Late Quaternary stable isotope record and meltwater discharge anomaly events to the south of the Antarctic Polar Front,Drake Passage

Marine isotope stages (MISs) 1 to 5 were identified in the planktonic ¹⁸O record in sediment core DP00-02 just south of the Antarctic Polar Front in the Drake Passage, Antarctica. The oxygen isotope record, based on Neogloboquadrina pachyderma sinistral, is correlated with the contemporaneous global ¹⁸O stratigraphy. Marked deviations from the global climate curve suggest a local/regional overprint, particularly during MIS 3 which is considered a colder time period in the ocean record than MIS 1 and MIS 5 during the last interglacial. The comparison shows that negative ¹⁸O shifts in core DP00-02 during MIS 3 are larger than mean global changes which show a shift equal to or smaller than 0.5. The isotope shift, exceeding the glacial-interglacial ice volume effect, probably resulted from changes in the isotope composition of seawater, which is linearly related to decreases in salinity rather than to increases in sea-surface temperature. Increased ice-rafted debris (IRD) content during this interval indicates a strong influx of IRD from melting ice shelves and icebergs, which may be related to upwelling of warmer circumpolar deep water.     

Surge hindcast in the East China sea

Two typhoon surges generated during July–August 1978 are investigated numerically with the use of a vertically-integrated finite-difference model of the Yellow Sea and the East China Sea. The hindcast scheme involves processing pressure data from weather charts to provide the necessary meteorological forcing to a sea model that computes the response in terms of water levels and currents. Computed residuals are compared with hourly records from selected tide gauges (Inchon, Kunsan, Mokpo, Jeju and Yeosu) along the coast of Korea. Some of the preliminary results are presented and discussed.     

Molecular phylogenetic analyses of threeSynechococcus strains isolated from seawater near the ieodo ocean research station

ThreeSynechococcus strains were isolated from seawater near the Ieodo Ocean Research Station (IORS), and their 16S rDNA genes and the internal transcribed spacer (ITS) between the 16S and 23S rRNA genes were sequenced to investigate their phylogenetic relationships. Phylogenetic trees based on the 16S rDNA and ITS sequences showed that they clustered in the main MC-ASynechococcus group (subcluster 5.1), but formed branches differentiating them from the described clades. As the IORS is located in an area affected by diverse water masses, highSynechococcus diversity is expected in the area. Therefore, the IORS might be a good site to study the diversity, physiology, and distribution of theSynechococcus group. Key words —Synechococcus, Phylogeney, 16S rRNA, ITS gene, Ieodo     

Recent sediment accumulation and origin of shelf mud deposits in the Yellow and East China Seas

Modern (last 100 yr) accumulation rates of shelf mud deposits in the Yellow and East China Seas were investigated using the distribution of excess ²¹⁰Pb (²¹⁰Pb_ex) in sediment core samples. Compilation and merger of new and previously published data helped clarify sediment accumulation in these seas. The estimated accumulation rates, together with data of suspended sediment concentrations, provided findings on the sediment budget, origin, and transport pathway of the mud deposits. The overall accumulation distribution in the Yellow and East China Sea shelf revealed a general, cross-shelf decreasing trend along the sediment dispersal system away from the rivers, except for the South Sea (SSM) and southeastern Yellow Sea (SEYSM) mud patches found along the Korean coast. Notably, ²¹⁰Pb_ex activity profiles within the SSM and the SEYSM yielded a relatively high accumulation rate of 2-5 mm/yr, implying a sedimentation rate of 4-15 × 10⁷ tons per year in this coastal zone. Such an annual accumulation rate is about one order of magnitude greater than the total sediment discharge (6-20 × 10⁶ tons/yr) from Korean rivers, suggesting an additional offshore source. The distribution pattern of the well-defined suspended plume clearly showed the possible transport and exchange of fine-grained sediments between the ECS shelf and the coastal area of Korea, especially during winter. Such a high accumulation in Korean coastal areas is attributable to the sediments supplied from the mud deposit of the ECS (i.e., SWCIM), with origins in Chinese rivers. Therefore, the Korean coastal area may be an important sink for some of Chinese river sediments being transported from the south by the Yellow Sea Warm Current.     

Accumulation and biological mixing of Peru margin sediments

Rates of sediment accumulation and biological particle mixing in eight cores from the Peru shelf have been estimated by application of uranium-series disequilibrium techniques and radiocarbon dating. Activities of ²¹⁰Pb, ²²⁶Ra, ²³⁴Th and ²³⁸U have been determined in closely spaced intervals in each sediment core. Biological particle mixing coefficients were determined via a two-box advection-diffusion steady-state mixing model based on the distribution profiles of excess ²¹⁰Pb and, in some cases, excess ²³⁴Th activities.

The sedimentation rates estimated were in the order of a few millimeters/yr except for cores enriched in phosphatic components which displayed rates a few orders of magnitude slower. Bioturbation was significant in most cores studied with the exception of one core collected from within the middle of the oxygen-minimum zone. Estimated biological mixing coefficients were in the order of 10⁰–10¹ cm² yr⁻¹ for the surface mixed layer and 10⁻¹–10⁰ cm² yr⁻¹ for the layer below. Sediment slumping appears to have affected the ²¹⁰Pb distribution of two or three of our cores.     

Circulation and its seasonal variability in region around the Kerguelen Plateau

A coupled ice-ocean isopycnal numerical model of the Southern Ocean is established tostudy the circulation and its seasonal variability in the region around the Kerguelen Plateau. An analysis of the simulated results shows significant stripe-like structure and non-zonal feature of the Antarctic Cir-cumpolar Current (ACC) in this region. ACC begins to bifurcate and to turn its direction before meeting the plateau. The southernmost branch of ACC is near to the Antarctic coast and displays its strong interaction with the westward Antarctic Slope Current. The northern branch of ACC has a tendency of annual variations while the southern one varies in a semiannual cycle. The variation phases of both branches are coincident with that of the wind stress in this region.     

Storm-induced fine-sediment transport,west coast of south Korea

Archived data, together with field observations collected between 1980 and 1982 off the west coast of Korea, suggest that the onset of winter monsoon winds in late fall initiates a residual southward flow that potentially carries large volumes of resuspended bottom sediments into the Korea Strait. During the calm conditions of summer, muds are replenished by high river discharges and reform the band of soft material, which characteristically occurs as a series of mudflats near the coast. Thus, these mudflats serve as a temporary storage facility during summer accumulation and as a source during winter erosion.     

Redescription of free-living marine nematode, dracograllus filipjevi allen and noffsinger, 1978 (nematoda: draconematidae) from korea

A draconematid nematode species,Dracograllus filipjevi Allen and Noffsinger, 1978, is described from the washings of shallow littoral coralline algae at Guryongpo in the eastern coast of Korea. This species is recognized by the following characteristics: larger body size, number of posterior sublateral adhesion tubes (9 in male and 12-13 in female) and subventral adhesion tubes (8-9 in male and 9-10 in female), the absence of cephalic acanthiform setae on rostrum, the presence of longitudinally areolated body cuticle with dot-like punctations, the presence of some cuticular collar in swollen pharyngeal region, the shape of amphidial fovea (large, elongate, and loop-shaped in both sexes), the absence of preanal corniform setae, and the absence of lateral differentiation on narrow body region. Morphological features of the species using differential interference contrast photomicrographs are described in detail in the present work. This is the first report ofD. filipjevi in Korea.     

Effects of several salt marsh plants on mouse spleen and thymus cell proliferation using mtt assay

In the present study, we have tested the effects of 21 salt marsh plants on cell proliferation of mouse immune cells (spleen and thymus) using MTT assay in culture. The methanolic extracts of six salt marsh plants (Rosa rugosa, Ixeris tamagawaensis, Artemisia capillaris, Tetragonia tetragonoides, Erigeron annus, and Glehnia littoralis) showed very powerful suppressive effects of mouse immune cell death and significant activities of cell proliferationin vitro. Especially, the methanolic extract ofRosa rugosa was found to have fifteen times compared to the control treatment, demonstrating that Rosa rugosa may have a potent stimulation effect on immune cell proliferation. These results suggest that several salt marsh plants includingRosa rugosa could be useful for further study as an immunomodulating agent.     

Numerical modeling of tide and tidal current in the kangjin bay,south sea,Korea

This study is based on a series of numerical modeling experiments to understand the tidal circulation in the Kangjin Bay (KB). The tidal circulation in the KB is mostly controlled by the inflow from two channels, Noryang and Daebang which introduce the open ocean water into the northern part of the KB with relatively strong tidal current, while in the southern part of the KB, shallowest region of the entire study area, weak tidal current prevails. The model prediction of the sea level agrees with observed records at skill scores exceeding 90 % in terms of the four major tidal constituents (M2, S2, K1, O1). However, the skill scores for the tidal current show relatively lower values of 87, 99, 59, 23 for the semi-major axes of the constituents, respectively. The tidal ellipse parameters in the KB are such that the semi-major axes of the ellipse for M2 range from 1.7 to 38.5 cm/s and those for S2 range from 0.5 to 14.4 cm/s. The orientations of the major-axes show parallel with the local isobath. The eccentricity values at various grid points of ellipses for M2 and S2 are very low with 0.2 and 0.06 on the average, respectively illustrating that the tidal current in the KB is strongly recti-linear. The magnitude of the tidal residual current speed in the KB is on the order of a few cm/s and its distribution pattern is very complex. One of the most prominent features is found to be the counter-clockwise eddy recirculation cell at the mouth of the Daebang Channel.