North Yellow Sea Research Articles

Illicit drugs and their metabolites in 36 rivers that drain into the Bohai Sea and north Yellow Sea, north China.

Illicit drugs and their metabolites have recently been recognized as an emerging group of contaminants due to their potential ecotoxicological impact in aquatic ecosystems. To date, information on the occurrence of these compounds in the aquatic environment of China remains limited. In this study, we collected surface water samples from 36 rivers in north China that discharge into the Bohai Sea and north Yellow Sea and measured the concentrations of amphetamine-like compounds, ketamines, cocainics, and opioids. The occurrence and spatial patterns of these substances show significant differences between the rivers and regions. Two designer drugs, methamphetamine (METH) and ketamine (KET), were the most abundant compounds detected in the entire set of samples (detection frequency of 92 and 69%). The concentrations of METH and KET ranged from <0.1 to 42.0ngL(-1) (mean = 4.53ngL(-1)) and <0.05 to 4.50ngL(-1) (mean = 0.49ngL(-1)), respectively. The high detection frequencies of METH and KET are consistent with the fact that they are the main illicit drugs consumed in China. The high concentrations of these illicit drugs and their metabolites were found in areas that have a high population density. The riverine input of total illicit drugs into the Bohai Sea and north Yellow Sea was estimated to be in the range of 684 to 1160kg per year.

Spectral Classification of the Yellow Sea and Implications for Coastal Ocean Color Remote Sensing

Remote sensing reflectance (Rrs) classification of coastal waters is a useful tool to monitor environmental processes and manage marine environmental resources. This study presents classification work for data sets that were collected in the Yellow Sea during six cruises (spring and autumn, 2003; summer and winter, 2006/2007; and spring and autumn, 2007). Specifically, we analyzed classification features of Rrs spectra and obtained spatio-temporal characteristics of reflectance and bio-optical properties in the coastal waters. Yellow Sea waters were classified into the following four typical regions based on their spatial distribution characteristics: middle of the Yellow Sea (MYS), north Yellow Sea (NYS), coastal Shandong (CS), and Jiangsu shoal (JS), and five water type categories consisting of Classes A–E were used to represent water colors from clear to very turbid. Application of this classification scheme to Medium Resolution Imaging Spectrometer (MERIS) imagery revealed seasonal variations in the data, which suggests that the water types have both significant temporal and spatial distributions. In particular, the area of Class E waters in the Jiangsu shoal tended to gradually shrink in summer and expand in winter. The spatio-temporal variability was due to the influence of various environmental factors such as currents, tidal activity, fresh water discharges, monsoon winds, and typhoons.

Paleo‐Fluvial Systems during Marine Isotope Stages 6, 4 and 2 in the North Yellow Sea

Paleo‐Fluvial Systems during Marine Isotope Stages 6, 4 and 2 in the North Yellow Sea

Monthly CO2 at A4HDYD station in a productive shallow marginal sea (Yellow Sea) with a seasonal thermocline: Controlling processes

Based upon 21 field surveys conducted from March 2011 to November 2013, monthly variation of carbon dioxide partial pressure (pCO2) and other carbon system parameters were investigated for the first time (to our knowledge) at A4HDYD station (38°40′N, 122°10′E) located in the North Yellow Sea, a region with a seasonal thermocline. Surface pCO2 was undersaturated from March to May and nearly in equilibrium with the atmosphere from June to August. During September and November, pCO2 declined to a lower level than that from June to August, but reached the highest level in December. In contrast, pCO2 declined to atmospheric CO2 levels in February. Overall, the study area was a net CO2 sink at a rate of 0.85±0.59molCm−2yr−1. The underlying processes governing the variation of pCO2 were also examined. In general, temperature had an important influence on the monthly variation of pCO2, but its effect was counterbalanced by biological production in spring and vertical mixing in early winter. Our study indicated that dynamic mechanism studies based on high temporal resolution observations are urgently needed to understand the complexity of the carbon cycle and detect biogeochemical changes or ecosystem responses to climate change on continental margins.

Sedimentary evolution during the last ~ 1.9 Ma near the western margin of the modern Bohai Sea

Because the Bohai Sea is a semi-enclosed sea connected to the North Yellow Sea only via the Bohai Strait, its sedimentary evolution during the Quaternary has been complex. In particular, the timing of Quaternary transgressions, especially Pleistocene transgressions, in the region, has long been a matter of controversy. Thus, the sedimentary history of the Bohai Sea in the Quaternary is still poorly understood. Borehole core YRD-1101 (200.30m long), drilled in 2011 on the northern coast of the modern Yellow River delta, covers the last ~1.90Ma, as indicated by paleomagnetic measurements. Here we report the results of integrated analyses of the core, including its sedimentary characteristics, downcore changes in environmental proxies (benthic foraminifers and ostracods), and accelerator mass spectrometry (AMS) 14C and optically stimulated luminescence (OSL) dates. From ~1.9 to ~0.83Ma, the environment was fluvial. The first Quaternary transgression occurred at ~0.83Ma (the latest Early Pleistocene), presumably caused by minor subsidence of the Miaodao Islands Uplift. Several relatively weak transgressions occurred from ~0.83Ma to the end of the Middle Pleistocene, and three major marine sedimentary beds, here called T-3, T-2, and T-1 in ascending order, recorded in the early to middle MIS 5, the early MIS 3, and the middle to late Holocene, respectively, were presumably caused by major subsidence of the Miaodao Islands Uplift. In transgression strength, T-3 was weaker than T-2, which was basically the same as T-1. We interpret the change in transgression strength to reflect the interplay of sea-level changes, neotectonic subsidence, and sediment supply changes. Comparisons with other cores from around the Bohai Sea showed that the thickness of the Quaternary sedimentary sequence differs significantly among them, and both the T-2 and T-3 clearly display differences in thickness, facies sequence, and completeness among the cores, highlighting the important role of tectonic activity in the evolution of the Quaternary stratigraphy in the Bohai Bay Basin.

Risk of Surface Sediment Erosion in the Bohai Sea, North Yellow Sea and Its Indication to Tidal Sand Ridge Occurrence

ABSTRACT Tang, C.; Li, Y. F.; Liu, X.; Zhao, Y., and Zhang, H., 2016. Risk of surface sediment erosion in the Bohai Sea, North Yellow Sea and its indication to tidal sand ridge occurrence. Bottom geomorphological evolution and sediment distribution are under strong control of tidal forcing along China's coast. To quantify and assess the temporal-spatial change of bottom environment, a risk-based probabilistic concept of erosion is applied and maps of erosion risk are constructed. Sediment data categorized into 5 classes, together with hydrodynamic data in a temporal resolution of one hour and a model time of one month, are used to calculate the potential of erosion of surface sediments in the Bohai Sea, North Yellow Sea. Comparison with results of the tidal ellipse and bottom shear stress from model output shows that the highest risk of erosion is located in the Yalujiang Estuary, West Korea Bay, north of the Bohai Bay and in the surroundings of the Laotieshan channel of Bohai Strait, which may explain th...

Spatial and temporal variations of pelagic copepods in the North Yellow Sea

This study aims to analyze the spatial and temporal variations of the abundance and biodiversity of pelagic copepods and their relationships with the environmental factors in the North Yellow Sea (NYS). These variations were analyzed on the basis of the survey data of the NYS in four seasons from 2006 to 2007. A total of 31 copepod species that belong to 17 genera, 13 families and 4 orders were identified in the four seasons. Of these copepods, the species belonging to Calanoida is the most abundant component. The dominant species include Calanus sinicus, Centropages abdominalis, Paracalanus parvus, Acartia bifilosa, Oithona plumifera, and Corycaeus affinis. C. sinicus is the most important and widely distributed dominant species in all of the seasons. The dominant species have not shown any significant variation for the past 50 years. However, the richness of warm-water species increased. The abundance of copepods significantly varied among different seasons: the average abundance was higher in spring (608.2 ind m−3) and summer (385.1 ind m−3) than in winter (186.5 ind m−3) and autumn (128.0 ind m−3). Factor analyses showed a high correlation between the spatial distributions of dominant copepods and environmental parameters, and Chl-a was the most important factor that influenced the distribution of copepods. This research can provide the fundamental information related to zooplankton, especially pelagic copepods. This research is also beneficial for the long-term monitoring of zooplankton ecology in the NYS.

Quality Indices as Potential Markers Indicating the Origin of Cultured Scallop (Argopecten irradians) in the North China Sea

The authentication of seafood origin is essential to establish a reliable product traceability system. In principle, appropriate markers can confirm the product origin without additional information. Scallop is an important shellfish product around the world. Its nutritional quality can be closely related to several environmental factors and varies between different habitats, yet it is not known if quality variation can be a reliable marker indicating product origin. In this study, the regional quality characteristics of scallop (Argopecten irradians) harvested from 18 farms in the North China Sea was investigated. Seven nutritional indices (moisture, ash content, sugar, crude protein, ω;3 polyunsaturated fatty acids, condition index, amino acid chemical score) show considerable geographic differences. Based on quality composition data, cluster analysis demonstrates three different scallop product origins: those from the North Yellow Sea and Bohai Sea, Middle Yellow Sea, and Laizhou Bay. Fatty acid biomarkers reveal that quality variations are caused by regional differences in pelagic food sources. Results suggest that nutritional quality indices could be a potential marker to indicate geographic sources of cultured scallop.

Biological production and spatial variation of dimethylated sulfur compounds and their relation with plankton in the North Yellow Sea

The concentrations of dimethylated sulfur compounds and chlorophyll a, as well as biological production and consumption rates of dimethylsulfide (DMS), were measured in the surface water of the North Yellow Sea (NYS, 37–40°N to 121–124°E) in winter 2007. Surface DMS, dissolved and particulate dimethylsulfoniopropionate (DMSPd and DMSPp) concentrations in the study area increased significantly from offshore to inshore sites, with the average values of 2.00, 4.52 and 7.21nM, respectively. The biological production and consumption rates of DMS were estimated, with the average values of 5.41 and 3.84nMd−1, respectively. The spatial variation of chlorophyll a was consistent with that of DMS and DMSP, as well as with that of DMS biological production, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMS and DMSP in the study area. According to the collective data of dimethylated sulfur compounds and DMS biological conversion in China Seas, the dimethylated sulfur compounds concentrations in the NYS during winter were a factor of 2 and 1.3 higher than those in the East China Sea and South China Sea, respectively. Less DMS (DMSP) in NYS was released in winter than that in spring and summer, which could be attributed to the shift in phytoplankton community composition dominated by diatoms to non-diatoms from winter to summer. Quantitative comparison analysis pointed to DMSPp rather than DMSPd as an important precursor of DMS in the surface water. The estimated sea-to-air fluxes of DMS using Liss and Merlivat (LM86), Wanninkhof (W92) and Nightingale (N2000) formulae were 2.72, 5.12 and 4.28μmolm−2d−1, respectively. In the surface water, the biological turnover time of DMS varied from 0.21 to 1.73d with an average of 0.83d, which was about 5.43-fold faster than the mean DMS sea–air turnover time (3.12d), implying that microbial consumption was a main sink of DMS in the surface water.

Spatial distribution of dimethylsulfide and dimethylsulfoniopropionate in the Yellow Sea and Bohai Sea during summer

The distributions of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in surface water of the Yellow Sea and the Bohai Sea were studied during June 2011. The mean concentrations and ranges of DMS, dissolved DMSP (DMSPd), and particulate DMSP (DMSPp) in surface waters were 6.85 (1.60-12.36), 7.25 (2.28-19.05) and 61.87 (6.28-224.01) nmol/L, respectively. There were strong correlations between DMSPp and chlorophyll a in the Bohai Sea and the North Yellow Sea, respectively, and concentrations of DMS and DMSP were high, with a relatively high proportion of dinoflagellates, in the region of the South Yellow Sea Cold Water Mass. Results show that phytoplankton biomass and species composition were important factors that controlled the distribution of DMS and DMSP. Complex environmental factors, including nutrients, transparency, and terrestrial runoff, might also influence the variability in DMS and DMSP. Biological production and consumption rates of DMS in the Bohai Sea were higher than those in the Yellow Sea. DMS production rates were closely correlated with DMSPd concentrations. DMS and DMSP exhibited obvious diel variations, with high concentrations occurring in the late afternoon (16:00-19:00) and low concentrations occurring during the night, implying that the intensity of solar radiation had a significant influence on these variations. Size distributions of chlorophyll a and DMSPp were also investigated and large nanoplankton (5-20 mu m), mainly diatoms, contributed significantly to chlorophyll a and DMSPp at most stations. The average sea-to-air flux of DMS in the study area was estimated to be 11.07 mu mol/(m(2)center dot d) during the summer.

Occurrence of aragonite corrosive water in the North Yellow Sea, near the Yalu River estuary, during a summer flood

To understand seawater CaCO3 saturation state (Ωarag for aragonite and Ωcal for calcite) dynamics in river-dominated ocean margins, we investigated the carbonate system and ancillary parameters in the North Yellow Sea, near the Yalu River estuary, during and after a summer flood (August and September 2013, respectively). During the flood period, nearshore Ωarag ranged from 0.76 to 1.61 and Ωcal ranged from 1.22 to 2.53. Aragonite undersaturation values were associated with quite low salinity of 14.58–25.18 and a broad dissolved oxygen saturation range from 58% to 102%. A week after the flood period, aragonite undersaturated waters together with the estuarine plumes disappeared. Based on field data analyses and simplified model simulation, we suggest that net community respiration/remineralization and the dilution of riverine water discharge both contributed to the low CaCO3 saturation states.

Unexpected Diversity of Magnetococci in Intertidal Sediments of Xiaoshi Island in the North Yellow Sea

Magnetotactic bacteria (MTB) are a group of prokaryotes that, despite their high morphological, phylogenetic, and ecological diversity, share a common capability of forming intracellular nanocrystals of magnetite (Fe3O4) or greigite (Fe3S4), called magnetosomes, and swimming along geomagnetic field lines in a process called magnetotaxis. In this study, we investigated the MTB diversity within the intertidal sediments near Xiaoshi Island (Weihai) in the North Yellow Sea using a combination of molecular ecology techniques and transmission electron microscopy (TEM). The combination of restriction fragment length polymorphism (RFLP) analysis and 16S rRNA gene sequencing revealed seven new MTB genera affiliated with the Alphaproteobacteria class. Fluorescence in situ hybridization (FISH) analyses suggested that one magnetotactic coccus (designated as WHI‐2) is the dominant species. TEM observations and energy dispersive X‐ray analyses revealed that MTB cells mainly form magnetite magnetosomes that are organized into two chains of magnetosomes composed of e‐prismatic magnetite crystals. This finding suggests the adaptation of a magnetotactic bacterial population to the marine tide. This is the first report of magnetotactic bacteria near Xiaoshi Island, which should be useful for studies of biogeochemical cycling and the geohistory of this area.

北黄海獐子岛养殖海域营养水平与虾夷扇贝增殖渔获量评估

PDF HTML阅读 XML下载 导出引用 引用提醒 北黄海獐子岛养殖海域营养水平与虾夷扇贝增殖渔获量评估 DOI: 10.5846/stxb201304220767 作者: 作者单位: 中国科学院海洋研究所海洋生态与环境科学重点实验室,中国科学院海洋研究所海洋生态与环境科学重点实验室,中国科学院海洋研究所海洋生态与环境科学重点实验室,中国科学院海洋研究所海洋生态与环境科学重点实验室,中国科学院海洋研究所海洋生态与环境科学重点实验室,中国水产科学研究院黄海水产研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金创新研究群体科学基金(41121064);国家重点基础研究发展计划973项目课题(2011CB403602) Estimation of nutrient level and fishery yield of Patinopecten yessoensis in mariculture area near the Zhangzidao Island of the north Yellow Sea Author: Affiliation: Key Laboratory of Marine Ecology and Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences,Key Laboratory of Marine Ecology and Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences,Key Laboratory of Marine Ecology and Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences,Institute of Oceanology, Chinese Academy of Sciences,Institute of Oceanology, Chinese Academy of Sciences,Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:营养盐作为浮游植物生长的物质基础,对海洋生态系统的物质循环起着决定性作用。调查研究了獐子岛附近海域营养盐含量水平、空间分布及营养盐结构,并据此估算了现有营养水平可支持的潜在生物量,评估了该海域虾夷扇贝增殖渔获量。结果表明,獐子岛附近海域海水总体营养水平较低,底层水中的营养盐浓度是表层水的2-3倍,海水中的营养盐浓度基本高于浮游植物生长的最低阈值,且溶解无机氮与磷酸盐的比值(DIN/PO4-P)和硅酸盐与磷酸盐的比值(SiO3-Si/PO4-P)均 > 22,全海域为磷营养限制。根据磷限制因子及食物链能流转移理论估算,该海域1000 km2现有的营养水平可支持一个生长周期内虾夷扇贝增殖的动态理论生产量为3.8-6.1万t,如人为增加5%-20%的水体磷,则虾夷扇贝增殖产量可增加0.25-1.00万t。 Abstract:Nutrients as the material basis for phytoplankton growth, play a decisive role in energy flow and matter cycling in marine ecological systems. In this study, the concentrations, spatial distributions and nutrient structure in seawaters near the Zhangzidao Island were studied. Besides, the potential biomass and fishery yield of Patinopecten yessoensis which could be supported by the current nutrient level also were estimated. Results suggested that the concentrations of phosphate (PO4-P), dissolved inorganic nitrogen (DIN) and silicate (SiO3-Si) were in the ranges of 0-0.67, 0.77-9.91 and 1.62-18.77 μmol/L, with averages of 0.19, 4.50 and 7.00 μmol/L, respectively. Among them, DIN was mainly dominated by nitrate nitrogen (NO3-N) with concentrations of 0.04-6.82 μmol/L (average of 2.12 μmol/L), followed by ammonium nitrogen (NH4-N) with concentrations of 0.40-6.07 μmol/L (average of 1.95 μmol/L), and nitrite nitrogen (NO2-N) was lowest with concentrations of 0.05-2.10 μmol/L (average of 0.42 μmol/L). Nutrients in the surface waters displayed a decreasing trend from coastal water to the middle area. This distribution was attributed to the riverine inputs (e.g., the Yalu River), which carried a certain amount of nutrients to the north Yellow Sea (NYS). In contrast, nutrients in the bottom waters presented higher values at the middle area and were 2-3 times higher than those in the surface waters. These distribution models were mainly influenced by the Yellow Sea Cold Water Mass (YSCWM), biological activities and Yellow Sea Warm Current (YSWC). In summer, due to the weak vertical mixing, a stable cold water mass having a large number of organic particles entrenched at the bottom layer in the central part of the NYS. By September, organic particles began to decompose, accompanied by the nutrient release to the bottom waters. These released nutrients were difficult to diffuse to the upper layers due to strong thermocline and pycnocline. Consequently, the nutrient values in the bottom waters at the central part of the NYS were higher. Besides the above reasons, biological activities were also an important factor causing the higher nutrient concentrations in the bottom waters than that in the surface waters. Phytoplankton activities in the euphotic layer were frequent and needed to absorb a lot of nutrients to sustain growth and reproduction, resulting in the loss of nutrients in the surface waters. Moreover, the YSWC could carry waters with high temperature and low nutrients to the surface waters of the NYS, diluting the nutrient concentrations in the surface waters. Therefore, the nutrient concentrations in the surface waters were lower than that in the bottom waters. In addition, nutrient concentrations in waters of the study area were higher than the minimum threshold values for the phytoplankton growth, and DIN/PO4-P ratio (averages of 28.90) and SiO3-Si/PO4-P ratio (averages of 47.27) were > 22, suggesting that PO4-P was the limiting factor. Based on the current PO4-P concentration and energy flow theory of food chain, the potential enhancement field of Patinopecten yessoensis at a growth cycle in 1000 km2 sea area was estimated to be 3.8-6.1×104 t. If 5%-20% of PO4-P was added in this area, the yield of Patinopecten yessoensis would increase 0.25-1.00×104 t. 参考文献 相似文献 引证文献

Bacterial and archaeal communities in sediments of the north Chinese marginal seas.

Microbial communities of the Chinese marginal seas have rarely been reported. Here, bacterial and archaeal community structures and abundance in the surface sediment of four sea areas including the Bohai Sea (BS), North Yellow Sea (NYS), South Yellow Sea (SYS), and the north East China Sea (NECS) were surveyed by 16S ribosomal RNA (rRNA) gene pyrosequencing and quantitative PCR. The results showed that microbial communities of the four geographic areas were distinct from each other at the operational taxonomic unit (OTU) level, whereas the microbial communities of the BS, NYS, and SYS were more similar to each other than to the NECS at higher taxonomic levels. Across all samples, Bacteria were numerically dominant relative to Archaea, and among them, Gammaproteobacteria and Euryarchaeota were predominant in the BS, NYS, and SYS, while Deltaproteobacteria and Thaumarchaeota were prevalent in the NECS. The most abundant bacterial genera were putative sulfur oxidizer and sulfate reducer, suggesting that sulfur cycle processes might prevail in these areas, and the high abundance of dsrB (10(7)-10(8) copies g(-1)) in all sites verified the dominance of sulfate reducer in the north Chinese marginal seas. The differences in sediment sources among the sampling areas were potential explanations for the observed microbial community variations. Furthermore, temperature and dissolved oxygen of bottom water were significant environmental factors in determining both bacterial and archaeal communities, whereas chlorophyll a in sediment was significant only in structuring archaeal community. This study presented an outline of benthic microbial communities and provided insights into understanding the biogeochemical cycles in sediments of the north Chinese marginal seas.

Population genetic structure of chub mackerel Scomber japonicus in the Northwestern Pacific inferred from microsatellite analysis.

Marine pelagic fishes are usually characterized by subtle but complex patterns of genetic differentiation, which are influenced by both historical process and contemporary gene flow. Genetic population differentiation of chub mackerel, Scomber japonicus, was examined across most of its range in the Northwestern Pacific by screening variation of eight microsatellite loci. Our genetic analysis detected a weak but significant genetic structure of chub mackerel, which was characterized by areas of gene flow and isolation by distance. Consistent with previous estimates of stock structure, we found genetic discontinuity between Japan and China samples. Local-scale pattern of genetic differentiation was observed between samples from the Bohai Sea and North Yellow Sea and those from the East China Sea, which we ascribed to differences in spawning time and migratory behavior. Furthermore, the observed homogeneity among collections of chub mackerel from the East and South China Seas could be the result of an interaction between biological characteristics and marine currents. The present study underlies the importance of understanding the biological significance of genetic differentiation to establish management strategies for exploited fish populations.

Analyzing geochemical characteristics and hydrocarbon generation history of the Middle and Upper Jurassic source rocks in the North Yellow Sea Basin

The North Yellow Sea Basin is still in the early stages of exploration. Oil has been recovered from Mesozoic sandstone intervals, but the characteristics of source rocks are not fully understood in this basin. In this study, the geochemical characteristics and the hydrocarbon generation history of the Jurassic source rocks in the North Yellow Sea Basin have been evaluated. The major findings of the study are as follows: (1) The Middle and Upper Jurassic dark gray and gray black mudstones are the main source rocks in the North Yellow Sea Basin. (2) The organic matter of the Middle Jurassic source rocks is derived from terrigenous higher plants and the type of organic matter is predominantly Type III kerogen. The content of organic carbon is moderate for this type of kerogen, and the hydrogen index (HI) is below 100 mg HC/g TOC mostly; therefore, the Middle Jurassic source rocks will produce gas mainly. The organic matter in the Upper Jurassic source rocks was derived from a mixture of terrigenous higher plants and aquatic lower organisms, and is characterized by the coexistence of Types I, II and III kerogen, there are some excellent local source rock intervals with high organic carbon and higher HI values, which constitute the main oil source rocks. (3) The Middle Jurassic source rocks have fair-poor hydrocarbon-generative potential and the Upper Jurassic source rocks have fair-good hydrocarbon-generative potential. (4) Hydrocarbon generation history models indicate that the Middle Jurassic source rocks reached late mature stages and the Upper Jurassic source rocks reached the oil window at the present-day. These two sets of source rocks all didn’t reach the peak of oil and gas generation in NYS2 well.

The importance of Yalu Jiang coastal wetland in the north Yellow Sea to Bar-tailed GodwitsLimosa lapponicaand Great KnotsCalidris tenuirostrisduring northward migration

SummaryBar-tailed GodwitsLimosa lapponicaand Great KnotsCalidris tenuirostrisare long-distance migratory shorebirds with declining numbers in the East Asian-Australasian Flyway. One of the most important staging sites for these two species during northward migration is Yalu Jiang coastal wetland in the north Yellow Sea. Historical counts have been limited to once a year and conducted at different periods; these yield inadequate data for population monitoring. We estimated the numbers of Bar-tailed Godwits and Great Knots and described their migration phenology during northward migration from 2010 to 2012 at the Yalu Jiang coastal wetland, using a combination of periodic area-wide counts over the migration period and a modelling approach that estimates passage times and total numbers of birds transiting. The mean arrival date forL. l. bauerigodwits was 29 March and mean departure date was 8 May. Corresponding dates were 11 April and 15 May forL. l. menzbierigodwits and 7 April and 14 May for Great Knots. We estimated that an annual average of over 68,000 Bar-tailed Godwits and 44,000 Great Knots used the area on northward migration from 2010–2012. Our results indicate that the Yalu Jiang coastal wetland supports on average at least 42% of the flyway’s northward-migratingL. l. bauerigodwits, 19% ofL. l. menzbierigodwits, and 22% of the Great Knots. Comparisons with historical counts conducted during peak migration periods indicate a 13% decline in Bar-tailed Godwits since 2004 and an 18% decline in Great Knots since 1999. Our results confirm that the study area remains the most important northward migration staging site for Bar-tailed Godwits and indicate that it has become the most important northward migration staging site for Great Knots along the flyway.

Factors Affecting the Distribution Patterns of Benthic Invertebrates at a Major Shorebird Staging Site in the Yellow Sea, China

The tidal flats of the Yellow Sea support benthic communities that are vitally important to migratory birds, but baseline information on benthic community structure and variability is largely lacking. We investigated spatial and temporal patterns of macrobenthic invertebrates in areas used by large numbers of shorebirds and how these patterns related to environmental factors at Yalu Jiang coastal wetland in the north Yellow Sea during boreal spring (March–May) from 2010 to 2012. At least 61 species were documented during the study. Monthly benthos sampling from 54 stations indicated that polychaetes and bivalves dominated the benthic communities, with capitellid or maldanid polychaetes dominating upper tidal flats and the bivalve Potamocorbula laevis dominating intermediate and lower tidal flats. The middle and eastern sites approximately 10 km apart showed substantial differences in benthic species abundance and distribution, with bivalves dominating in the middle but not the eastern site. The spatial distribution of benthos was correlated with both exposure time during the tidal cycle and sediment particle size. Benthic communities showed both annual and within season variation. Two of the frequent prey for migratory birds, namely ghost shrimps Nihonotrypaea japonica and young Potamocorbula laevis, were relatively common in 2010 and 2011, respectively, but not in 2012.

SSU rDNA sequence diversity and seasonally differentiated distribution of nanoplanktonic ciliates in neritic Bohai and Yellow Seas as revealed by T-RFLP.

Nanociliates have been frequently found to be important players in the marine microbial loop, however, little is known about their diversity and distribution in coastal ecosystems. We investigated the molecular diversity and distribution patterns of nanoplanktonic oligotrich and choreotrich (OC) ciliates in surface water of three neritic basins of northern China, the South Yellow Sea (SYS), North Yellow Sea (NYS), and Bohai Sea (BS) in June and November 2011. SSU rRNA gene clone libraries generated from three summertime samples (sites B38, B4 and H8) were analyzed and revealed a large novel ribotype diversity, of which many were low-abundant phylotypes belonging to the subclass Oligotrichia, but divergent from described morphospecies. Based on the data of terminal-restriction fragment length polymorphism (T-RFLP) analysis of all 35 samples, we found that the T-RF richness was generally higher in the SYS than in the BS, and negatively correlated with the molar ratio of P to Si. Overall, multidimensional scaling and permutational multivariate analysis of variance of the community turnover demonstrated a distinct seasonal pattern but no basin-to-basin differentiation across all samples. Nevertheless, significant community differences among basins were recognized in the winter dataset. Mantel tests showed that the environmental factors, P:Si ratio, water temperature and concentration of dissolved oxygen (DO), determined the community across all samples. However, both biogeographic distance and environment shaped the community in winter, with DO being the most important physicochemical factor. Our results indicate that the stoichiometric ratio of P:Si is a key factor, through which the phytoplankton community may be shaped, resulting in a cascade effect on the diversity and community composition of OC nanociliates in the N-rich, Si-limited coastal surface waters, and that the Yellow Sea Warm Current drives the nanociliate community, and possibly the microbial food webs, in the coastal ecosystem in winter.

Distribution and abundance of pelagic tunicates in the North Yellow Sea

In this paper, the distribution patterns and abundance of pelagic tunicates in the North Yellow Sea of China during the period 2006–2007 were analyzed. Zooplankton samples were obtained with vertical towing from bottom to surface using a WP2 plankton net (200 μm mesh size; mouth area: 0.25 m2). Five species belonging to two classes were identified: Oikopleura dioica, O. longicauda and Fritillaria borealis belonging to class Appendicularia; Salpa fusiformis and Doliolum denticulatum of class Thaliacea. O. dioica and O. longicauda were the dominant species, occurring in the samples of all four seasons, with different distribution patterns. Their maximum abundance were 1664.7 ind. m−3 (spring) and 1031.7 ind. m−3 (spring) respectively. Following Oikopleura spp. were D. denticulatum, which was found only in autumn with an average abundance of 149.6 ind. m−3, and S. fusiformis, which was detected all the year long except for autumn with low abundance (max. abundance 289.4 ind. m−3 in summer). Only a very small amount of F. borealis was detected in summer samples, with an average abundance of 2.7 ind. m−3. The relationship between tunicates abundances and the environmental factors was analyzed using the stepwise regression model for each species. The variation of appendicularian abundance showed a significant correlation with the surface water temperature and with the concentration of Chl-a. No relationship was found between tunicates abundance and salinity, likely due to the slight changes in surface salinity of the studied area during the four seasons. Salps abundance and that of doliolids were significantly correlated to bottom water temperature, indicating that these two species (S. fusiformis and D. denticulatum) migrate vertically in the water column. In particular D. denticulatum, known to be a warm water species, showed not only an important correlation with water temperature, but also a spatial distribution connected to the warm currents in the North Yellow Sea. The occurrence of D. denticulatum represents an interesting result never found in past research work. Water temperature, algal distribution and currents were the most relevant environmental factors influencing the tunicate abundance and distribution in the North Yellow Sea. Further research is needed in order to get more information on the ecology of these organisms and to better understand their role in the ecosystem including the oceanic food web.