Depth distribution of radiolarians from the Chukchi and Beaufort Seas, western Arctic

The depth distributions of the radiolarian fauna in the Chukchi and Beaufort Seas, marginal seas of the western Arctic Ocean, were examined quantitatively in depth-stratified plankton tows from 4 or 5 intervals above 500 m and in surface sediments from various depths between 163 and 2907 m. The radiolarian assemblage from the water column in September 2000 was dominated by Amphimelissa setosa and followed by the Actinomma boreale/leptoderma group, Pseudodictyophimus gracilipes and Spongotrochus glacialis. These species are related to the Arctic Surface Water shallower than 150 m. This assemblage is similar to that in the Greenland Sea relating to the ice edge, but did not contain typical Pacific radiolarians in spite of the flow of water of Pacific origin in this region. The living depth of Ceratocyrtis historicosa was restricted to the relatively warm water between 300 and 500 m corresponding to the upper Arctic Intermediate Water (AIW) originating from the Atlantic Ocean. Radiolarian assemblages in the surface sediments are similar to those in the plankton tows, except for common Cycladophora davisiana in sediment samples below 500 m. C. davisiana is probably a deep-water species adapted to the lower AIW or the Canadian Basin Deep Water ventilated from the shelves.     

The statistical distributions for the elevation,velocity and acceleration of the surface of wind waves

Water surface elevations(t), vertical surface velocities and vertical surface acceleration of wind-generated waves have been measured in a laboratory wind wave channel by using resistance-type wave gauges combined with an electronic differentiation circuits. Probability distributions of the values of(t), , and have been determined from the wave records.In an initial stage of wave generation,i.e., when wind waves are generated at short fetches and low wind speeds, the observed distributions for(t), and are appreciately good fit to the distributions given by successive sum of a Gram-Charlier series, which has been derived following the formulation ofLonguet-Higgins (1963), by taking the weakly nonlinear effect into account.However, when wind waves develop with increasing wind speeds and fetches, the observed distributions deviate gradually from the Gram-Charlier series. Particularly, the deviations are remarkable for the distribution of .When the wind speed increases, the observed distributions of(t), and show the following characteristics: (i) the skewnesses of the distributions of(t) and decrease slightly, (ii) the skewness of changes, at some wind speed, from positive small values to relatively large negative values, (iii) the kurtosis of the distribution of(t) decreases slightly but that of increases slightly and these characteristics seem to depend not so much on fetches, (iv) the kurtosis of the distribution of increases rapidly.     

Air-Sea Interactions under the Existence of Opposing Swell

Data of a comprehensive laboratory study on the coexistent system of wind waves and opposing swell (Mitsuyasu and Yoshida, 1989) have been reanalyzed to clarify the air-sea interaction phenomena under the coexistence of wind waves and swell. It is shown that the magnitude of the decay rate of swell due to an opposing wind is almost the same as that of the growth rate of swell caused by a following wind, as measured by Mitsuyasu and Honda (1982). The decay rate is much smaller than that obtained recently by Peirson et al. (2003), but the reason for the disagreement is not clear at present. The effect of an opposing swell on wind waves is very different from that of a following swell; wind waves are intensified by an opposing swell while they are attenuated by a following one. The phenomenon contradicts the model of Phillips and Banner (1974), but the reason for this is not clear at this time. The high-frequency spectrum of wind waves shows a small increase of the spectral density. Wind shear stress increases a little due to the effect of opposing swell. The intensification of wind waves by opposing swell and the small increase of the spectral density in a high-frequency region can be attributed to the increase of wind shear stress. Such organized phenomena lead to the conclusion that the hypothesis of local equilibrium for pure wind waves (Toba, 1972) can also be satisfied for wind waves that coexist with opposing swell. The recent finding of Hanson and Phillips (1999) can be explained by this mechanism.     

Detection of Vibrio (Listonella) Anguillarum Porin Homologue Proteins and Their Source Bacteria from Coastal Seawater

The molecular distribution of dissolved proteins in seawater from coastal marine environments in Uranouchi Bay, Kochi Prefecture, is first reported in this article. Occurrence of bacteria-derived dissolved proteins and their source bacteria were examined using a probe of the antibody (anti-Omp35La) against a porin outer membrane protein (Omp35La) of the fish pathogenic bacterium Vibrio (Listonella) anguillarum. The electrophoretograms of dissolved proteins from coastal seawater showed a large number of discrete and individual proteins overlapped each other over a wide range of molecular masses indicating active processes in coastal environments in transferring proteins from organisms to the inanimate dissolved protein pool. Among the dissolved proteins, 37 kDa- and 18 kDa-proteins reacted with the Omp35La. In order to isolate the source bacteria of such dissolved proteins, bacteria from seawater and diseased fish were screened by colony Western blotting with anti-Omp35La. The reactive strains were further examined in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western blotting to verify the presence of Omp35La homologues among the outer membrane proteins of such strains. Outer membrane proteins reacting with anti-Omp35La were detected in only 4 strains of the 129 strains that were positive in the colony Western blotting. The level of possible source bacteria of 37 kDa- and 18 kDa-dissolved proteins was suggested to be 5–6 orders of magnitude lower than the total bacterial count. The present study leads us to hypothesize that a minor portion of the bacterial assemblage is responsible for the dissolved proteins in the coastal waters.     

Sedimentary inorganic nitrogen and its isotope ratio in the western subarctic Pacific over the last 145 kyr

We have measured inorganic nitrogen (IN) content and the isotope ratio of IN (δ¹⁵N_IN) in a sediment core covering the last 145 kyr in the western subarctic Pacific (WSAP). IN content was generally high during glacial periods and shows positive correlations with both eolian dust content and the ratio of organic carbon (C) to organic nitrogen (ON) (C/ON) found in our previous studies. This means that IN was transported from continental areas to the WSAP together with eolian dust and that the IN was not contaminated by volcanic materials, because the eolian dust content was reconstructed using metal components to remove contaminating volcanic materials. Therefore, IN content in the WSAP sediments, the clay fraction of which is not greatly affected by drift deposits seen at the other sites in this region, may potentially be an effective proxy for eolian dust, without the need to consider contamination by volcanic materials. δ¹⁵N_IN was generally low during glacial periods and shows negative correlations with IN, eolian dust, and C/ON. The possible causes of the observed variations in δ¹⁵N_IN are as follows: (1) authigenic fixation of NH₄ ⁺ in water-column and pore water of sea-floor sediments to clay minerals; (2) contamination of measured IN by highly resistant organic matter; or (3) variations in the continental source region of the eolian dust supplied to the WSAP and climatically induced changes in δ¹⁵N of soil organic matter there. The last mechanism shows the potential for δ¹⁵N_IN to be used as a proxy for climate change on land, and is consistent with other published explanations of the spatial distribution of δ¹⁵N_IN in modern sea-floor sediments.     

Isotope dilution sector-field inductively coupled plasma mass spectrometry combined with extraction chromatography for rapid determination of 241Am in marine sediment samples: A case study in Sagami Bay, Japan

²⁴¹Am is a useful tracer for understanding biogeochemical processes in the marine environment. ²⁴¹Am also poses a potential radiation threat to human health due to the continuous increase of its concentration in the global environment. We report a rapid analytical method for determining ²⁴¹Am in marine sediments using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) combined with a high-efficiency sample introduction system (APEX-Q). A selective CaF₂ co-precipitation procedure followed by TRU extraction chromatography was employed to effectively remove the major sediment matrix and to pre-concentrate ²⁴¹Am. We achieved an extremely low detection limit of 0.32 fg/g or 0.041 mBq/g (for 1 gram sediment), which is better than that of alpha spectrometry, and it allowed the accurate determination of ²⁴¹Am in low-level marine sediment samples. The accuracy and precision of the developed analytical method was evaluated using a laboratory prepared Am isotope standard solution and Ocean Sediment reference material (IAEA-368). The results were satisfactory. For sediment samples, overall chemical recoveries varied from 60–90%. The developed method was applied to the study of ²⁴¹Am depth distribution in Sagami Bay, Japan, where we observed different depth profiles between ²⁴¹Am activity and ^239+240Pu activity.     

Spatial variation in organic matter utilization by benthic communities from Yura River–Estuary to offshore of Tango Sea,Japan

We investigated the distribution of δ¹³C and δ¹⁵N of organic matter among benthic communities from the upper estuary of Yura River to offshore of Tango Sea, Japan, to determine spatial variation in utilization of organic matter by benthic communities. The δ¹³C values of benthic animals ranged from −27 to −15‰ in the upper estuary, −21 to −15‰ in the lower estuary, −20 to −16‰ in the shallow coast (5–10 m depths), −18 to −16‰ in the deep coast (30–60 m depths) and −19 to −15‰ in offshore (100–150 m depths) stations. Adapting the dual isotope values to mixing models, we estimated the relative contributions of potential food sources to the benthos diet. Phytoplankton and macroalgae that intruded the estuary in summer were utilized as alternative food aside from the terrestrial-origin organic matter assimilated by the estuarine benthic consumers. Resuspended benthic microalgae were important source of energy in the shallow coastal stations, while abundant supply of phytodetritus fueled the deep coastal and offshore benthic food webs. Spatial difference in the diet of benthic communities depends largely on the shifts in the primary carbon source. Thus, benthic communities are important link of autochthonous/allochthonous production and secondary production in the continuous river–estuary–marine system.     

Radium isotopes in coastal and open ocean surface waters of the Western North Pacific

Using manganese-impregnated fiber extraction and high-efficiency gamma counting techniques, we measured the distribution of ²²⁸Ra and ²²⁶Ra in surface waters near the coast of Japan and in the western North Pacific. There is no evidence in our data that any significant amount of ²²⁸Ra is added to open ocean surface waters from the coastal waters around Tokyo Bay. High ²²⁸Ra concentrations (> 10 dpm/10³ kg), were observed along the Kuroshio Current as compared to < 2.5 dpm/10³ kg between 10° and 30°N of the central gyre, and hence the major source of ²²⁸Ra in the surface water is likely to be the East Asian continental shelf zones. A simple one-dimensional eddy diffusion and advection model is used to explain the observed decrease of ²²⁸Ra from coast to the open ocean. The model results indicate two mixing regimes across the Kuroshio Current System with apparent eddy diffusion coefficients of K_y = 4 × 10⁵ cm² s⁻¹ at distance y < 200 km from the coast, and K_y = 4 × 10⁷ cm² s⁻¹ at y > 200 km. Along 40°N where an eastward flow of the ‘Kuroshio Extension’ prevails, an advective flow of > 0.1 knot is consistent with the observation of nearly constant ²²⁸Ra along the track.The geographical distribution pattern of ²²⁸Ra is clearly different from that of atmospherically derived ²¹⁰Pb. Thus the ²²⁸Ra in surface water serves as a useful tracer that accompanies fluvially and coastally derived elements during their subsequent lateral transport toward the central gyre.     

Problems concerning the Directivity of Tsunami

If knowledge of our theories on the directivity of tsunamis had received worldwide attention, the following operations could have been carried out internationally just after the large earthquake of 19 September 1985 which occurred near Acapulco, Mexico. Having found the great circle, “line S” which is perpendicular to the coast around Acapulco, we could have calculated the angles between line S and line A and between line S and line D, where line A and line D are the great circle connecting Acapulco and Auckland, New Zealand and that connecting Acapulco and Duke of York Island (Chile), respectively. The resultant angles are 30?43′ and 41?49′(>68?48′/2), we could thereafter neglect the eastern half of the offshore energy flux. When we assume that the speed of trans-Pacific tsunami is 400 knots, the probability that the actual tsunami will come earlier than the calculated arrival time proves to be $$\frac{1}{{\sqrt {2\pi } }}\int_{ - {\text{ }}\infty }^{ - {\text{ }}0.689} {e^{ - t^{{2 \mathord{\left/ {\vphantom {2 2}} \right. \kern-\nulldelimiterspace} 2}} } dt = 0.2454} $$ Contact with New Zealand prior to the forecasted arrival time was essential, but the tsunami attention for the Japanese coast was unnecessary. Without such application of our directivity theories, frequent fruitless warnings will be issued for future trans-Pacific tsunamis. Quick improvements in warning procedures are required.     

A comparison of observed and calculated directional wave spectra in the East China Sea

Directional wave spectra measured by a cloverleaf buoy in the East China Sea during AMTEX '75 have been compared with those calculated with the operational numerical MRI wave model developed at the Meteorological Research Institute of the Japan Meteorological Agency (J.M.A.). It is shown that the numerical wave model MRI can predict rather well, not only the frequency spectrum, but also the angular distribution function of the spectrum. The frequency dependence of the calculated angular distribution function is quite similar to that observed; the angular distribution is narrower for the spectral components near the peak spectral frequency but widens toward high frequencies and approaches the cos²-distribution.