Geochemical characteristics of nitrogen in the southern Yellow Sea surface sediments

Roles and distributions of various forms of nitrogen in biogeochemical cycling in the southern Yellow Sea surface sediments were investigated. The southern Yellow Sea could be divided into three regions (I, II and III) according to the proportion of fine-grained sediment in > 65%, 35-65% and < 35%, respectively. The ratios of different forms of nitrogen contents between each two of the three regions indicated that the nitrogen contents increased with the proportion of fine-grained sediment increasing. The quanta of exchangeable forms of nitrogen were similar in the three regions, while their releasing time increased from regions I to III, indicating that the cycle of nitrogen in fine-grained sediments was shorter than that in coarse-grained sediments. Nitrogen burial fluxes were also similar in these regions, while the burial efficiency increased from regions I to III. The highest burial efficiency was 30.21% in region III, indicating that more than 70% of nitrogen in the southern Yellow Sea surface sediments could be released to take part in biogeochemical recycling. When all the four forms of exchangeable nitrogen (nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidant extractable form (SOEF-N)) were released to take part in recycling, their potential contributions were 80% (SOEF-N), 11% (IEF-N), 6% (SAEF-N), 3% (WAEF-N) respectively, which showed that SOEF-N was the predominant one, and its contribution to biogeochemical cycling was the highest. (c) 2004 Elsevier B.V. All rights reserved.

Impact of tidal front on the distribution of bacterioplankton in the southern Yellow Sea, China

Three surveys were carried out in anchovy spawning periods in southern Yellow Sea in May and June 2001, and June 2002. Chlorophyll a (Chl-a) concentration, bacterioplankton abundance, biomass and their variations along the zone of tidal fronts were investigated. The results showed that (1) high Synechococcus abundance distributed more often in frontal area and middle-surface layer of a stratified zone; and (2) the maximal abundance of bacteria occurred in stratified and mixed zone. 2006 Elsevier B.V. All rights reserved.

Meso-scale spatial distribution of large tintinnids in early summer in southern Yellow Sea

The spatial distribution of some large tintinnid species (nominally>76 mu m) was investigated according to samples collected by vertical towing in cruises to the southern Yellow Sea in summer 2000-2002 and 2004. Eight species were identified: Codonellopsis mobilis, Leprotintinnus netritus, Tintinnopsis karajacensis, T. japonica, T. kiaochowensis, T. butschlii, T. radix, and Parafavella sp. With maximum abundance of 158.2 ind/L in June 2004, C mobilis was the dominant species, lasting from May to July 2004. Tintinnid communities were patchy and distributed mainly in shallow waters along the shore.

PCBs and its coupling with eco-environments in Southern Yellow Sea surface sediments

In this paper, the spatial distribution and source of the PCBs in surface sediments of the Southern Yellow Sea (SYS) and influencing factors, such as the sediment characteristics (components, relative proportions and total organic carbon contents), and hydrodynamic conditions were analyzed. PCB concentrations in the surface sediments ranged from 518-5848 pg/g, with average values of 1715 pg/g decreasing sharply compared to last year. In the study area, the PCB pollution level in the middle area was the highest, followed by that of the east coast and the west coast, respectively. Although the PCB level in the coastal areas was lower than that in the middle areas, it was proven in our study that the Yellow Sea obtained PCBs by virtue of river inputs. There was a positive and pertinent correlation between the clay proportion and PCB concentrations, and the increase of the PCB concentrations was directly proportional to the increase of TOC contents, with r = 0.61, but it was contrary to the sediment grain size. Consequently, the factors controlling PCB distribution had direct or indirect relationships with sediment grain size; moreover, the hydrodynamic conditions determined the sediment components and grain size. In conclusion, hydrodynamic conditions of the Yellow Sea were the most important influencing factors effecting the distribution of PCBs in the surface sediments of the SYS. (C) 2007 Elsevier Ltd. All rights reserved.

Observational evidence of the Yellow Sea warm current

The Yellow Sea Warm Current (YSWC) is one of the principal currents in the Yellow Sea in winter. Former examinations on current activity in the Yellow Sea have not observed a stable YSWC because of the positioning of current meters. To further understand the YSWC, a research cruise in the southern Yellow Sea was carried out in the winter of 2006/2007. Five moorings with bottom-mounted acoustic Doppler current profilers (ADCP) were deployed on the western side of the central trough of the Yellow Sea. The existence and distributional features of the YSWC were studied by analyzing three ADCP moorings in the path of the YSWC in conjunction with conductivity-temperature-depth (CTD) data over the observed area in the southern Yellow Sea. The results show the following. (1) The upper layer of the YSWC is strongly influenced by winter cold surge; its direction and speed often vary along a south-north axis when strong cold surges arrive from the north. (2) The YSWC near the bottom layer is a stable northwest flowing current with a speed of 4 to 10 cm/s. By combining the analyses of the CTD data, we speculate that the core of the YSWC may lie near the bottom. (3) On a monthly average timescale, the YSWC is stably oriented with northward flow from the sea surface to the sea floor.

Observation of the seasonal evolution of the Yellow Sea Cold Water Mass in 1996-1998

We use the hydrographic data obtained during the joint survey of the Yellow Sea by the First Institute of Oceanography, China and the Korea Ocean Research and Development Institute, Korea, to quantify the spatial structures and temporal evolution of the southern Yellow Sea Cold Water Mass (YSCWM). It is indicated that the southern YSCWM is a water mass that develops in summer and decays in fall. In winter, due to the intrusion of the Yellow Sea Warm Current (YSWC), the central area (approximately between 34 degrees N and 35 degrees N, 122 degrees E and 124 degrees E) of the Yellow Sea is mainly occupied by relatively high temperature water (T > 10 degrees C). By contrast, from early summer to fall, under the seasonal thermocline, the central area of Yellow Sea is occupied by cold water (T < 10 degrees C). In summer, the southern YSCWM has two cold cores. One is formed locally southeast of Shandong Peninsula, and the other one has a tongue-like feature occupying the area approximately between 34 degrees N and 37 degrees N, 123 degrees E and 126 degrees E. The bottom layer temperature anomalies from February to July in the cold tongue region, along with the trajectories of the bottom floaters, suggest that the cold water mass in the northeast region has a displacement from the north to the central area of the Yellow Sea during the summer. (c) 2007 Elsevier Ltd. All rights reserved.

The Yellow Sea cold bottom water - an oversummering site for Calanus sinicus (Copepoda, Crustacea)

The vertical distribution and stage-specific abundance of Calanus sinicus were investigated on three key transects in the southern Yellow Sea and the northern East China Sea in August 1999. The results showed that in summer C. sinicus shrank its distribution area to the central cold (less than or equal to10degreesC) bottom water in the Yellow Sea, i.e. the Yellow Sea Cold Bottom Water, remaining in high abundance (345.7 ind m(-3)). In the northern East China Sea on a transect from the mouth of the Yangtze River to the Okinawa trench, only a few individuals appeared in the inner side and none had been found either in the upper layer or in the deep layer of the outer shelf area. The population of C. sinicus in YSCBW consisted of mainly adults (46.83%) and C5 (37.41%). C1-C4 only accounted for 15.76%. The low proportion of the earlier copepodite stages and the high female:male ratio (11.39) indicated that the reproduction of C. sinicus in YSCBW was at a very low level due to the low temperature and low food concentration. It is concluded that the dramatic decrease of C. sinicus population in the shelf area of China seas in summer is caused by the shrinkage of its distribution area and the YSCBW served as an oversummering site.

Petroleum geological framework and hydrocarbon potential in the Yellow Sea

Sedimentary basins in the Yellow Sea can be grouped tectonically into the North Yellow Sea Basin (NYSB), the northern basin of the South Yellow Sea (SYSNB) and the southern basin of the South Yellow Sea (SYSSB). The NYSB is connected to Anju Basin to the east. The SYSSB extends to Subei Basin to the west. The acoustic basement of basins in the North Yellow Sea and South Yellow Sea is disparate, having different stratigraphic evolution and oil accumulation features, even though they have been under the same stress regime since the Late Triassic. The acoustic basement of the NYSB features China-Korea Platform crystalline rocks, whereas those in the SYSNB and SYSSB are of the Paleozoic Yangtze Platform sedimentary layers or metamorphic rocks. Since the Late Mesozoic terrestrial strata in the eastern of the NYSB (West Korea Bay Basin) were discovered having industrial hydrocarbon accumulation, the oil potential in the Mesozoic strata in the west depression of the basin could be promising, although the petroleum exploration in the South Yellow Sea has made no break-through yet. New deep reflection data and several drilling wells have indicated the source rock of the Mesozoic in the basins of South Yellow Sea, and the Paleozoic platform marine facies in the SYSSB and Central Rise could be the other hosts of oil or natural gas. The Mesozoic hydrocarbon could be found in the Mesozoic of the foredeep basin in the SYSNB that bears potential hydrocarbon in thick Cretaceous strata, and so does the SYSSB where the same petroleum system exists to that of oil-bearing Subei Basin.

An N-shape thermal front in the western South Yellow Sea in winter

An N-shape thermal front in the western South Yellow Sea (YS) in winter was detected using Advanced Very High Resolution Radiation (AVHRR) Sea Surface Temperature data and in-situ observations with a merged front-detecting method. The front, which exists from late October through early March, consists of western and eastern wings extending roughly along the northeast-southwest isobaths with a southeastward middle segment across the 20-50 m isobaths. There are north and south inflexions connecting the middle segment with the western and eastern wings, respectively. The middle segment gradually moves southwestward from November through February with its length increasing from 62 km to 107 km and the southern inflexion moving from 36.2A degrees N to 35.3A degrees N. A cold tongue is found to coexist with the N-shape front, and is carried by the coastal jet penetrating southward from the tip of the Shandong Peninsula into the western South YS as revealed by a numerical simulation. After departing from the coast, the jet flows as an anti-cyclonic recirculation below 10 m depth, trapping warmer water originally carried by the compensating Yellow Sea Warm Current (YSWC). A northwestward flowing branch of the YSWC is also found on the lowest level south of the front. The N-shape front initially forms between the cold tongue and warm water involved in the subsurface anti-cyclonical recirculation and extends upwards to the surface through vertical advection and mixing. Correlation analyses reveal that northerly and easterly winds tend to be favorable to the formation and extension of the N-shape front probably through strengthening of the coastal jet and shifting the YSWC pathway eastward, respectively.

Feeding and egg production of the planktonic copepod Calanus sinicus in spring and autumn in the Yellow Sea, China

Shipboard incubations were conducted in spring (April) and autumn (October/November) 2006 to measure the feeding and egg production rates (EPR) of Calanus sinicus in the Yellow Sea, China. The ingestion rate (2.08-11.46 and 0.26-3.70 mu g C female(-1) day(-1) in spring and autumn, respectively) was positively correlated with microplankton carbon concentrations. In the northern part of the Yellow Sea, feeding on microplankton easily covers the respiratory and production requirements, whereas in the southern part in spring and in the frontal zone in autumn, C. sinicus must ingest alternative food sources. Low ingestion rates, no egg production and the dominance of the fifth copepodite (CV) stage indicated that C. sinicus was in quiescence inside the Yellow Sea Cold Bottom Water (YSCBW) area in autumn. Calanus sinicus ingested ciliates preferentially over other components of the microplankton. The EPR (0.16-12.6 eggs female(-1) day(-1) in spring and 11.4 eggs female(-1) day(-1) at only one station in autumn) increased with ciliate standing stock. Gross growth efficiency (GGE) was 13.4% (3-39%) in spring, which was correlated with the proportion of ciliates in the diet. These results indicate that ciliates have higher nutrient quality than other food items, but the low GGE indicates that the diet of C. sinicus is nutritionally incomplete.

Characteristics of nitrogen forms in the southern Huanghai Sea surface sediments

The distributions of different forms of nitrogen in the surface sediments of the southern Huanghai Sea are different and affected by various factors. The contents of IEF-N, SOEF-N and TN gradually decrease eastward, and those of SAEF-N northward, while those of WAEF-N westward. Around the seaport of the old Huanghe (Yellow) River, the contents of both SOEF-N and TN are the highest. Among all the factors, the content of fine sediment is the predominant factor to affect the distributions of different forms of nitrogen. The contents of IEF-N, SOEF-N, and TN have visibly positive correlation with the content of fine sediments, and the correlative coefficient is 0.68, 0.58 and 0.71 respectively, showing that the contents of the three forms of nitrogen increase with those of fine sediments. The content of WAEF-N is related to that of fine sediments to a certain extent, with a correlative coefficient of 0.35; while the content of SAEF-N is not related to that of fine sediments, showing that the content of SAEF-N is not controlled by fine grain-size fractions of sediments. In addition, the distributions of different forms of nitrogen are also interacted one another, and the contents of IEF-N and SOEF-N are obviously affected by TN, while those of inorganic nitrogen (WAEF-N, SAEF-N and IEF-N) are not affected by SOEF-N and TN obviously, although they are interacted each other.

Optical, radiative, and source characteristics of aerosols at Minicoy, a remote island in the southern Arabian Sea

Extensive measurements of aerosol radiative and microphysical properties were made at an island location, Minicoy (8.3 degrees N, 73.04 degrees E) in the southern Arabian Sea. A large variability in aerosol characteristics associated with changes in air mass and precipitation characteristics was observed. Six distinct transport pathways were identified on the basis of cluster analysis. The Indo-Gangetic Plain, along with the northern Arabian Sea and west Asia (NWA), was identified to be the region having the highest potential for aerosol mass loading at the island. This estimate is based on the concentration weighted trajectory as well as cluster analysis. Dust transport from the NWA region was found to make a substantial contribution to the supermicron mass fraction. The black carbon mass mixing ratios observed were the lowest compared to previous measurements over this region. Consequently, the atmospheric radiative forcing efficiency was low and was in the range 10-28 W m(-2).

Mellum Island (southern North Sea): dynamic processes and sedimentary structures. I. Southern tidal flat, transition zone and high-surface.[p.72 (Blasensand) only][Translation from: Senckenbergiana Maritima 11, 59-113, 1979]

This partial translation of a longer article describes the phenomenon of ”Blasensand”. Blasensand is formed when sedimentation of dried out sand is suddenly flooded from above. A more detailed explanation of Blasensand is given in this translated part of the paper.