephthalate. This study revealed that, microplastics widely existed in sea cucumber farms, and that sea cucumbers ingest microplastics as suitable with their mouth open. Moreover, the microplastics might transfer to the coelomic fluid of the sea cucumber. Further investigations are needed to assess the chronic effect of the microplastics on the growth and physiological status of the sea cucumber.

Transient expression of the enhanced green fluorescent protein (egfp) gene in Sargassum horneri

Sargassum horneri is a macroalga widespread in North Asia-Pacific region, and these years its bloom has caused huge damage to the environment and the economic in China. To make up the blank on genetic engineering research, a transient transformation system for the multicellular marine brown alga S. horneri was established in this research. The algae used in this research were collected from the Yellow Sea of China and verified as a same species S. horneri with analysis of molecular markers. The S. horneri parietal leaves were transformed with the enhanced green fluorescent gene as the reporter by micro-particle bombardment. The results show that GFP is an effective transgene reporter for S. horneri and that particle bombardment is a suitable method for transformation of S. horneri. Through selection of four different promoters for EGFP and six groups’ bombardment characters, the highest transformation efficiency approximately 1.31% was got with the vector pEGFP-N1 at bombardment characters 900 spi and 6 cm distance. This research paves a way for the further research and application of S. horneri.

Alternative habitat: the importance of the Nanpu Saltpans for migratory waterbirds in the Chinese Yellow Sea

SummaryThe natural coastal wetlands of the East Asian-Australasian Flyway (EAAF) are disappearing at alarming rates, leading to rapid declines of many populations of waterbirds in the most species-rich flyway in the world. The identification and assessment of possible alternative habitats that may buffer the loss of natural wetlands should, therefore, be a priority for the conservation of migratory waterbirds using this flyway. Coastal saltpans are functional wetlands that support large numbers of waterbirds worldwide. The Nanpu Saltpans in the northern Bohai Bay of the Yellow Sea in China are one of the largest (290 km2) saltpan complexes in the world. In this paper, we document the value of the Nanpu Saltpans for supporting waterbirds. The surveys, carried out from 2013 to 2016, included waterbird counts in the saltpans (93 km2) at high and low tide and on the adjacent natural tidal flats (57 km2) at low tide. Of the 89 waterbird species recorded, 27 had maximum counts exceeding the 1% threshold value of estimated flyway populations. The maximum counts of waterbirds in northward migration and southward migration in the Nanpu Saltpans were 96,000 and 93,500, respectively, including both foraging and roosting birds; these figures do not account for turnover, so the total number of birds using the site is likely to be higher. The maximum counts on the adjacent tidal flats at low tide amounted to 73,000 and 20,000 waterbirds during northward and southward migration, respectively, and most of them were foraging birds. In the boreal winter, few birds fed in the saltpans, but several thousand fed on the tidal flats. Waterbirds used the inland ponds (2.0–18.0 km from the intertidal area) mainly for feeding both during low tide and high tide and used the nearshore ponds (0.3–4.3 km from the intertidal area) mainly for high-tide roosting. Some species, such as Black-tailed Godwit Limosa limosa, Marsh Sandpiper Tringa stagnatilis, Pied Avocet Recurvirostra avosetta, and Black-winged Stilt Himantopus himantopus, occurred mainly in the saltpans; other species preferred tidal flats, such as Red Knot Calidris canutus, Great Knot Calidris tenuirostris, Bar-tailed Godwit Limosa lapponica, Eurasian Curlew Numenius arquata, Relict Gull Larus relictus, and Grey Plover Pluvialis squatarola. This study clearly demonstrates the joint ecological function of the Nanpu Saltpan complex and adjacent tidal flats as a key staging area for waterbirds in the EAAF, and as such both urgently warrant protected status.

Sedimentary Characteristics of the Second Marine Layer During the Late Marine Isotope Stage 3 in Southern Yellow Sea and Their Response to the East Asian Monsoon

We use the particle size of sediments in core YS01A to study the sedimentary environment of the mud deposit in the central South Yellow Sea of China during late Marine Isotope Stages 3 (MIS3; 40.5 kyr–31.3 kyr). In addition, the East Asian Monsoon and its relationship with the North Atlantic Ocean climate change are discussed based on the sensitive grain-size calculation and the spectrum analysis. The results show that during late MIS3, the muddy area in the central South Yellow Sea experienced the evolution of coastal facies, shallow marine facies, coastal facies, and continental facies, with weak hydrodynamic conditions. Compared with other climate indicators, we found that there were many century to millennium-scale climate signals documented in the muddy area sediments in the central South Yellow Sea. According to our particle size results, three strong winter monsoon events occurred at 37.6 kyr, 35.6 kyr and 32.2 kyr. The East Asian Winter Monsoon records in core YS01A are consistent with the Greenland ice core and the Hulu cave stalagmite δ18O. The millennial and centennial scale cycles, which are 55 yr, 72 yr, 115 yr, 262 yr respectively, correspond to solar activity cycles, while the 1049 yr and 2941 yr cycles correspond to the Dansgaard-Oeschger cycles. These cycles indicate that the paleoclimate evolution of the area was controlled by the solar activities, with the high-latitude driving thermohaline circulation as the main energy conveyor belt, followed by the sea-air-land amplification of the winter monsoon variation in the central Yellow Sea in the late MIS3.

Complete genome sequence of the marine fish pathogen Vibrio anguillarum and genome-wide transposon mutagenesis analysis of genes essential for in vivo infection

Vibrio anguillarum is a notorious bacterial pathogen that causes vibriosis in various marine farmed fish species. The highly pathogenic V. anguillarum strain MVM425 has been isolated from moribund turbot in the China Yellow Sea, but the genetic basis for its pathogenesis is undefined. Complete genome sequencing uncovered that the bacterium encodes 3985 protein-coding sequences (CDSs) on two chromosomes and 62 CDSs on the virulence plasmid pEIB1. To investigate the genes that are essential for its in vitro and in vivo growth, we applied transposon insertion sequencing technology (Tn-seq) to screen a highly saturated transposon insertion mutant library grown in Luria-Bertani broth with 2% NaCl (LB20) and in its natural host turbot. Tn-seq identified 473 and ∼173 putative genes as essential for its growth in rich medium and the in vivo infection process, respectively. Additionally, our analysis revealed that the genes are associated to various fitness levels in the liver, spleen and kidney, suggesting different genetic requirements for colonization in these organs. Furthermore, we validated our Tn-seq data using gene knockout mutants and in vivo infection experiments. Comprehensive functional genomics analysis highlighted the conditionally essential genes for important pathways involved in energy metabolism, nitrogen metabolism, nucleotide synthesis, amino acid synthesis, cofactors, siderophore synthesis, secretion (T1SS, T2SS, and T6SS), quorum sensing, and flagellum biosynthesis. This study provides a wealth of information about V. anguillarum genes related to infection in fish and will facilitate the understanding of its pathogenesis as well as the development of diagnostics and vaccines against the pathogen.

Karlodinium zhouanum, a new dinoflagellate species from China, and molecular phylogeny of Karenia digitata and Karenia longicanalis (Gymnodiniales, Dinophyceae)

:Little is known about the diversity and biogeography of the toxigenic dinoflagellate genera Karlodinium and Karenia because their cells are unarmoured and often small. We isolated single cells from Chinese waters to establish five Karlodinium cultures, and carried out single-cell polymerase chain reactions of eight cells of Karlodinium and Karenia isolated directly from field samples. We also obtained large-subunit (LSU) ribosomal DNA and internal transcribed spacer (ITS) sequences from the same samples used for descriptions of Karenia digitata and Karenia longicanalis. Five cultures of Karlodinium from the South China Sea and Yellow Sea of China were established and subjected to light, scanning electron, and transmission electron microscopy. These strains had a sulcal intrusion, a short apical groove, and six chloroplasts, each with an internal lenticular pyrenoid, but lacked a ventral pore. Pigment analysis showed that fucoxanthin was the main accessory pigment. On the basis of unique morphology and corroboration by molecular phylogeny, these strains were described as Karlodinium zhouanum sp. nov. LSU or ITS sequences (or both) of another eight cells revealed the presence of Karlodinium australe, Karenia longicanalis, and K. papilionacea in the East China Sea for the first time. LSU sequences showed that Karenia digitata differed from Karlodinium decipiens at only one position (99.86% similarity), and Karenia longicanalis differed from K. umbella at only four positions (99.45% similarity). Maximum-likelihood and Bayesian inference analyses supported the classification of Karenia digitata within Karlodinium, and demonstrated that presence of a ventral pore was not a reliable generic character for Karlodinium. Our results also indicated that LSU sequences might be too conservative to differentiate species of Karenia and Karlodinium.

Drag on and flow through the hydroid-fouled nets in currents

Biofouling is an inevitable problem in marine aquaculture and it is prone to cause many negative effects on the hydrodynamic behavior of the aquaculture facility. In this study, the dominant biofouling on the netting of fish farms in the Yellow Sea of China was determined by field sampling. Plane nets with various levels of biofouling were obtained by submerging nets at different depths and for different durations. Drag acting on the biofouled nets in currents were investigated using laboratory experiment. The results indicate that drag acting on the net increases with increasing level of biofouling. Compared to the clean net, the accumulation of biofouling can lead to over 10 times more hydrodynamic load on nets. Flow fields around the biofouled nets were simulated using a porous-media fluid model which was validated by corresponding laboratory experiment. As the level of biofouling increases, the flow velocity downstream from the net decreases continuously. The net with the greatest level of biofouling produces the most serious shielding effect with 21.4% reduction in flow velocity. Using the proposed empirical equations, both the drag on and flow velocity downstream from a hydroid-fouled net can be predicted.

Distribution Characteristics of the Extreme Storm Tides in the Radial Sand Ridges Area of the South Yellow Sea in China

Xie, D.H.; Tan, Y.; Chu, A.; Zhou, T.Y., and van Maanen, B., 2018. Distribution characteristics of the extreme storm tides in the radial sand ridges area of the South Yellow Sea in China In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 856–860. Coconut Creek (Florida), ISSN 0749-0208.The aim of this study is to understand the tidal characteristics in the radial sand ridges area (South Yellow Sea, China) considering the most adverse metrological and hydrodynamic condition. Based on data analysis, at least 30% of the annual highest tidal levels in the South Yellow Sea are caused by the combination of storm surge and astronomical spring tides. Among the top 10 extreme high tidal levels, such combinational effects account for over 60%. A 2-D numerical model is applied to study distributions of the extreme high tidal levels influenced by typhoons with various tracks in the South Yellow Sea. Typhoon characteristics are classified into four categories: the front landing, the front leaving, the offshore moving and other types. As such, four different combinations with the same astronomical tide are examined. The front landing and the offshore moving tracks are of specific interest, as they lead to the most significant surge in coastal areas, especially at Jianggang and Liyashan. Temporal-spatial patterns of the extreme storm tides are presented to identify risks of coastal flooding in the radial sand ridges area.

Assessing Impacts of large-scale Coastal Land Reclamation on Marine Environment on the Coast of China

Coastal land reclamation increases at a high speed on the coast of China in the last few decades. It is estimated that nearly 65% of tidal flats around the Yellow Sea of China have been reclaimed. This study is to undertake a comprehensive study of the coastal land reclamation in China by analyzing the coverage area of index system and the determination method of weight. In order to undertake the comprehensive evaluation, a new assessment method is also developed by combining the analytic hierarchy process(AHP) with the Delphi method. The Multi Indexing model for assessing impacts of land reclamation project on marine environment has been established. The weight for multi indexes has been obtained based on the AHP and Delphi methods. The evaluation standard for assessing impacts of reclamation project on marine environment is also proposed. With these new standards, the newly developed model has been applied to undertake a case study for a large-scale land reclamation project at a coastal site of Caofeidian located in the center of Bohai Bay.

Insights on the Sargassum horneri golden tides in the Yellow Sea inferred from morphological and molecular data

AbstractLarge‐scale drifting Sargassum biomass, known as golden tides, has caused considerable damage to the local environment and economy associated with the Yellow Sea of China. To understand the reoccurrence of Sargassum horneri golden tides in the Yellow Sea, large‐scale spatio‐temporal sampling was performed across nine cruises and five coastal surveys. Morphological data indicated that the floating S. horneri thalli with differing reproductive timing coexisted in the Yellow Sea. A total of 196 S. horneri samples had identical sequences of partial cox3 and rbcL‐S spacer region, revealing very low genetic diversity in the floating biomass. A total of 19 haplotypes for partial cox3 previously found in the Yellow Sea were not detected in our large‐scale sampling. Based on four novel mtDNA markers, the 196 samples could be further distinguished into two forms, which varied in proportions at various locations, but coexisted in each of the spatio‐temporal sampling. These results indicated that the floating Sargassum biomass in the Yellow Sea came from only two dominating haplotypes. The novel findings uncovered by this work will provide further insight into the underlying mechanisms of reoccurring golden tides in the Yellow Sea, and lead to the improved management of the Sargassum biomass.

Intensity division of the sea ice zones in China

The intensity division of sea ice regions can provide useful information for disaster prevention. According to different ice conditions, the Bohai Sea and the northern part of the Yellow Sea in China have been divided into twenty-one ice zones, and subsequently grouped in five intensity levels. But this division has many discrepancies and cannot reflect most of the properties of the ice zones. Based on the multivariate statistical sample of the twenty-one ice zones, the principal component analysis and hierarchical cluster analysis are applied to obtain a new intensity division. The cluster results indicate that, the regionalization obtained by the Ward method is recommended. The new criteria increases the number of sea ice zones with higher intensity levels. It is more practical and more conservative for the disaster prevention of marine structures. In addition, this method can present any groups of the intensity division wanted, so it provides more possibilities and flexibility for the application.

Organelle genomes of Sargassum confusum (Fucales, Phaeophyceae): mtDNA vs cpDNA

The drifting biomass of golden tide in the Yellow Sea of China mainly consisted of Sargassum horneri with a small fraction composed of Sargassum confusum thalli. In this study, the circular-mapping organelle genomes (mtDNA and cpDNA) of S. confusum were sequenced and coupled with comparative genomic and phylogenomic analyses within the Sargassum genus. This revealed 34,721-bp mitochondrial and 124,375-bp chloroplast genomes of S. confusum harboring 65 and 173 genes, respectively, figures which are highly comparable to those reported in other Sargassum species. The mtDNA of S. confusum displayed lower values in A+T and intergenic spacer contents than cpDNA. Mitochondrial phylogenomics revealed a close relationship between Sargassum muticum and S. confusum. The Sargassum mtDNAs had an approximately three-fold greater mutation rate than cpDNAs indicating a higher evolution rate in mtDNAs than cpDNAs for Sargassum species. Therefore, mtDNA is a more effective molecular marker and could aid in tracking the source of the golden tides.

A curvelet-based method to determine wave directions from nautical X-band radar images

A new method to determine wave directions from nautical X-band images is proposed. The signatures of ocean waves show obvious scale and directional characteristics in nautical X-band radar images. Curvelet transform (CT) possesses very high scale and directional sensitivities. Therefore, it has good capability to analyze ocean wave fields. The radar images are decomposed at different scales, in different directions, and at different positions by CT, and curvelet coefficients are obtained. Given to the scale and directional characteristics of surface waves, the information of ocean waves is centralized in the curvelet coefficients of certain directions and at certain scales. Therefore, the wave orientations can be determined. The 180 ambiguity is removed by calculating crosscorrelation coefficients (CCCs) between continuous collected images. The proposed method is verified by the dataset collected on the Northwest coast of the Zhangzi Island in the Yellow Sea of China from March to April 2009.

A time-varying Doppler spectrum model of radar sea clutter based on different scattering mechanisms

The Doppler spectrum modeling of the sea clutter is of great significance for using the Doppler radar to suppress the sea clutter and detect the target on sea surface. Taking into account the characteristics of the Doppler spectrum components corresponding to three scattering mechanisms, the Bragg, whitecap, and breaking-wave, we propose a time-varying Doppler spectrum model of radar sea clutter in this paper. The Doppler spectrum shifts and bandwidths of the three scattering mechanisms are considered respectively, and a Doppler shift of an added wave speed is introduced into this model. Because the spectrum intensity is defined as a random variable being a function of the measuring time of the sea clutter series, the model has the ability to model both the long-time averaged Doppler spectra and the short-time Doppler spectra. By modeling the short-time Doppler spectra and the long-time averaged Doppler spectra of the shore-based radar sea clutter measured in the China Yellow Sea at P and S bands, it is indicated that the proposed model has a higher precision than the conventional model, and especially, the modeling errors decrease significantly in the cases of the short-time Doppler spectra with long measuring time and the long-time averaged Doppler spectra with complex shapes.

On the classification of mixed floating pollutants on the Yellow Sea of China by using a quad-polarized SAR image

This study explored different methodologies using a C-band RADARSAT-2 quad-polarized Synthetic Aperture Radar (SAR) image located over China’s Yellow Sea to investigate polarization decomposition parameters for identifying mixed floating pollutants from a complex ocean background. It was found that solitary polarization decomposition did not meet the demand for detecting and classifying multiple floating pollutants, even after applying a polarized SAR image. Furthermore, considering that Yamaguchi decomposition is sensitive to vegetation and the algal variety Enteromorpha prolifera, while H/A/alpha decomposition is sensitive to oil spills, a combination of parameters which was deduced from these two decompositions was proposed for marine environmental monitoring of mixed floating sea surface pollutants. A combination of volume scattering, surface scattering, and scattering entropy was the best indicator for classifying mixed floating pollutants from a complex ocean background. The Kappa coefficients for Enteromorpha prolifera and oil spills were 0.7514 and 0.8470, respectively, evidence that the composite polarized parameters based on quad-polarized SAR imagery proposed in this research is an effective monitoring method for complex marine pollution.

Complete chloroplast genome of green tide algae Ulva flexuosa (Ulvophyceae, Chlorophyta) with comparative analysis.

Ulva flexuosa, one kind of green tide algae, has outbroken in the Yellow Sea of China during the past ten years. In the present study, we sequenced the chloroplast genome of U. flexuosa followed by annotation and comparative analysis. It indicated that the chloroplast genomes had high conservation among Ulva spp., and high rearrangement outside them. Though U. flexuosa was closer to U. linza than U. fasciata in phylogenetic tree, the average Ka/Ks between U. flexuosa and U. linza assessed by 67 protein-coding genes was higher than those between U. flexuosa and other species in Ulva spp., due to the variation of psbZ, psbM and ycf20. Our results laid the foundation for the future studies on the evolution of chloroplast genomes of Ulva, as well as the molecular identification of U. flexuosa varieties.

Croceitalea marina sp. nov., isolated from marine particles of Yellow Sea, and emended description of the genera Croceitalea

A Gram-staining-negative, rod-shaped, non-motile, golden yellow-coloured and strictly aerobic bacterial strain, designated H01-35T, was isolated from a surface marine particles sample collected from the Yellow Sea in China. According to the phylogenetic analysis based on 16S rRNA gene sequences, the strain H01-35T belonged to the genus Croceitalea and showed the highest sequence similarity to Croceitalea litorea CBA3205T (96.4 %). Strain H01-35T grew optimally at pH 8.0-9.0, 28 °C and in the presence of 3 % (w/v) NaCl. The DNA G+C content was 52.7 mol%. Strain H01-35T contained MK-6 as the predominant respiratory quinone and held iso-C15 : 1 G, iso-C15 : 0 and iso-C17 : 0 3-OH as the major cellular fatty acids. The major polar lipids were phosphatidylethanolamine, two unidentified aminolipids and five unidentified lipids. Exoenzymes for starch, gelatin and Tween 20 degradation were detected in Strain H01-35T but the strain was negative for sulfur and indole production. On the basis of the polyphasic analyses, this isolate was considered to represent a novel species in the genus Croceitalea, for which the name Croceitalea marina sp. nov. is proposed. The type strain is H01-35T (MCCC 1K03229T=KCTC 52368T). The emendation of description of the genus Croceitalea is also given.

The complete mitochondrial genomes of green tide algae Ulva flexuosa (Ulvophyceae, Chlorophyta)

Ulva flexuosa, one kind of green tide algae, has outbroken in the Yellow Sea of China during the past 10 years. The blooms have now become the world’s largest green tide, making great disaster for the ecosystem. In the present study, we sequenced the mitochondrial genome of U. flexuosa for the first time (GenBank Accession Number KX455878). It was found that the annular-shape genome was made up of 71545 bases pairs, including 29 protein coding genes. We then aligned amino acid of chlorophyta species containing the 29 genes in series as cladogram, which shows U. flexuosa is the closest sister species of U. fasciata, U. prolifera and U. linza.

Research on a Direct-Drive Wave Energy Converter Using an Outer-PM Linear Tubular Generator

An outer-permanent magnet tubular linear generator has been designed to increase the power density and distance of relative movement. The design of the two buoys has been completed. This paper describes the detailed design process of the proposed generator. The magnetic network model of the proposed generator is implemented to analyze the performance. Considering the cogging force and voltage, the linear generator has been optimized and the final parameters have been determined. Based on the design results, the integrated wave converter system has been manufactured and put into China's Yellow Sea. The measured voltage is highly consistent with the simulation data. All of results show that the proposed generator is well suitable for wave energy conversion.