Bottom currents in Nankai Trough and Sagami Trough

Taira, Keisuke; Teramoto, Toshihiko

doi:10.1007/bf02109033

Cited by 18 publications

(6 citation statements)

References 7 publications

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“…The first survey around the islands (K6 and K7) also showed higher densities in the immediate and eastern regions, especially in the lower epipelagic layer ( Figure 3b). As it is known that one of the branches of Oyashio, the western boundary current of the western subarctic gyre, reaches Sagami Bay or flows westward from the Izu Islands (Marumo, 1966;Sekine & Uchiyama, 2002;Senjyu, Asano, Matsuyama, & Ishimaru, 1998;Taira & Teramoto, 1985;Yang, Nagata, Taira, & Kawabe, 1993a, 1993b, the higher densities are attributed to the influence of Oyashio water. In the Kuroshio Extension area, the highest water density (lowest temperature and salinity) was shown north of the axis (Oyashio side) on the eastern side of…”

Section: Characteristics Of the Water Massmentioning

confidence: 99%

Environmental characteristics of spawning and nursery grounds of Japanese sardine and mackerels in the Kuroshio and Kuroshio Extension area

Sogawa

Hidaka

Kamimura

et al. 2019

Fisheries Oceanography

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The sustainable use of marine resources requires understanding the surrounding ecosystem and elucidating mechanisms of variation. However, we still lack a comprehensive understanding of environmental variation in the spawning and nursery grounds of important fisheries species Japanese sardine (Sardinops melanostictus) and mackerels (Scomber japonicus and Scomber australasicus) in the northwest Pacific. Here, we investigate detailed physical, chemical, and biological environment variations in the spawning and nursery grounds along the Kuroshio and Kuroshio Extension area from intensive investigation in spawning season (April) of 2013. We found similar water mass property and copepod community in the egg‐rich Kuroshio area and the larvae‐rich downstream Kuroshio Extension area, indicating environmental variability is small during transportation and development processes. The egg‐rich northern Izu Islands region showed high copepod abundance, although low nutrient and chlorophyll concentrations were observed. Eggs were scarce or absent in the second survey 10 days after abundant eggs were observed in the region, along with differences in water property and copepod community. This indicates that not only the location but also the specific water characteristic and copepod community are a determining factor for spawning. Indicator communities of copepod found in our study (indicator community of transportation process from spawning ground, of non‐spawning ground, and of reproductive area in the Kuroshio Extension area) would be a key factor for recruitment prediction.

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Section: Characteristics Of the Water Massmentioning

confidence: 99%

Environmental characteristics of spawning and nursery grounds of Japanese sardine and mackerels in the Kuroshio and Kuroshio Extension area

Sogawa

Hidaka

Kamimura

et al. 2019

Fisheries Oceanography

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“…The variance between I 0 and 30 hours periods, occupied mainly by tidal current energy, are shown to be 42-82% of the total variance. Although no detailed analysis associated with the tidal periods have been made by Taira and Teramoto (1985), the strong tidal currents are likely to exist even near the sea bottom south of the Suruga Trough.…”

Section: Summary and Discussionmentioning

confidence: 98%

“…The strong tidal currents were actually experienced in the axial floor of Suruga Bay during submersible dives (Otsuka and Niitsuma, 1985;Midorikawa et al, 1988). Taira and Teramoto (1985) carried out long-term current measurements near the sea bottom south of the Suruga Trough for about one year. The current meters were set at 7 m above the sea bottom at Stn.…”

Section: Summary and Discussionmentioning

confidence: 99%

Strong tidal currents observed near the bottom in the Suruga Trough, central Japan

et al. 1993

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Current measurements carried out at the depth of 4 m above the sea bottom near the northern edge of the Suruga Trough in the early fall of 1985 indicated the existence of strong semidinrnal tidal currents, which were considered to be associated with internal tides. In order to examine the spatial structure of the bottom intensified tidal flow, more detailed current observations were carried out at three or four depths at two stations along the main axis of the Suruga Trough during about 70 days from August to October 1988. We obtained the following results: (1) the variations of the current velocity caused by the semidiurnal and diurnal internal tides are evident in all of the records, and the orientation of the major axis of each tidal ellipse nearly coincides with that of the main axis of the trough; (2) the'semidiurnal internal tide is dominant over the diurnal internal tide at 4 m above the sea bottom at both stations; (3) at the northern station the semidiurnal internal tide is dominant over the diurnal internal tide, whereas they are nearly equal at the southern station except at 4 m above the sea bottom; (4) the biharmonic internal tides with 1/3 day and 1/4 day periods, are found near the sea bottom and the major axis of the tidal ellipse is perpendicular to the orientation of the main axis of the Suruga Trough.

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“…Significantly different clusters formed during different seasons at 100 m depths (clusters 1, 3 and 4 for eukaryotic community and clusters 1 and 4-3 for bacterial community). Upwelling of deep seawater supplies rich nutrients to the coastal areas from Sagami Trough (more than 1000 m deep), located in the centre of the Bay (Takahashi et al 1980;Taira and Teramoto 1985;Kawabe and Yoneo 1987). In our study, deep-waters, rich in nutrients, were supplied to deeper layers (100 m) when vertical mixing weakened.…”

Section: Overall Plankton Community and Diversity Dynamicsmentioning

confidence: 99%

Annual dynamics of eukaryotic and bacterial communities revealed by 18S and 16S rRNA metabarcoding in the coastal ecosystem of Sagami Bay, Japan

Sogawa¹,

Tsuchiya²,

Nagai³

et al. 2022

MBMG

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Sagami Bay, Japan is influenced by both the warm Kuroshio Current and the cold Oyashio Current and rich nutrients are supplied from multiple river sources and the deep-sea, forming a dynamic ecosystem. The aim of the present study was to investigate eukaryotic and bacterial communities in the coastal waters of Sagami Bay, using 16S rRNA and 18S rRNA sequencing and to assess the seasonal and vertical dynamics in relation to physicochemical and biological conditions. Eukaryotic and bacterial communities showed synchronous seasonal and vertical changes along with environmental variability. Diversity of plankton community suspended in the surface was lower than those at the subsurface layers in both the eukaryotes and bacteria communities; however, community diversity showed different characteristics in the subsurface where the eukaryotic community at the deeper layer (100 m) was as low as the surface and highest in intermediate depth layers (10–50 m), while that of bacterial community was highest in the deeper layer (100 m). The annual variability of the coastal microbial communities was driven, not only by the seasonal changes of abiotic and biotic factors and short-term rapid changes by river water inflow and phytoplankton blooms, but also largely influenced by deep-seawater upwellings due to the unique seafloor topography.

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Bottom currents in Nankai Trough and Sagami Trough

Cited by 18 publications

References 7 publications

Environmental characteristics of spawning and nursery grounds of Japanese sardine and mackerels in the Kuroshio and Kuroshio Extension area

Environmental characteristics of spawning and nursery grounds of Japanese sardine and mackerels in the Kuroshio and Kuroshio Extension area

Strong tidal currents observed near the bottom in the Suruga Trough, central Japan

Annual dynamics of eukaryotic and bacterial communities revealed by 18S and 16S rRNA metabarcoding in the coastal ecosystem of Sagami Bay, Japan

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Bottom currents in Nankai Trough and Sagami Trough

Cited by 18 publications

References 7 publications

Environmental characteristics of spawning and nursery grounds of Japanese sardine and mackerels in the Kuroshio and Kuroshio Extension area

Environmental characteristics of spawning and nursery grounds of Japanese sardine and mackerels in the Kuroshio and Kuroshio Extension area

Strong tidal currents observed near the bottom in the Suruga Trough, central Japan

﻿Annual dynamics of eukaryotic and bacterial communities revealed by 18S and 16S rRNA metabarcoding in the coastal ecosystem of Sagami Bay, Japan

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Annual dynamics of eukaryotic and bacterial communities revealed by 18S and 16S rRNA metabarcoding in the coastal ecosystem of Sagami Bay, Japan