Seasonal variation of pteropods from the Western Arabian Sea sediment trap

Sediment trap samples collected from the Western Arabian Sea yielded a rich assemblage of intact and non-living (opaque white) pteropod tests from a water depth of 919 m during January to September 1993. Nine species of pteropods were recorded, all (except one) displaying distinct seasonality in abundance, suggesting their response to changing hydrographical conditions influenced by the summer/winter monsoon cycle. Pteropod fluxes increased during the April–May peak of the intermonsoon, and reached maximum levels in the late phase of the southwest summer monsoon, probably due to the shallowing of the mixed layer depth. This shallowing, coupled with enhanced nutrient availability, provides ideal conditions for pteropod growth, also reflected in corresponding fluctuations in the flux of the foraminifer Globigerina bulloides. Pteropod/planktic foraminifer ratios displayed marked seasonal variations, the values increasing during the warmer months of April and May when planktic foraminiferal fluxes declined. The variation in fluxes of calcium carbonate, organic carbon and biogenic opal show positive correlations with fluxes of pteropods and planktic foraminifers. Calcium carbonate was the main contributor to the total particulate flux, especially during the SW monsoon. In the study area, pteropod flux variations are similar to the other flux patterns, indicating that they, too could be used as a potential tool for palaeoclimatic reconstruction of the recent past.     

In situ velocity profiles in gassy sediments: Kiel Bay

Acoustic behavior of gas-bearing sediments is significantly different from that of gas-free sediments. In situ velocity profiles and acoustic signal characteristics in gas-bearing sediments of the upper several meters of the sea floor in Kiel Bay are presented in this study. Observed velocities in gas-bearing sediments are both higher and lower than those of the gas-free sediments. Small amounts of gas appear to cause signal reverberation without much attenuation. whereas large amounts of gas cause substantial attenuation.     

Seasonal variation of global surface pressure and water vapor

Previous studies have shown that the seasonal variation of global-mean surface pressure ( p _s) results from variation of global-mean water vapor pressure ( p _w). The current study, employing the global data generated by Version 1 of the Goddard Earth Observing System (GEOS-1) Data Assimilation System, shows that seasonal variations of regional p _s and p _w tend to be out of phase (particularly in the subtropics of the two hemispheres) and that the magnitude of the former variation is generally much larger than that of the latter. The seasonal variations of these two quantities are maintained by airmass and water vapor transports by the global divergent circulation, which is driven by the latent heat released by cumulus convection over the water vapor sink, as the "water mass forcing" mechanism predicted. Since p _w and p _s are used often in depicting the climate system, assessments of climate change in terms of the global-mean and regional variations of these two variables should be interpreted with caution.     

Bedrock morphology and structures within overlying sediments,Start Bay,Southwest England,determined by continuous seismic profiling,side-scan sonar,and core sampling

The bedrock morphology of Start Bay, Southwest England, and the Structures within overlying sediments have been determined by a combined geophysical and geological survey. It has been established that the Skerries Bank consists of a drape of possibly coarse, unconsolidated material (bank deposits) overlying medium- to fine-grained silty sand (bay deposits). A break of slope in the bedrock surface, traced along the entire length of the Bay, and a step profile in the southern part of the Bay, may be either a legacy of submerged topography produced by vigorous tidal action, or alternatively the product of subaerial and marine processes. Other significant geological features in the Bay include infilled valleys, and “terraces” possibly pertaining to relict barrier beaches.     

Immunological characterization of metallothionein in marine and freshwater fish

Metallothionein (MT) is a low-molecular-weight, cysteine-rich, metalbinding protein found in all vertebrates. The primary structure of the protein is evolutionary conserved, especially the location of cysteine-residues. There are nonetheless significant differences between MTs from different vertebrate classes, notably in major antigenic epitopes. Previous work has shown that MT from different fish species also differ. The objective of the present work was to characterize MT from temperate, sub-tropical and tropical fish species by their relative reactivities with two anti-fish MT antisera. One or both antisera cross-reacted with MT from all fish species investigated. Surprisingly, the relative reactivities of the two antisera with MT from species belonging to different taxonomic groups appeared to reflect differences at the level of family rather than differences between major phylogenetic lineages.     

Zinc concentration effect at the organismal,cellular and subcellular levels in the eastern oyster

The purpose of this research was to demonstrate a concentration effect of zinc exposure at organismal, cellular and sub-cellular levels in the eastern oyster and to find associated protein expression signatures (PES) for each concentration of zinc. Oysters were exposed to six concentrations of zinc for 48 h in a controlled environment. At the organismal level, fecal material was observed as a measure of physiological health during metal exposures. At the cellular level, lysosomal destabilization was measured using hemolymph. This cellular response was significant only at the highest concentration, when the fecal index was lowest. Protein responses were monitored in the oyster following exposure to zinc. Gill tissue was excised and homogenized, and then analyzed using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and digital image analysis. Protein expression signatures were found to be specific to each concentration. The protein responses were linked to the other biological parameters measured, each of which followed a concentration gradient of zinc.     

钝顶螺旋藻部分原生质体及单细胞的制备与培养

于1992年1月-1994年4月，进行超声波处理方法制备钝顶螺旋藻部分原生质体以作为基因工程受体，以及制备单细胞用于固体平板克隆化培养的研究。研究结果表明：超声波以20kHz频率、15W功率作用30s，可使藻丝体断裂成15．0±1．6个细胞长度；延长作用时间，至2－6个细胞长度时，细胞壁结构遭到破坏，形成部分原生质体；继续作用，可形成少量原生质体和大量单细胞。断裂藻丝体、部分原生质体、单细胞以及原生质体均可涂布于固体培养基上再生或生长。以一定密度涂布单细胞与原生质体，能够形成彼此分开的单个克隆，可用于筛选及遗传分析。本文提供了一种节省溶菌酶的制备螺旋藻透性体的方法，超声波作用利于外源基因的导入，而涂布培养利于进一步的筛选和形成克隆。     

A shipborne magnetic survey in Hudson Bay

A marine magnetic total-field survey of Hudson Bay was conducted from 1975 to 1978. Approximately 62 000 line-km of data, or 35 000 five-minute averages, were acquired. The data were corrected for secular variation by means of a polynomial in latitude, longitude, and time, first fitted to annual mean differences from nine observatories and then integrated over time. The data were corrected for diurnal and transient variations by means of a linear interpolation, over geomagnetic latitude, of running hourly mean values from two neighbouring magnetic stations (numbering seven in all). Crossover differences are analysed in terms of a mixture of normal distributions resulting from the intermittent transient variations, and indicate the effectiveness of the corrections. The variance of the data is reduced, as a result of the corrections, by 87% during quiet periods and by 53% during disturbed periods, the weighted variance being reduced by 66%. Navigational accuracy is estimated, from a novel method utilizing crossover differences and field gradients, to be approximately 300 m. Anomalies are presented in profile form, and discussed briefly.Contribution from the Earth Physics Branch No. 973.     

A general method for calculating three-dimensional laminar and turbulent boundary layers on ship hulls

A general method for representing the flow properties in the three-dimensional boundary layers around ship hulls of arbitrary shape is described. It makes use of an efficient two-point finite-diffirence schem to solve the boundary-layer equations and includes an algebraic eddy-viscosity representaion of the Reynolds-stress ternsor. The numericzal method contains novel and desirable features and allows the calculation of flows in which the circumferential velocity component contains regions of flow reversal across the boundary layer. The inviscid pressure distribution is determined with the Douglas-Neumann method which, if necessary, can conveniently allow for the boundary-layer displacement surface. To allow its application to ships, and particularly to those with double-elliptic and flat-bottomed hulls, a non-orthogonal coordinate system has been developed and is shown to be economical, precise and comparatively easy to use. Present calculations relate to zero Froude number but they can be extended to include the effects of a water wave and local regions of flow separation which may stem from bulbous-bow geometries.