Mesoscale decrease of surface phosphate and associated phytoplankton dynamics in the vicinity of the subtropical South Pacific islands

Surface distributions of nutrients and phytoplankton were investigated in the vicinity of the subtropical South Pacific islands by using a continuous underway system with a highly sensitive nutrient analysis. A total of 17 transects, whose lengths ranged between 42 and 271 km, were sampled for continuous nutrient measurements. The study area was characterized by an overall depletion of nitrate+nitrite (<15 nM), but phosphate varied from 7 to 192 nM. The transects were grouped into 4 patterns according to distribution of phosphate concentrations. In 7 transects, a mesoscale decrease in phosphate occurred, coinciding with an elevation of in vivo chlorophyll fluorescence, which was accompanied by an increase in phytoplankton abundance as revealed by microscopy, flow cytometry, and accessory pigments. This mirror–image relationship between the phosphate concentration and phytoplankton abundance was most apparent on both a 99-km transect east of Tonga, where the phosphate concentration ranged from 17 to 125 nM, and on a 98-km transect west of Fiji, where the phosphate concentration ranged from 23 to 136 nM. Both these transects contained distinct blooms of Trichodesmium in areas with the lowest concentrations of phosphate. In other 2 transects, fluctuations in phosphate concentrations showed no distinct relationship with chlorophyll fluorescence. Other patterns that emerged included consistently high concentrations, ranging from 109 to 192 nM, in 5 transects and consistently low phosphate concentrations, ranging from 7 to 50 nM, in 3 transects. Abundance of Trichodesmium, Prochlorococcus, Synechococcus, and all accessory pigments examined tended to be higher in the low phosphate transects than in the high phosphate ones. In particular, Trichodesmium occurred in low phosphate water (<25 nM). There was no significant relationship between phosphate concentrations and nanoplanktonic unicellular cyanobacteria. Our observations suggest that surface phosphate decreases are associated with phytoplankton utilization of phosphate, and that nitrogen supply from Trichodesmium may contributes to this utilization.     

Sensitive determination of enzymatically labile dissolved organic phosphorus and its vertical profiles in the oligotrophic western North Pacific and East China Sea

Trace concentrations of labile dissolved organic phosphorus (LDOP) in oligotrophic seawater were measured by use of an enzymatic procedure and a nanomolar phosphate analytical system consisting of a gas-segmented continuous flow analyzer with a liquid waveguide capillary cell. LDOP, defined as DOP hydrolyzed by alkaline phosphatase (AP) from Escherichia coli, was quantified as the difference between the phosphate concentrations of the seawater sample with and without AP treatment. For sensitive measurement of LDOP, we found that phosphate contamination derived from commercially available AP must be corrected, and azide treatment before AP treatment proved effective in removing biological effect that occurs during DOP hydrolysis. Field observations at six stations of the western North Pacific and the East China Sea during the boreal summer revealed that, in the upper 200 m of the water column, LDOP concentrations ranged from the detection limit (3 nM) to 243 nM, and phosphate concentrations ranged from 5 to 374 nM. The spatial distribution patterns of LDOP were similar to those of phosphate. Most of the depth profiles for LDOP and phosphate showed concentrations were extremely low, <25 nM, between the surface and the deep chlorophyll maximum layer (DCML) and increased below the DCML. Strongly depleted LDOP and phosphate above the DCML suggest that LDOP is actively hydrolyzed under phosphate-depleted conditions and utilized by microbes.     

<Emphasis Type="Italic">Landslides</Emphasis>: a review of achievements in the first 5 years (2004–2009)

The international journal Landslides was initiated in April 2004. It is the core project (IPL-C100) of the International Programme on Landslides, a joint initiative of the International Consortium on Landslides and the United Nations and other global organizations. The aims of Landslides are to promote landslide sciences, technology, and capacity building and strengthen global cooperation for landslide risk reduction within the United Nations International Strategy for Disaster Reduction. This paper presents an analysis of the first 5 years of Landslides, the study methods employed, the types and major causes of landslides, the number of different contributors per country, and the “times cited” per issue and most frequently cited papers and briefly discusses some of these. Strategies for future development of the journal involve obtaining input and suggestion from researchers and readers worldwide.     

Trends and relationships in victims’ recovery perceptions: a case study of the recovery process following the Great East Japan Earthquake

Natural Hazards - In the aftermath of a disaster, the recovery process has long-term, multi-dimensional, and interactive aspects. To clarify the recovery conditions and victims’ perceptions...     

Comparison of community structures between particle-associated and free-living prokaryotes in tropical and subtropical Pacific Ocean surface waters

The subtropical and tropical regions of the Pacific Ocean are less productive than other oceanic regions. Although particle association should be an important strategy for heterotrophic prokaryotes to survive in such environments, we have little information on particle-associated (PA) prokaryotes in these regions. The specific aim of this study was to determine bacterial and archaeal community structures in the PA assemblage in comparison to the free-living (FL) assemblage in the North Pacific Subtropical Gyre, the South Pacific Subtropical Gyre, and an eastern equatorial region of the Pacific Ocean. Community profiles and phylogenetic identities were obtained by denaturing gradient gel electrophoresis, 454-pyrosequencing, and cloning followed by Sanger sequencing of 16Sr RNA gene amplicons. The distribution patterns of some abundant groups in three regions and two lifestyles (PA and FL) are shown in this study. Also, the PA community structures of bacteria differed from the FL ones and exhibited higher diversity than the FL ones, while the archaeal community structures did not show significant differences between PA and FL assemblages. We found that specific phylotypes of Gammaproteobacteria and Flavobacteria were abundant in PA bacterial assemblages, suggesting that they prefer to attach and consume particulate organic matter. In summary, the surface seawater PA assemblages represent very different bacterial and archaeal community structures between three different oceanic regions, each of which had distinct PA and FL community structures. These results imply that environmental factors determine microbial community structures.     

Basin-scale distribution of NH<Subscript>4</Subscript><Superscript>+</Superscript> and NO<Subscript>2</Subscript><Superscript>−</Superscript> in the Pacific Ocean

We used more than 25,000 nutrient samples to elucidate for the first time basin-scale distributions and seasonal changes of surface ammonium (NH₄ ⁺) and nitrite (NO₂ ^?) concentrations in the Pacific Ocean. The highest NH₄ ⁺, NO₂ ^?, and nitrate (NO₃ ^?) concentrations were observed north of 40°N, in the coastal upwelling region off the coast of Mexico, and in the Tasman Sea. NH₄ ⁺ concentrations were elevated during May–October in the western subarctic North Pacific, May–December in the eastern subarctic North Pacific, and June–September in the subtropical South Pacific. NO₂ ^? concentrations were highest in winter in both hemispheres. The seasonal cycle of NH₄ ⁺ was synchronous with NO₂ ^?, NO₃ ^?, and satellite chlorophyll a concentrations in the western subtropical South Pacific, whereas it was synchronous with chlorophyll-a but out of phase with NO₂ ^? and NO₃ ^? in the subarctic regions.     

The linear stability of the post-Newtonian triangular equilibrium in the three-body problem

Continuing a work initiated in an earlier publication (Yamada et al. in Phys Rev D 91:124016, 2015), we reexamine the linear stability of the triangular solution in the relativistic three-body problem for general masses by the standard linear algebraic analysis. In this paper, we start with the Einstein–Infeld–Hoffmann form of equations of motion for N-body systems in the uniformly rotating frame. As an extension of the previous work, we consider general perturbations to the equilibrium, i.e., we take account of perturbations orthogonal to the orbital plane, as well as perturbations lying on it. It is found that the orthogonal perturbations depend on each other by the first post-Newtonian (1PN) three-body interactions, though these are independent of the lying ones likewise the Newtonian case. We also show that the orthogonal perturbations do not affect the condition of stability. This is because these do not grow with time, but always precess with two frequency modes, namely, the same with the orbital frequency and the slightly different one due to the 1PN effect. The condition of stability, which is identical to that obtained by the previous work (Yamada et al. 2015) and is valid for the general perturbations, is obtained from the lying perturbations.     

Mineral distribution within polymineralic veins in the Sanbagawa belt,Japan: implications for mass transfer during vein formation

Pelitic schists of the Sanbagawa metamorphic belt contain several types of polymineralic veins that formed during the late stages of exhumation. The vein mineral assemblages are quartz + albite + K-feldspar + chlorite ± calcite (Type I, II) and quartz + albite + calcite (Type III). Type I and II veins contain quartz and albite with stretched-crystal and elongate-blocky textures, respectively. The mineral species within Type I veins vary with compositional bands within the host rocks. Type III veins are characterized by euhedral to subhedral quartz grains with concentric zoning and a homogeneous distribution along the vein length. The vein textures vary depending on the crack aperture during multiple crack-seal events: <0.08 mm for Type I, and 0.5–10 mm for Type III. Type II veins show intermediate features between Type I and III veins in terms of mineral distribution (weak dependence on the host rock composition) and apparent crack aperture (less than 1–15 mm). These observations suggest a transition in the dominant transport mechanism of vein components with increasing crack aperture, from diffusion from host rocks to fluid advection along cracks.