The Brittlestar Amphiodia urtica; A Candidate Bioindicator?

Abstract. The ophiuroid Amphiiodia urtica L yman is presently under study as a potential wastewater discharge indicator species from ocean outfalls in the Southern California Bight. On the San Pedro Shelf, the maximum abundance of A. urtica was found at depths from 30 to 100 m, and in sediment with a median grain size of 0.085 nim, 60–80% sand. 15–30% silt, 0–37% clay, and 0.2–0.5% TOC. The mean abundance of A. urtica fluctuated annually with a slight increase from 1977 through 1993.
The hypothesis was posed that the distribution and abundance of A. urtica is not influenced by an ocean outfall and its operation on the San Pedro Shelf. Based on long-term (1977–1994) and intensive (2860 samples) sampling. the hypothesis was rejected. However, the effect of the outfall is not clear because sediment bioassays from test stations and controls produced no significant differences in survivorship and growth of juveniles. Amphiodia presently occupies areas within the Zone of Initial Dilution (ZID) where it was not found during the mid-1970s and early 1980s. While recognizing that A. urtica abundance responds to proximity to the outfall, the mechanism for this response is still unclear. The application of a single species as a bioindicator is not recommended, and most certainly not without fully essing its role in community structure and function.     

Effect of saline intrusion on the properties of cohesive soils in the Red River Delta,Vietnam

Abstract

This study conducted a series of laboratory experiments and established numerical models on selected undisturbed soil samples in the Red River Delta (RRD) to determine the effect of change in soils intruded by saline water. The variation in the technical parameters of soils was verified in soils fully saturated by solution of four salt concentrations, that is, 0.0, 9.9, 19.8, and 33.0?g/L. Results show that the content and composition of clay minerals in cohesive soils before and after saline intrusion are unchanged. The same finding is obtained for clay after removing absorbed water layer by using a centrifuge apparatus. The zeta potential and settlement velocity of soils in the RRD increase when salt is added to the saturated solution. Similarly, the deformation of soils increases proportionally with the salt concentrations of that solution. This result is attributed to the linear decrease in deformation modulus. The decrease in modulus versus salinities is nearly consistent for pressure stages from 100 to 400?kPa. The safety factor of bearing capacity also decreases linearly with salinities. The decrease reaches 12.5–16.3% when soils are in the maximum saline solution. All these changes are considered as the degradation of soils in saline media.     

Monsoon-induced upwelling off the Vietnamese coast

During the southwest monsoon from July 8 to 28, 2003, an interdisciplinary cruise took place in the central area of Vietnamese upwelling with “MV Nghien Cuu Bien” in the South China Sea. Physical observations in the upwelling area are analyzed with respect to local/regional wind forcing and far field forcing. Nutrients and phytoplankton measurements are discussed with respect to exchange processes between different water masses. The wind-induced coastal upwelling by local wind forcing is much weaker than in the previous years due to weaker-than-normal winds. This can be attributed to the far field forcing of the 2002/2003 El Niño event which modulates the upwelling intensity. The atmospheric conditions reflect the typical situation after an El Niño event which weakens the wind-induced coastal upwelling, reduces the latent heat flux, and results in higher-than-normal sea-surface temperatures. The general circulation pattern during SW monsoon is driven by the spatial asymmetry in the monsoon forcing. The flow pattern is characterized by an upwelling-induced northward undercurrent and a recently detected southward countercurrent. The resulting stretching deformation of this flow pattern forms an offshore jet between ～12°N and 12.5°N and causes a local enhancement of the upwelling intensity. The upwelling due to stretching deformation is a peculiarity, which makes the Vietnamese upwelling area different to other upwelling areas. A budget of the upwelling components is presented: the strongest contribution in 2003 to the Vietnamese upwelling is the dynamical upwelling due to the clockwise rotation of the northward undercurrent. The internal radius of deformation separates the upwelling area from the offshore area as well as different water masses. Mekong River and the Gulf of Thailand waters which are offshore show nutrient depletion. Therefore, high chlorophyll maxima cannot be explained by nutrient supply from river runoff. The dynamical upwelling brings in nutrient-rich Maximum Salinity Water into the euphotic zone. This causes a subsurface chlorophyll maximum between 20 and 40 m water depth along the northward undercurrent. Deflection from the Redfield ratio in the C:N ratio and negative excess nitrogen identifies the region as nitrogen-limited which may favor cyanobacteria blooms. The consequence is a unique feature in new production: in the upwelling area, new production is based on upwelled nitrate, whereas offshore in the nutrient-depleted Mekong and Gulf of Thailand water, new production is based in addition on nitrogen fixation.     

Distribution of convection associated with tropical cyclones making landfall along the South China coast

Summary This study examines the convection distribution associated with 18 TCs that made landfall along the South China coast during 1995 and 2005. Cloud-top temperatures from high-resolution satellite imageries of the Geosynchronous Meteorological Satellite 5 are used as proxy of strong convection. It is found that convection tends to be enhanced on the western side of the TC as it makes landfall in 10 of the cases, in agreement with the conclusion of some previous studies. Four cases have stronger convection on the eastern side. This “deviation” from the general rule appears to be related to the TCs being more slow-moving or their interaction of the TC with another land surface prior to its making landfall along the South China coast. For the remaining cases in which no significant asymmetries in convection can be identified, the vertical wind shear appears to enhance convection on the east side.     

临沂市紫外线辐射变化特征分析

利用临沂市2004年7月至2005年6月逐日紫外线观测资料,分析太阳紫外线辐射强度指数和等级的年、季、月和日变化特征。指出临沂市日紫外线最大辐射强度为4级的日数为多数,即紫外线辐射指数为7~9的日数占52%,4级以上紫外线辐射主要出现在春夏季节,冬季紫外线辐射较弱,出现4级辐射日数很少且无5级辐射。晴空条件下,冬季太阳紫外线辐射强度日变幅明显小于其他季节,夏季日最大辐射强度出现在12-14时,较其他季节的日最大辐射强度出现时段滞后1小时。     

Cenozoic lithospheric extension induced magmatism in Southwest Japan

Island chains off western Kyushu are the surface exposure in the northern margin of the Taiwan–Sinzi Folded Zone that spreads along the arc–trench system in the back-arc side from SW Japan to Taiwan. Intermittent igneous activity between the Middle Miocene and Holocene occurred on these islands and widely covered or intruded sedimentary rocks of Early–Middle Miocene. Geochemistry of the volcanic rocks from the Hirado, Ikitsuki and Takushima islands believed to relate to the back-arc opening along the East China and Japan Seas shows a temporal change in source material. Submarine to sub-aerial volcanism occurred on Hirado Island at 15 Ma during the final opening stage of the East China Sea producing tholeiitic basalt and associated andesite–dacite. These eruptives show low incompatible element contents and high FeO*/MgO ratios and reflect a tholeiitic differentiation trend. High Sr and Pb and low Nd isotopic ratios suggest the involvement of EM2-like lithospheric mantle and crustal material in the formation of these syn-opening volcanic rocks. Post-opening alkali basalt volcanism occurred at 9–6 Ma on the islands is characterized by OIB-like higher large ionic lithophile elements (LILE) and high field strength elements (HFSE) compared to 15 Ma basalts in this region and Quaternary basalts along the volcanic front. They have variable range of incompatible element concentrations and ratios along with variable Sr, Pb and Nd isotopic ratios suggesting the involvement of both lithospheric and asthenospheric sources at variable melting degrees (from 4% to less than 15%). The observation that the isotopic compositions of Quaternary alkali basalts south of the studied area are even more depleted suggests an increase in the involvement of asthenospheric source with time.     

Seasonal Variation of Dimethylsulfoxide in Rainwater at Amsterdam Island in the Southern Indian Ocean: Implications on the Biogenic Sulfur Cycle

A continuous record of dimethylsulfoxide (DMSO) in rainwater was performed at Amsterdam island (37°S 77°E) from December 1995 to February 1997. Eighty one rainwater samples were collected. DMSO, methanesulfonic acid (MSA), the major anions, and cations were analyzed. DMSO concentrations ranged from 7.0 to 369 nM, with a distinct seasonal variation. The mean concentrations during the summer and the winter periods were 90 nM and 25.6 nM respectively. The observed DMSO seasonal cycle is in line with the observations of DMS in the atmosphere and MSA in rainwater, measured simultaneously during the reported period. However, the summer to winter ratio of DMSO is significantly lower than that observed for DMS and MSA. The DMSO to MSA ratio and its observed seasonal variability are also presented. The implications on the biogenic sulfur cycle are discussed.     

Unsupervised separation of seismic waves using the watershed algorithm on time-scale images

This paper illustrates the use of image processing techniques for separating seismic waves. Because of the non‐stationarity of seismic signals, the continuous wavelet transform is more suitable than the conventional Fourier transforms for the representation, and thus the analysis, of seismic processes. It provides a 2D representation, called a scalogram, of a 1D signal where the seismic events are well localized and isolated. Supervised methods based on this time‐scale representation have already been used to separate seismic events, but they require strong interactions with the geophysicist. This paper focuses on the use of the watershed algorithm to segment time‐scale representations of seismic signals, which leads to an automatic estimation of the wavelet representation of each wave separately. The computation of the inverse wavelet transform then leads to the reconstruction of the different waves. This segmentation, tracked over the different traces of the seismic profile, enables an accurate separation of the different wavefields. This method has been successfully validated on several real data sets.     

赣东北地区早白垩世火山岩的Nd,Sr同位素地球化学特征

赣东北早白垩世处于陆内造山环境向陆内拉张环境过渡的过渡性构造环境，形成了一套富碱的火山岩组合。Nd,Sr同位素特征显示，酸性岩石具有较高的εSr(T)值与较低的εNd(T)值，其N^87Sr/N^86Sr初始比值为0.71020与0.71050，上壳端员组分介于67％－50％之间，表明其源区处于地壳中较深的位置，且有地幔流体的加入。玄武质岩石具有较高的εSr(T)值与负的εNd(T)值，其N^87Sr/N^86Sr初始比值为0.7063-0.7087，玄武质岩石在其形成过程中遭受过壳源岩浆的混合或大陆地壳物质的混染。