著者

Hanamiya Yurika Murase Hiroto Matsuno Kohei Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.77-89, 2020-08-24

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This study conducted diel vertical migration and active migration flux estimation of macrozooplanktonic amphipods and euphausiids at 0-250 m water column of the three stations in the western North Pacific during summer. For amphipods, 25 species belonging to 17 genera were identified. Their standing stock was 60-574 ind. m−2 during the daytime and 35-5,228 ind. m−2 at night-time. For euphausiids, 19 species belonging to 7 genera were identified. The standing stock of euphausiids was 80-382 ind. m−2 and 286-2,156 ind. m−2 during the day and at night, respectively. Feeding impacts during the night were estimated to be 0.19-11.76 mg C m−2 day−1 (amphipods) and 5.12-16.42 mg C m−2 day−1 (euphausiids). Respiration during the daytime accounted for 0.08-6.38 mg C m−2 day−1 (amphipods) and 2.33-7.70 mg C m−2 day−1 (euphausiids). The feeding impact and respiratory flux by active migration of macrozooplankton taxa were estimated as 8.34-28.18 mg C m−2 day−1 and 3.15-14.08 mg C m−2 day−1, respectively. These values corresponded to 3.7-12.4% of primary production (feeding impact) and 2.4-10.7% of sinking passive flux from the euphotic zone (respiratory flux). Thus, this study emphasizes the importance of active flux by macrozooplankton for vertical material flux in the western North Pacific.

著者

Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.1, pp.29-37, 2021-08-03

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Respiratory oxygen consumption rates (at the two temperatures of 0-50 m and 50-200 m depth strata) and day/night biomass in the top 50 m water column were determined on adult female Metridia pacifica at twelve stations in the western/ eastern subarctic Pacific and one station in the oceanic Bering Sea during summer. At each station, the respiration rates at 0-50 m depth temperatures were used to estimate ingestion rates during nighttime by assuming empirical carbon budget efficiencies, and rates at 50-200 m to estimate respiratory carbon flux during daytime. The abundance of the females in the upper 50 m at night varied between 27 and 5,422 inds. m−2 and no specimen was collected from the same layer at daytime throughout the stations. The size of the females varied regionally from 25 to 77 μg C ind.−1. As a result, diel vertical migrant biomass of the females varied greatly from one station to the next (1 and 309 mg C m−2). Weight-specific respiration rates of the females were 2.2-6.3 μl O2 mg C−1 h−1, which was a function of experiment temperatures and body mass (C) of the females. Taking into account of residence time at 0-50 m and 50-200 m in the day, daily population ingestion was estimated as 0.04-11.04 mg C m−2 day−1, which accounted for 0-2.4% of primary production at each station. Daily population respiration in the 50-200 m was calculated as 0.02-9.39 mg C m−2 day−1, which corresponds to 0-10% of the POC flux down from the euphotic zone.

著者

Abe Yoshiyuki Hildebrandt Nicole Matsuno Kohei Niehoff Barbara Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.91-102, 2020-08-24

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We compared copepod abundance, biomass and community structure in the Atlantic sector (Fram Strait) and Pacific sector (Canada Basin) of the Arctic Ocean by using vertical stratified zooplankton samples collected from 0-1,000 m or 0-1,500 m during daytime in summer. Abundance and biomass were high at the surface layer and decreased with increasing depth in both regions. Abundance and biomass in the surface layer in the Fram Strait were 6-18 times higher than those in the Canada Basin. According to cluster analysis, the copepod communities were separated into three groups that varied vertically and included both locations. Regional differences were marked for Calanus finmarchicus, which was distributed only in the Fram Strait. In the Canada Basin, Spinocalanidae composed 56.1% of calanoid copepod abundance for the bathypelagic groups and also contributed 7.5% of abundance throughout the water column. The dominance of Spinocalanidae may reflect the oligotrophic environment in the Pacific sector of the Arctic Ocean.

著者

Sato Kaede Matsuno Kohei Arima Daichi Abe Yoshiyuki Yamaguchi Atsushi

出版者

SpringerOpen

雑誌

Zoological Studies (ISSN:1810522X)

巻号頁・発行日

vol.54, no.1, 2015-01-16

被引用文献数

18 1

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Background An optical plankton counter (OPC) was used to examine spatial and temporal changes in the zooplankton size spectra in the neighboring waters of Japan from May to August 2011. Results Based on the zooplankton biovolume of equivalent spherical diameter (ESD) in 45 bins for every 0.1 mm between 0.5 and 5.0 mm, a Bray-Curtis cluster analysis classified the zooplankton communities into six groups. The geographical distribution of each group varied from each of the others. Groups with a dominance of 4 to 5 mm ESD were observed in northern marginal seas (northern Japan Sea and Okhotsk Sea), while the least biovolume with a dominance of a small-size class (0.5 to 1 mm) was observed for the Kuroshio extension. Temporal changes were observed along the 155° E line, i.e., a high biovolume group dominated by 2 to 3 mm ESD during May shifted to other size spectra groups during July to August. These temporal changes were caused by the seasonal vertical descent of dominant large Neocalanus copepods during July to August. As a specific characteristic of the normalized biomass size spectra (NBSS), the slope of NBSS was moderate (−0.90) for the Neocalanus dominant spring group but was at −1.11 to −1.24 for the other groups. Theoretically, the slope of the NBSS of the stable marine ecosystem is known to settle at approximately −1. Conclusions Based on the analysis by OPC, zooplankton size spectra in the neighboring waters of Japan were separated into six groups. Most groups had −1.11 to −1.24 NBSS slopes, which were slightly higher than the theoretical value (−1). However, one group had a moderate slope of NBSS (−0.90) caused by the dominance of large Neocalanus copepods.

著者

Sugioka Rikuto Matsuno Kohei Takahashi Keigo D. Makabe Ryosuke Takahashi Kunio T. Moteki Masato Odate Tsuneo Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.1, pp.39-50, 2021-08-03

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Various zooplankton studies have been conducted in the Indian sector of the Southern Ocean, but studies investigating spatial changes in both meso- and macro-zooplankton populations are limited. To reveal the north-south change of the mesoand macro-zooplankton community structure and the population structure of large copepods, we investigated zooplankton communities collected by the Ocean Research Institute (ORI) net along the 110°E transect in the Indian sector of the Southern Ocean during the austral summer. The zooplankton abundance and biomass were high at the stations north of 60°S and was dominated by large copepods, especially Calanoides acutus. A cluster analysis identified four zooplankton community groups. The distribution pattern of the community groups is likely to be related to the frontal system. The population structure of the dominant species of C. acutus, Calanus propinquus and Rhincalanus gigas had a similar tendency ; early copepodite stages were abundant in the northern region, while late copepodite stages dominated in the southern region. The meridional changes in the population structure are explained by different reproduction periods in each region related to sea-ice melt timing.

著者

Yamaguchi Atsushi Kodama Yasuhiro Matsuo Hiroto Ohno Minoru Osugi Satomi Maeno Yoshiaki Higuchi Masahiro

出版者

INSTITUTE OF PURE AND APPLIED PHYSICS

雑誌

Jpn J Appl Phys (ISSN:00214922)

巻号頁・発行日

vol.45, no.8, pp.6326-6327, 2006-08-15

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Polylactic acid (PLA) is a biomass material made of starch. Compact disc recordable (CD-R) discs with a PLA substrate were prepared and their properties were measured. Although the glass transition point of PLA is lower than that of polycarbonate (PC), the PLA substrate is usable for CD-R discs. It was confirmed that the substrate is usable for recordable optical discs at temperatures under 50 °C.

著者

Yamaguchi Atsushi Hibino Katsutoshi Suzuki Yoshihisa Terasaki Hitoshi Ichiura Shuichi

出版者

INSTITUTE OF PURE AND APPLIED PHYSICS

雑誌

Jpn J Appl Phys (ISSN:00214922)

巻号頁・発行日

vol.45, no.2, pp.1129-1130, 2006-02-15

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A laser beam axis compensator was fabricated for an optical pickup unit with blue and red lasers. The device consisted of multiwavelength wave plates and a double-refractive-index material. The wave plates were realized by a photonic crystal technique. By measuring the beam profiles of the blue and red lasers, the device was confirmed to function as a laser axis compensator. Under 110 μm laser beam axis shift setting conditions, readout signal patterns from an optical disc were measured.

著者

Wu Hsin-Lun Sato Ryota Yamaguchi Atsushi Kimura Masato Haruta Mitsutaka Kurata Hiroki Teranishi Toshiharu

出版者

American Association for the Advancement of Science

雑誌

Science (ISSN:10959203)

巻号頁・発行日

vol.351, no.6279, pp.1306-1310, 2016-03-18

被引用文献数

102

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常温・常圧でのイオン性ナノ結晶の結晶構造制御に成功 -新しい光エネルギー変換材料開発に期待-. 京都大学プレスリリース. 2016-03-18.