Complex vertical migration of larvae of the ghost shrimp, Nihonotrypaea harmandi, in inner shelf waters of western Kyushu,Japan     

Akio Tamaki  Sumit Mandal  Yoshihiro Agata  Ikumi Aoki  Toshikazu Suzuki  Hisao Kanehara  Takashi Aoshima  Yasushi Fukuda  Hideshi Tsukamoto  Tetsuo Yanagi 《Estuarine, Coastal and Shelf Science》2010

The position of meroplanktonic larvae in the water column with depth-dependent current velocities determines horizontal transport trajectories. For those larvae occurring in inner shelf waters, little is known about how combined diel and tidally-synchronized vertical migration patterns shift ontogenetically. The vertical migration of larvae of Nihonotrypaea harmandi (Decapoda: Thalassinidea: Callianassidae) was investigated in mesotidal, inner shelf waters of western Kyushu, Japan in July–August 2006. The larval sampling at seven depth layers down to 60 m was conducted every 3 h for 36 h in a 68.5-m deep area 10 km off a major coastal adult habitat. Within a 61–65-m deep area 5–7.5 km off the adult habitat, water temperature, salinity, chlorophyll a concentration, and photon flux density were measured, and water currents there were characterized from harmonic analysis of current meter data collected in 2008. The water column was stratified, with pycnocline, chlorophyll a concentration maximum, and 2% of photon flux density at 2 m, recorded at around 22–24 m. The stratified residual currents were detected in their north component, directed offshore and onshore in the upper and lower mixed layers, respectively. More than 87% of larvae occurred between 20 m and 60 m, producing a net onshore transport of approximately 1.3 km d⁻¹. At the sunset flooding tide, all zoeal-stage larvae ascended, which could further promote retention (1.4-km potential onshore transport in 3 h). The actual onshore transport of larvae was detected by observing their occurrence pattern in a shallow embayment area with the adult habitat for 24 h in October 1994. However, ontogenetic differences in the vertical migration pattern in inner shelf waters were also apparent, with the maximum mean positions of zoeae deepening with increasing stages. Zoeae I and II performed a reverse diel migration, with their minimum and maximum depths being reached around noon and midnight, respectively. Zoeae IV and V descended continuously. Zoeae III had behaviors that were intermediate to those of the earlier- and later-stage zoeae. Postlarvae underwent a normal diel migration (nocturnal ascent) regardless of tides, with the deepest position (below 60 m and/or on the bottom) during the day. These findings give a new perspective towards how complex vertical migration patterns in meroplanktonic larvae enable their retention in inner shelf waters before the final entry of postlarvae into their natal populations.  相似文献   

Iron deficiency in micro-sized diatoms in the Oyashio region of the Western subarctic Pacific during spring     

Ai Hattori-Saito  Jun Nishioka  Tsuneo Ono  R. Michael L. McKay  Koji Suzuki 《Journal of Oceanography》2010,66(1):105-115

In order to detect iron (Fe) stress in micro-sized (20–200 μm) diatoms in the Oyashio region, western subarctic Pacific during spring, immunological ferredoxin/flavodoxin assays were applied to samples collected from the surface layer in May 2005. Concomitantly, the community composition of the micro-sized phytoplankton and hydrographic conditions, including dissolved Fe and macronutrient concentrations, were also examined. Chlorophyll (Chl) a concentrations were <2 mg m⁻³ at all sampling stations, except at a station where the Chl a level was 9.0 mg m⁻³ and a micro-sized diatom bloom occurred. A high abundance of ferredoxin in micro-sized diatoms was detected only at a rather near-shore station where dissolved Fe and macronutrient concentrations were higher, indicating that the micro-sized diatoms did not suffer from iron deficiency. On the other hand, flavodoxin in micro-sized diatoms was often observed at the other stations, including the bloom station, where macronutrients were replete but dissolved Fe concentration was low (0.31 nM). A significant amount of chlorophyllide a, a degradation product of Chl a, was also observed at the bloom station, suggesting a decline of the diatom bloom. The micro-sized phytoplankton species at all the stations were mainly composed of the diatoms Thalassiosira, Chaetoceros, and Fragilariopsis spp. Our study indicates that micro-sized diatoms were stressed by Fe bioavailability during the spring season in the Oyashio region  相似文献   

Non-food-chain transfer of sediment-associated persistent organic pollutants to a marine benthic fish     

Takeo Sakurai  Jun Kobayashi  Yoshitaka Imaizumi  Noriyuki Suzuki 《Marine pollution bulletin》2009,58(7):1072-1077

We investigated the transfer of persistent organic pollutants (POPs) from unspiked bottom sediment to a benthic marine fish, marbled sole (Pleuronectes yokohamae), via non-food-chain pathways, i.e., via sediment particles and water column. One-year-old sole were held for 28 days in an exposure tank with bottom sediment or in a control tank. o,p′-DDE and tri- to penta-chlorobiphenyls were transferred from the sediment to the fish via non-food-chain pathways, as demonstrated by concentrations in the exposed fish at 2.5-30 times the control levels. A model analysis based on first-order kinetic equations indicated that the overall rate constant of transfer of these compounds from sediment to fish was generally lower than that from food (median of ratio, 0.48). It also suggested that relatively high concentrations of the other POPs in the food and the longer times necessary for them to reach a steady state masked any transfer of them from the sediment.  相似文献   

Oxygen and carbon isotope records of cultured freshwater pearl mussel <Emphasis Type="Italic">Hyriopsis</Emphasis> sp. shell from Lake Kasumigaura,Japan     

Toshihiro Yoshimura  Rei Nakashima  Atsushi Suzuki  Noriko Tomioka  Hodaka Kawahata 《Journal of Paleolimnology》2010,43(3):437-448

We present oxygen and carbon isotope ratios and the morphological structure of the cultured freshwater pearl mussel (Hyriopsis sp., Unionidae) shell and pearl. The number of first-order fluctuations of δ¹⁸O of the outer shell layer along the maximum growth axis was consistent with the number of cultured years. The dominant factor controlling annual δ¹⁸O fluctuations was water temperature with a minor contribution from the variation in δ¹⁸O of ambient water, especially during the rainy season. The δ¹³C values were approximately constant throughout the life of the mussel, suggesting that the contributions of body size to δ¹³C of the shell were minor. We observed nine distinct disturbance rings on the outer surface of the shell. Five rings coincided with the five winter peaks of the δ¹⁸O profile, indicating winter growth cessation below approximately 10°C, probably because of either inactive growth at low water temperatures or reproduction. Summer disturbance rings were not observed in all years. Moreover, some summer rings showed discontinuity in the inner structure. These findings suggest that summer growth cessation may be caused by occasional events such as heavy rains, as the decrease of dissolved oxygen concentration. The δ¹⁸O profile and shell structures indicated that shell aragonite was precipitated at close to equilibrium conditions with respect to the oxygen isotope composition of the ambient water. Hyriopsis sp. shells can potentially be used for reconstruction of past hydrologic conditions. The δ¹⁸O of a pearl indicated that calcification occurred over a temperature range of at least 13–23°C. The optimal temperature for pearl calcification in this species is lower than that for marine pearl calcification.  相似文献   

Crustal structure of central Japan and its petrological implications     

Oguz Ozel  Takaya Iwasaki  Takeo Moriya  Shin'ichi Sakai  Takuya Maeda  Chengshi Piao  Toshikatsu Yoshii  Shinya Tsukada  Akihito Ito  Masayuki Suzuki  Akira Yamazaki  & Hiroki Miyamachi 《Geophysical Journal International》1999,138(1):257-274

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Combined effects of photosynthesis and calcification on the partial pressure of carbon dioxide in seawater   总被引：2，自引：0，他引：2  

Atsushi Suzuki 《Journal of Oceanography》1998,54(1):1-7

The effects of marine photosynthesis and calcification on the partial pressure of carbon dioxide in seawater (P _{CO 2}) are examined in the light of recent studies and using original model calculations. The ratio of organic carbon to inorganic carbon production (R _OI) determines whether an ecosystem is a net sink or source for atmospheric CO₂. TheP _{CO 2} maintains its initial value when the photosynthetic rate is approximately 0.6 times the calcification rate under normal sea surface condition. In case of higherR _OI, theP _{CO 2} decreases and seawater can absorb atmospheric CO₂. The ratio of organic carbon to inorganic carbon production can be used as a potential indicator of sink-source behavior in aquatic photo-calcifying systems.  相似文献   

New developments of performance-based design codes and practice,honouring Prof. Yusuke Honjo     

Makoto Suzuki  Masahiro Shirato 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(3)

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Quantitative micro‐X‐ray fluorescence scanning spectroscopy of wet sediment based on the X‐ray absorption and emission theories: Its application to freshwater lake sedimentary sequences     

Nagayoshi Katsuta  Masao Takano  Naomi Sano  Yukinori Tani  Shinya Ochiai  Sayuri Naito  Takuma Murakami  Masakazu Niwa  Shin‐ichi Kawakami 《Sedimentology》2019,66(6):2490-2510

Micro‐X‐ray fluorescence scanning spectroscopy of marine and lake sedimentary sequences can provide detailed palaeoenvironmental records through element intensity proxy data. However, problems with the effects of interstitial pore water on the micro‐X‐ray fluorescence intensities have been pointed out. This is because the X‐ray fluorescence intensities are measured directly at the surfaces of split wet sediment core samples. This study developed a new method for correcting X‐ray fluorescence data to compensate for the effects of pore water using a scanning X‐ray analytical microscope. This involved simultaneous use of micro‐X‐ray fluorescence scanning spectroscopy and an X‐ray transmission detector. To evaluate the interstitial pore water content from the X‐ray transmission intensities, a fine‐grained sediment core retrieved from Lake Baikal (VER99‐G12) was used to prepare resin‐embedded samples with smooth surfaces and uniform thickness. Simple linear regression between the linear absorption coefficients of the samples and their porosity, based on the Lambert–Beer law, enabled calculation of the interstitial pore spaces and their resin content with high reproducibility. The X‐ray fluorescence intensities of resin‐embedded samples were reduced compared with those of dry sediment samples because of: (i) the X‐ray fluorescence absorption of resin within sediment; and (ii) the sediment dilution effects by resin. An improved micro‐X‐ray fluorescence correction equation based on X‐ray fluorescence emission theory considers the instrument's sensitivity to each element, which provides a reasonable explanation of these two effects. The resin‐corrected X‐ray fluorescence intensity was then successfully converted to elemental concentrations using simple linear regression between the data from micro‐X‐ray fluorescence scanning spectroscopy and from the conventional analyzer. In particular, the calculated concentration of SiO₂ over the depth of the core, reflecting diatom/biogenic silica concentration, was significantly changed by the calibrations, from a progressively decreasing trend to an increasing trend towards the top of the core.  相似文献   

Aftershocks in modern perspectives: Complex earthquake network,aging, and non-Markovianity     

Sumiyoshi Abe  Norikazu Suzuki 《Acta Geophysica》2012,60(3):547-561

The phenomenon of aftershocks is studied in view of science of complexity. In particular, three different concepts are examined: (i) the complex-network representation of seismicity, (ii) the event-event correlations, and (iii) the effects of long-range memory. Regarding (i), it is shown that the clustering coefficient of the complex earthquake network exhibits a peculiar behavior at and after main shocks. Regarding (ii), it is found that aftershocks experience aging, and the associated scaling holds. And regarding (iii), the scaling relation to be satisfied by a class of singular Markovian processes is violated, implying the existence of the long-range memory in processes of aftershocks.  相似文献   

Horizontal distribution and population dynamics of the dominant mysid Hyperacanthomysis longirostris along a temperate macrotidal estuary (Chikugo River estuary, Japan)     

Keita W. Suzuki  Kouji Nakayama  Masaru Tanaka 《Estuarine, Coastal and Shelf Science》2009,83(4):516-528

The estuarine turbidity maximum (ETM) that develops in the lower salinity areas of macrotidal estuaries has been considered as an important nursery for many fish species. Mysids are one of the dominant organisms in the ETM, serving as a key food source for juvenile fish. To investigate the horizontal distribution and population dynamics of dominant mysids in relation to the fluctuation of physical conditions (temperature, salinity, turbidity, and freshwater discharge), we conducted monthly sampling (hauls of a ring net in the surface water) along the macrotidal Chikugo River estuary in Japan from May 2005 to December 2006. Hyperacanthomysis longirostris was the dominant mysid in the estuary, usually showing peaks of density and biomass in or close to the ETM (salinity 1–10). In addition, intra-specific differences (life-cycle stage, sex, and size) in horizontal distribution were found along the estuary. Larger males and females, particularly gravid females, were distributed upstream from the center of distribution where juveniles were overwhelmingly dominant. Juveniles increased in size toward the sea in marked contrast with males and females. The findings suggest a possible system of population maintenance within the estuary; gravid females release juveniles in the upper estuary, juveniles grow during downstream transport, young males and females mature during the upstream migration. Density and biomass were primarily controlled by seasonal changes of temperature, being high at intermediate temperatures (ca. 15–25 °C in late spring and fall) and being low at the extreme temperatures (ca. 10 °C in midwinter and 30 °C in midsummer). High density (up to 666 ind. m⁻³) and biomass (up to 168 mg dry weight m⁻³) of H. longirostris were considered to be comparable with those of copepods in the estuary.  相似文献