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Approximately 1 million tons of green tides decompose naturally in the Yellow Sea of China every year, releasing large quantities of nutrients that disrupt the marine ecological balance and cause significant environmental consequences. Currently, the identification of areas affected by green tides primarily relies on certain methods, such as ground sampling and biochemical analysis, which limit the ability to quickly and dynamically identify decomposition regions at large spatial and temporal scales. While multi-source remote sensing data can monitor the extent of green tides, accurately identifying areas of algal decomposition remains a challenge. Therefore, satellite data were integrated with key biochemical parameters, such as the carbon-to-nitrogen ratio (C/N), to develop a method for identifying green tide decomposition regions (DRIM). The DRIM shows a high accuracy in identifying green tide decomposition areas, validated through regional repetition rates and UAV measurements. Results indicate that the annual C/N threshold for green tide decomposition regions is 1.2. The method identified the primary decomposition areas in the Yellow Sea from 2015 to 2020, concentrated mainly in the southeastern region of the Shandong Peninsula, covering an area of approximately 1909.4 km2. In 2015, 2016, and 2017, the decomposition areas were the largest, with an average annual duration of approximately 35 days. Our method provides a more detailed classification of the dissipation phase, offering reliable scientific support for accurate and detailed monitoring and management of green tide disasters. [ABSTRACT FROM AUTHOR]

To estimate annual sea–air CO2 flux in the southern Yellow Sea (SYS), surface CO2 partial pressure (pCO2) was determined using high-resolution underway observations across four seasons. Surface CO2 exhibited large seasonal variation in the SYS, with high values in summer and low values in spring. Surface pCO2 had no clear relationship with sea surface temperature (SST) or sea surface salinity (SSS) on the seasonal timescale. Apart from the thermal effect, the main processes affecting surface pCO2 varied among seasons, i.e., photosynthetic carbon fixation from winter to spring, sea–air CO2 exchange from spring to summer, vertical mixing and sea–air CO2 exchange from summer to autumn, and vertical mixing and sea–air CO2 exchange from autumn to winter. In spring, sea–air CO2 flux ranged from − 77.3 to − 0.05 mmol m−2 day−1, with an average of − 18.9 ± 5.3 mmol m−2 day−1. In summer, sea–air CO2 flux ranged from 0.01 to 30.4 mmol m−2 day−1, with an average of 3.8 ± 1.6 mmol m−2 day−1. In autumn, sea–air CO2 flux ranged from − 16.1 to − 0.03 mmol m−2 day−1, with an average of − 2.9 ± 1.7 mmol m−2 day−1. In winter, sea–air CO2 flux ranged from − 36.7 to 10.9 mmol m−2 day−1, with an average of − 4.5 ± 2.2 mmol m−2 day−1. Annual sea–air CO2 flux in the SYS was calculated as − 5.6 ± 1.8 mmol m−2 day−1, suggesting that the SYS absorbs atmospheric CO2 at an annual rate of 2.1 ± 0.6 mol m−2 yr−1. [ABSTRACT FROM AUTHOR]

This study analyzes sea surface water turbidity variability in the coastal region of the Yellow Sea and investigates the relationships with environmental factors. By applying spectral analysis, harmonic analysis, wavelet transformation, and multivariate linear regression to in situ measurements of seawater turbidity data, we examined the temporal turbidity variability and the fractional contributions of tidal currents and atmospheric components to turbidity variations. A multivariate linear regression was used to determine the daily variations in the fractional contributions of tidal currents and atmospheric components to turbidity. The results showed that seawater turbidity exhibited dominant fluctuations corresponding to major tidal harmonics (M2, S2, K1, and O1), along with shallow-water tides (MS4 and M4) and the M2 variation-related semi-diurnal tides (H1 and H2). The amplitudes of turbidity variations associated with these shallow-water tides and semi-diurnal tides demonstrated a linear relationship with those of the tides, with a rate of 0.24 NTU cm−1. This rate was four times greater than the rate of 0.06 NTU cm⁻1 observed for the major tides, addressing the important roles of non-linear tidal processes in shallow regions. In addition, an inertial motion in coastal turbidity (19.56 h) was detected when external forces were relatively weak. The impact of tidal currents on turbidity fluctuations was significantly reduced during typhoon periods due to pronounced atmospheric influences. Investigations of high-resolution Sentinel-2 turbidity over the past 6 years (2018–2023) illustrated more distinctive responses to extreme environmental conditions. This study is expected to enhance the comprehensive understanding of turbidity fluctuations and their linkages to tidal currents and atmospheric conditions in the Yellow Sea. [ABSTRACT FROM AUTHOR]

We investigated the total sediment O2 uptake (TOU), sulfate reduction rate (SRR), and benthic nutrient flux (BNF) at the Yellow Sea cold water mass (YSCWM) sediments (N3509 and N3507) and the coastal sediment (N3503) in the southern Yellow Sea. The organic carbon (OC) content increased from coarse- to fine-grained sediment, which was by far the highest at N3503 (0.89% and 6.1 Ø), followed by N3509 (0.72% and 4.5 Ø) and N3507 (0.15% and 3.0 Ø). The bottom water temperature at N3503 (16.0°C) was 6‒7°C higher than N3509 (10.2°C) and N3507 (9.0°C). The TOU and SRR at N3503 were 24.5 ± 5.0 mmol O2 m–2 d–1 and 6.5 mmol S m–2 d–1, 3‒6 times higher than the values measured at N3509 and N3507 (5.5 ± 0.2 and 4.2 ± 0.3 O2 mmol m–2 d–1 and 0.9 and 0.7 mmol S m–2 d–1, respectively). TOU showed a positive correlation with both the OC content and the bottom water temperature (R = 0.71, p < 0.001). The BNF at N3503 (3.4 mmol N m–2 d–1, 0.5 mmol P m–2 d–1, 3.8 mmol Si m–2 d–1) was 3‒37 times higher than the values measured at N3509. The BNF contributed 72–179% of the nutrients required for primary production at N3503, whereas the contribution was less than 30% at N3509. [ABSTRACT FROM AUTHOR]

The West Korea Coastal Current (WKCC) is known to flow northward in summer and southward in winter along the eastern boundary of the Yellow Sea (YS). To examine the variation in the WKCC in the eastern YS, the current was observed at four stations at 15 km intervals along the 36° N line from May to August 2012 using acoustic Doppler current profilers. In particular, the summertime monthly variation in the WKCC was examined including its strength, vertical structure, and horizontal distribution using current meter and hydrographic data. Over the entire observation period, a northward surface current and a weaker southward subsurface countercurrent were observed. In May and June, the monthly mean surface current velocity ranged from 6.4 to 8.6 cm/s at the onshore stations, while the velocity was slower at the offshore stations. In July and August, the monthly mean surface current velocity reached 11.4 cm/s at the onshore stations and 6.9 cm/s at the offshore stations. The thickness of the upper layer flowing northward ranged from 18 to 50 m. The monthly vertical structure of the geostrophic current estimated using the observed water density data was similar to that of the observed current. This indicates that monthly changes in the WKCC are mainly affected by regional changes in the zonal density gradient. This study is the first to provide data for the monthly vertical structure of the WKCC and the subsurface countercurrent in the eastern YS, thus enhancing the understanding of the summer circulation patterns in the YS. [ABSTRACT FROM AUTHOR]

To better understand the tidal effects on dynamics of inorganic nutrients and its implications for outwelling processes, we conducted time-series observations on the fluctuations in concentrations and benthic flux of inorganic nutrients with tidal cycle in macrotidal Garolim Bay (GB), Yellow Sea. The strong tidal current and rapid mixing stimulated resuspension of suspended particulate matter (SPM), particulate organic carbon (POC), and chlorophyll-a (Chl-a), which were predominant during the spring tide. Concentrations of ammonium (NH4+) and NOx (sum of nitrite and nitrate) were not correlated with tidal variation, while concentrations of phosphate (PO43−) and silicate (SiO2) were inversely correlated with tidal levels, except for PO43− at surface layer during neap tide. In addition, analyses of the benthic nutrient fluxes (0.04–3.48 mmol m−2 d−1 for NH4+, 0.18–0.39 mmol m−2 d−1 for NOx, 0.03–0.12 mmol m−2 d−1 for PO43−, and 1.62–5.47 mmol m−2 d−1 for SiO2) and nutrient ratio revealed that there was a relatively excess efflux of PO43− and SiO2. The inverse fluctuations of P and Si with tidal level and their excess benthic release indicated that GB sediment acts as a net source of PO43− and SiO2 to the water column and to offshore water, which further suggested that the benthic nutrient flux in the GB may have a substantial effect on phytoplankton production in the adjacent coastal water column. [ABSTRACT FROM AUTHOR]

A Gram-stain-negative, non-motile, aerobic, pale-yellow coloured and oval-shaped bacterium designated GRR-S6-38T was isolated from a tidal flat sediment that collected from Garorim Bay of the Yellow Sea, Republic of Korea. Strain GRR-S6-38T grew at 15–40 °C (optimum, 30 °C) at pH 6–9 (optimum, pH 7) and at 2–6% (w/v) NaCl (optimum, 2% NaCl). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain GRR-S6-38T was closely related to those of J. seosinensis CL-SP26T (98.1%), J. helgolandensis DSM 14858T (97.4%), J. rubra CECT 5088T (97.4%), J. faecimaris DSM 100420T (97.4%), J. marina SHC163T (97.3%), J. donghaensis CECT 7802T (97.2%) and J. pohangensis DSM 19073T (97.1%). The average nucleotide identity and digital DNA-DNA hybridization value between GRR-S6-38T and related type strains were 71.47–78.59% and 17.80–21.40%. Strain GRR-S6-38T was characterized as having Q-10 as the predominant respiratory quinone and the major principle fatty acids (> 10%) were SF 8 (C18:1ω7c/C18:1ω6c, 39.3%), C19:0ω8c cyclo (13.2%) and C18:1ω7c 11-methyl (10.6%). The polar lipids consisted of diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an unidentified lipid, two unidentified aminolipids and two unidentified phospholipids. The assembled genome of strain GRR-S6-38T has a total length of 3.32 Mbp, and a G + C content is 69.98%. Based on the polyphasic taxonomic evidence presented in this study, GRR-S6-38T is regarded to represent a novel species within the genus Jannaschia, for which name Jannaschia ovalis sp. nov. is proposed. The type strain is GRR-S6-38T (= KCTC 82518 = KACC 22240 = JCM 36187). [ABSTRACT FROM AUTHOR]

To analyze variations in the vertical distribution of water temperatures and the impact of advection in the central Yellow Sea, multi-layer water temperature and current observations were conducted from 31 May to 8 June 2021. Water temperatures exhibited a typical three-layer summer structure, with a uniform deep-layer temperature averaging 8.23 ± 0.05 °C. The current field was dominated by northeast–southwest tidal currents, but residual current characteristics indicated that non-tidal components significantly influenced circulation. Water temperature changes lagged tidal changes by about 3 h, with strong correlations (R > 0.7), especially in deep layers. Residual currents showed significant correlations with water temperature variations, which were attributed to advective displacement or baroclinic currents. Empirical orthogonal function (EOF) and complex EOF analyses revealed that thermocline variations (T1, explaining approximately 75% of total variance) were driven by strong northward (C1, approximately 34%) and cyclonic (C2, approximately 32%) advection. In deep layers, slight temperature changes were caused by southward Yellow Sea Cold Water Mass (C1) and northward Yellow Sea Warm Current Water (C2) propagation. This study confirms that vertical water temperature variations result from a complex interaction between various advection patterns, with southward tide-induced residual currents (C3, approximately 12%) playing a key dynamic role. [ABSTRACT FROM AUTHOR]

Introduction: The nearshore sea off the northeastern Shandong Peninsula is characterized by intensive mariculture, whose ecosystem is involved in the large marine ecosystem of the Yellow Sea. However, ocean currents in this area are poorly explored. Observations suggested overturning currents were robust phenomena in winter in this area. Methods: Numerical simulations and experiments were used to investigate the mechanisms of overturning currents. Results: There were two classes of wind-driven overturning currents. One consisted of surface southeastward currents, nearshore downwelling currents, and bottom northeastward currents. The other consisted of surface northeastward currents, nearshore upwelling currents, and bottom southwestward currents. Discussion: The underlying dynamics involved local wind forcing and propagation of coastal trapped waves (CTWs). Northwesterly winds in the Bohai Sea and North Yellow Sea drove surface southward currents and converged water toward coastline off the northeastern Shandong Peninsula, generating nearshore sea level rising. The resultant southward sea level slope drove nearshore bottom northward currents. Meanwhile, high sea level in the southern part of Bohai Sea and North Yellow Sea also propagated as CTWs clockwise around the Shandong Peninsula, which further enhanced nearshore bottom northward currents and caused eastward currents in the entire water column off the northeastern Shandong Peninsula. Southwesterly winds in the Bohai Sea and North Yellow Sea drove surface northward currents, generating nearshore sea level dropping off the northeastern Shandong Peninsula. The resultant northward sea level slope caused bottom southward currents. Meanwhile, the southwesterly winds caused CTWs with low sea level in the south part of the Bohai Sea and Yellow Sea. The northward sea level slope of CTWs enhanced nearshore bottom southwestward currents. The current study emphasized winds in winter drove not only local currents but also propagation of CTWs in the Bohai Sea and North Yellow Sea. The sea level slope of CTWs regulated surface and bottom Ekman layers driven by local winds. [ABSTRACT FROM AUTHOR]

Background: Thoracophelia Ehlers, 1897 is a genus of Opheliidae characterised by the body divided into three distinct regions, modified parapodia in chaetiger 10 and a ventral groove restricted to the posterior half of the body. To date, 18 species have been described in the genus. Amongst them, six species have been recorded in northeast Asia. New information: A new species, Thoracophelia foliformis sp. nov., was discovered in the intertidal zone of the Yellow Sea, South Korea. This is the first Thoracophelia species report from the Yellow Sea. This new species is closely related to T. dillonensis (Hartman, 1938) from California and T. ezoensis Okuda, 1936 from Japan in having pectinate branchiae. However, the new species can be distinguished from the two species by the unique combination of the following characteristics: 15 pairs of wrinkled pectinate branchiae with 12–15 filaments at best development and a foliaceous mid-ventral plate in the pygidium instead of one or two thick ventral cirri. Detailed descriptions and illustrations of T. foliformis sp. nov. are provided. Sequences of the mitochondrial cytochrome c oxidase subunit I (COI), nuclear 18S ribosomal DNA (rDNA) and 28S rDNA of the new species were determined and analysed. [ABSTRACT FROM AUTHOR]

Ocean change due to anthropogenic activities and climate change are causing a decline in coldwater fish species and emergence of subtropical fish species in Korean waters. Therefore, environmental change-dependent time-space distribution of fishery resources in Korea, which has a big fisheries industry, needs to be investigated. Environmental DNA (eDNA) metabarcoding is an environmentally noninvasive method for understanding the spatiotemporal distribution of marine organisms at high spatial resolution. The highly variable cytochrome oxidase-1 (CO1) gene is used in eDNA studies for species identification across diverse taxa. However, it exhibits genetic differences depending on geographical distribution. For improving the accuracy of eDNA research, the CO1 database should be expanded by incorporating sequence information for individuals inhabiting the Korean seas. Here, 106 biological samples from the Yellow Sea were identified morphologically and their nucleotide sequences were compared with those in the GenBank. Most sequences were 100% identical with those in the GenBank. In most samples, the morphological and molecular identification results were consistent, indicating the utility of CO1. However, some nucleotide sequences differed from those in the database. Amino acid sequences translated from nucleotide sequences with less than 97% similarity showed high similarity to the amino acid database, indicating intraspecies variation due to "silent mutations". These results highlight the need for a sequence database of fishery resources in Korean coastal waters to improve the reliability of eDNA studies using CO1. However, because of the same CO1 sequences in several species, genetic markers need to be developed and the database should be supplemented with more sequences for reliable high-resolution eDNA studies. [ABSTRACT FROM AUTHOR]

In recent years, Ulva prolifera green tide, as a large-scale marine ecological phenomenon, has occurred frequently in coastal areas such as the Yellow Sea and the East China Sea, significantly affecting marine ecosystems and fishery resources. With the continuous advancement of remote sensing technologies, these technologies have become indispensable tools for monitoring Ulva prolifera green tides. This review provides a comprehensive overview of the advances in remote sensing band indices for detecting green tides, including spatiotemporal distribution analysis, area and biomass estimation, drift trajectory modeling, and investigations of their driving mechanisms. Additionally, it identifies the limitations and unresolved challenges in current approaches, such as constraints on data resolution, algorithmic biases, and environmental variability. The potential for integrating multi-source remote sensing data with marine environmental parameters and deep learning techniques is discussed, emphasizing their roles in improving the accuracy and reliability of monitoring and predicting Ulva prolifera green tides. This review aims to guide future research efforts and technological innovations in this field.

Abstract In recent years, the exploration of seabed has been intensified, but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so far. In this study, the physical and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron microscope. The test results suggest that the shear strength of silt and sand increases linearly with the increase of normal stress. Based on the direct shear test, the scanning electron microscope was used to observe the section surface of sand. It is observed that the section surface becomes rough, with many “V”‐shaped cracks. Many particles appear on the surface of the silt structure and tend to be disintegrated. The X‐ray diffraction experiment reveals that the sand and silt have different compositions. The shear strength of sand is slightly greater than that of silt under high stress, which is related to the shape of soil particles and the mineral composition. These results can be a reference for further study of other soils in the Yellow Sea; meanwhile, they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.

More than 30 species of benthic Prorocentrum have been identified, some of which produce okadaic acid (OA) and its derivatives, dinophysistoxins (DTXs), which cause diarrhetic shellfish poisoning (DSP). Increasing numbers of benthic Prorocentrum species have been reported in tropical and subtropical waters of China. In contrast, only a few benthic Prorocentrum species have been reported in temperate waters. In this study, morphological descriptions obtained using light microscopy, scanning electron microscopy and molecular characterization of one Prorocentrum clipeus strain isolated from the Yellow Sea are presented. Prorocentrum clipeus cells were nearly circular in shape, with a collar, ridge, and one protrusion. The periflagellar area was wide U-shaped, with two curved projections on platelet 1a. Nine periflagellar platelets of different sizes were observed. The morphology closely fits that of the species isolated from other locations. Phylogenetic analysis based on the molecular sequences of the small subunit (SSU) rDNA, internal transcribed spacer (ITS), and large subunit (LSU) rDNA was performed. A comprehensive metabolomic analysis incorporating target, suspect and non-target screenings was first applied to investigate the intracellular and extracellular metabolite profiles of the current isolate of P. clipeus. According to the results of the target and suspect screenings, 179 metabolites or toxins produced by DSP-related algal species, including OA, dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2) and pectenotoxin-2 (PTX2), were not detected. Non-target screening involving feature-based molecular networking (FBMN) provided a global view of major metabolites produced by the P. clipeus DF128 strain and revealed 23 clusters belonging to at least 13 compound classes, with organometallic compounds, lipids and lipid-like molecules, phenylpropanoids and polyketides, and benzenoids as major types. To date, this is the first record of the characterization of P. clipeus in samples from Chinese waters. Our results support the wide distribution of epibenthic Prorocentrum species. [ABSTRACT FROM AUTHOR]

Since 2007, the Yellow Sea green tide has broken out every summer, causing great harm to the environment and society. Although satellite remote sensing (RS) has been used in biomass research, there are several shortcomings, such as mixed pixels, atmospheric interference, and difficult field validation. The biomass of green tide has been lacking a high-precision estimation method. In this study, high-resolution unmanned aerial vehicle (UAV) RS was used to quantitatively map the biomass of green tides. By utilizing experimental data from previous studies, a robust relationship was established to link biomass to the red-green-blue floating algae index (RGB-FAI). Then, the lab-based model for green tide biomass from visible images taken by the UAV camera was developed and validated by field measurements. Results show that the accurate and cost-effective method is able to estimate the green tide biomass and its changes in given local waters of the near and far seas. The study provided an effective complement to the traditional satellite RS, as well as high-precision quantitative techniques for decision-making in disaster management. [ABSTRACT FROM AUTHOR]

Sargassum horneri golden tides are increasingly becoming a marine ecological problem in the Yellow Sea (YS) and East China Sea. To understand the genetic relationship between the attached S. horneri along the China coast and the floating biomass in the YS, we used partial rbcL, ITS2, cox1, cox3, and cob-cox2 to analyze the population genetic evolution of 165 Sargassum samples. The results showed that all samples were a single species of S. horneri. Partial sequences of each gene had major haplotypes, and other haplotypes evolved from the occurrence of base mutations. The cob-cox2 gene haplotype research showed only the attached samples from ZJ, LN, and KR contained Hap3, and the distribution proportions of Hap2 and Hap4 in SS and the YS were closest to the distribution of the attached samples from SD. These novel findings provided information about the genetic evolutionary relationship between attached S. horneri along the coast of China and floating S. horneri in the YS, as well as new ideas for tracing the source of floating S. horneri in the YS from a molecular biological perspective. [ABSTRACT FROM AUTHOR]

Despite the predation on picoplankton by diverse protist groups in marine ecosystems, heterotrophic nanoflagellates (HNF) have mainly been used to estimate the predation effect of protists on heterotrophic bacteria. A preliminary investigation was conducted to estimate the predation potential of protist communities including HNF, heterotrophic dinoflagellates, and ciliates on picoplankton in natural assemblages of the Yellow Sea (YS) during summer. A higher density of picoplankton was observed in nearshore waters (station 35-03) than in off-shore waters (stations 35-11 and 35-13). Among the protists, naked ciliates were also distributed in high abundance near the shore. Specifically, small ciliate cells (20–50 µm) were dominant there. HNF showed a different distribution, with higher abundance in off-shore water than in nearshore water. Although predation and ingestion rates of protists on the picoplankton were relatively higher in the nearshore, its predation pressure was on the average of approximately 33% d−1 without a considerable change, despite the different water sampling depths and locations along 35° N. The lower variation in predation pressure by protist predators may have been caused by complementary predation effects between small ciliates and HNF. Further studies are necessary to understand the specific predation of protist groups in the YS. [ABSTRACT FROM AUTHOR]

The Sulu orogenic belt, formed by the collision between Sino‐Korean and South China blocks, has important geological implications due to its unique tectonic setting. To understand the deep crustal structure of the extension of the Sulu orogenic belt in the Yellow Sea, we presented a 220‐km long active‐source ocean‐bottom seismometer wide‐angle reflection/refraction profile across the Yellow Sea. The obtained P‐wave velocity structure exhibits significant horizontal and vertical variations. The middle and upper crustal regions of the north beneath the survey line exhibit a higher velocity and larger thickness than those of the south, whereas the opposite is the case with the lower crust. The lower crustal high‐velocity zone in the Northern Depression of the South Yellow Sea Basin is a manifestation of the mantle material upwelling and accretion to the lower crust. Magmatic intrusions occurred along the faults and formed a high‐velocity zone in the middle and upper crusts. Due to undulating Moho interface and varying crustal velocities, the Qingdao–Rongcheng fault is identified as a fault in the Sulu orogenic belt without the significance of tectonic zoning. This study shows that the Sino‐Korean Block, Sulu orogenic belt and South China Block are bounded by the Jimo–Muping faults (an extension to the sea), Qianliyan fault and deep fault of the South Yellow Sea. Furthermore, the Sulu orogenic belt may have been formed by the northward subduction of the South China Block beneath the Sino‐Korean Block during the Indosinian orogeny to the east of the Shandong Peninsula. [ABSTRACT FROM AUTHOR]

In 2022, Yellow Sea green tide caused by Ulva prolifera reached a historic minimum and the coastal areas of Shandong Peninsula were less affected. However, the largest amount of seaweed biomass has been washed ashore on Lianyungang and Rizhao coasts since 2015. We studied the development pattern of Yellow Sea green tide in 2022, and analyzed the key environmental factors on the growth and drifting, then discussed the possible reasons that resulted in the massive stranding of green tide biomass in Lianyungang and Rizhao. Results show under the combined influence of the east to southeast winds and currents with shoreward anomalies, green tide drifted to the coastal waters between Shandong and Jiangsu provinces and the distribution areas located westward compared with previous years (2008–2021). Floating U. prolifera rafts from the coastal waters of Binhai and Sheyang drifted continuously into the coastal waters of Lianyungang and Rizhao, providing important supplements for Yellow Sea green tide. Because green tide in 2022 distributed close to the coastal waters, the abundant nutrients might support their continuous high growth rate. In addition, the amount of rainfall around Shandong Peninsula from late June to early July were significantly higher than in previous years, which might promote the development of green tide to some extent. [ABSTRACT FROM AUTHOR]

Annual outbreaks of floating Ulva prolifera blooms in the Yellow Sea have caused serious local environmental and economic problems. Rapid and effective monitoring of Ulva blooms from satellite observations with wide spatial-temporal coverage can greatly enhance disaster response efforts. Various satellite sensors and remote sensing methods have been employed for Ulva detection, yet automatic and rapid Ulva detection remains challenging mainly due to complex observation scenarios present in different satellite images, and even within a single satellite image. Here, a reliable and fully automatic method was proposed for the rapid extraction of Ulva features using the Tasseled-Cap Greenness (TCG) index from satellite top-of-atmosphere reflectance (RTOA) data. Based on the TCG characteristics of Ulva and Ulva-free targets, a local adaptive threshold (LAT) approach was utilized to automatically select a TCG threshold for moving pixel windows. When tested on HY1C/D-Coastal Zone Imager (CZI) images, the proposed method, termed the TCG-LAT method, achieved over 95% Ulva detection accuracy though cross-comparison with the TCG and VBFAH indexes with a visually determined threshold. It exhibited robust performance even against complex water backgrounds and under non-optimal observing conditions with sun glint and cloud cover. The TCG-LAT method was further applied to multiple HY1C/D-CZI images for automatic Ulva bloom monitoring in the Yellow Sea in 2023. Moreover, promising results were obtained by applying the TCG-LAT method to multiple optical satellite sensors, including GF-Wide Field View Camera (GF-WFV), HJ-Charge Coupled Device (HJ-CCD), Sentinel2B-Multispectral Imager (S2B-MSI), and the Geostationary Ocean Color Imager (GOCI-II). The TCG-LAT method is poised for integration into operational systems for disaster monitoring to enable the rapid monitoring of Ulva blooms in nearshore waters, facilitated by the availability of near-real-time satellite images. [ABSTRACT FROM AUTHOR]

Ulva prolifera (U. prolifera) green tide outbreaks have occurred in the Yellow Sea of China for many years, causing serious losses to marine ecology and the marine economy. The monitoring and tracking of U. prolifera green tide is a crucial aspect of marine ecological disaster prevention and control management. This paper aims to investigate the spatiotemporal distribution changes in U. prolifera green tide in the Yellow Sea throughout its life cycle. A survey of the Yellow Sea from 2008 to 2023 was conducted using multi-source remote sensing images. Long-term monitoring and analysis of U. prolifera revealed the evolution process of the green tide, including the early development, outbreak, decline, and extinction stages, considering time, space, and frequency of occurrence. Additionally, this study examined peak coverage change patterns over the past 16 years and analyzed the influence of environmental factors such as sea surface temperature and sea surface wind field on the development of U. prolifera. The research results serve as a valuable reference for the monitoring, early warning, and scientific prevention and control of U. prolifera green tide in the Yellow Sea, as well as other similar marine disaster areas. [ABSTRACT FROM AUTHOR]

The influence of continental emissions on the origin and formation mechanisms of atmospheric particulate nitrate (ρ‐NO3−) aerosols in the marine boundary layer remains unclear. Here, synchronous observations of nitrogen isotope ratios (δ15N–NO3−) and oxygen isotope anomaly (Δ17O–NO3−) in ρ‐NO3− were conducted across the Yellow Sea and Bohai Sea in Eastern China. Nitrate concentrations, δ15N–NO3− and Δ17O–NO3− exhibited a pronounced north‐to‐south latitudinal gradient. Combined with backward air mass trajectory analysis, the high nitrate concentration and isotopic characteristics in the northern sea area were found to be affected by the continental outflow near China while the low values in the southern sea area were more related to the oceanic inflow. Stable isotope analysis in R (SIAR) indicated that near the northern sea area, the nitrate radicals (NO3) reacted with hydrocarbons (HC) or dimethyl sulfides (DMS) pathway (NO3 + HC/DMS) played a leading role in nitrate production, whereas the NO2 + OH pathway dominated near the southern sea area. Nitrate in the northern seas originated mainly from nitrogen oxides (NOx = NO + NO2, the gaseous precursor of nitrate) emitted from continental sources, especially coal combustion and biomass burning. While closer to the southern seas, the proportion of NOx generated in the marine environment (from ship and biogenic emissions) increased. Overall, the differential relative contributions of continental and marine atmospheric chemistry and NOx sources lead to the spatial distribution characteristics of atmospheric nitrate concentrations and isotopic values over the Yellow and Bohai Seas. Plain Language Summary: This study investigated the impact of emissions from land sources on the formation of nitrate particles in the air above the marine boundary layer. The researchers conducted observations of nitrogen and oxygen isotopes in nitrate particles across the Yellow Sea and Bohai Sea in Eastern China. They found that nitrate concentrations and isotopic ratios showed a clear gradient from north to south. By analyzing the trajectory of air masses, they determined that high nitrate concentrations in the northern sea area were influenced by emissions from the nearby continent, while lower values in the southern sea area were more related to the ocean. The analysis also revealed that different chemical pathways were responsible for nitrate production in these regions. In the northern seas, nitrate production was primarily driven by the reaction of nitrate radicals with hydrocarbons or dimethyl sulfides, while in the southern seas, the dominant pathway involved the reaction of nitrogen dioxide with hydroxyl radicals. The study further showed that nitrate in the northern seas mainly originated from nitrogen oxides emitted by continental sources such as coal combustion and biomass burning, whereas closer to the southern seas, a larger proportion of nitrogen oxides were generated within the marine environment. Key Points: Continental outflow significantly affects the sources and formation mechanisms of atmospheric nitrate in nearshore marine areasAs continental outflow diminishes, local chemistry and marine‐generated NOx become pivotal in producing atmospheric NO3− in the open ocean. In polluted marine boundary layers, NO3 radical‐related chemistry may play a significant role in the formation of nitrate [ABSTRACT FROM AUTHOR]

The first record of abnormal body coloration in Sebastes koreanus Kim and Lee, 1994, from the Yellow Sea of China, was documented based on morphological characteristics and DNA barcoding. The two rockfish specimens were collected from the coastal waters of Qingdao, China, and the whole body and all fins of them were red. Of the two red-colored rockfish, there were tiny deep red spots on each fin, 2 red radial stripes behind and below the eyes and 1 large deep red blotch on the opercula, while the similar stripe and spot patterns are also present in the S. koreanus specimens with normal body coloration. The countable characteristics of the two specimens are in the range of the morphometry of S. koreanus. To further clarify the species identity and taxonomic status of the two specimens, DNA barcode analysis was carried out. The genetic distance between the red-colored rockfish and S. koreanus was 0, and the minimum net genetic distances between the red-colored rockfish and other Sebastes species except for S. koreanus were 3.0%, which exceeds the threshold of species delimitation. The phylogenetic analysis showed that the DNA barcoding sequences of the two red-colored rockfish clustered with the S. koreanus sequences. The above results of DNA barcode analysis also support that the two red-colored rockfish could be identified as the species of S. koreanus. The mechanism of color variation in S. koreanus is desirable for further research and the species could be an ideal model to study the color-driven speciation of the rockfishes. [ABSTRACT FROM AUTHOR]

Chlorophyll-a (Chl-a) concentration is a primary indicator for marine environmental monitoring. The spatio-temporal variations of sea surface Chl-a concentration in the Yellow Sea (YS) and the East China Sea (ECS) in 2001–2020 were investigated by reconstructing the MODIS Level 3 products with the data interpolation empirical orthogonal function (DINEOF) method. The reconstructed results by interpolating the combined MODIS daily +8-day datasets were found better than those merely by interpolating daily or 8-day data. Chl-a concentration in the YS and the ECS reached its maximum in spring, with blooms occurring, decreased in summer and autumn, and increased in late autumn and early winter. By performing empirical orthogonal function (EOF) decomposition of the reconstructed data fields and correlation analysis with several potential environmental factors, we found that the sea surface temperature (SST) plays a significant role in the seasonal variation of Chl a, especially during spring and summer. The increase of SST in spring and the upper-layer nutrients mixed up during the last winter might favor the occurrence of spring blooms. The high sea surface temperature (SST) throughout the summer would strengthen the vertical stratification and prevent nutrients supply from deep water, resulting in low surface Chl-a concentrations. The sea surface Chl a concentration in the YS was found decreased significantly from 2012 to 2020, which was possibly related to the Pacific Decadal Oscillation (PDO). [ABSTRACT FROM AUTHOR]

Abstract Background Site fidelity, the tendency to return to a previously visited site, is commonly observed in migratory birds. This behaviour would be advantageous if birds returning to the same site, benefit from their previous knowledge about local resources. However, when habitat quality declines at a site over time, birds with lower site fidelity might benefit from a tendency to move to sites with better habitats. As a first step towards understanding the influence of site fidelity on how animals cope with habitat deterioration, here we describe site fidelity variation in two species of sympatric migratory shorebirds (Bar-tailed Godwits Limosa lapponica and Great Knots Calidris tenuirostris). Both species are being impacted by the rapid loss and deterioration of intertidal habitats in the Yellow Sea where they fuel up during their annual long-distance migrations. Methods Using satellite tracking and mark-resighting data, we measured site fidelity in the non-breeding (austral summer) and migration periods, during which both species live and co-occur in Northwest Australia and the Yellow Sea, respectively. Results Site fidelity was generally high in both species, with the majority of individuals using only one site during the non-breeding season and revisiting the same sites during migration. Nevertheless, Great Knots did exhibit lower site fidelity than Bar-tailed Godwits in both Northwest Australia and the Yellow Sea across data types. Conclusions Great Knots encountered substantial habitat deterioration just before and during our study period but show the same rate of decline in population size and individual survival as the less habitat-impacted Bar-tailed Godwits. This suggests that the lower site fidelity of Great Knots might have helped them to cope with the habitat changes. Future studies on movement patterns and their consequences under different environmental conditions by individuals with different degrees of site fidelity could help broaden our understanding of how species might react to, and recover from, local habitat deterioration.

To analyze variations in the vertical distribution of water temperatures and the impact of advection in the central Yellow Sea, multi-layer water temperature and current observations were conducted from 31 May to 8 June 2021. Water temperatures exhibited a typical three-layer summer structure, with a uniform deep-layer temperature averaging 8.23 ± 0.05 °C. The current field was dominated by northeast–southwest tidal currents, but residual current characteristics indicated that non-tidal components significantly influenced circulation. Water temperature changes lagged tidal changes by about 3 h, with strong correlations (R > 0.7), especially in deep layers. Residual currents showed significant correlations with water temperature variations, which were attributed to advective displacement or baroclinic currents. Empirical orthogonal function (EOF) and complex EOF analyses revealed that thermocline variations (T1, explaining approximately 75% of total variance) were driven by strong northward (C1, approximately 34%) and cyclonic (C2, approximately 32%) advection. In deep layers, slight temperature changes were caused by southward Yellow Sea Cold Water Mass (C1) and northward Yellow Sea Warm Current Water (C2) propagation. This study confirms that vertical water temperature variations result from a complex interaction between various advection patterns, with southward tide-induced residual currents (C3, approximately 12%) playing a key dynamic role.

AbstractMugil cephalus Linnaeus, 1758 is a teleost fish widely distributed in coastal waters that plays an important role in commercial fisheries. In the present study, the complete mitogenome of M. cephalus from the Yellow Sea, China, was sequenced using Illumina Novaseq sequencing. The mitogenome of the M. cephalus was 16,744 bases in length (GenBank accession No. ON262567) including 2 rRNA genes, 22 tRNA genes, 13 protein-coding genes and a D-loop control region. The overall base composition of the genome was 28.2% A, 29.5% C, 26.9% T, and 15.4% G. The analysis of genetic similarity and phylogenetic relationship of M. cephalus from different geographic regions of the world indicated that the species from the Yellow Sea was most similar to NWP1 which is one of the three cryptic species of M. cephalus in Northwestern Pacific.

Stomach contents of three commercially important species, anchovy (Engraulis japonica), small yellow croaker (Larimichthys polyactis) and yellow goosefish (Lophius litulon) were analyzed to investigate difference of prey between Spring and Fall. Trawl surveys for target fishes were conducted at 12 stations by the RV Tamgu-8 in the Yellow Sea-Korean side in Spring and Fall 2008 as a part of the United Nations Development Programme/Global Environment Facility (UNDP/GEF), Yellow Sea Large Marine Ecosystem (YSLME) survey. Stomach contents of 50 individuals of each species were analyzed to species level of prey, if the number of specimens was more than 50 for each species. Fullness and digestion condition of stomach contents were determined by five and six levels, respectively. In anchovy stomachs, 23 species in Spring and 15 species in Fall were identified, respectively. Stomach contents were mostly occupied by copepods and euphausiids, mostly Euphausia spp., calyptopis in Spring while by copepods and amphipods in Fall. In small yellow croaker stomachs, 23 species in Spring and 11 species in Fall were identified. Stomach contents were mostly occupied by copepods and euphausiids in Spring, but by only euphausiids in Fall. Total 368 yellow goosefish (151 in Spring and 217 in Fall) were captured, but stomach contents only in Fall were analyzed. Most of stomach contents were anchovy with small proportion of Hakodate sand shrimp, Tanaka’s snailfish, Pacific cod, and miscellaneous things. The present research unveiled that main food items of plankton feeder were distinctly different by species and seasons in the Yellow Sea-Korean side, as coincided with previous reports.

Migratory stopping regions are regarded as geographic bottlenecks. However, knowledge about constraints on migratory communities remains limited. This study proposed hypothetical spatial constraints (SCs) and tested the predictions by examining the response of multifaceted shorebird diversity to the tidal flat area and latitude of the stopping sites along the Yellow Sea coast. We estimated species richness (SR), phylogenetic and functional diversity (PD and FD) by building a species-level phylogenetic tree and measuring five functional traits of all species, using data on the shorebird community at 11 internationally important stopping sites of 2020–2021. We used multiple linear regression models and null models to examine the relationships between diversity metrics and stopping site variables (area and latitude). Functional and phylogenetic rarity of non-least concern species was calculated to estimate their risk of disappearance. The three dimensions of biodiversity decreased with decreasing area despite different slopes (i.e., FD was less sensitive to area than SR, whereas PD was lost more rapidly in smaller areas). In addition, only FD increased at sites approaching the terminal stopping area, implying that SR and PD were restricted from growing by latitude. Inferred from the PD and FD patterns, competitive exclusion tends be the dominant mechanism structuring the community, and the FD-inferred process was intensified in smaller sites toward the northerly terminal site. The area- and latitude-shaped diversity patterns indicate SCs on the migratory community, while a more intensive process of competitive exclusion tends to take place in smaller and near-terminal stopping sites. Consequently, the threatened shorebirds with less competitive capacity may be more prone than others in the SCs. This study highlighting the significance of the multifaceted biodiversity in monitoring the impacts of SCs and facilitating the development of conservation strategies in internationally critical migration bottlenecks.

Two new diatom species belonging to the genus Gomphonemopsis are described, Gomphonemopsis nana sp. nov. and Gomphonemopsis gaoi sp. nov. These two species were compared in detail with congeners. Gomphonemopsis nana is distinguished by its high stria density and small size. This species was found so far to be epiphytic only on the eelgrass collected from Qingdao Bay (Yellow Sea). Gomphonemopsis gaoi is characterized by its isopolar valves, simple proximal raphe endings and acutely rounded apices. This taxon was separated from the exoskeleton of marine copepods sampled from the Futian Mangrove Nature Reserve (South China Sea). In addition, two new combinations, Gomphonemopsis oahuensis (Hustedt) Lang Li, Yuhang Li & Changping Chen, comb. nov. and Gomphonemopsis platypus (Østrup) Lang Li, Yuhang Li & Junxiang Lai, comb. nov. are proposed. This study increases the records and knowledge of Gomphonemopsis along the coast of China. [ABSTRACT FROM AUTHOR]

We estimated the total production of Calanus sinicus over four seasons by measuring somatic and egg production rates in the Yellow Sea. In the process of measuring somatic production, the length–weight relationship and growth rates of C. sinicus in this region were also derived. The population abundance and biomass of C. sinicus were especially high in spring. All copepodite stages had similar proportions in spring, whereas the late stages and adults were most common in summer. The mean total production of the C. sinicus population was 107.6–259.7 μg C m−3 day−1, ranging from higher values in spring to lower values in summer. The annual total production of C. sinicus in the Yellow Sea was 64.3 mg C m−3 year−1 (4032 mg C m−2 year−1). The production of C. sinicus was positively correlated with chlorophyll a concentration, rather than water temperature or salinity. This study is the first to quantify the secondary production of C. sinicus in the Yellow Sea. These findings will broaden our understanding of the ecology of C. sinicus and its contribution to the Yellow Sea food web. [ABSTRACT FROM AUTHOR]

The Yellow Sea (YS) and East China Sea (ECS) are highly dynamic marginal seas of the northwestern Pacific Ocean. To gain an in-depth understanding of zooplankton community structure, zooplankton abundance, biovolume, and size structure in summer 2017 in the YS and ECS were assessed using ZooScan imaging analysis. Zooplankton abundance and biovolume ranged 2.94–1 187.14 inds./m3 and 3.13–3 438.51 mm3/m3, respectively. Based on the biovolume data of the categorized size classes of 26 identified taxonomic groups, the zooplankton community was classified into five groups, and each group was coupled with distinctive oceanographic features. Under the influence of the Yellow Sea Cold Water Mass, the Yellow Sea offshore group featured the lowest bottom temperature (10.84±3.42 °C) and the most abundant Calanoids (mainly in the 2–3 mm size class). In the Yellow Sea inshore group, Hydrozoans showed the largest biovolume and dominated in the 3–4-mm and > 5-mm size classes. The East China Sea offshore group, which was affected by the Kuroshio Branch Current, featured high temperature and salinity, and the lowest bottom dissolved oxygen (2.58±0.5 mg/L). The lowest values of zooplankton abundance and biovolume in the East China Sea offshore group might be attributed to the bottom dissolved oxygen contents. The East China Sea inshore group, which was mainly influenced by the Zhejiang-Fujian Coastal Current and Changjiang Diluted Water, was characterized by high chlorophyll a and the largest biovolume of carnivorous Siphonophores (280.82±303.37 mm3/m3). The Changjiang River estuary offshore group showed the most abundant Cyclopoids, which might be associated with the less turbid water mass in this region. Seawater temperature was considered the most important factor in shaping the size compositions of Calanoids in different groups. [ABSTRACT FROM AUTHOR]

A seasonal variability in flow and sediment flux at the Socheongcho Ocean Research Station (SORS) on the west coast of Korea in 2018 was investigated to elucidate the formation of a two-layered flow structure and changes in sediment transport during stratification. An analysis of SORS data revealed stable temperatures (5–10 °C) in deeper waters, while surface temperatures rose from 6 °C in April to a peak of 30 °C in late August, gradually declining and leading to full water column mixing by late November. This temperature variation induced stratification, influencing the development of a two-layered flow structure. In winter, a singular flow structure was observed, contrasting with the emergence of a two-layered structure as stratification progressed. In the surface layer, residual currents flowed northward in summer and southward in winter, consistent with previous studies. In deeper layers, a southward residual current persisted, irrespective of the season. Sediment flux consistently moved southward, regardless of the season or water depth, with notably higher cumulative sediment flux in the deeper layer (1300 kg·m−2s−1) compared to the surface layer (300 kg·m−2s−1). These findings diverge notably from previous studies, providing new insights into ocean currents and material transport in the Yellow Sea. [ABSTRACT FROM AUTHOR]

Background: Site fidelity, the tendency to return to a previously visited site, is commonly observed in migratory birds. This behaviour would be advantageous if birds returning to the same site, benefit from their previous knowledge about local resources. However, when habitat quality declines at a site over time, birds with lower site fidelity might benefit from a tendency to move to sites with better habitats. As a first step towards understanding the influence of site fidelity on how animals cope with habitat deterioration, here we describe site fidelity variation in two species of sympatric migratory shorebirds (Bar-tailed Godwits Limosa lapponica and Great Knots Calidris tenuirostris). Both species are being impacted by the rapid loss and deterioration of intertidal habitats in the Yellow Sea where they fuel up during their annual long-distance migrations. Methods: Using satellite tracking and mark-resighting data, we measured site fidelity in the non-breeding (austral summer) and migration periods, during which both species live and co-occur in Northwest Australia and the Yellow Sea, respectively. Results: Site fidelity was generally high in both species, with the majority of individuals using only one site during the non-breeding season and revisiting the same sites during migration. Nevertheless, Great Knots did exhibit lower site fidelity than Bar-tailed Godwits in both Northwest Australia and the Yellow Sea across data types. Conclusions: Great Knots encountered substantial habitat deterioration just before and during our study period but show the same rate of decline in population size and individual survival as the less habitat-impacted Bar-tailed Godwits. This suggests that the lower site fidelity of Great Knots might have helped them to cope with the habitat changes. Future studies on movement patterns and their consequences under different environmental conditions by individuals with different degrees of site fidelity could help broaden our understanding of how species might react to, and recover from, local habitat deterioration. [ABSTRACT FROM AUTHOR]

A regional ocean ensemble simulation with slightly different initial conditions demonstrates that internal variability is formed (not only) in the Bohai and Yellow Sea. In this paper, we analyze the relationship between the internal variability and the baroclinic instability, (represented by the Eady predicted theoretical diffusivity K t ; the larger the K t , the stronger the baroclinic instability level). In the ensemble, with tidal forcing, the spatial correlation between the Eady predicted theoretical diffusivity K t and the internal variability amounts to 0.80. Also, the time evolution trends of baroclinic instability and internal variability are similar. Based on this evidence, baroclinic instability may be a significant driver for internal variability. This hypothesis is validated using an additional ensemble of simulations, which is identical to the first ensemble, but this time, the tides are inactivated. This modification leads to an increase in internal variability, combined with the strengthening of baroclinic instability. In addition, the baroclinic instability level and internal variability variation co-vary consistently when comparing summer and winter seasons, both with and without tides. Our interpretation is that a stronger baroclinic instability causes more potential energy to be transformed into kinetic energy, allowing the unforced disturbances to grow. [ABSTRACT FROM AUTHOR]

A new 3D S-velocity model for the crust and upper mantle beneath the Yellow Sea, the East China Sea, the Japan Sea, and the Philippine Sea is determined by means of Rayleigh-wave analysis for depths ranging from 0 to 400 km, and the most conspicuous features of the earth structure in this region are revealed from this model. In the depth range from 5 to 30 km, the S-velocity is principally affected by the thickness of the crust. In the areas with thin crust (oceanic crust), the highest S-velocity values are determined, while the lower S-velocity values are shown for the areas with a transitional crust. For the Japan Sea, the decrease observed in crustal thickness towards the north can be the result of the back-arc spreading that formed this sea from 32 to 10 Ma. Thus, from the four models proposed to explain the oceanic structure of this sea, the model supported by the results determined in the present study is the back-arc spreading model. For the Philippine Sea, the difference in the type of crust determined for the western part and the eastern-northeastern part is consistent with the two different theories, proposed to explain the origins of both parts of this sea. In the depth range from 30 to 60 km, the western part of the Philippine Sea shows higher S-velocity values than the eastern part, because the age of western part of this sea is greater than that of eastern part. The S-velocity difference of 0.2 km/s determined between both parts of this sea implies that the temperature difference within the lithosphere may reach ~370°C. For the western part of this sea, the controversy between the previous different lithospheric-thickness determinations is solved in the present study determining a lithosphere thickness of 90 km. The Japan Sea, the East China Sea, and Okinawa Trough are characterized by thin lithosphere, thick asthenosphere, and low S-velocities. These results and other evidence suggest that from the two models proposed to explain the formation of East Asian rifting system, the model of the back-arc spreading is the most realistic model. The asthenosphere beneath all study area has been precisely located and mapped in S-velocity, for the first time. The Pacific and Philippine Sea slabs and their corresponding mantle wedges above the slabs are also mapped with S-velocities. [ABSTRACT FROM AUTHOR]

Due to the regional differences between the North and South Yellow Sea, and under the influence of winter winds, the relative changes in the coastal current and the Yellow Sea warm current will lead to the instability of the front, which will lead to the cross-front transport of sediment. Therefore, the study of sediment exchange between the North and South Yellow Sea has become an indispensable part of the study of the Yellow Sea environment. In this study, the current field and sediment concentration in the southern part of Chengshantou, a representative area of the Yellow Sea, were observed in winter in order to analyze the sediment exchange process between the North Yellow Sea and the South Yellow Sea in winter. The observation results show that in the southern sea area of Chengshantou, in winter, the current velocity does not change with the water depth when it exceeds 15 m, and the tides are regular semi-diurnal tides. When the water depth is less than 15 m, the current direction changes clockwise with the increase in the water depth. The turbidity increases rapidly when the wind direction is offshore and the bottom residual current is onshore, which may cause the sediment transported offshore under the action of wind and ocean current to settle under the obstruction of the Yellow Sea warm current, resulting in the rise of bottom turbidity. This also indicates that the change in residual current direction at different water depths may also lead to an increase in suspended sediment concentration. Based on this, in the estuarine area, the relative change in the current direction between the wind current and the coastal current may also be the cause of the change in the maximum turbidity zone. [ABSTRACT FROM AUTHOR]