Language：English   Publishing type：Research paper (scientific journal)  

A part of the radiocaesium from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was emitted as glassy, water-resistant caesium-bearing microparticles (CsMPs). Here, we isolated and investigated seven CsMPs from marine particulate matter and sediment. From the elemental composition, the 134Cs/137Cs activity ratio, and the 137Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3, as suggested by (i) the presence of calcium and absence of zinc and (ii) the direction of the atmospheric plume during the radionuclide emission event from Unit 3. The presence of CsMPs can cause overestimation of the solid-water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.

DOI： 10.1038/s41598-021-85085-w

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FRONTIERS MEDIA SA  

Seasonal and interannual variabilities in the partial pressure of CO2 (pCO(2)), pH, and calcium carbonate saturation state (omega) were investigated in the highly eutrophicated Tokyo Bay, Japan, based on monthly observations that were conducted from 2011 to 2017. There were large variabilities in these parameters for surface and bottom waters due to photosynthesis and respiration, respectively. Warming/cooling and freshwater input also altered the surface omega. During the observation period, calcium carbonate undersaturation was observed twice in the anoxic bottom waters in summer. The data indicate that anaerobic remineralization under anoxic conditions lowers the omega, causing undersaturation. These findings suggest that de-eutrophication can decelerate ocean acidification in the bottom waters of Tokyo Bay. However, if atmospheric CO2 exceeds 650 ppm, aragonite undersaturation will be a common feature in the summer bottom water, even if hypoxia/anoxia are alleviated by de-eutrophication.

DOI： 10.3389/fmars.2021.642041

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Publisher：Copernicus GmbH  

Abstract. To better understand the nutrient assimilation characteristics of subtropical phytoplankton, deep water addition incubation experiments were carried out on surface waters collected at seven stations across the subtropical North and South Pacific Ocean. These deep water additions induced phytoplankton blooms with nutrient drawdown at all stations. The drawdown ratios of dissolved inorganic nitrogen (DIN) to phosphate (PO4) varied from 14.1 to 29.6 at the PO4-replete stations in the central North Pacific (CNP) and eastern South Pacific (ESP). These ratios were similar to the range represented by the canonical Redfield ratio (16) through to typical particulate N:P ratios in the surface subtropical ocean (28). In contrast, lower DIN:PO4 drawdown ratios (8.0–12.9) were observed in induced blooms at the PO4-depleted stations in the western North Pacific (WNP). The DIN:PO4 drawdown ratios in the PO4-replete ESP were associated with eukaryote-dominated blooms, while those in PO4-depleted WNP were associated with eukaryotic and cyanobacterial blooms. The surplus PO4 assimilation, relative to DIN, by phytoplankton in the WNP was not expected based on their typical cellular N:P ratio, and was likely due to the high PO4 uptake capability as induced by low PO4-adapted phytoplankton. The low and high P* (=PO4-DIN/16) regimes geographically corresponded to the low and high DIN:PO4 drawdown ratios in the WNP and the CNP or ESP, respectively. The basin-wide P* distribution in the oligotrophic Pacific surface waters showed a clear regional trend from low in the WNP (<50 nM) to high in the ESP (>100 nM). These results suggest that the subtropical phytoplankton blooms as observed in our experiments could be an important factor controlling P* as well as the commonly recognized dinitrogen fixation and denitrification characteristics.

DOI： 10.5194/bg-18-897-2021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature Research  

The carbon budget of Tokyo Bay, a highly urbanized coastal basin, was estimated using a box model that incorporated inorganic and organic carbon data over an annual cycle (2011–2012). The surface water represented net autotrophic system in which the annual net community production (NCP) was 19 × 1010 gC year−1. The annual loading of dissolved inorganic carbon and total organic carbon (TOC) from freshwater inputs was 11.2 × 1010 and 4.9 × 1010 gC year−1, respectively. The annual TOC sedimentation rate was 3.1 × 1010 gC year−1, similar to the annual air–sea CO2 uptake (5.0 × 1010 gC year−1). Although the NCP and TOC loading from freshwater inputs were respectively 3.0 and 2.7 times lower than those in the 1970s, the TOC sedimentation rate was similar. Therefore, a relatively high carbon efflux from Tokyo Bay likely occurred in the 1970s, including CO2 efflux to the atmosphere and/or export of labile organic carbon to the open ocean. The changes in carbon flow between the 1970s and 2011–2012 resulted from improved water quality due to increased sewage treatment facilities and improved sewage treatment efficiency in the catchment, which decreased the amount of labile organic carbon flowing into the bay.

DOI： 10.1038/s41598-020-77385-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.talo.2020.100016

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Sedimentary cesium-137 concentrations around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were measured from 2011 to 2017 at eight stations. Although high values were observed until 2013, decreasing trends were observed at the surface sediments of seven stations. We isolated 25 radioactive Cs-bearing microparticles (CsMPs; 1.0-5385 Bq per particle). The contribution ratio of CsMPs to each sample ranged from 4.1% to 99.5% (median 58.8%), with the contribution ratio of the CsMPs in the southern part of the FDNPP was low compared to that from the northern part. In the southern part of the FDNPP, small CsMPs that could not be isolated in this study were present in large quantities immediately after the accident, and gradually diffused away and/or were dissolved over time. In contrast, the CsMPs in the northern part of the FDNPP have most likely accumulated over time, as suggested by the silty nature of the sediments there.

DOI： 10.1016/j.marpolbul.2020.111769

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

We investigated basin-wide distributions of total particulate phosphorus (TPP) and associated biogeochemical parameters in the euphotic zone (EZ) of the subtropical North and South Pacific Ocean. TPP is primarily composed of living microorganisms, and its distribution is likely controlled by nitrogen (N) supply in typical N-limited Pacific waters as well as phosphorus (P) supply in P-limited western North Pacific. TPP concentrations showed a vertically uniform distribution (approximately 15 nM) within the EZ at most stations, but at several northern North Pacific stations, TPP peaks (>20 nM) were observed in the lower EZ where nitrate and nitrite concentrations were high. Relationships between TPP and biogeochemical parameters indicate that a possible factor controlling TPP in the upper EZ was dinitrogen fixation and that in the lower EZ was shoaling of the nitracline. Geographical distribution of TPP was relatively uniform compared to that of phosphate, which varied from 100 nM in the eastern North and South Pacific. The western North Pacific was a domain characterized by lower dissolved organic P (DOP) concentrations, higher alkaline phosphatase activities, and higher particulate polyphosphate (PpolyP):TPP ratios compared to other domains. These characteristics indicated that active DOP utilization and PpolyP accumulation could play important roles in the maintenance of TPP stocks as alternatives to phosphate utilization in this distinctive domain. Our results demonstrated that TPP distributions were vertically and geographically uniform across the subtropical Pacific Ocean, concealing that TPP stocks were likely underpinned by a range of nutrient supply mechanisms.

DOI： 10.1029/2020GB006669

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The Southern Ocean is a vast net sink for atmospheric carbon dioxide (CO2), with marine phytoplankton playing a crucial role in CO2 fixation. We assessed how changes in the dominant phytoplankton community and net primary productivity (NPP) affected variations in the partial pressure of CO2 in surface water (pCO(2)(sw)) in the Indian sector of the Southern Ocean during austral summer. pCO2sw was negatively correlated with total phytoplankton and diatom abundances, as estimated from pigment signatures, in the zone south of the Antarctic Circumpolar Current; however, pCO(2)(sw) was not correlated with haptophyte abundance. Additionally, a stronger correlation was found between pCO(2)(sw) and total phytoplankton NPP than between chlorophyll a concentration and pCO(2)(sw). We reconstructed pCO(2)(sw) at inter-annual scale using satellite data and assessed the inter-annual variability of air-sea CO2 flux. Over the period from 1997 to 2007, the integrated CO2 fluxes over the study region showed very large variations from a small source to a strong sink. Variations in the integrated CO2 fluxes were also correlated with changes in satellite-derived phytoplankton community in the Indian sector of the Southern Ocean and changes in the dominant phytoplankton community may control CO2 dynamics in the marginal ice zone.

DOI： 10.1016/j.dsr.2020.103263

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DOI： 10.1016/j.jenvrad.2020.106172

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DOI： 10.1016/j.talanta.2019.120371

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Cesium-137 concentrations in sediment (137Cs) at Tokyo Bay were measured at 26 stations during 2017. Average 137Cs concentrations at the Arakawa river mouth (117 ± 46 Bq kg-1) were approximately six times higher than those of the other stations in the bay (20 ± 16 Bq kg-1). There were radiocesium-bearing microparticles in the bay sediment as well as in suspended matter of Fukushima coastal waters. Radioactivity of radiocesium-bearing microparticles was estimated to be 0.12 Bq. However, the contributions of radiocesium-bearing microparticles to each 137Cs concentration of the bulk sample were low; 3% was the maximum. The 137Cs inventory in sediment at the entire bay was 0.67 TBq, showing that a large amount of 137Cs was supplied to the bay from the river following the Fukushima Daiichi Nuclear Power Plant accident. Approximately 9.2% of the 137Cs which was fallout in the drainage basin has already flowed into the bay from the watershed, which is approximately 3.2 times higher than that of a previous estimate.

DOI： 10.1016/j.chemosphere.2019.06.215

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Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The March 2011 earthquake and tsunami resulted in significant damage to the Fukushima Daiichi Nuclear Power Plant (FDNPP) and the subsequent release of radionuclides into the ocean. Here, we investigated the spatial distribution of strontium-90 (90Sr) and cesium-134/cesium-137 (134, 137Cs) in surface seawater of the coastal region near the FDNPP. In the coastal region, 90Sr activity was high, from 0.89 to 29.13 mBq L−1, with detectable FDNPP site-derived 134Cs. This indicated that release of 90Sr from the power plant was ongoing even in May 2013, as was that of 134Cs and 137Cs. 90Sr activities measured at open ocean sites corresponded to background derived from atmospheric nuclear weapons testing fallout. The FDNPP site-derived 90Sr/137Cs activity ratios in seawater were much higher than those in the direct discharge event in March 2011, in river input, and in seabed sediment; those ratios showed large variability, ranging from 0.16 to 0.64 despite a short sampling period. This FDNPP site-derived 90Sr/137Cs activity ratio suggests that these radionuclides were mainly derived from stagnant water in the reactor and turbine buildings of the FDNPP, while a different source with a low 90Sr/137Cs ratio could contribute to and produce the temporal variability of the 90Sr/137Cs ratio in coastal water. We estimated the release rate of 90Sr from the power plant as 9.6 ± 6.1 GBq day−1 in May 2013 on the basis of the relationship between 90Sr and 137Cs activity (90Sr/137Cs = 0.66 ± 0.05) and 137Cs release rate.

DOI： 10.3390/ijerph16214094

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Biologically toxic arsenate is physicochemically similar to biologically essential phosphate. Because arsenate and phosphate are indiscriminately incorporated by microbes, their ambient concentration ratios can be an important factor controlling microbial growth and metabolism. This study investigated the spatial distributions of arsenate and phosphate and the associated biogeochemical dynamics in the subtropical North and South Pacific Ocean. Vertical arsenate and phosphate profiles (<= 150 m) in most of the study areas showed a nutrient-type distribution where the concentrations increased below the euphotic zone. The arsenate and phosphate concentrations in the surface waters ranged from the detection limits (5 nM and 4 nM, respectively) to approximately 40 nM and 400 nM, respectively. The surface arsenate:phosphate ratios were typically lower than 1, but those in the western subtropical North Pacific (WSNP) were frequently higher than 1 due to phosphate depletion. In the WSNP surface waters, Prochlorococcus and Pelagibacter arsenic detoxification and phosphorus acquisition genes were abundant. Results of the onboard bioassays involving the addition of arsenate or phosphate to the surface water indicated that microbes throughout the study areas possessed arsenate resistance and those in the WSNP during summer were under serious phosphate limitation. Although phosphate limitation likely accelerates the relative cellular accumulation of toxic arsenate, the lowest particulate As:P ratios were observed in the summer WSNP, concurrent with the lowest dissolved organic P (DOP) concentrations and the highest alkaline phosphatase activities. These results imply that active As excretion and/or DOP utilization could alleviate As accumulation while maintaining the cellular P quota.

DOI： 10.1016/j.pocean.2019.05.007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

Surface ocean phosphate is commonly below the standard analytical detection limits, leading to an incomplete picture of the global variation and biogeochemical role of phosphate. A global compilation of phosphate measured using high-sensitivity methods revealed several previously unrecognized low-phosphate areas and clear regional differences. Both observational climatologies and Earth system models (ESMs) systematically overestimated surface phosphate. Furthermore, ESMs misrepresented the relationships between phosphate, phytoplankton biomass, and primary productivity. Atmospheric iron input and nitrogen fixation are known important controls on surface phosphate, but model simulations showed that differences in the iron-to-macronutrient ratio in the vertical nutrient supply and surface lateral transport are additional drivers of phosphate concentrations. Our study demonstrates the importance of accurately quantifying nutrients for understanding the regulation of ocean ecosystems and biogeochemistry now and under future climate conditions.

DOI： 10.1126/sciadv.aax0341

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DOI： 10.1016/j.jenvrad.2019.03.012

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Fatty acids in triacylglycerol (TAG) are catabolized after digestion. However, the catabolic rates of several fatty acids bound to the α (sn-1, 3) or β (sn-2) position of TAG have not been thoroughly compared. In this study, the catabolic rates of 13C-labeled palmitic acid, oleic acid, linoleic acid, α-linolenic acid, eicosapentaenoic acid (EPA), or docosahexaenoic acid (DHA) bound to the α and β position of TAG were compared using isotope ratio mass spectrometry. The catabolic rates of the studied fatty acids were evaluated using the ratio of 13C and 12C in carbon dioxide expired from mice. The results indicated that palmitic acid, oleic acid, or α-linolenic acid bound to the β position was slowly catabolized for a long duration compared to that when bound to the α position. In contrast, EPA bound to the β position was quickly catabolized, and EPA bound to the α position was slowly catabolized for a long time. For linoleic acid or DHA, no difference in the catabolic rates was detected between the binding positions in TAG. Furthermore, EPA and DHA were less catabolized than the other fatty acids. These results indicate that the catabolic rates of fatty acids are influenced by their binding positions in TAG and that this influence on the catabolic rate differed depending on the fatty acid species.

DOI： 10.5650/jos.ess19012

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DOI： 10.1002/lno.10796

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© 2019 by Japan Oil Chemists’ Society. The absorption efficacies and catabolic rates of fatty acids are affected by their binding position on triacylglycerol (TAG). However, the kind of effect calcium treatment has on the catabolism of fatty acids is unclear. In this study, the catabolic rates of 13C-labeled palmitic acid, oleic acid, and linoleic acid bound to sn-1, 3 (α) and sn-2 (β) position of TAG in the presence of calcium were compared using isotope ratio mass spectrometry. The catabolic rates of 13C-labeled fatty acids were evaluated using the ratio of 13C to 12C in the carbon dioxide expired by mice. The catabolic rate of palmitic acid bound to the α position was significantly lower than that of palmitic acid bound to the β position of TAG. The rates of 13CO2 formation from palmitic acid at the β position remained higher for a long time. In contrast, oleic and linoleic acids at the α position were as well catabolized as those at the β position. These results indicate that in the presence of calcium, the saturated fatty acid bound to the β position is highly catabolized, whereas that bound to the α position is not well catabolized. Saturated fatty acid at the α position is hydrolyzed by pancreatic lipase to promptly form insoluble complexes with calcium, which are excreted from the body, and thereby reducing the catabolic rate of these fatty acids.

DOI： 10.5650/jos.ess19197

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Publishing type：Research paper (scientific journal)   Publisher：Copernicus {GmbH}  

DOI： 10.5194/acp-18-9207-2018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

Radioactive cesium concentrations in the suspended matter of the coastal waters around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were investigated between January 2014 and August 2015. The concentrations of radioactive cesium in the suspended matter were two orders higher in magnitude than those determined in the sediment. In addition, we discovered highly radioactive Cs particles in the suspended matter using autoradiography. The geometrical average radioactivity of particles was estimated to be 0.6 Bq at maximum and 0.2 Bq on average. The contribution ratio of highly radioactive Cs particles to each sample ranged from 13 to 54%, and was 36% on average. A major part of the radioactive Cs concentration in the suspended matter around the FDNPP was strongly influenced by the highly radioactive particles. The subsequent resuspension of highly radioactive Cs particles has been suggested as a possible reason for the delay in radioactive Cs depuration from benthic biota.

DOI： 10.1016/j.marpolbul.2018.04.042

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DOI： 10.2331/suisan.WA2573-5

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Copyright © 2018 by The Geochemical Society of Japan. To elucidate the activity concentration and behavior of radiocaesium, we observed the spatial and vertical distributions of radiocaesium in sediment collected at 12 monitoring stations off the coast of Fukushima Prefecture in 2013–2015. In bulk surface-layer sediment (core depth: 0–3 cm), high 134Cs activity concentrations were observed at stations around the water depth of 100 m, where the sediment was rich in silt to clay particles and organic matter. The activity concentrations generally decreased with increasing core depth and the extent of the decrease was different between the stations. The difference trend for temporal change of 134Cs activity concentrations between the two zones of off Onahama and within 30 km of the FDNPS was partly attributed to the mobility of sediment particles reflecting water content, porosity and permeability. At some stations, shaped peaks for activity concentrations were temporarily observed in upper-layer sediment (core depth: 0–1 cm) or sediment below that. The 134Cs activity concentrations in the surface-layer sediment were not always accompanied by an increase in the contribution from fine (i.e., silt to clay) particle-bound 134Cs in the sediment. In October 2014, sediment collected at a station about 1.5 km from FDNPS was found to have broad 134Cs peaks in the middle-layer sediment (core depth: 5–16 cm). In this middle-layer sediment, both sand and silt to clay fractions contributed to the increased 134Cs activity concentrations. On the other hand, such broad peaks were not found in October 2015. These results suggest that the activity concentrations in sediment had changed significantly by a complicated process of sediment mixing, erosion or re-sedimentation that affected the broad peak for the activity concentration in the middle-layer sediment.

DOI： 10.2343/geochemj.2.0504

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Sensitive methods for the determination of arsenate and particulate arsenic (PAs), as well as phosphate and particulate phosphorus (PP), in seawater are described. The method for arsenate and phosphate was established by applying automated liquid waveguide spectrophotometry. Because the reaction time for the formation of the arsenate-molybdate complex is longer than that for the phosphate-molybdate complex, a long Teflon tube submerged in a heating bath was installed in the conventional phosphate flow system. The arsenate was quantified as the difference between absorbances of molybdenum blue dyes with (only phosphate) and without (phosphate + arsenate) arsenate reduction treatment. Contamination was observed in the reagent for arsenate reduction and must be corrected. Linear dynamic ranges up to 1000 nM were confirmed for arsenate and phosphate. The detection limits for arsenate and phosphate were 5 and 4 nM, respectively. Freezing was a reliable sample preservation technique for both arsenate and phosphate. The method for PAs and PP was established by combining conventional persulfate oxidation of PP and the automated liquid waveguide spectrophotometry of arsenate and phosphate. The digestion efficiencies of organic As analogs were &gt;93%. Contamination in the glass fiber filter was negligible. Field tests confirmed that the coefficients of variation (CVs) of 10-19 nM arsenate and 4-151 nM phosphate were 7-20 and 1-25%, respectively, while the CVs of 0.9 nM PAs and 10.2 nM PP were 11 and 4%, respectively.

DOI： 10.1007/s10872-017-0412-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN OIL CHEMISTS SOC  

Starfish oil (SO) is characterized by functional lipids, including n-3 polyunsaturated fatty acid (both in the form of triacylglycerol and in the form of phospholipid), and carotenoids, which may exert beneficial effects on metabolic disorders in obesity-associated diseases. In the present study, the effect of SO on dysregulation of lipid metabolism was examined using C57BL/6N mice treated with high-fat (HF) diet. Mice were fed HF, HF with 2% SO, or HF with 5% SO diet for 8 weeks. Weight gain, blood glucose, serum and hepatic lipid contents, and hepatic fatty acid composition were measured. Fatty acid (3-oxidation activity was monitored by measuring the catabolic rate of C-13-labeled fatty acid, assessed as (CO2)-C-13/(CO2)-C-12 ratio using isotope ratio mass spectrometry (IR-MS). Although there were no differences in body weight or white adipose tissue weight among the test groups, dietary SO reduced blood glucose, and dose-dependently improved hyperlipidemia and decreased hepatic lipid accumulation. Analysis of hepatic fatty acid composition revealed a significant decrease in the ratio of monounsaturated fatty acid to saturated fatty acid, which is attributed to stearoyl-CoA desaturase activity. IR-MS analysis suggested that (3-oxidation activity was enhanced in the mice treated with 5% SO. These results demonstrate that dietary SO improves lipid metabolism measures in HF diet-induced obese mice, suggesting that SO holds promise as an agent for the prevention and treatment of lipid metabolism disorders in the liver.

DOI： 10.5650/jos.ess17038

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Most estuaries and inland waters are significant source for atmospheric CO2 because of input of terrestrial inorganic carbon and mineralization of terrestrially supplied organic carbon. In contrast to most coastal waters, some estuaries with small freshwater discharge are weak source or sometimes sink for CO2. Extensive surveys of pCO(2) in Tokyo Bay showed that the overall bay acts as a strong net sink for atmospheric CO2. Although small area was a consistent source for CO2, active photosynthesis driven by nutrient loading from the land overwhelmed the CO2 budget in the bay. Here we show a comprehensive scheme with a border where air-sea CO2 flux was +/- 0 between nearshore waters emitting CO2 and offshore waters absorbing CO2. The border in Tokyo Bay was extremely shifted toward the land-side. The shift is characteristic of highly urbanized coastal waters with an extensive sewage treatment system in the catchment area. Because highly urbanized coastal areas worldwide are expected to quadruple by 2050, coastal waters such as Tokyo Bay are expected to increase as well. Through extrapolation of Tokyo Bay data, CO2 emission from global estuaries would be expected to decrease roughly from the current 0.074 PgC year(-1) to 0.014 PgC year(-1) in 2050.

DOI： 10.1038/srep44355

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

During 2013-2015, the dissolved Cs-137 activity concentrations in seawater off the coast of Fukushima were one or two orders as high as those before the Fukushima accident. The activity concentrations in the surface-layer seawater at NPE2, NP0, NP2, NPE1, AN7, I01, E and A stations, which are located within about 10 km from the coast, relatively higher than those outside the 10 km zone. These relatively high concentrations (&gt; 10 mBq L-1) seem to be affected by several factors, including increased river input or contaminated water input from the Fukushima Dai-ichi Nuclear Power Station due to heavy rain events.

DOI： 10.1007/s10967-016-5009-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Radiocesium (Cs-134 and Cs-137) released from the Fukushima Dai-ichi Nuclear Power Plant (1FNPP) accident contaminated the fish inhabiting the port of 1FNPP. Radiocesium concentrations in some fishes, especially rockfish, have still remained at elevated levels, while concentrations in olive flounder have decreased in 2015 to the level which is close to the Japanese regulatory limit for seafood products (0.1 kBq kg-wet(-1)). In this study a dynamic food chain transfer model was applied to reconstruct radiocesium levels in olive flounder residing around the port area. As a result, the observed Cs-137 concentrations in olive flounder collected from the port could be explained by the simulated values in the fish, using the seawater level records at the port entrance. The reconstructed maximum Cs134+137 concentration in olive flounder inhabiting the port area was 72 kB kg-wet(-1) in July 2011 and the ecological halflife (EHL) was estimated as being 180 days during the period of 2014-2015. Short term simulation which assumed that the coastal water fish swam into the port during 1 month, demonstrated that the radio cesium level in the olive flounder may become equivalent to the depurated level in the fish which were initially contaminated. This result indicated that the increase of radiocesium levels in wandering fish is unlikely to change total radiocesium concentrations in the olive flounder. In this sense, the radiocesium levels in the olive flounder of the port area can be interpreted as being convergent in 2015, regardless of the differences in their contamination histories. On the other hand, the higher Cs-137 concentrations in fat greenling, compared to the olive flounder, can be attributed to a history of exposure to the contaminated seawater and food at the inner area of the port, such as the shallow draft quay and seawall area. As a result of the reconstructed initial higher radiocesium concentration, constrained by exposure history at the inner area of the port, the depurated radiocesium concentration in fat greenling is still likely to be greater than the regulatory level in the port area in 2015. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jenvrad.2016.02.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN OIL CHEMISTS SOC  

Fatty acids in triacylglycerols (TAGs) are catabolized after digestion. However, the catabolic rates of the fatty acids at the sn-1, sn-2, and sn-3 positions of TAGs have not been compared. To elucidate the differences, we studied the catabolic rates of C-13-labeled palmitic acid, oleic acid, and capric acid at the sn-1, sn-2, or sn-3 position of TAGs using isotope-ratio mass spectrometry. Specifically, we measured the C-13-to-C-12 ratio in CO, (Delta C-13 (parts per thousand)) exhaled by mice. For all analyzed fatty acids, we observed significant differences between sn-2 and other binding positions. In contrast, no significant difference was detected between the sn-1 and sn-3 positions. These results indicated that the catabolic rates of fatty acids are strongly influenced by their positions in TAGs.

DOI： 10.5650/jos.ess16124

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Total organic carbon (TOC), total nitrogen (TN) contents, their stable C and N isotope ratio (delta C-13 and delta N-15), and chlorophyll a ([ChI a](sed)) of surface sediments were investigated monthly to identify the seasonal variations and sources of organic matter in Tokyo Bay. The sedimentary TOC (TOCsed) and TN (TNsed) contents, and the sedimentary delta(3C) and delta N-15 (delta(13)Csed and delta N-15(sed)) values were higher in summer than other seasons. The seasonal variations were controlled by high primary production in the water column and hypoxic water in the bottom water during summer. The fraction of terrestrial and marine derived organic matter was estimated by Bayesian mixing model using stable isotope data and TOC/TN ratio. Surface sediments in Tokyo Bay are dominated by marine derived organic matter, which accounts for about 69 +/- 5% of TOCsed. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpolbul.2016.10.030

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DOI： 10.5650/jos.ess16124

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

At four stations in Tokyo Bay, pore water profiles of dissolved organic carbon (DOC), nitrogen (DON), phosphorus (DOP), and inorganic nutrients were determined at 3-month intervals over 6 years. Concentrations of dissolved organic matter (DOM) and nutrients were significantly higher in pore waters than in the overlying waters. Pore water DOC, DON, and DOP concentrations in the upper most sediment layer (0-1 cm) ranged from 246 to 888 mu M, from 14.6 to 75.9 mu M, and from 0.02 to 9.83 mu M, respectively. Concentrations of DOM and nutrients in pore waters occasionally showed clear seasonal trends and were highest in the summer and lowest in the winter. The seasonal trends in the pore water DOM concentrations were coupled with trends in the overlying water temperature and dissolved oxygen concentration. Benthic effluxes of DON and DOP were low compared with those of inorganic nutrients, accounting for only 1.0 and 1.5 % of the total benthic effluxes of nitrogen and phosphorus, respectively; thus benthic DOM fluxes were quantitatively insignificant to the inorganic nutrient fluxes in Tokyo Bay. The DOM fluxes represented about 7, 3, and 10 % of the riverine discharge of DOC, DON, and DOP to Tokyo Bay, respectively.

DOI： 10.1007/s10872-016-0382-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Determining the total particulate phosphorus (TPP) and particulate inorganic phosphorus (PIP) in oligotrophic oceanic water generally requires the filtration of a large amount of water sample. This paper describes methods that require small filtration volumes for determining the TPP and PIP concentrations. The methods were devised by validating or improving conventional sample processing and by applying highly sensitive liquid waveguide spectrophotometry to the measurements of oxidized or acid-extracted phosphate from TPP and PIP, respectively. The oxidation of TPP was performed by a chemical wet oxidation method using 3% potassium persulfate. The acid extraction of PIP was initially carried out based on the conventional extraction methodology, which requires 1 M HCl, followed by the procedure for decreasing acidity. While the conventional procedure for acid removal requires a ten-fold dilution of the 1 M HCl extract with purified water, the improved procedure proposed in this study uses 8 M NaOH solution for neutralizing 1 M HCl extract in order to reduce the dilution effect. An experiment for comparing the absorbances of the phosphate standard dissolved in 0.1 M HCl and of that dissolved in a neutralized solution [1 M HCl: 8 M NaOH=8:1 (v:v)] exhibited a higher absorbance in the neutralized solution. This indicated that the improved procedure completely removed the acid effect, which reduces the sensitivity of the phosphate measurement. Application to an ultraoligotrophic water sample showed that the TPP concentration in a 1075 mL-filtered sample was 8.4 nM with a coefficient of variation (CV) of 4.3% and the PIP concentration in a 2300 mL-filtered sample was 13 nM with a CV of 6.1%. Based on the detection limit (3 nM) of the sensitive phosphate measurement and the ambient TPP and PIP concentrations of the ultraoligotrophic water, the minimum filtration volumes required for the detection of TPP and PIP were estimated to be 15 and 52 mL, respectively. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.talanta.2016.02.058

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Estuarine and shallow coastal systems (ESCS) are recognized as not only significant organic carbon reservoirs but also emitters of CO2 to the atmosphere through air-sea CO2 gas exchange, thus posing a dilemma on ESCS's role in climate change mitigation measures. However, some studies have shown that coastal waters take up atmospheric CO2 (C-atm), although the magnitude and determinants remain unclear. We argue that the phenomenon of net uptake of C-atm by ESCS is not unusual under a given set of terrestrial inputs and geophysical conditions. We assessed the key properties of systems that show the net C-atm uptake and found that they are often characteristic of human-dominated systems: (1) input of high terrestrial nutrients, (2) input of treated wastewater in which labile carbon is highly removed, and (3) presence of hypoxia. We propose that human-dominated ESCS are worthy of investigation as a contributor to climate change mitigation.

DOI： 10.1007/s13280-015-0725-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Radiocesium (Cs-134 and Cs-137) released into the Fukushima coastal environment was transferred to marine biota inhabiting the Pacific Ocean coastal waters of eastern Japan. Though the levels in most of the edible marine species decreased overtime, radiocesium concentrations in some fishes were still remained higher than the Japanese regulatory limit for seafood products. In this study, a dynamic food chain transfer model was applied to reconstruct Cs-137 levels in olive flounder by adopting the radiocesium concentrations in small demersal fish which constitute an important fraction of the diet of the olive flounder particularly inhabiting area near Fukushima. In addition, Cs-137 levels in slime flounder were also simulated using reported radiocesium concentrations in some prey organisms. The simulated results from Onahama on the southern border of the Fukushima coastline, and at Choshi the southernmost point where the contaminated water mass was transported by the Oyashio current, were assessed in order to identify what can be explained from present information, and what remains to be clarified three years after the Fukushima Dai-ichi nuclear power plant (1FNPP) accident. As a result, the observed Cs-137 concentrations in planktivorous fish and their predator fish could be explained by the theoretically-derived simulated levels. On the other hand, the slow Cs-137 depuration in slime flounder can be attributed to uptake from unknown sources for which the uptake fluxes were of a similar magnitude as the excretion fluxes. Since the reported Cs-137 concentrations in benthic invertebrates off Onahama were higher than the simulated values, radiocesium transfer from these benthic detritivorous invertebrates to slime flounder via ingestion was suggested as a cause for the observed slow depuration of Cs-137 in demersal fish off southern Fukushima. Furthermore, the slower depuration in the demersal fish likely required an additional source of Cs-137, i.e. contaminated detritus or sediment which was entrained with the prey during the active sediment feeding of this fish species. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jenvrad.2015.05.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN OIL CHEMISTS SOC  

Trans fatty acids (TFA) are considered risk factors for cardiovascular disease (CVD), while the details of distribution and metabolism of the individual isomers are not clear. Here we investigated the accumulation and catabolic rate of TFA positional isomers of octadecenoic acid (18:1) in mice. ICR mice were fed deuterium- and [1-C-13] stable isotope-labeled trans-9-18:1 (9t-18:1(star)), trans-10-18:1 (10t-18:1(star)), or trans-11-18:1 (11t-18:1(star)) for 2 or 4 weeks, or a TFA mixture (9t-18:1(star), 10t-18:1(star), and 11t-18:1(star)) for 3 weeks. Analysis of whole-body tissues by gas chromatography-chemical ionization mass spectrometry revealed the highest 9t-18:1(star) levels in the heart. Significant differences in the accumulation of the respective trans-18:1 were observed in the heart and erythrocytes, where 9t- &gt; 11t- &gt; 10t-18:1(star), but no significant difference was observed in the liver or white adipose tissue (WAT). Mice fed on 11t-18:1 demonstrated accumulation of endogenously synthesized conjugated linoleic acid in the liver, WAT, and heart, but any other metabolites were not found in other groups. Furthermore, we analyzed catabolic rates of single-dose-administered trans-18:1(star) isomers into [C-13]-labeled CO2 using isotope-ratio mass spectrometry, and the 10t-18:1*catabolic rate was significantly higher than those of 9t- and 11t-18:1(star). We found that the accumulation and catabolism of trans-18:1 positional isomers varied in these mice. Differential accumulation in tissues suggests that individual TFA positional isomers may play different roles in human health.

DOI： 10.5650/jos.ess15139

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We describe a highly sensitive colorimetric method for the determination of nanomolar concentrations of ammonium in seawater based on the indophenol reaction with o-phenylphenol [(1,1'-biphenyl)-2-ol, abbreviated as OPP]. OPP is available as non-toxic, stable flaky crystals with no caustic odor and has some advantages over phenol in practical use. The method was established by using a gas-segmented continuous flow analyzer equipped with two types of long path liquid waveguide capillary cell, LWCCs (100 cm and 200 cm) and an UltraPath (200 cm), which have inner diameters of 0.55 mm and 2 mm, respectively. The reagent concentrations, flow rates of the pumping tubes, and reaction path and temperature were determined on the basis of a manual indophenol blue method with OPP (Kanda, Water Res. 29 (1995) 2746-2750). The sample mixed with reagents that form indophenol blue dye was measured at 670 nm. Aged subtropical surface water was used as a blank, a matrix of standards, and the carrier. The detection limits of the analytical systems with a 100 cm LWCC, a 200 cm LWCC, and a 200 cm UltraPath were 6, 4, and 4 nM, respectively. These systems had high precision ( &lt; 4% at 100 nM) and a linear dynamic range up to 200 nM. Non-linear baseline drift did not occur when using the UltraPath system. This is due to the elimination of cell clogging because of the larger inner diameter of the UltraPath compared to the LWCCs. The UltraPath system is thus more suitable for long-term measurements compared with the LWCC systems. The results of the proposed sensitive colorimetry and a conventional colorimetry for the determination of seawater samples showed no significant difference. The proposed analytical systems were applied to underway surface monitoring and vertical observation in the oligotrophic South Pacific. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.talanta.2015.05.007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Radiocesium (Cs-134 and Cs-137) originating from the Fukushima Dai-ichi Nuclear Power Plant (1FNPP) has contaminated coastal waters and been subsequently transferred to the marine biota along the Pacific coastal region of eastern Japan. To clarify the mechanism of radiocesium biokinetics in olive flounder, a commercially valuable and piscivorous predator, the biokinetics of Cs-137 was simulated using a dynamic biological compartment model and then validated with the measured concentrations in available monitoring data. The Cs-137 concentrations in seawater of the Pacific coastal sites of eastern Japan, from Kesen-numa (170 km north from the 1FNPP) to Choshi (190 km south from the 1FNPP), were reconstructed by fitting the simulated levels to the observed concentrations. Simulated values were verified by measured radiocesium levels in sedentary organism such as macro-algae and mussels inhabiting each study site which had accumulated radiocesium in their ambient environment from the beginning of the accident. Using reconstructed Cs-137 concentrations in seawater, the Cs-137 levels in olive flounder and its main planktivorous prey fish, e.g. anchovy, sand lance, whitebait, etc., were simulated and compared with observed concentrations to clarify the biokinetics of radiocesium in these organisms. This assessment showed that the determining factor for the maximum radiocesium concentrations in fish in the plankton food chain is likely to be the initial radiocesium concentration which they were exposed to during the contamination stage. Furthermore, the simulated Cs-137 concentrations in gut contents of olive flounder were verified by measured Cs-137 concentrations in the stomach contents of this fish collected within 30 km from the 1FNPP. These results indicated that the decrease of Cs-137 levels in their prey organisms was the primary determining factor of radiocesium deputation, and the resultant ecological half-lives were 140-160 d in the olive flounder, by the simulation. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jenvrad.2015.05.025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

From April 2011 to January 2012, seasonal variation of the aragonite saturation state (Omega ar) was observed for the first time in Tokyo Bay, in order to understand the current state of ocean acidification in a highly eutrophicated bay in Japan. Omega ar in the bay ranged between 1.55 and 5.12, much greater than observed in offshore waters. At the surface, Omega ar was high during summer as a result of photosynthesis with some conflicting effect of freshwater input. At the bottom, Omega ar was low during summer due to remineralization of organic matter. Based on an assumption that our observations represent current conditions in Tokyo Bay, it is estimated that the emission of anthropogenic CO2 has already decreased Omega ar by 0.6 since the preindustrial period and will further decrease by 1.0-1.6 by the end of this century if emission of CO2 is continued at a high level [representative concentration pathway (RCP) 8.5 scenario]. With other conditions remaining the same, bottom waters of the bay will reach seasonal aragonite undersaturation by 2060-2070. However, because coastal regions have a large interannual variability, we need further observations to evaluate our estimations and future predictions presented here. Nevertheless, it should be safe to say that the larger seasonal variation in Omega causes the Tokyo Bay to reach aragonite undersaturation earlier than offshore regions and such conditions have negative consequences on the variety of calcifying organisms living in Tokyo Bay. Ocean acidification could thus give an additional stress to the ecosystem of the bay, which is now suffering from eutrophication and hypoxia.

DOI： 10.1007/s10872-015-0302-8

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DOI： 10.5194/bg-12-269-2015

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Publishing type：Research paper (scientific journal)  

© 2014 Elsevier Ltd. Radioactive cesium (134Cs and 137Cs) concentrations in invertebrates of benthic food web (10 taxonomic classes with 46 identified families) collected from wide areas off Fukushima Prefecture (3-500 m depth) were inspected from July 2011, four months after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, to August 2013 to elucidate time-series trends among taxa and areas. Cesium-137 was detected in seven classes (77% of 592 specimens). Higher 137Cs concentrations within detected data were often found in areas near or south of the FDNPP, which is consistent with the reported spatial distribution of 137Cs concentrations in highly contaminated seawater and sediments after the FDNPP accident. Overall 137Cs concentrations in invertebrates, the maxima of which (290 Bq kg-1-wet in the sea urchin Glyptocidaris crenularis) were lower than in many demersal fishes, had decreased exponentially with time, and exhibited taxon-specific decreasing trends. Concentrations in Bivalvia and Gastropoda decreased clearly with respective ecological half-lives of 188 d and 102 d. In contrast, decreasing trends in Malacostraca and Polychaeta were more gradual, with longer respective ecological half-lives of 208 d and 487 d. Echinoidea showed no consistent trend, presumably because of effects of contaminated sediments taken into their digestive tract. Comparison of 137Cs concentrations in the invertebrates and those in seawater and sediments suggest that contaminated sediments are the major source of continuing contamination in benthic invertebrates, especially in Malacostraca and Polychaeta.

DOI： 10.1016/j.jenvrad.2014.08.008

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

To reveal spatial dynamics of silicic acid [Si(OH)(4)1 in the poorly sampled oligotrophic western North Pacific, we investigated the surface distribution of Si(OH)(4) and associated biogeochemical parameters by using an underway survey system with a highly sensitive nutrient analyzer along the 138 degrees E transect (between 30 and 34 degrees N) and the 155 degrees E transect (between 10 and 35 degrees N) during the summers of 2007 and 2008. Surface Si(OH)(4) concentrations ranged from the detection limit (11 nmol L-1) to 2462 nmol L-1. High Si(OH)(4) concentrations ( &gt; 1000 nmol L-1) and dynamic fluctuations were generally observed north of 23 degrees N, while consistently stable low concentrations of 415-751 nmol L-1 were observed south of 23 degrees N. Surface nitrate+nitrite (N+N) and phosphate (PO43-) were typically depleted to &lt; 20 nmol L-1 except for PO43- in the area south of 16 degrees N. The majority of the study area was characterized by high-Si (OH)(4) and low-N+N and POI43-. However, submesoscale/mesoscale depressions of Si(OH)(4) were locally observed in the cyclonic eddy fields north of 23 degrees N. Among a total of six Si(OH)(4) depressions within the eddies, a complete Si(OH)(4) depletion ( &lt; 11 nmol L-1) was observed on the cyclonic side near the Kuroshio axis (33.1 degrees N, 138 degrees E). This depletion was closely coupled with a diatom bloom, suggesting that Si(OH)(4) was exhausted by diatoms. All of the Si(OH)(4) depressions were selective and not accompanied by local depressions of N+N and POI43-. This unique phenomenon might be driven by biogeochemical processes such as selective Si export (Si pump), anomalous Si uptake associated with diatom physiology, and/or Si uptake supported by N-2 fixation. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dsr.2014.05.004

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Atmospheric deposition of Pu isotopes from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has been observed in the terrestrial environment around the FDNPP site; however, their deposition in the marine environment has not been studied. The possible contamination of Pu in the marine environment has attracted great scientific and public concern. To fully understand this possible contamination of Pu isotopes from the FDNPP accident to the marine environment, we collected marine sediment core samples within the 30 km zone around the FDNPP site in the western North Pacific about two years after the accident. Pu isotopes (Pu-239, Pu-240, and Pu-241) and radiocesium isotopes (Cs-134 and Cs-137) in the samples were determined. The high activities of radiocesium and the Cs-134/Cs-137 activity ratios with values around 1 (decay corrected to 15 March 2011) suggested that these samples were contaminated by the FDNPP accident-released radionuclides. However, the activities of Pu239+240 and Pu-241 were low compared with the background level before the FDNPP accident. The Pu atom ratios (Pu-240/Pu-239 and Pu-241/Pu-239) suggested that global fallout and the pacific proving ground (PPG) close-in fallout are the main sources for Pu contamination in the marine sediments. As Pu isotopes are particle-reactive and they can be easily incorporated with the marine sediments, we concluded that the release of Pu isotopes from the FDNPP accident to the marine environment was negligible.

DOI： 10.1021/es502480y

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer Japan  

Monitoring and surveying of radioactivity in seawater and biota in the marine environment off the coast of Fukushima Prefecture in the Pacifi c Ocean are important for understanding the dispersion of artifi cial radionuclides after the TEPCO Fukushima Daiichi Nuclear Power Station (FD1NPS) accident. Marine biota were collected in the coastal area off Fukushima Prefecture after this accident to investigate the radioactivity of 134 Cs, 137 Cs, and 110m Ag in marine biota, including not only fi sh and shellfi sh but also benthos. It is well known that 108m Ag, one of the radioactive isotopes of Ag, was observed in some kinds of squid and octopus before this accident. As a result, 110m Ag was observed in many kinds of marine biota off the coastal area of Fukushima. It is suggested that rapid change in the radioactivity in seawater, resuspension of particles from sediments, and food chain effects led to high radionuclide activities in the marine biota after this accident.

DOI： 10.1007/978-4-431-54583-5_11

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Language：English   Publishing type：Research paper (conference, symposium, etc.)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

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, &lt; 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.

DOI： 10.1007/s10872-013-0178-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EMERALD GROUP PUBLISHING LIMITED  

Purpose - The purpose of this paper is to draw lessons for developing community-university partnerships from experiences in promoting coastal education for sustainable development (ESD).
Design/methodology/approach - Qualitative data collected from two coastal community outreach projects were analyzed.
Findings - The outreach projects improved the relationship between university and community members. It is important to conduct interviews at the early stages of the projects to understand the needs of the community and set project outcomes to meet community-defined priorities. The most effective means for promoting an ESD program based upon community-university partnerships is to reach out to and network with local individuals who have been active in community projects and embed the program concept into the activities of those individuals. Mediators who link the academic community with the local community are helpful in promoting the partnerships, and university students were found to be successful mediators.
Originality/value - On the basis of the experiences gained from starting an ESD program in the community, this research provides some clues to initiate service learning or community-based research based upon community-university partnerships.

DOI： 10.1108/14676371311312842

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Language：English   Publishing type：Research paper (scientific journal)  

The rate of cesium-137 (137Cs) release to the sea from the Fukushima Dai-ichi Nuclear Power Plant for the period until September 2012 was estimated. Publicly released data on 137Cs radioactivity in seawater near the power plant by Tokyo Electric Power Company strongly suggest a continuing release of radionuclides to the sea. The plant has an artificial harbour facility, and the exchange rate of harbour water with surrounding seawater was estimated by the decrease in radioactivity immediately after an intense radioactive water release. The estimated exchange rate of water in the harbour was 0.44 d-1 during the period from 6 to 19 April. The 137Cs radioactivity in the harbour water was substantially higher than that of seawater outside and remained relatively stable after June 2011. A quasi-steady state was assumed with continuous water exchange, and the average release rate of 137Cs was estimated to be 93 GBq d-1 in summer 2011 and 8.1 GBq d-1 in summer 2012. © 2013 Author(s).

DOI： 10.5194/bg-10-6107-2013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The catabolism rates of a medium chain fatty acid (octanoic acid), an even-numbered fatty acid (palmitic acid), and odd-numbered fatty acids (pentadecanoic acid and heptadecanoic acid) in mice were compared using stable isotope (13C) labeled fatty acids and isotope-ratio MS (IRMS). The catabolism rates of respective fatty acids were evaluated by the ratio of 13C and 12C in carbon dioxide expired from mice. The results show that the catabolism rate of octanoic acid is three times faster than that of palmitic acid. This result is in agreement with previous knowledge that medium chain fatty acids are easily beta-oxidized as compared to long chain fatty acids. The catabolism rates of odd-numbered fatty acids such as pentadecanoic acid and heptadecanoic acid were significantly lower as compared to those of even-numbered fatty acids such as palmitic acid. This finding supports our previous report that odd-numbered fatty acids are easily accumulated into body fat. The high accumulation of odd-numbered fatty acids in body fat would be a direct result of their low beta-oxidizability. Practical applications: 13C-labeled fatty acids were administered to mice and the rates of 13CO2 formation were compared among medium chain, even-numbered, and odd-numbered fatty acids using IRMS. We found that the catabolism rates of odd-numbered fatty acids such as pentadecanoic acid and heptadecanoic acid were significantly lower in comparison to those of even-numbered fatty acids such as palmitic acid. These findings could be valuable for the development of the lipid metabolism field.

DOI： 10.1002/ejlt.201200164

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Language：English   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

DOI： 10.1126/science.1219493

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Concentrations of bromodichloromethane (CHBrCl2), chlorodibromomethane (CHBr2Cl), bromoform (CHBr3) and isoprene were measured along with cell counts of phytoplankton in the surface waters of Sagami Bay, from April 2001 to December 2001, to evaluate their biological sources and their relative contributions to Br in the marine boundary layer. The mean (range) chlorophyll a (Chl. a) concentrations were 0.46 (0.23-1.0) mu g L-1 from April to December. Observations of temporal variations in cell volume showed that diatoms were predominant in the April, July, and December samples, and that dinoflagellates were dominant in the June and September samples. In the May, August, October and November samples, coccolithophorids were relatively more abundant when diatoms were absent. The mean concentrations of trace gases were 7.4 pmol L-1 CHBrCl2, 8.4 pmol L-1 CHBr2Cl, 33.8 pmol L-1 CHBr3, and 7.3 pmol L-1 isoprene. The mean sea-to-air fluxes of trace gases were 7.4 nmol m(-2) d(-1) CHBrCl2, 8.7 nmol m(-2) d(-1) CHBr2Cl, 32.2 nmol m(-2) d(-1) CHBr3, and 5.9 nmol m(-2) d(-1) isoprene. A significant positive correlation between CHBrCl2 and CHBr2Cl was observed in this study (r(2) = 0.79, n=48, p&lt;0.001). Bromoform, however, was not correlated with CHBrCl2 or CHBr2Cl. These results suggest that the production and fate of CHBrCl2 and CHBr2Cl in the surface seawater were similar, and that the production and fate of CHBr2Cl and CHBrCl2 were different from those of CHBr3. A significant positive correlation was observed between the isoprene and Chl. a concentrations (r(2)=0.49. n = 8, p = 0.05). No significant correlation was found between Chl. a and any of brominated methanes (i.e., CHBrCl2, CHBr2Cl, and CHBr3). No individual or group of phytoplankton could be attributed as the source of CHBr3 (or CHBrCl2,CHBr2Cl) in this study. The results thus highlighted the difficulty of estimating production of brominated methanes in seawater using Chl. a data or phytoplankton assemblage analysis and the necessity of determining the essential factors that control production of brominated methanes. The bromine fluxes of short-lived brominated methanes from the ocean to the atmosphere were estimated at 7.4 nmol Br m(-2) d(-1) for CHBrCl2, 17.4 nmol Br m(-2) d(-1) for CHBr2Cl, and 96.5 nmol Br m(-2) d(-1) for CHBr3. The relative contribution of CHBr3 to bromine in the marine boundary layer from surface ocean was calculated to be from 5.2 +/- 0.6 (November) to 27 +/- 5.5 (September) for Br-CHBr3/Br-CHBrCl2. Our results underscore the importance of CHBr3 as a source of atmospheric bromine from the ocean. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.marchem.2012.04.001

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2331/suisan.78.525

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Language：English   Publishing type：Research paper (scientific journal)  

In order to clarify the dynamics of oligotrophic ecosystems at the Subsurface Chlorophyll a Maximum (SCM), we investigated the distribution of phytoplankton and availability of nutrients in the euphotic layer along the Ogasawara transect (North-West Pacific Ocean). Depending on the distribution of underwater light and microphytoplankton communities a gradient between oceanic and coastal stations around Chichijima Island was identified. The vicinity of island is marked by lack of clear maximum peak of Chl. a and higher values of inorganic nutrients which pointed out a possible effect of island on this oligotrophic area. In contrast, significant SCMs reaching 5 times the Chl. a concentration at the surface were measured at the offshore stations. The SCM is located under the thermocline (60 to 68 m), the organisms mainly dominated by diatoms community were exposed to low light condition (4 to 1% of surface irradiance) and were associated with nutriclines (0.35 to 1.15 μ M of nitrogen and 0.03 to 0.07μ M of PO 4 3-). Changes in the nutrient potential limitation were detected at the SCM. In the epipelagic layer of offshore stations, Si:N:P stoichiometries values mainly oscillated between phosphorus and nitrogen potential limitation. However, nitrogen suddenly shifted to a phosphorus potential limiting factor at the SCM. If this result can be confirmed by complementary studies, it adds evidence that regeneration or predation mechanisms and availability of phosphorus mainly control the growth of phytoplankton in this oligotrophic area.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

Nutrient concentrations at the nanomolar level were monitored in the East China Sea and the Philippine Sea during summer using a continuous underway system with a highly sensitive colorimetric method. Concentrations of both nitrate and soluble reactive phosphorus (SRP) varied generally at &lt;10 nM. However, nitrate frequently showed local elevations of 20 to &gt;1000 nM at a horizontal scale of &lt;10 km to tens of kilometers compared with neighboring waters. These nitrate patches were grouped into three types according to the associated environmental conditions with (1) lowered salinity and no changes in SRP and in vivo chlorophyll fluorescence, (2) lowered temperature and elevations of SRP and in vivo chlorophyll fluorescence, and (3) no consistent environmental variations. The first type was ascribed to rainfall, which is rich in nitrate but phosphate free. The second type was formed near islands/landmasses and was ascribed to upwelling or intense vertical mixing. The third type was not characterized and was considered to include several sources. Nine out of 20 nitrate patches belonged to the first type. Within each of these nine patches, nitrate concentration was negatively correlated with salinity. By extrapolating this correlation, nitrate concentrations in the rainwater were estimated to be within 0.14-6.2 mu M, which is well within the reported concentrations of nitrate in rainwater. On the basis of the estimated nitrate concentrations and amount of precipitation, nitrogen supply from rainfall in the study area was evaluated to be in the same order as that of diffusive upward flux and N(2) fixation in summer.

DOI： 10.1029/2010JC006814

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Blackwell Publishing Ltd  

Nutrient concentrations at the nanomolar level were monitored in the East China Sea and the Philippine Sea during summer using a continuous underway system with a highly sensitive colorimetric method. Concentrations of both nitrate and soluble reactive phosphorus (SRP) varied generally at &lt
10 nM. However, nitrate frequently showed local elevations of 20 to &gt
1000 nM at a horizontal scale of &lt
10 km to tens of kilometers compared with neighboring waters. These nitrate patches were grouped into three types according to the associated environmental conditions with (1) lowered salinity and no changes in SRP and in vivo chlorophyll fluorescence, (2) lowered temperature and elevations of SRP and in vivo chlorophyll fluorescence, and (3) no consistent environmental variations. The first type was ascribed to rainfall, which is rich in nitrate but phosphate free. The second type was formed near islands/landmasses and was ascribed to upwelling or intense vertical mixing. The third type was not characterized and was considered to include several sources. Nine out of 20 nitrate patches belonged to the first type. Within each of these nine patches, nitrate concentration was negatively correlated with salinity. By extrapolating this correlation, nitrate concentrations in the rainwater were estimated to be within 0.14-6.2 M, which is well within the reported concentrations of nitrate in rainwater. On the basis of the estimated nitrate concentrations and amount of precipitation, nitrogen supply from rainfall in the study area was evaluated to be in the same order as that of diffusive upward flux and N2 fixation in summer. Copyright 2011 by the American Geophysical Union.

DOI： 10.1029/2010JC006814

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

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 (&lt; 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 (&lt; 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. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dsr.2009.12.005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

The distribution of N-2 fixation was examined using a N-15(2) tracer with accompanying measurements of abundance of Trichodesmium spp. and Richelia intracellularis, nitrate plus nitrite (N+N) and soluble reactive phosphorus at the nanomolar level, and primary production in the western and central Pacific Ocean. N-2 fixation occurred only in &gt;similar to 20 degrees C oligotrophic (i.e., N+N &lt; 100 nM) waters except at a station in the equatorial upwelling zone where N+N was 1880 nM. High N-2 fixation rates were observed in the Kuroshio and East China Sea (KECS) and near Fiji and other isolated islands with concomitant high abundance of Trichodesmium spp. In contrast, N-2 fixation in the western and central oligotrophic North Pacific (WCONP) was significantly lower, and Trichodesmium spp. were rarely observed. These observations hint that KECS and waters around isolated islands are N-2 fixation "hot spots" because of the occurrence of Trichodesmium spp. The average N2 fixation rate in the KECS of 232 +/- 54.8 (+/- SE, n=13) mu mol N m(-2) d(-1) was almost 1 order of magnitude higher than that in the WCONP of 39.2 +/- 7.51 +/- (n = 26) mu mol N m(-2) d(-1). On the basis of these estimates and reported values obtained using N-15(2), depth-integrated N-2 fixation in the North Pacific was estimated to be 2.6 +/- 0.3 x 109 (n = 63) mol N d(-1), which is less than half of previous estimates. This difference was ascribed primarily to the unavailability of N-2 fixation rates in the WCONP, which occupies a vast area of the subtropical North Pacific, and the use of data obtained in the hot spots which represent small areas that likely led to the previous overestimation.

DOI： 10.1029/2009GB003620

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

This paper reviews the initial phase of a coastal education for sustainable development program for Edomae, the innermost reaches of Tokyo Bay. The program has been steered by a working group of Tokyo University of Marine Science and Technology faculty members from different academic backgrounds. Although the process began with conventional educational ideas, the ESD practice framework evolved to include more interactive activities. The overall goal is to Pursue discussions of a plan for the sustainable use of Tokyo Bay in the coastal communities through a University-community partnership by developing Edomae ESD leaders in the coastal community. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.marpol.2009.02.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Seasonal variations in the picoplankton community were investigated from June 2002 to March 2004 within the photic zone of Sagami Bay, Japan. The study area was mostly dominated by coastal waters during the warm period (mixed layer water temperature a parts per thousand yen 18A degrees C). During the cold period (mixed layer water temperature a parts per thousand currency sign 18A degrees C), the water mass was characterized by low temperature and high saline waters indicative of the North Pacific Subtropical Mode Water (NPSTMW). Occasionally, a third type of water mass characterized by high temperature and low saline properties was observed, which could be evidence of the intrusion of warm Kuroshio waters. Synechococcus was the dominant picophytoplankton (5-28 x 10(11) cells m(-2)) followed by Prochlorococcus (1-5 x 10(11) cells m(-2)) and picoeukaryotes during the warm period. Heterotrophic bacteria dominated the picoplankton community throughout the year, especially in the warm period. During the Kuroshio Current advection, cyanobacterial abundance was high whereas that of picoeukaryotes and heterotrophic bacteria was low. During the cold period, homogeneously distributed, lower picophytoplankton cell densities were observed. The dominance of Synechococcus in the warm period reflects the importance of high temperature, low salinity and high Photosynthetically Active Radiation (PAR) on its distribution. Cyanobacterial and heterotrophic bacterial abundance showed a positive correlation with temperature. Prochlorococcus and picoeukaryotes showed a positive correlation with nutrients. Picoeukaryotes were the major contributors to the picophytoplankton carbon biomass. The annual picophytoplankton contribution to the photosynthetic biomass was 32 +/- 4%. These observations suggest that the environmental conditions, combined with the seasonal variability in the source of the water mass, determines the community structure of picoplankton, which contributes substantially to the phytoplankton biomass and can play a very important role in the food web dynamics of Sagami Bay.

DOI： 10.1007/s10872-009-0019-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC LIMNOLOGY OCEANOGRAPHY  

Latitudinal distribution of diazotrophs and their nitrogen (N(2)) fixation activity were investigated in the western North Pacific in winter (Nov to Dec 2004) and summer (May to Jun 2005) along meridional transects from 37 degrees N to the equator. N(2) fixation activity in whole seawater and seawater passed through a 10-mu m filter was assayed by acetylene reduction. The whole-water N(2) fixation was markedly elevated in winter throughout the study area compared to that in summer, probably due to the increased upward supply of phosphate as a result of deeper mixed layer in winter. During both periods a distinct latitudinal variation was observed in N(2) fixation of the whole-water samples at the surface; further, higher activity was observed between the Kuroshio Extension and the salinity front in the North Equatorial Current than in the neighboring areas. The elevated N(2) fixation was primarily ascribed to &lt; 10-mu m diazotrophs during both seasons. Flow cytometry conducted in summer revealed that distribution of nanoplanktonic cyanobacteria was closely correlated with that of N(2) fixation activity in the &lt; 10-mu m fraction, indicating that nanoplanktonic cyanobacteria were the major diazotrophs in that area. In contrast, microplanktonic diazotrophs, Trichodesmium spp. and Richelia intracellularis exhibited different latitudinal distributions from that of nanoplanktonic cyanobacteria, with maximum numerical abundance of R. intracellularis around 8 degrees N and 30 degrees N, and that of Trichodesmium spp. at 26.5 degrees N. Few microplanktonic diazotrophs occurred in the winter. The distribution of the diazotrophs and their N(2) fixation activity may be controlled by the supply of phosphate and aeolian dust deposition.

DOI： 10.4319/lo.2009.54.2.0537

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

In the subtropical oceans, nutrient concentrations are frequently below the detection limits of standard analytical methods. We applied a highly sensitive method to the surface water of the western and central Pacific between 42 degrees N and 40 degrees S and between 141 degrees E and 158 degrees W except in the equatorial zone, and detected overall depletion of nitrate + nitrite and an excess of SRP. However, a remarkable exception was found: an almost complete exhaustion of SRP (&lt; 10 nM) existed at a horizontal scale of &gt; 2000 km in the western subtropical North Pacific in both summer and winter. The SRP exhaustion was a consequence of an elevated dinitrogen fixation, which occurred in areas with high dust deposition from the Asian continent that likely enhanced SRP consumption. A coupling among nutrient dynamics, dinitrogen fixation and dust deposition produces the extremely low P availability spanning a large area, which appears to be unique to the western North Pacific. Citation: Hashihama, F., K. Furuya, S. Kitajima, S. Takeda, T. Takemura, and J. Kanda (2009), Macro-scale exhaustion of surface phosphate by dinitrogen fixation in the western North Pacific, Geophys. Res. Lett., 36, L03610, doi: 10.1029/2008GL036866.

DOI： 10.1029/2008GL036866

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Language：English   Publisher：National Institute of Polar Research  

We investigated the size fraction and pigment-derived class compositions of phytoplankton within the euphotic zone of the Antarctic marginal ice zone between 63.3°S and 66.5°S along the 140°E meridian on two consecutive cruises in the late austral summer and early austral autumn of 2003. We observed significant temporal and spatial variations in phytoplankton size and taxonomic composition, although chlorophyll a concentrations were generally below 1 μgl^<-1> during both periods. Microphytoplankton (>20 μm), mainly diatoms, were prominent in the euphotic zone in the southernmost area around 66.5°S during late summer. In the rest of the study area during both cruises, the phytoplankton community was dominated by pico- and nano-sized populations (<20 μm) throughout the euphotic zone. The small-size populations mostly consisted of diatoms and haptophytes, although chlorophytes were dominant in extremely cold water (-1.5°C) below the overlying warm water around 65.5°S during late summer. From late summer to early autumn, chlorophytes declined in abundance, probably due to increasing temperature within the euphotic zone (-1 to 0°C). These pico- and nano-phytoplankton-dominated populations were often accompanied by relatively high concentrations of ammonium, suggesting the active regeneration of nutrients within the small-size plankton community.

DOI： 10.1016/j.polar.2008.05.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Vertical profiles of nitrate uptake were obtained in pelagic waters of the western North Pacific. Uptake rates were determined by a conventional, particulate-based N-15 tracer method with in situ incubations for 24 h. Among the five profiles reported in this paper, three of them are obtained at one station in the subarctic Pacific (45 degrees N, 165 degrees E) on different occasions, and two of them are obtained at stations in the subtropical Pacific (25 degrees N, 165 degrees E and 25 degrees N, 170 degrees E). Nitrate uptake sharply decreased with depth at the subarctic station. At the subtropical stations where nitrate concentrations in surface waters were low, N-15-nitrate was added both at a trace level (ca. 4 nM-8 nM) and at a saturated level (ca. 8 mu M). Uptake of the trace N-15 varied less pronouncedly with depth, and the rates were slightly higher in the upper 70 m. Uptake of the saturated N-15 was substantially higher in the upper 50 in and decreased with depth. No uptake near the depths of nitracline or deep chlorophyll maximum was larger than those at other depths in the euphotic zone. The estimated depth-integrated uptake rates were 0.97-1.22 mmol N m-2 d(-1) at the subarctic station and 0.36-0.54 mmol N m(-2) d(-1) at the subtropical stations. (c) 2007 Elsevier B.V All rights reserved.

DOI： 10.1016/j.jmarsys.2007.05.005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Temporal variations in water mass properties and the composition of phytoplankton pigments in the central part of Sagami Bay were investigated by monthly observations from June 2002 to May 2004. Eleven pigments were quantified using high-performance liquid chromatography (HPLC) from 100%, 20%, and 5% light depths relative to the surface; the class-specific composition of phytoplankton community was then obtained by CHEMTAX analysis. The study area was influenced by the Kuroshio water for most of the observation period. The mean contribution of diatoms in all samples was relatively low (29%), while that of flagellates, mainly chlorophytes or cryptophytes, was quite high (60%). The phytoplankton composition at the three depths was uniform throughout the observation period, indicating that the vertical structure of the phytoplankton community did not develop significantly over time. A distinct temporal pattern was observed: flagellates dominated during the summer of 2002 and the winters of 2002-2003 and 2003-2004, while diatoms dominated during the summer of 2003. This pattern was associated with water mass changes. The community in the summer of 2003 was influenced by coastal water. While no distinct spring bloom of phytoplankton was observed, a weak increase in chlorophyll a was observed during the spring of 2004. Ocean color satellite data showed that fluctuations in chlorophyll a concentrations at time scales much shorter than a month occurred during the spring of 2003 and that the elevations in chlorophyll a levels were not continuous. The fluctuations were probably associated with rapid flushing by the Kuroshio water, which has low chlorophyll a content.

DOI： 10.1007/s10872-008-0002-8

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Language：English   Publishing type：Research paper (scientific journal)  

Trace nitrate in surface waters at several stations of the North Pacific Ocean and East China Sea were determined by a high-sensitivity chemiluminescence method. The detailed vertical distribution of nitrate within the surface layer based on water samples taken at small depth intervals revealed that nitrate concentrations were approximately uniform within the euphotic zone, then increased abruptly with depth from the upper end of the nitracline. Nitrate concentrations above the nitracline ranged 3.1-96.2nM, likely reflecting nitrate supply from depths. The depth of the upper end of the nitracline was located at a light depth of 0.58-3.5% at all stations except two, at which the surface mixed layer extended down to the upper end of the nitracline. These depths corresponded closely to the conventional bottom of the euphotic zone, indicating a strong biological control on the nitrate distribution. If the observed nitrate distribution is maintained steadily, net biological nitrate consumption should occur over a narrow depth range near the upper end of the nitracline and no net uptake or regeneration should occur in the upper layers of the euphotic zone.

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Deep-sea benthic ecosystems are mainly sustained by sinking organic materials that are produced in the euphotic zone. &quot;Benthic-pelagic coupling&quot; is the key to understanding both material cycles and benthic ecology in deep-sea environments, in particular in topographically flat open oceanic settings. However, it remains unclear whether &quot;benthic-pelagic coupling&quot; exists in eutrophic deep-sea environments at the ocean margins where areas of undulating and steep bottom topography are partly closely surrounded by land. Land-locked deep-sea settings may be characterized by different particle behaviors both in the water column and in relation to submarine topography. Mechanisms of particle accumulation may be different from those found in open ocean sedimentary systems. An interdisciplinary programme, &quot;Project Sagami&quot;, was carried out to understand seasonal carbon cycling in a eutrophic deep-sea environment (Sagami Bay) with steep bottom topography along the western margin of the Pacific, off central Japan. We collected data from ocean color photographs obtained using a sea observation satellite, surface water samples, hydrographic casts with turbidity sensor, sediment trap moorings and multiple core samplings at a permanent station in the central part of Sagami Bay between 1997 and 1998. Bottom nepheloid layers were also observed in video images recorded at a realtime, sea-floor observatory off Hatsushima in Sagami Bay. Distinct spring blooms were observed during mid-February through May in 1997. Mass flux deposited in sediment traps did not show a distinct spring bloom signal because of the influence of resuspended materials. However, dense clouds of suspended particles were observed only in the spring in the benthic nepheloid layer. This phenomenon corresponds well to the increased deposition of phytodetritus after the spring bloom. A phytodetrital layer started to form on the sediment surface about two weeks after the start of the spring bloom. Chlorophyll-a was detected in the top 2 cm of the sediment only when a phytodetritus layer was present. Protozoan and metazoan meiobenthos increased in density after phytodetritus deposition. Thus, &quot;benthic-pelagic coupling&quot; was certainly observed even in a marginal ocean environment with undulated bottom topography. Seasonal changes in features of the sediment-water interface were also documented. © 2003 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0079-6611(03)00047-8

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier Ltd  

Temporal variations of sinking particle flux, together with their organic chemical properties, were monitored in the deep basin of Sagami Bay, Japan, using sediment traps with very high time resolutions from March 1997 to August 1998. At a height of 350 m above the bottom (about 1200 m water depth), the averaged total mass flux was more than 1000 mg/m2/day, which is about 10 times higher than those obtained for open ocean regions near Sagami Bay. While large amounts of phytodetritus, derived from phytoplankton blooms in the surface water, were transported downward in spring, the following extraordinary patterns in the temporal variability of sinking particle flux were also observed: (1) A sustained large flux of sinking particles during low productive periods from summer to winter in 1997. (2) An episodic increase of sinking particle flux in June 1998. (3) A difference in the temporal variability of sinking particles between the spring bloom periods of 1997 and 1998. The content of total organic carbon (TOC) and the stable carbon isotopic ratio (δ13C) of TOC demonstrated that the large fluxes observed in (1) and (2) could be attributed to the resuspension of phytodetritus deposited on the sea floor during the spring bloom period, and the abrupt erosion of surface sediment on the continental slope, respectively. The concentration of suspended particles in the deep water column affect the apparent flux of sinking particles. At the same time, sinking particles exported from surface waters during the spring bloom both decrease and increase suspended particle concentration through scavenging and rebound processes, respectively. Finally, the apparent difference in sinking particle flux between 1997 and 1998, (3), could be explained by differences in the extent of the scavenging process, which depend on the flux and quality of exported particles from the surface waters. © 2003 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0079-6611(03)00049-1

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Language：English   Publishing type：Research paper (scientific journal)  

Nitrate uptake rate was determined in the East China Sea by a simulated in situ 15N incubation technique during four cruises representing different seasons in the period from 1993 to 1996. Stations were occupied on an observational line extending from the inner continental shelf to the adjacent oceanic water in the Pacific. The nitrate uptake rate integrated over the euphotic zone was higher on the average on the continental shelf (56 mg N m-2 d-1) than at the outer waters of the shelf-break and pelagic regions (21 mg N m-2 d-1). Both seasonal and spatial variations were larger on the shelf. Uptake rates were low in summer when the water columns were stratified. Nitrate in the summer surface waters was found to be almost completely depleted by determination with a chemiluminescence technique, and kinetic uptake experiments conducted concurrently suggested severe limitation of uptake due to the low nitrate concentrations. Uptake rates were also low in well-mixed water columns in winter and spring when the water temperature was low. High rates of uptake were observed in a spring bloom as well as at some of the inner-shelf stations in autumn. In the latter case, high phytoplankton biomass was accompanied by detectable amounts of nutrients and by lower salinity at the surface of the stratified water columns. Chlorophyll specific uptake capacity was higher and was significantly correlated with water temperature at a group of stations mostly on the shelf, while the capacity was lower and unaccountably varied at other stations. An empirical prediction model of nitrate uptake from chlorophyll concentration, temperature, light intensity, and nitrate concentration was developed and applied to these data. © 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0967-0645(02)00464-2

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier Ltd  

Seasonal variations in the primary production regime in the upper water column were assessed by shipboard observations using hydrocasts and natural fluorescence profiling at a fixed station in the central part of Sagami Bay, Japan. The observations were conducted as a part of 'Project Sagami' dedicated to the interdisciplinary study of seasonality in bathyal benthic populations and its coupling with water column processes. Based on the time-series observations at intervals of about 1 to 2 months, primary productivity in terms of chlorophyll abundance appeared to be elevated during the spring of 1997, but the observed peaks of biomass were much less significant in the spring of 1998. Meanwhile, the organic matter flux, as indicated by sediment trap data and benthic observations, had a significant peak in the spring of 1998 as well, and its magnitude was comparable to that in 1997. Satellite images of ocean color obtained during the spring of 1997 indicate the importance of events with time scales much shorter than a month, and suggest qualitative differences in the phytoplankton community in the euphotic zone for each bloom event during this period. The possible mechanisms that could yield the spring maximum of material input to the benthic community are discussed. © 2003 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0079-6611(03)00048-X

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Language：English   Publishing type：Research paper (scientific journal)  

This paper compares the variations of nitrate-based "new" production (NP) in the continental shelf of the East China Sea (ECS) between summer, when seawater stratification was strong, and winter when seawater was well mixed. New production and f-ratio (ratio of nitrate-based new production to primary production) showed no obvious seasonality and were generally low with two exceptions: one in the coastal upwelling off China in summer, and the other in the Kuroshio upwelling off northeastern Taiwan in winter. When not counting the two exceptional areas which were relatively small area-wise, integrated nitrate-based new production (INP) ranged 0.06-0.41 g Cm-2d-l in summer and 0.08-0.27g Cm-2d-1 in winter with f-ratios of 0.25-0.42 and 0.18-0.35. In summer, NP in the Changjiang-influenced coastal waters was significantly correlated to a high ambient nitrate concentration, which originated from the Changjiang discharge or from the coastal upwelling. Phosphate from the coastal upwelling alleviated the phosphorus deficiency caused by the river mixing, and the nitrate to phosphate ratio was near the Redfield ratio. Nitrate was readily consumed and converted into phytoplankton biomass. This leads to a low surface nitrate concentration (mostly below the detectable limit of 0.1 μM) and thus resulting in low NP in the surrounding shelf waters. NP in winter, in contrast, was not correlated to the nitrate concentration. Despite the abundant nitrate on the continental shelf (ranging between 0.52 and 14.24 μM), INP remained relatively low (0.01-0.55g Cm-2d-1). Light limitation hampered nitrate utilization. The deep mixing layer (&gt
euphotic depth), low photosynthesis available radiation, and a significant correlation between new production and stratification index indicated that NP in winter was controlled by irradiation intensity rather than nutrient concentration. The present results strongly suggest that production in the ECS was limited by N deficiency in summer and by light in winter. P deficiency did not seem to play a major limiting role. © 2001 Elsevier Science Ltd.

DOI： 10.1016/S0278-4343(00)00108-4

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Language：English   Publishing type：Research paper (international conference proceedings)  

The seasonal carbon cycle was studied in the bathyal environment of Sagami Bay, Japan, to determine whether 'benthic-pelagic coupling' takes place in this eutrophic marginal oceanic setting. Both Japanese sea color observation satellite (ADEOS) photography and sediment trap moorings have been used since 1996 for monitoring sea surface primary production. Video records at a real time deep-sea floor observatory off Hatsushima Island in Sagami Bay were also used to monitor the deposition of phytodetritus on the sea floor. At this location, a spring bloom starts in mid-February and ends in mid-April. About 2 weeks after the start of the spring bloom, phytodetrital material is deposited on the sea floor. Video records clearly show that phytodetritus deposition has taken place in the spring of every year since 1994, even though the exact timing is different from year to year. The population size of benthic foraminifera is highly correlated to this phytodetritus deposition. The phytodetritus triggers rapid, opportunistic reproduction of the shallow infaunal taxa, Bolivina pacifica, Stainforthia apertura and Textularia kattegatensis. Shallow infaunal species mainly occur in the phytodetrital layer or just below this layer during the spring. This indicates that such opportunistic species are key indicators of phytodetrital deposition. The deep infaunal taxa Globobulimina affinis and Chilostomella ovoidea show less pronounced seasonal fluctuations in population size, but nevertheless exhibit some response to phytodetrital deposition. Thus the seasonal flux of organic matter is the most important determinant of population size, microhabitats and reproduction of benthic foraminifera in Sagami Bay. (C) 2000 Elsevier Science B.V.

DOI： 10.1016/S0377-8398(00)00036-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Academic Press  

This paper reports the first results of the direct measurements of nitrate-based new production and f-ratio on the continental shelf of the East China Sea. The Kuroshio-induced upwelling off north-eastern Taiwan and river runoff from the Changjiang are two principal sources of new nitrogen on the shelf. New production ranged from 70 to 1610 mgC m-2 d-1, and values of the f-ratio were 0.17 to 0.82. Enhanced new production in the upwelling was significantly related to the ambient nitrate concentration. This implies that the nutrients brought up to the euphotic zone by the intrusion of the subsurface Kuroshio water were quickly reflected by the enhancement of new production. The prediction of f-ratio is feasible in the upwelling region from two ship-measured parameters: light intensity and surface nitrate concentration, but not feasible in the river-influenced shelf waters. New production on the riverine shelf waters, in contrast, was not related to the nitrate input from the Changjiang, but was positively (P&lt
0.05) related to water temperature. Low rates of NO3/- utilization imply that factors other than nitrate (e.g. phosphate or light) could be the limiting factors determining the new production dynamics in the river mouth.

DOI： 10.1006/ecss.1999.0404

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Gordon &amp; Breach Science Publ Inc  

A method is described for application of an automated carbon-nitrogen elemental analyzer for organic matter collected on glass fiber filters. The method allows a large size glass-fiber filter (47-mm diameter), which is commonly used in aquatic environmental researches, being processed for the automated elemental and isotopic analysis. A hydraulic press was used to destroy the fiber structure of the filter and to form a tablet covered with tin foil with bulk volume of about 0.2 cm3. The tablet can be introduced in an autosampler that drops a sample into the combustion tube of the analyzer. We also modified the combustion furnace tube by inserting a ceramic inner tube. The ceramic tube protects the quartz combustion tube from invasion by melted glass residue and facilitates post-combustion removal. While the procedure proposed here eliminated much of the operational problems associated with handling of larger glass-fiber filters, we found that analysis of large amount of organic matter (approximately more than 1000 μgC and 200 μg N) by this procedure may result in apparent lower output of carbon and nitrogen signals. Restriction of the amount of organic matter and addition of cobalt oxide as catalytic agent within the tablet is suggested as precautionary measure for the method. Careful examination of combustion yield depending on nature of the sample will also be necessary for actual application of the method.

DOI： 10.1080/03067319808035888

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Terra Scientific Publishing Company  

A method has been developed for determination of 15N isotope ratio in nitrate nitrogen, which is a major analytical step in tracer experiments for studies of nitrate metabolism in the marine environment. The method is based on diazotization of nitrite with sulfanilic acid following reduction of nitrate to nitrite by a cadmium-copper column. The diazonium compound is then subject to the azo coupling reaction with 2-naphthol, and the azo dye formed is extracted by a solid phase extraction column. The dye eluted from the column is collected, and total nitrogen and 15N content of the dye are determined by mass spectrometry. Sulfanilic acid can also remove preexisting nitrite by heating the sample under acidic conditions before passing through the cadmium-copper reduction column. The average recovery of nitrate nitrogen was 86%. A procedure for reducing the background nitrogen that derives from the analytical operations has been developed
background nitrogen was limited to about 0.25 μg-atom N. The variation in the background nitrogen levels reflects the range of error in 15N determination of nitrate nitrogen by this method. Application of the present method to a 15NO3 - isotope dilution experiment for determination of nitrification rate in sea water is demonstrated.

DOI： 10.1007/BF02742617

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Language：English   Publishing type：Research paper (scientific journal)  

The nitrogen budget of the rotifer, Brachionus plicatilis, fed on algae (Nannochloropsis oculate) was examined using a 15N tracer technique. It was found that this technique could be used to measure the nitrogen budget of zooplankton using the difference in the turnover time between egestion and excretion. When food was unlimited, the assimilation efficiency, the gross growth efficiency (K1), and the net growth efficiency (K2) were 22.8, 17.4 and 77.5% respectively. Therefore, approximately 80% of the ingested nitrogen was egested into the culture medium and about 80% of the assimilated nitrogen was utilized for reproduction. The turnover time of egestion and excretion were about 20 min and 2.5 h, respectively. The obtained short turnover time for excretion is consistent with the hypothesis that assimilated nitrogen is used immediately and primarily for reproduction and the excess is stored in body tissue when food is abundant. © 1995, The Japanese Society of Fisheries Science. All rights reserved.

DOI： 10.2331/fishsci.61.406

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Language：English   Publishing type：Research paper (scientific journal)  

A method for the determination of ammonium in seawater is described. The method is based on the indophenol (or the Berthelot) reaction with o-phenylphenol [(1,1′-biphenyl)-2-ol, abbreviated as OPP] as an alternative of phenol. Unlike phenol, OPP is available as stable flaky crystal with no caustic odor. This nature of OPP can eliminate much of the inconvenience associated with the use of phenol. The sensitivity of detection is comparable to that of the common phenol-based methods. The indophenolic compound obtained from the reaction with OPP is more hydrophobic than that from the reaction with phenol. Thus the indophenolic compound can be extracted directly from the alkaline reaction solution of the present method either with organic solvent or with reversed-phase column. The extracted indophenol can be used to recover ammonium nitrogen for the determination of 15-N isotope ratio. The experimental procedure of the extraction of indophenolic compound is relatively simple compared to the other existing methods. © 1995.

DOI： 10.1016/0043-1354(95)00149-F

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Language：Japanese   Publisher：Japan Radioisotope Association  

DOI： 10.3769/radioisotopes.43.263

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic Publishers  

I present here a review of my work concerning nitrogen assimilation by marine phytoplankton. This opportunity was provided to me as the recipient of the Okada Prize for 1990 from the Oceanographical Society of Japan. Assimilation of nitrogenous nutrients by phytoplankton has received considerable research effort since it is an essential process in organic matter production in the sea surface. The use of15N technique is necessary for tracing nitrogen assimilation by natural marine phytoplankton, but nitrogen metabolism of heterogenous natural populations significantly complicates flow of isotope. Dilution of15N isotope by heterotrophic regeneration of ammonium causes underestimates of uptake rates. I made an evaluation of isotope dilution effects in available data sets of15N-ammonium uptake experiments in literature. Incorporated15N in particulates might revert back to dissolved organic or inorganic nitrogen. I conducted pulse-chase experiments which can quantify such loss of tracer. From these studies, a short term experiment with sufficient amount of tracer enrichment is found to overwhelm these problems. In such an experiment, however, the elevation of nutrient concentration by tracer addition may likely perturb the uptake process. An initial rapid uptake is expected if the population is nitrogen deficient, but I found that this phenomenon is not common to surface oligotrophic open oceans. Uptake rate from such an experiment, or capacity of nitrogen uptake, was obtained using surface waters from an extended area in the North Pacific, and its regional variability was discussed. In addition to overall15N uptake, time series analysis of intracellular15N partitioning between hot ethanol soluble and insoluble fractions was found to be useful. When15N-ammonium is added to nitrogen deficient cells of phytoplankton,15N is accumulated in the ethanol soluble fraction. Using cultured strains of marine phytoplankton, this accumulation was proved to be caused by the difference of rates of nitrogen uptake and nitrogenous macromolecule synthesis. Uptake rate per cell is relatively constant irrespective of nutritional status, but macromolecule synthesis decreases with nitrogen deficiency. This accumulation of15N in the ethanol soluble fraction was used as an index of nutritional status with respect to nitrogen of the natural populations of phytoplankton from the western North Pacific. The uptake capacity of nitrate was observed to be higher than that of ammonium in the regional upwelling around Izu Islands and during the spring bloom in Alaskan coastal water. The15N partitioning technique revealed that nitrate taken up was rapidly incorporated in the macromolecule fraction. This suggests that ammonium uptake is suppressed to be smaller than intracellular nitrogen assimilation, rather than that nitrate is taken up in excess and accumulates within the cell. Regulation of nitrate uptake by light intensity was also discussed in detail for the Alaskan data. Several other studies currently conducted are also mentioned. © 1989 Oceanographical Society of Japan.

DOI： 10.1007/BF02123506

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Language：English   Publishing type：Research paper (scientific journal)  

Specific growth rates and grazing mortality of phycoerythrin-dominant (PE-dominant) Synechococcus spp. populations have been evaluated in oceanic surface waters off Japan. Diel changes in cell numbers and frequency (patterns) of dividing cells (FDC) of the Synechococcus population indicated that cell divisions occurred throughout the day and that a maximum is reached at dusk. The specific growth rate of the Synechococcus population determined by diffusion chamber cultures in which the micrograzers were removed by 1-μm Nuclepore filters, and by the FDC method, was as high as 0.10·h-1 which can double the population size in &lt
1 day. The grazing mortality by the small-sized (2-5 μmn) colorless flagellates and by the other large (&gt
10 μm) and less abundant heterotrophs (mostly ciliates) determined by diffusion chamber cultures was 0.04 and 0.06 · h-1, respectively. As a result, the growth rates and grazing mortality are expected to be balanced and the PE-dominant Synechococcus maintained its population size at a certain low level in the study areas. © 1990.

DOI： 10.1016/0022-0981(90)90091-P

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Language：English   Publishing type：Research paper (scientific journal)  

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right. © 1988, by the Association for the Sciences of Limnology and Oceanography, Inc.

DOI： 10.4319/lo.1988.33.6part2.1568

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Language：English   Publishing type：Research paper (scientific journal)  

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right. © 1988, by the Association for the Sciences of Limnology and Oceanography, Inc.

DOI： 10.4319/lo.1988.33.6part2.1580

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/analsci.3.279

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Language：English   Publishing type：Research paper (scientific journal)  

Uptake of NH4 by Anabaena cells in the dark at the physiological pH range of 6 to 8 occurred only under aerobic conditions and was accompanied by an efflux of H + ions. Uptake of NH4 also stimulated a K+ net efflux in the dark but not in the light. Uptake of NH4 and efflux of H+ and K+ were strongly inhibited by DCCD, an inhibitor of H +-translocating ATPase. A protonophore CCCP, known to inhibit NH4+ uptake, greatly stimulated K+ efflux. It is concluded that the uptake of NH4+ is an energy-dependent process and may be coupled to the H+ efflux. The K+ efflux may be secondarily stimulated by the NH4 uptake. © 1987, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.

DOI： 10.2323/jgam.33.311

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic Publishers  

Capacities for inorganic carbon, nitrate and ammonium uptake were measured around Hachijo Island, 300 km south of Tokyo, where local upwelling occurred. The phytoplankton population inside the upwelling area had a high capacity for nitrate uptake and a low capacity for uptake of ammonium. Nutrient concentration and phytoplankton biomass were higher in the upwelling plume than outside. On a chlorophyll a basis, phytoplankton populations inside the upwelling area showed a lower capacity for carbon and nitrogen uptake than those outside the upwelling. Low temperature, relatively limited availability of light caused by extensive water mixing within the upwelling plume, and the difference in species composition of phytoplankton must be considered in explaining these lower uptake capacities. © 1985 Oceanographical Society of Japan.

DOI： 10.1007/BF02109031

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Language：English   Publishing type：Research paper (scientific journal)  

This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right. © 1985, by the Association for the Sciences of Limnology and Oceanography, Inc.

DOI： 10.4319/lo.1985.30.5.0987

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Language：Japanese  

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Language：Japanese   Publisher：日本工業新聞新社  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Other Link： http://id.nii.ac.jp/1141/00047185/

Language：Japanese  

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Language：Japanese   Publisher：岩波書店  

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Language：Japanese  

J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：日本気象学会  

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J-GLOBAL

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Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Vertical distributions of turbidity & phytodetritus (Chl.a and pheopigment), and their seasonal variations were measured in the deep water column of Sagami Bay, Japan, in June 1999, February 2000 and May 2000. Observations were carried out at eight stations along an east-west section of Sagami Bay using a CTD/water sampling system equipped with a memory-type infrared back-scattering meter which had been calibrated for the suspended particles collected in Sagami Bay. Turbidity increased close to the bottom in both summer and winter, indicating the existence of a benthic nepheloid layer throughout the year. But the vertical gradient of turbidity was much larger in summer than in winter. The concentration of Chl.a and pheopigment also increased in the benthic layer in summer, sometimes reaching values of more than 0.01 and 0.2 mug/l, respectively, much higher than those reported in hemipelagic regions of the ocean. In winter, on the other hand, Chl.a kept a constant low value throughout the deep water column. This indicates that the turbid water mass formed in the benthic layer in summer derives from the deposition of large amounts of phytodetritus in spring and the resuspension of these aggregates, which are subsequently decomposed in the benthic layer during the following autumn. Unlike the benthic boundary layer, the turbidity of intermediate water was lower in summer rather than in winter. Because the phytoplankton aggregates exported from the surface water during the spring bloom not only supply phytodetritus to the benthic layer but also scavenge the suspended particles in the water column, the steep vertical gradient of turbidity observed in summer may reflect the dynamic interaction between suspended and sinking particles in the deep water column. (C) 2003 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0079-6611(03)00050-8

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Language：Japanese   Publisher：Japanese Society of Microbial Ecology  

Quantitative regulation of nutrient uptake by unicellular microalgae (phytoplankton) is the key physiological process that governs nutrient cycling and phytoplankton population dynamics in natural waters. Kinetic models are widely used in quantitative description of uptake and growth as functions of nutrient concentration. A review of both experimental and theoretical works on nitrogen and phosphorus uptake by cultured unicellular algae is presented here. At least three different values of half saturation constants are identified depending on the time scale of analysis, while a single system for ion transport is considered. Quantitative relationship is obtained theoretically and experimentally among these different values of half saturation constants.

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