Distribution of viable marine bacteria in neritic seawater around Japan

1980 ◽  
Vol 26 (3) ◽  
pp. 318-323 ◽  
Author(s):  
Kazuhiro Kogure ◽  
Ushio Simidu ◽  
Nobuo Taga
Keyword(s):  
Organic Matter ◽  
Viable Count ◽  
Tokyo Bay ◽  
Natural Seawater ◽  
Sagami Bay ◽  
Direct Count ◽  
Free Living ◽  
The Kuroshio ◽  
Kuroshio Region ◽  
Living Bacteria

The direct viable count (DVC) method of determining the number of living bacteria in natural seawater was applied to samples collected from areas around Japan ranging from polluted to oligotrophic. In summer, the DVC comprised 1.5–39.8% (mean, 11.2%) of the total direct count (TDC) in Tokyo Bay, which was highly eutrophic. In offshore areas (Sagami Bay and the Kuroshio region), the percentages ranged from 0.7 to 7.9 (mean, 2.8%). In winter, slightly higher percentages were observed in Sagami Bay. The majority of DVC cells were free-living. The distribution of bacteria correlated closely with particulate or dissolved organic matter.

Distribution of heterotrophic bacteria in relation to the concentration of particulate organic matter in seawater

1983 ◽  
Vol 29 (5) ◽  
pp. 570-575 ◽  
Author(s):  
Kimio Fukami ◽  
Usio Simidu ◽  
Nobuo Taga
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Heterotrophic Bacteria ◽  
Viable Count ◽  
Plate Count ◽  
Free Living ◽  
Count Method ◽  
Attached Bacteria ◽  
Geographical Scale ◽  
Living Bacteria

The relationship between the number of bacteria and the concentration of particulate organic carbon (POC) in seawater was investigated. In coastal seawater in summer, the POC concentration showed better correlation to the density of bacteria obtained by the viable plate count method (viable count, V.C.) than by the total direct count method (total count, T.C.). The number of attached bacteria (A) showed significant fluctuation, both laterally on a geographical scale and vertically in the water column; on the other hand, the number of free-living bacteria (F) was relatively constant. The POC concentration had a much higher correlation with A (r = 0.8795) than with T.C. (r = 0.7339), and had a low correlation with F (r = 0.6935). Moreover, a very good correlation was observed between the density of bacteria obtained by V.C. and A (r = 0.9153). These results indicate that when the concentration of particulate organic matter (POM) increases, some free-living bacteria become attached to POM, and grow on the surface of POM. These communities of attached bacteria have the ability to make colonies on plate media and can be counted as the "viable plate count."

scholarly journals Concentrations and activity ratios of 228Ra and 226Ra in surface seawater along the Pacific coast of Japan

2011 ◽  
Vol 1 (1) ◽  
pp. 183-188 ◽  
Author(s):  
T. Ohta ◽  
Y. Mahara ◽  
T. Kubota ◽  
J. Sato ◽  
T. Gamo
Keyword(s):  
Pacific Coast ◽  
Tokyo Bay ◽  
Surface Seawater ◽  
Sagami Bay ◽  
Surface Salinity ◽  
Shelf Sediment ◽  
The Pacific ◽  
Activity Ratios ◽  
Pacific Coast Of Japan ◽  
The Kuroshio

AbstractWe measured the 228Ra/226Ra activity ratios in surface seawater along the Pacific coast of Japan at five ports around the island of Izu-Oshima (n = 29), at Atami in Sagami Bay (n = 13), and at Umizuri Park in Tokyo Bay (n = 14). We also conducted these measurements along a transect from the open Pacific Ocean across the Kuroshio to the mouth of Tokyo Bay (n = 7). The activity ratios decreased with increasing salinity of the sampling sites. The 228Ra/226Ra activity ratios in surface seawater along the coast gradually decreased after at the end of autumn and were lowest in winter and the beginning of spring. The surface salinity along the coast decreased from summer into autumn and increased from winter to the beginning of spring. The activity ratios decreased with the increase of salinity.The variation in activity ratios at the three coastal sites is possibly caused by differing contributions of surface seawater from the Kuroshio and surrounding open ocean. The different patterns and ranges of variation in the 228Ra/226Ra activity ratios in surface seawater at Izu-Oshima, Atami, and Umizuri Park may reflect both the amount of water from the Kuroshio and vicinity, and the local bathymetry, because continental shelf sediment is the source of Ra isotopes in surface seawater.

Pre- and Post-Tsunami Depth Changes of Submarine Topography for the Analysis of Submarine Landslide-Induced Tsunami: Proposal of Digitization Method and Application to the Case of the 1923 Great Kanto Earthquake Tsunamis

2021 ◽  
Author(s):  
Kazuki Murata ◽  
Shinji Sassa ◽  
Tomohiro Takagawa ◽  
Toshikazu Ebisuzaki ◽  
Shigenori Maruyama
Keyword(s):  
Large Scale ◽  
Interpolation Method ◽  
Weighted Average ◽  
Tokyo Bay ◽  
Submarine Landslides ◽  
Sagami Bay ◽  
Seabed Topography ◽  
Kanto Earthquake ◽  
Before And After ◽  
Tsunami Event

Abstract We first propose and examine a method for digitizing analog data of submarine topography by focusing on the seafloor survey records available in the literature to facilitate a detailed analysis of submarine landslides and landslide-induced tsunamis. Second, we apply this digitization method to the seafloor topographic changes recorded before and after the 1923 Great Kanto earthquake tsunami event and evaluate its effectiveness. Third, we discuss the coseismic large-scale seafloor deformation at the Sagami Bay and the mouth of the Tokyo Bay, Japan. The results confirmed that the latitude / longitude and water depth values recorded by the lead sounding measurement method can be approximately extracted from the sea depth coordinates by triangulation survey through the overlaying of the currently available GIS map data without geometric correction such as affine transformation. Further, this proposed method allows us to obtain mesh data of depth changes in the sea area by using the interpolation method based on the IDW (Inverse Distance Weighted) average method through its application to the case of the 1923 Great Kanto Earthquake. Finally, we analyzed and compared the submarine topography before and after the 1923 tsunami event and the current seabed topography. Consequently, we found that these large-scale depth changes correspond to the valley lines that flow down as the topography of the Sagami Bay and the Tokyo Bay mouth.

scholarly journals Distribution of ultraphytoplankton in the western part of the North Pacific subtropical gyre during a strong La Niña condition: relationship with the hydrological conditions

2013 ◽  
Vol 10 (9) ◽  
pp. 5947-5965 ◽  
Author(s):  
M. Girault ◽  
H. Arakawa ◽  
A. Barani ◽  
H. J. Ceccaldi ◽  
F. Hashihama ◽  
...  
Keyword(s):  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Subtropical Gyre ◽  
La Niña ◽  
North Pacific Subtropical Gyre ◽  
Heterogeneous Distribution ◽  
La Nina ◽  
The Kuroshio ◽  
Kuroshio Region

Abstract. The distribution of ultraphytoplankton was investigated in the western North Pacific Subtropical Gyre (NPSG) during La Niña, a cold phase of El Niño Southern Oscillation (ENSO). Observations were conducted in a north-south transect (33.6–13.25° N) along the 141.5° E meridian in order to study the ultraplankton assemblages in various oligotrophic conditions. Analyses were performed at the single cell level by analytical flow cytometry. Five ultraphytoplankton groups (Prochlorococcus, Synechococcus, picoeukaryotes, nanoeukaryotes and nanocyanobacteria-like) defined by their optical properties were enumerated in three different areas visited during the cruise: the Kuroshio region, the subtropical Pacific gyre and a transition zone between the subtropical Pacific gyre and the Warm pool. Prochlorococcus outnumbered the other photoautotrophs in all the investigated areas. However, in terms of carbon biomass, an increase in the relative contribution of Synechococcus, picoeukaryotes and nanoeukaryotes was observed from the centre of the subtropical gyre to the Kuroshio area. In the Kuroshio region, a peak of abundance of nanoeukaryotes observed at the surface suggested an increase in nutrients likely due to the vicinity of a cold cyclonic eddy. In contrast, in the salinity front along the isohaline 35 and anticyclonic eddy located around 22.83° N, the mainly constant distribution of Prochlorococcus from the surface down to 150 m characterised the dominance by these microorganisms in high salinity and temperature zone. Results suggested that the distribution of nanocyanobacteria-like is also closely linked to the salinity front rather than low phosphate concentration. The maximum abundance of ultraphytoplankton was located above the SubTropical Counter Current (STCC) at depths > 100 m where higher nutrient concentrations were measured. Finally, comparison of the ultraphytoplankton concentrations during El Niño (from the literature) and La Niña (this study) conditions seems to demonstrate that La Niña conditions lead to higher concentrations of Synechococcus in the Subtropical gyre and a lower abundance of Synechococcus in the Kuroshio region. Our results suggest that the west part of NPSG is a complex area, where different water masses, salinity fronts and eddies lead to a heterogeneous distribution of ultraphytoplankton assemblages in the upper layer of the water column.

Short-term flow and water temperature fluctuations in Sagami Bay, Japan, associated with variations of the Kuroshio during the non-large-meander path

2012 ◽  
Vol 105 ◽  
pp. 47-60 ◽  
Author(s):  
Daisuke Takahashi ◽  
Akihiko Morimoto ◽  
Tetsuya Nakamura ◽  
Takuji Hosaka ◽  
Yoshihisa Mino ◽  
...  
Keyword(s):  
Water Temperature ◽  
Temperature Fluctuations ◽  
Large Meander ◽  
Short Term ◽  
Sagami Bay ◽  
The Kuroshio

scholarly journals Phytoplankton Increase Along the Kuroshio Due to the Large Meander

2021 ◽  
Vol 8 ◽  
Author(s):  
Daniel Andres Lizarbe Barreto ◽  
Ricardo Chevarria Saravia ◽  
Takeyoshi Nagai ◽  
Takafumi Hirata
Keyword(s):  
Chlorophyll A ◽  
Mixed Layer Depth ◽  
Local Environment ◽  
Trophic Levels ◽  
Large Meander ◽  
The Mean ◽  
Western Side ◽  
The Kuroshio ◽  
Cold Core ◽  
Kuroshio Region

The Kuroshio Large Meander (LM) is known to be highly aperiodic and can last from 1 to 10 years. Since a stationary cold core formed between the Kuroshio and the southern coast of Japan off Enshu-Nada and approaching warm saltier water on the eastern side of the LM changes the local environment drastically, many commercially valuable fish species distribute differently from the non-LM period, impacting local fisheries. Despite this importance of the LM, the influences of the LM on the low trophic levels such as phytoplankton and zooplankton have still been unclear. In this study, satellite daily sea surface chlorophyll data are analyzed in relation to the LM. The results show positive anomalies of the chlorophyll-a concentration along the Kuroshio path during the LM periods, 2004–2005 and 2017–2019, from the upstream off Shikoku to the downstream (140°E). These positive anomalies are started by the triggering meander generated off south of Kyushu, which then slowly propagates to the downstream LM region in both the LM periods. Even though the detailed patterns along the Kuroshio region in the two LM periods were different, similar formations of the positive anomalies on the western side of the LM with shallower mixed layer depth are observed. Furthermore, we found clear relationships between the minimum distance from several stations along the coast to the Kuroshio axis and the mean chlorophyll-a anomaly, with significant correlations with the distance from different stations.

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