Occurrence of coprostanol, 24-ethylcoprostanol and 5α-stanols in the marine sediments

The present study deals with the elucidation of sterol composition of the marine sediments in Kagoshima Bay. The identification of each sterol was performed by gas-liquid chromatography, Ag⁺ impregnated column chromatography, mass spectrometry, and nuclear magnetic resonance spectrometry. The sediment obtained near the estuary of River Koutsuki contained large portions of 5-stanols such as coprostanol and 24-ethylcoprostanol basides 5-stanols such as cholestanol, 24-methylcholestanol, and 24-ethylcholestanol in the sterol fraction. These 5-stanols in the marine sediment may be derived from the fecal contamination by domestic sewages.     

Respiration rates of planktonic crustaceans from the Inland Sea of Japan with special reference to the effects of body weight and temperature

A total of 293 measurements of respiration rate were made on planktonic crustaceans collected in different seasons from the Inland Sea of Japan. The relationship between the rate of oxygen consumption (R,μl O₂ indiv.⁻¹ hr⁻¹) and body dry weight (W, mg indiv.⁻¹), as expressed by a power function (R=aW ^b , or logR=loga+b logW), was established as a function of temperature (T, °C). The slope of the regression equation (b) was not significantly affected by seasonal temperature variation, but the intercept of the equation (loga) was strongly influenced by temperature. The equation describing this general relation is logR=(0.0444T−0.333)+0.713 logW.     

Space—time correlations between inland earthquakes in central Japan and great offshore earthquakes along the Nankai trough: Implication for destructive earthquake prediction

Based on the tectonic framework of central Japan, including the surrounding submarine areas, the space-time relationship between destructive inland earthquakes of magnitudesM 6.4 or greater and great offshore earthquakes along the Nankai trough was examined. From east to west, four tectonic lines are defined as lines linking active faults: the Itoigawa-Shizuoka tectonic line (ISTL), the Tsurugawan-Isewan tectonic line (TITL), the Hanaore-Kongo fault line (HKFL), and the Arima-Takatsuki tectonic line (ATTL). The TITL divides central Japan into the Chubu and Kinki districts, and probably extends southward to the Nankai trough. The Chubu district is subdivided into four blocks by boundary lines linking NW-SE trending active faults having left-lateral strike slip. In the Kinki district, N-S trending, active reverse, steep-dip faults are dominant in the triangular region north of the Median Tectonic line, between the TITL and HKFL, forming a basin-and-range province.

Starting from 1586 A.D., a seismic space-time sequence of high seismic activity in the Chubu district in which earthquake occurrence migrates from the eastern to western tectonic lines of central Japan was identified. The sequence also revealed that inland earthquakes preceded great offshore earthquakes which occurred along the Nankai trough. It was also found that a destructive earthquake tends to occur on the HKFL within 30 years after the occurrence on the TITL, and that the western Nankai trough generated great earthquakes ofM≥7.0 at intervals ranging from 8 to 49 years after the HKFL earthquakes. If the eastern Nankai trough is coupled with the western Nankai trough, a forthcoming greater earthquake measuringM 8.5 may be expected. Since such great earthquakes are always accompanied by large tsunamis, much attention should be focussed on possible tsunami disasters along the Pacific coast of central Japan.

Based on its tectonic structure, a tectonic model of central Japan is proposed. The seismic space-time sequence, which attempts to explain the cause of the sequential earthquake generation, is also discussed.     

Gas permeability evolution of cataclasite and fault gouge in triaxial compression and implications for changes in fault-zone permeability structure through the earthquake cycle

We report the results of permeability measurements of fault gouge and tonalitic cataclasite from the fault zone of the Median Tectonic Line, Ohshika, central Japan, carried out during triaxial compression tests. The experiments revealed marked effects of deformation on the permeability of the specimens. Permeability of fault gouge decreases rapidly by about two orders of magnitude during initial loading and continues to decrease slowly during further inelastic deformation. The drop in permeability during initial loading is much smaller for cataclasite than for gouge, followed by abrupt increase upon failure, and the overall change in permeability correlates well with change in volumetric strain, i.e., initial, nearly elastic contraction followed by dilatancy upon the initiation of inelastic deformation towards specimen failure. If cemented cataclasite suffers deformation prior to or during an earthquake, a cataclasite zone may change into a conduit for fluid flow. Fault gouge zones, however, are unlikely to switch to very permeable zones upon the initiation of fault slip. Thus, overall permeability structure of a fault may change abruptly prior to or during earthquakes and during the interseismic period. Fault gouge and cataclasite have internal angles of friction of about 36° and 45°, respectively, as is typical for brittle rocks.     

Cloning and sequencing of the allophycocyanin genes fromSpirulina maxima (Cyanophyta)

The genes coding for the α-and β-subunit of allophycocyanin (apcA andapcB) from the cyanophyteSpirulina maxima were cloned and sequenced. The results revealed 44.4% of nucleotide sequence similarity and 30.4% of similarity of deduced amino acid sequence between them. The amino acid sequence identities betweenS. maxima andS. platensis are 99.4% for α subunit and 100% for β subunit.

     

Transposable genetic elements inSpirulina and potential applications for genetic engineering

Transposable elements in cyanobacteria are briefly reviewed. Evidence is presented to show that transposable elements inSpirulina platensis is actually reflected on the phenotype change, i e., helical to straight filaments. Transposition intermediates of DNA were isolated from the extrachromosome and the transposition was related to helical variations inSpirulina. Uses of transposable elements for microalgal recombination are discussed based on the transposition mechanism.

     

Middle Miocene to Pleistocene radiolarian biostratigraphy in the Northwest Pacific Ocean, ODP Leg 186

Abstract The Upper Cenozoic sedimentary sequences drilled at Sites 1150 and 1151, Ocean Drilling Program Leg 186, enabled establishment of radiolarian zonation and calibration of the age of bioevents in the forearc area of the northern Japan Islands. The sequences were divided into nine zones from the Pleistocene Botryostrobus aquilonaris Zone to the Upper Miocene Lipmanella redondoensis Zone at Site 1150, and 11 zones from the Pleistocene Stylatractus universus Zone to the Middle Miocene Dendrospyris? sakaii Zone at Site 1151. These zones correlate successfully with the studied sequences of many of deep‐sea cores in the Northwest Pacific Ocean and with some sections of onshore Japan. Of 67 important radiolarian bioevents recognized during the study, 29 Pleistocene to Upper Miocene events were directly tied to the geomagnetic polarity time scale through the well‐defined paleomagnetic polarity records, and 21 Upper Miocene events were calibrated based on the diatom biostratigraphy. Of these events, 24 geographically widespread events were selected to test synchroneity and usefulness as time‐horizons within the mid‐to‐high latitude of the Northwest Pacific, involving eight other offshore and onshore sections. Examination showed that most of the zonal boundary events are synchronous within the considered region, and that many diachronous events, most of which are eliminated from the zonal scheme, are unreliable events linked to rare and sporadic occurrences of the species. Radiolarian biostratigraphy of the studied cores clearly indicates three major hiatuses in the Middle Pleistocene, Late Miocene and late Middle Miocene. The latter two hiatuses can be correlated to two global oceanic hiatuses, NH6 and NH3, respectively.     

Extracellular release of β-lactamase by osmotic shock inSynechococcus transformant

A unicellular cyanobacteriumSynechococcus sp. strain PCC 7002 was transformed with plasmid pQL1, on which β-lactamase gene (bla) and β-galactosidase gene (lacZ) were encoded. The transformant cells released β-lactamase into medium by an abrupt drop of osmotic pressure. This result indicates that this cyanobacterium recognizes and processes the signal sequence of β-lactamase, and accumulates the enzyme in periplasm. Repeated release of β-lactamase was possible by repeated osmotic shocks wihout, impairing cell viability. On the other hand, most of the β-galactosidase remained in cytoplasm under the osmotic shock.

     

Downstream transition of the Tsushima Current west of Kyushu in summer

In order to clarify detailed current structures west of Kyushu, ADCP measurements were carried out in July and September 1990 by the quadrireciprocal method (Katoh, 1988) for removing diurnal and semidiurnal tidal flows from observed flows. On the basis of these results, together with data of routine oceanographic observations, we study the downstream transition of the Tsushima Current west of Kyushu in summer. In the southwest of the Goto Islands, a northward current identified as the Tsushima Current was clearly found. In the south of Cheju, a westward current bifurcated from the Tsushima Current. In the northwest of the Goto Islands, the Tsushima Current narrowed and its velocity became strengthened. Salinity of the Tsushima Current water was much diluted by a current from the Cheju Strait. Near the west coast of the Goto Islands, a countercurrent bifurcating from the Tsushima Current often occurred. The volume transport of the Tsushima Current was 2.3 Sv (1 Sv=10⁶ m³s^–1) on the northern side of latitude 31°N. The substantial bifurcation of the Tsushima Current toward the Eastern and Western Channels of the Tsushima Strait occurred in the vicinity of Tsushima. The volume transport through the Western Channel was two to three times larger than that through the Eastern Channel. The baroclinic component in volume transport of the Tsushima Current west of Kyushu was much smaller than that in the Japan Sea.     

A carbon budget in Tokyo Bay

Organic carbon flux from eutrophicated Tokyo Bay to the Pacific Ocean is estimated as 260 ton C day^–1 based on the horizontal gradient of COD and the dispersion coefficient at the bay mouth. Also, carbon flux from the air or from the open ocean to Tokyo Bay is estimated as 156 ton C day^–1. If we suppose that five percent of the coastal seas in the world might be eutrophicated as Tokyo Bay and the organic carbon flux from the shelf to the open ocean in other coastal seas might be one third of that in Tokyo Bay, 1.12 G tons year^–1 would be transported from the eutrophicated coastal seas to the open ocean and such carbon flux may account for the missing sink in the global carbon budget.