Bohai Sea Of China Research Articles

Complete chloroplast genome of Ulva pertusa, one of the causal species of green macroalgal blooms in the coastal waters of Qinhuangdao, China

Since 2015, macroalgae blooms have appeared along the Qinhuangdao coast of the Bohai Sea in China and they have recurred annually during the months of April to September. One of the causal species that results in the macroalgal blooms, Ulva pertusa, has been detrimental to the environment and ecosystem along the coast of the Qinhuangdao, China. In the present study, we sequenced the chloroplast genome of U. pertusa for the first time (GenBank accession number MN853875) and found that the annular genome comprised 104,380 base pairs, including 71 protein-coding genes, 26 tRNAs, and 2 rRNAs. We then constructed a phylogenetic tree of U. pertusa and 17 other species based on core genes, which showed that U. pertusa is the closest sister species of U. fasciata.

Study on the influence of seawater density variation on sea water intrusion in confined coastal aquifers

The coupled influence of seawater density and groundwater level variation plays an import role in seawater intrusion in confined coastal aquifers. In this study, the effects of seawater density variations along with changing hydraulic gradients were investigated by conducting laboratory experiments and numerical simulations. Parameters of salinty and density in the experiments are based on the references related Bohai sea of China. The results indicate that the higher density of saltwater facilitates the seawater intrusion into the aquifers at the bottom and accelerates the circulation at the changing hydraulic gradient. Even slight variations in saltwater density can change the steady-state conditions in a confined aquifer, which should be considered when attempting to control the intrusion of seawater. Moreover, the influence of seawater density variations on transient salt-wedge dynamics was also examined in these experiments. Numerical modelling was simultaneously performed to mimic the behaviour of SW using the TOUGH2/EOS7 package. The simulated results were generally consistent with those obtained from the experiments. This study is conducive to further understand the mechanism of seawater intrusion, thereby leading to effective management of the problem in coastal areas.

Analysis of Offshore Structures Based on Response Spectrum of Ice Force

With the development of large-scale offshore projects, sea ice is a potential threat to the safety of offshore structures. The main forms of damage to bottom-fixed offshore structures under sea ice are crushing failure and bending failure. Referred to as the concept of seismic response spectrums, the design response spectrum of offshore structures induced by the crushing and bending ice failure is presented. Selecting the Bohai Sea in China as an example, the sea areas were divided into different ice zones due to the different sea ice parameters. Based on the crushing and bending failure power spectral densities of ice force, a large amount of ice force time-history samples are firstly generated for each ice zone. The time-history of the maximum responses of a series of single degree of freedom systems with different natural frequencies under the ice force are calculated and subsequently, a response spectrum curve is obtained. Finally, by fitting all the response spectrum curves from different samples, the design response spectrum is generated for each ice zone. The ice force influence coefficients for crushing and bending failure are obtained, which can be used to estimate the stochastic sea ice force acting on a structure conveniently in a static way. A comparison of the proposed response spectrum method with the Monte Carlo method by a numerical example shows good agreement.

Evaluation of metal pollution-induced biological effects in Chinese shrimp Fenneropenaeus chinensis by NMR-based metabolomics

Metal pollution in Laizhou Bay along the Bohai Sea in China has been posing a risk on fishery species and hence may affect seafood quality. In this work, shrimps Fenneropenaeus chinensis were sampled from three sites, namely, a reference (site 6334) and two metal-polluted (sites 6262 and 7262) sites, located in Laizhou Bay. The metal concentrations in shrimp muscle tissues were tested using the ICP-MS technique. The Cr and Cu concentrations were the highest in the shrimp samples from site 7262, exceeding the national seafood safety standard Ⅱ, and the As concentration was much higher than the national seafood safety standard Ⅲ. NMR-based metabolomics indicated that metal pollution induced oxidative and immune stresses, damaged the muscular structure, and disrupted energy metabolism in shrimps at sites 6262 and 7262, in particular disturbed osmotic regulation in shrimps at site 7262. Glycine and serine could serve as biomarkers for Cd in F. chinensis.

Ecological quality dynamics around marine reserves in the Bohai Sea coastal zone and their relationship with landscape artificialization

Numerous marine reserves worldwide are losing their ability to protect wild endemic species due to surrounding ecological deterioration caused by coastal landscape artificialization. Such risk of becoming invalid nature reserves is particularly high in China's Bohai Sea coastal zone, a region with rapid urbanization and industrialization. In this study, the ecological quality (EQ) status around Laizhou Bay Ostrea rivularis germplasm reserve (R1), Yellow River Estuary Meretrix meretrix germplasm reserve (R2), and Taoer Estuary Sinonovacula constricta germplasm reserve (R3) was dynamically diagnosed using seven indicators characterizing ecological support and threat from peripheral environments. A series of thresholds indicating EQ and corresponding landscape artificialization intensity (LAI) were determined based on multi-factor clustering analysis and relational regression simulation. The results show that the surroundings of these three reserves were favorable in 1984, insufficient in 2000, and unfavorable in 2015. With an average 7.5 times increase in LAI over the past three decades, the EQ levels around R1-R3 declined significantly and have deviated greatly from their optimal reference status by 2015, which stemmed mainly from intertidal landscape artificialization, such as establishing salt pans, industrial areas and ports after reclaiming wetlands. It was found that R3 > R1 > R2 in terms of overall peripheral ecological degradation, implying that the closer the marine reserve is to the land, the more likely it is to lose its effectiveness. The changes in EQ status and LAI were well indicated by the proportion of natural ecosystems, the distance between seawalls and protected boundaries, and the reserves' enclosed degree by artificial systems, which, as a quick and simple diagnostic approach, can facilitate spatial planning and management practices around marine reserves in the Bohai Sea coastal zone and elsewhere.

Evaluations of submarine groundwater discharge and associated heavy metal fluxes in Bohai Bay, China

Submarine groundwater discharge (SGD) has been recognized as an important source of dissolved heavy metals to the coastal ocean. Bohai Bay, the second largest bay of Bohai Sea in China, is subjected to serious environmental problems. However, SGD and SGD-derived heavy metal fluxes in the bay are seldom reported. In this study, we present mass balance models considering the radium losses caused by recirculated seawater to estimate water age, SGD and SGD-derived heavy metal fluxes in Bohai Bay during May 2017. The water age is estimated to be 56.7–85.0 days based on tidal prism model. By combining water and salt mass balance models, submarine fresh groundwater discharge (SFGD) is estimated to be (3.5–9.3) × 107 m3 d−1. The SGD flux estimated by the radium mass balance models is (3.2–7.7) × 108 m3 d−1, an order of magnitude larger than the discharge of the Yellow River during the sampling period. SGD-derived heavy metal fluxes were estimated to be (0.2–6.0) × 107 mol d−1 for Fe, (1.2–2.7) × 107 mol d−1 for Mn, (3.0–8.2) × 105 mol d−1 for Zn, (2.7–7.4) × 104 mol d−1 for Cr and (0.6–1.8) × 103 mol d−1 for Cd, which are significantly higher than those from local rivers. This study reveals that SGD is a significant source of heavy metals (Mn, Zn and Fe) into Bohai Bay, which may have important influences on the metal budgets and ecological environments in coastal areas.

Distribution of green algae micro-propagules and their function in the formation of the green tides in the coast of Qinhuangdao, the Bohai Sea, China

Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort along the coast. Micro-propagules of the green algae including gametes, spores, micro-germlings and micro-vegetative fragments play an important role in the formation of green tides. They serve as a “seed source” of green macroalgae, and their distributions could reflect and influence the “algae source” of green tides. In this study, monthly surveys in the inshore and offshore areas of the Qinhuangdao coast were conducted from April to September 2016 and in January 2017 to investigate the tempo-spatial distribution patterns and the biomass variations of the green algae micro-propagules. The obtained results show that micro-propagules were mainly distributed in the inshore areas with a significantly decreasing abundance towards offshore areas. Their biomass was highest in July and August, and lowest in winter. The areas that were affected by the green tides showed a remarkably higher abundance of micro-propagules compared to other areas. These micro-propagules could serve as the “seed” source of green tides. Their distribution patterns indicate that the green tide in the coastal areas of Qinhuangdao originated locally.

Nutrient dynamics and their interaction with phytoplankton growth during autumn in Liaodong Bay, China

Discharges of domestic sewage, industrial wastewater, and runoff of agricultural fertilizer have caused severe nutrient pollution and eutrophication in many estuaries and coastal areas around the world, especially in the Bohai Sea of China and its inner bay, Liaodong Bay. Subsequent to studies of this bay during the summer of 2013, an investigation was conducted in the autumn (dry season) to better understand the interactive effects of light, temperature, and nutrient concentrations on phytoplankton growth in the bay. Analyses of long-term data showed that dissolved inorganic nitrogen concentrations had increased roughly sixfold to eightfold since the 1980s as a result of nitrogen fertilizer use, pollution from industrial wastewater and domestic sewage, and loss of wetlands and their water purification service. In contrast, phosphate and silicate concentrations have decreased by factors of 2 and 5, respectively, during the past half century because of anthropogenic reductions of sediment loads (e.g., the construction of check dams and reservoirs and large-scale vegetation restoration projects). We found no evidence that phytoplankton growth was limited by nitrogen or phosphorus. Plots of nitrate and silicate concentrations versus salinity indicated conservative mixing in both cases. Analogous plots of ammonium and phosphate revealed a net uptake and net input, respectively. Phytoplankton uptake likely accounted for the net uptake of ammonium, and desorption of phosphorus from suspended particulate matter for the net input of phosphate. The major factors controlling phytoplankton growth in this study were light availability and temperature. Nearly all incoming photosynthetically active radiation was attenuated in the water column, and less than 1% of the light energy was absorbed by phytoplankton. Comparisons of this study with previous work in Liaodong Bay during the summer and similar case studies in contrasting regions of the world revealed a general pattern of regional maxima of phytoplankton biomass (or even harmful algal blooms) and changes of community structure associated with light availability and temperature variations in the presence of growth-rate-saturating nutrient concentrations.

Corallincola luteus sp. nov., a marine bacterium isolated from surface sediment of Bohai Sea of China.

A novel Gram-stain negative, strictly aerobic, rod-shaped motile bacterium with a single flagellum, designated strain DASS28T, was isolated from surface sediment of Bohai Sea in China. Growth occurred in the presence of 1.0-4.0% NaCl (w/v, optimum 2.0%), at 10-37°C (optimum 20°C) on the Marine agar 2216E and pH 6.0-10.0 (optimum pH 8.0). The major fatty acids (> 10% of total fatty acids) were summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH), C16:0 and C18:1ω7c. The polar lipids were phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid, an unidentified aminolipid and two unidentified polar lipids. The major respiratory quinone was ubiquinone-8 (Q-8). The genomic DNA G + C content calculated from the genome sequence of strain DASS28T was 48.8mol%. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain DASS28T belongs to the genus Corallincola and shows high 16S rRNA gene sequence similarity of 96.7% to Corallincola platygyrae JLT 2006T (= JCM18796T = CGMCC 1.10992T). On the basis of the polyphasic evidence, strain DASS28T is considered to represent a novel species in the genus Corallincola, for which the name Corallincola luteus sp. nov. is proposed. The type strain is DASS28T (= KCTC 52376T = MCCC 1K03208T).

The Characteristics and Distribution of Eukaryotic Phytoplankton Community in Liaodong Bay, China

Brown tides have occurred in the Bohai Sea of China since 2009 and caused serious losses in aquaculture. In recent years, phytoplankton identification has been greatly promoted by the development of high-throughput sequencing technologies. In this study, V4 region of 18S rDNA was used as the target gene to design the primer V4 (F/R), and high-throughput sequencing technology was adopted to evaluate the diversity of composition and characteristics of the eukaryotic phytoplankton community. A total of 93 alga species were identified, and about 60% (56 out of 93) of them were undetected or unreported in Chinese waters. There were 59% of the total algal species identified as autotrophy in trophic mode while heterotrophy and mixotrophy accounted for 12% and 29% of the total algal species, respectively. 8 species of picophytoplankton that were mainly distributed in the south and a partial area of the east and west formed the scientific basis for the quality and safety early-warning in aquatic products and brown rides study. Diversity index analysis also revealed a trend of fluctuations of marine phytoplankton diversity in different sample sites in Liaodong Bay. In conclusion, our work provides a detailed evaluation of eukaryotic phytoplankton diversity in Liaodong Bay, suggesting the need for long-term monitoring to further study and guard against the potential risk of harmful algal blooms.

Use of biological detection methods to assess dioxin-like compounds in sediments of Bohai Bay, China

Bohai Bay, in the western region of northeastern China's Bohai Sea, receives water from large rivers containing various pollutants including dioxin-like compounds (DLCs). This study used the established zebrafish (Danio rerio) model, its known developmental toxicity endpoints and sensitive molecular analyses to evaluate sediments near and around an industrial effluent site in Bohai Bay. The primary objective was to assess the efficacy of rapid biological detection methods as an addition to chemical analyses. Embryos were exposed to various concentrations of sediment extracts as well as a 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) positive control. Exposure to sediment extract nearest the discharge site (P1) resulted in the most severe- and highest rates of change in embryos and larvae, suggesting that DLC contaminated sediment probably did not occur much beyond it. P1 extract resulted in concentration dependent increases in mortality and pericardial edema. Its highest concentration caused up-regulation of P-450 (CYP)-1A1(CYP1A) mRNA expression at 72 h post fertilization (hpf), an increase in its expression in gill arches as observed by whole mount in situ hybridization, and an increased signal in the Tg(cyp1a: mCherry) transgenic line. The pattern and magnitude of response was very similar to that of TCDD and supported the presence of DLCs in these sediment samples. Follow-up chemical analysis confirmed this presence and identified H7CDF, O8CDF and O8CDD as the main components in P1 extract. This study validates the use of biological assays as a rapid, sensitive, and cost-effective method to evaluate DLCs and their effects in sediment samples. Additionally, it provides support for the conclusion that DLCs have limited remobilization capacity in marine sediments.

C band transhorizon signal characterisations in evaporation duct propagation environment over Bohai Sea of China

Evaporation duct is an anomalous mechanism of transhorizon propagation in marine and coastal regions. In order to better understand the characteristics of signal fading, a C band signal transhorizon propagation experiment was carried out with a 107km path length over the Bohai Sea of China. Using an iron tower with meteorological and oceanographic (METOC) sensors at multiple altitudes, a direct diagnostic method of evaporation duct is presented. The dependence of signal strength on evaporation duct height, antenna height, and METOC parameters is analysed. The experimental results indicate that the signal strength tends to be linearly dependent on the evaporation duct height when the transmitter and receiver antennas are submerged within the duct layer. Normally, the signal strength is stronger when the relative humidity is lower. Stronger signal strength tends to occur under near-neutral or stable atmospheric conditions or when the air-sea temperature difference is higher. The results indicate that the signal strength distribution of fast fading is close to Rayleigh distribution, and the probability density of fade slope is symmetric at 0dB/s. These results have important implications for the design of ducting communications system.

GIS-Based Simulation Methodology for Evaluating Ship Encounters Probability to Improve Maritime Traffic Safety

Evaluating ship encounters probability efficiently is significant for maritime transportation risk analysis as well as improving maritime traffic safety. In practice, ship encounters probability estimate by using traditional observation or field experiments is nearly impossible due to the expensive cost. In this paper, we propose a methodology framework for evaluating ship encounters probability based on an agent-based simulation paradigm. Individual ship’s navigation behavior is modeled as an agent, and their encounters are detected by an innovative geographic information system (GIS)-based intelligent algorithm. We then design and implement a prototype simulator based on the methodology framework and apply it in the mid-western waters of Bohai Sea of China to demonstrate its functionalities and utility. The findings show that the framework proposed in this paper has potential to provide decision support for guiding future marine transportation planning. This paper offers new insights and valuable demonstration on promoting maritime traffic safety management with the integration of GIS and emerging complex system simulation technology.

137Cs and 239+240Pu in the Bohai Sea of China: Comparison in distribution and source identification between the inner bay and the tidal flat

We investigated artificial radionuclides (239+240Pu and 137Cs) in surface sediments and sediment cores collected from the Bohai Bay and the tidal flat of the Liaodong Bay, China. Increasing trends for 239+240Pu activities and 240Pu/239Pu atom ratios (˃0.18) were observed from land to sea and from north to south in the Bohai Bay. This spatial pattern implied that the scavenging process between riverine sediments and Pacific Proving Ground (PPG) source Pu transported by the currents such as Yellow Sea Warm Current had occurred in the Bohai Bay. In contrast, relatively lower 240Pu/239Pu atom ratios in the tidal flat of Liaodong Bay were due to the mixing process between more global out and less PPG source Pu. The riverine Pu contributions to the total global fallout Pu in the Haihe River (32.8%) were much lower than those in the Yangtze River estuary (77%–80%), indicating better soil conservation in the Haihe River Catchment.

Relationship between Shell Morphological Traits and Body Weight in Two Estuarine Clams, Meretrix meretrix and Cyclina sinensis in Shuangtaizi Estuary, Bohai Sea in China

Wild clams of Meretrix meretrix and Cyclina sinensis were collected from intertidal flats of Shuangtaizi estuary during low tide in 2016. Morphometric traits including shell length (SL), shell height (SH), shell width (SW), and total body weight (TW) of the clams were measured. Correlation, path, and regression analyses were conducted to evaluate the relationship between morphometric traits and total body weight and determine the optimal indices for artificial breeding of M. meretrix and C. sinensis. Significant differences in correlation coefficient among various characteristics were found. Shell height and SW showed the strongest influence on total body weight. The optimal regression equation of the measured traits was established in both clams by using a stepwise regression method: TW = –27.404 + 0.948 SW + 0.422 SH + 0.291 SL for M. meretrix and TW = –36.965 + 1.107SH + 0.564SW for C. sinensis. These results provide baseline information for selective breeding and conservation management of the two commercially important clam species in Shuangtaizi estuary.

Identifying channel sand-body from multiple seismic attributes with an improved random forest algorithm

Machine learning provides numerous data-driven tools for automatic pattern recognition. Even though various algorithms such as neural networks and support vector machines have been widely applied, it is still necessary to explore new paradigms and algorithms to improve the machine learning assisted seismic interpretation. Random Forest (RF) is a widely used ensemble algorithm, however, only limited studies of random forest in the seismic application were published. In this article, the methodology of random forest is introduced systematically. Meanwhile, to solve the problem of hyper-parameter determination, we propose an improved algorithm named Pruning Random Forest (PRF). To reveal the advantages of PRF in terms of predictive performance, robustness, and feature selection compared with support vector machine, neural network, and decision tree, several well-designed experiments are executed based on the seismic data of the western Bohai Sea of China. The potential and advantages of random forest in the present case are confirmed by various experiments, which substantiates that the proposed pruning random forest algorithm provides a reliable alternative way for further machine learning assisted seismic interpretation.

Heterocapsa bohaiensis sp. nov. (Peridiniales: Dinophyceae): a novel marine dinoflagellate from the Liaodong Bay of Bohai Sea, China

A small armed dinoflagellate bloomed in the aquaculture ponds off the coast of Liaodong Bay, Bohai Sea of China, resulting in heavy mortalities of the cultured prawns (Penaeus japonicus) and larvae of Chinese mitten handed crabs (Eriocheir sinensis). The bloom-forming species was successfully isolated, and cellular morphology of the specimen was consequently investigated through light, fluorescent and electron microscopy. The small ((14.4±1.6) μm in length) ellipsoid cells show typical Heterocapsa thecal plate arrangement (Po, cp, 5′, 3a, 7′′, 6c, 5s, 5′′′, 2′′′′). The episome is evidently bigger than the hyposome. One to three spherical pyrenoids are located above or beside the large elongated nucleus. The body scale is characterized by a triangle basal plate with one central upright and nine peripheral spines. Above all, Heterocapsa bohaiensis could be distinguished from other Heterocapsa species by the combination of the cell size, morphology, cellular structure and body scale. Sequence analyses of both ITS and LSU regions reveal the significant genetic divergence between H. bohaiensis and other established species in this genus, further supporting novelty of this species. Noticeably, different sample treatment methods resulted in morphological variation of the apical pore complex (APC) of H. bohaiensis, which needs to be taken into account in future study.

Isolation and Complete Genome Sequence of a Novel Marinobacter Phage B23.

We used the double-agar layer method to isolate a novel Marinobacter marina bacteriophage, B23, from the surface water sample of the Bohai sea of China. There is some work to better understand the phage. The result of transmission electron microscopy revealed that B23 belongs to the family Siphoviridae with a head of 80nm in diameter and a tail of 230nm. Microbiological characterization evidenced that phage B23 is stable at the temperatures from - 25 to 60°C, and showed vigorous vitality at pH between 4.0 and 12.0. One-step growth experiment showed that it had a longer latent period and higher lysis efficiency. Furthermore, the complete genome of B23 was sequenced and analyzed, which consists of a 35132bp DNA with a G + C content of 59.8% and 50 putative open reading frames. The genome was divided into five parts, consisting of DNA replication and regulation, phage packaging, phage structure, host lysis and hypothetical protein.

A decision model responding to the refuge request from a ship in need of assistance

When a ship in need of assistance has requested a place of refuge with regards to the maritime administration, deciding on the most suitable form of refuge is often both a political and technical problem. To avoid opposition by local communities, a decision model responding to such ship requests is generally established to enable the refuge designation on a case-by-case basis. Within this framework, a step-by-step ranking process is proposed, first selecting indices for potential candidate refuge sites according to the purpose of requesting refuge, with all indices then ordered by pairwise comparison. The weight of each index is determined according to the tone word used for adjacent comparison, and the suitability score for each candidate port obtained. The model is then applied to a hypothetical ship accident in the Bohai Sea in China, which further illustrates the envisaged response process and provides a solution to contemporary maritime administration.

Cotton Responses to Saline Water Irrigation in the Low Plain around the Bohai Sea in China

AbstractThe use of shallow saline groundwater may alleviate the shortage of freshwater resources in the Low Plain around the Bohai Sea in China. The soil salt levels and the responses of cotton see...