222Rnを指標とした大阪湾沿岸域における地下水湧出の評価
梅澤 有、安元 純、山口 聖、林 美鶴、清水 裕太、小野寺 真一
月刊海洋
2024年03月, (MISC)総説・解説(学術雑誌), 共同
Long-term variability in larval recruitment rates of a callianassid shrimp population on an intertidal sandflat in an estuary-to-coastal ocean interface area in relation to river discharge and shelf water movement, western Kyushu, JapanTamaki, Akio; Umezawa, Yu; Hongo, Yuichiro; Takikawa, Tetsutaro
JOURNAL OF OCEANOGRAPHY
SPRINGER
Food availability is believed to affect macro-invertebrate larval survival at sea, which was poorly demonstrated. On the coast immediately outside an estuary (Ariake Sound, Kyushu, Japan), a population of the callianassid shrimp, Neotrypaea harmandi, with diatom-feeding larvae, lies on an intertidal sandflat. It is likely from previous research that the shrimp population is self-recruited by larvae in 20-50-m water depths of an interface area influenced by estuary and inner shelf and growth of a dominant diatom species in the estuary is nitrogen-limited. Apparent shrimp self-recruitment rates were monitored each year during 1989-2013. Public databases were used about the largest river's flow and dissolved inorganic nitrogen (DIN) in the estuary. A high positive correlation was detected between shrimp recruitment rate and DIN concentration which was in turn correlated with river flow rate. Hydrographic surveys were conducted from inner shelf to estuary in 2011-2013. Chlorophyll-fluorescence was positively related with DIN concentration in the near-surface for estuary and in the lower subsurface for inner shelf. Based on a public reanalysis model database for temperature in the western North Pacific were examined yearly variations in the degree of western Kyushu-coastward movement by potentially nutrient-rich, cold bottom waters from offshore. The contributions of DIN from estuary and from inner shelf to shrimp recruitment rate were assessed by multiple regression, with, as explanatory variables, estuarine DIN concentration and lower temperature anomaly in inner-shelf water (surrogate for the higher DIN concentration). DIN of estuary and 'DIN' of inner shelf explained recruitment-rate variations by 77% and 23%, respectively.
2023年12月, 研究論文(学術雑誌), 共同, 79, 6, 0916-8370,
DOI(公開)(r-map), 593, 618
Investigation of inter-annual variation in the feeding habits of Japanese sardine (Sardinops melanostictus) and mackerels (Scomber spp.) in the Western North Pacific based on bulk and amino acid stable isotopesOhno, Yosuke; Umezawa, Yu; Okunishi, Takeshi; Yukami, Ryuji; Kamimura, Yasuhiro; Yoshimizu, Chikage; Tayasu, Ichiro
FRONTIERS IN MARINE SCIENCE
FRONTIERS MEDIA SA
Inter-annual variation in the feeding habits and food sources of Japanese sardine and mackerel at age-0 and age-1+ caught in the Kuroshio-Oyashio transition zone of the Western North Pacific were investigated based on analyses of bulk stable isotopes (delta C-13, delta N-15) and amino acid nitrogen isotopes (delta N-15(AA)). Differences in delta C-13 and delta N-15 between Japanese sardine and mackerel were small for age-0, and inter-annual variation trends were similar, suggesting they depend on similar food sources in the same food web at this age. In contrast, inter-annual variation in delta C-13 and delta N-15 were significantly different between both species at age-1+, and both delta N-15 of phenylalanine (delta N-15(Phe): an indicator of nitrogen source) and trophic position estimated from delta N-15(AA) (TPAA) were higher in mackerel, suggesting that the two species depend on distinct food webs as they age. Inter-annual variations in delta N-15(Phe) were considered to have different causes for the two species; differences in food web structure due to the degree of southward intrusion of the Oyashio Current for Japanese sardine, compared to a shift in migration area and depth for mackerel. Furthermore, competition for food due to the recent increases in the population densities of both fishes appeared to be reflected in increased TPAA of mackerel. Although they are caught in the same region, the mechanism of variation in food sources differs because of differences in migration area, depth, and feeding habits. Differences in the feeding habits of Japanese sardine and mackerel may affect trophic status and spawning characteristics, potentially leading to different shifts in stock abundances.
2023年11月21日, 研究論文(学術雑誌), 共同, 10,
DOI(公開)(r-map) Total phosphorus and phosphorus forms change in sediments along the Tone RiverKozyrev, Roman; Umezawa, Yu; Yoh, Muneoki
FRONTIERS IN EARTH SCIENCE
FRONTIERS MEDIA SA
Phosphorus (P) is an essential element for the metabolism, growth, and development of living organisms, and it often limits primary production in freshwater ecosystems. During flood events, rivers can transport considerable amounts of particulate organic P (org-P) and inorganic P from the basin to the ocean. Understanding the transport mechanisms and changes in P distribution from upstream to downstream areas of rivers is crucial to estimate its flux to the ocean. However, the processes involved in P transformation and cycling among different forms in rivers are not well understood. To better understand P transformation and total P (TP) concentrations in river basins, this study examined various P forms in bottom sediments, river bank sediments, parent rock material, and soil samples along the Tone River, Japan. P forms such as org-P, Ca-bound phosphorus (apatite, Ca-P), P bound with iron oxides/hydroxides (Fe-P), bio unavailable non-apatite inorganic P (NAIP), and TP were analyzed. The results showed an increase in TP concentration in bottom and bank sediment samples along the course of the Tone River. This change in TP was mostly due to the increases in Fe-P and bioavailable org-P, while Ca-P and NAIP decreased toward the downstream area. Analysis of parent rock in three main mountain group areas (Mount Tanigawa, Mount Akagi, and Mount Tsukuba) showed their downstream impacts on TP and the distribution of P forms. Sediment grain size distribution analysis suggested that Fe-P and org-P fractions increased with decreasing sediment particle size, while Ca-P and NAIP were relatively evenly distributed among all grain sizes. The data revealed the transformation of P forms in sediments of the largest river in the Kanto region, Japan, which influence its flux to the Pacific Ocean. The results suggest that Fe-P and org-P may play a more significant role in P transport from river basins to the ocean than previously thought. The findings of this study can be useful for estimating P fluxes to the ocean and for the management of freshwater ecosystems.
2023年03月28日, 研究論文(学術雑誌), 共同, 11,
DOI(公開)(r-map) Haptophyte communities along the Kuroshio current reveal their geographical sources and ecological traitsEndo, Hisashi; Umezawa, Yu; Takeda, Shigenobu; Suzuki, Koji
MOLECULAR ECOLOGY
WILEY
Haptophytes are one of the most ecologically successful phytoplankton groups in the modern ocean and tend to maintain balanced and stable communities across various environments. However, little is known about the mechanisms that enable community stability and ecological success. To reveal the community characteristics and interactions among haptophytes, we conducted comprehensive observations from the upstream to downstream regions of the Kuroshio Current. Haptophyte abundance and taxonomy were assessed using quantitative polymerase chain reaction and metabarcoding of 18S rRNA sequences, respectively. The haptophyte community structure changed abruptly at sites on the shelf-slope of the East China Sea, indicating the strong influence of shelf waters with high phytoplankton biomass on downstream communities. Correlation network analysis combined with the phylogeny suggested that haptophytes can coexist with their close relatives, possibly owing to their nutritional flexibility, thereby escaping from resource competition. Consistently, some noncalcifying haptophyte genera with high mixotrophic capacities such as Chrysochromulina constituted a major component of the co-occurrence network, whereas coccolithophores such as Emiliania/Gephyrocapsa were rarely observed. Our study findings suggest that noncalcifying haptophytes play crucial roles in community diversity and stability, and in sustaining the food web structure in the Kuroshio ecosystems.
2023年01月, 研究論文(学術雑誌), 共同, 32, 1, 0962-1083,
DOI(公開)(r-map), 110, 123
"Haptophyte communities along the Kuroshio current reveal their geographical sources and ecological traitsEndo H., Umezawa Y, Takeda S, Suzuki K
Molecular Ecology
2022年10月01日, 研究論文(学術雑誌), 共同,
DOI(公開)(r-map) Free-living marine bacterioplankton composition and diversity along the Kuroshio regionLiu, Ariana Chih-Hsien; Chang, Feng-Hsun; Yang, Jinny Wu; Saito, Hiroaki; Umezawa, Yu; Chen, Chung-Chi; Jan, Sen; Hsieh, Chih-hao
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
PERGAMON-ELSEVIER SCIENCE LTD
We investigated how free-living bacterioplankton's diversity and taxonomic composition vary along the Kuroshio from south Taiwan to the east coast of Honshu Japan (similar to 22-35 degrees N). We collected samples from both surface and deep chlorophyll-a maximum (DCM) layers and then applied high-throughput sequencing techniques to study communities of bacterioplankton. Along the Kuroshio, we found a general decreasing richness (R-2 = 0.077, p = 0.02, regression coefficient = 13.092) and Shannon diversity (R-2 = 0.327, p = 0.027, regression coefficient = 0.029), which was best explained by decreasing temperature and phosphate concentration. Whereas bacterial evenness increased in the surface (R-2 = 0.3, p = 0.002, regression coefficient = 0.545) but decreased in the DCM along the Kuroshio (R-2 = 0.2, p = 0.014, regression coefficient = 0.451); this pattern coincided with the patterns that chlorophyll-a concentration significantly increased in the surface but decreased in the DCM layer. The results suggest that physiological constrain and nutrient availability influenced the richness and Shannon diversity, while productivity influenced the evenness of bacterioplankton. In terms of bacterial community composition, the surface and the DCM layers were significantly different. The compositional change of bacterioplankton along the Kuroshio was also different in the two layers because different bacterial taxa exhibited distinct responses to different environments. In the surface layer, compositional change of bacterioplankton was associated with temperature, dissolved inorganic nitrogen, and salinity, while in the DCM layer, phosphate concentration was also important. In terms of the bacterial taxa that showed significant changes along the Kuroshio, the relative abundance of genus NS5_marine_group significantly decreased, while genus Sva0996_marine_group and Pseudohongiella significantly increased in the surface layer. In addition, genus Clade_Ia and HIMB11 showed significantly lower relative abundance around the transect near Taiwan, while genus Alteromonas was significantly more abundant at the transect around 30 degrees N. In the DCM layer, the relative abundance of genus Candidatus_Actinomarina, Sva0996_marine_group, and NS5_marine_group significantly decreased along the Kuroshio. We argue that bacteria's preference for temperature, salinity, and resource availability are related to their compositional variation along the Kuroshio. Our findings, for the first time, document how bacterial diversity and composition change along the Kuroshio, providing the foundation to studying the bacterioplankton in the northwestern Pacific Ocean.
2022年05月, 研究論文(学術雑誌), 共同, 183, 0967-0637,
DOI(公開)(r-map) Evaluation of origin-depended nitrogen input through atmospheric deposition and its effect on primary production in coastal areas of western Kyusyu, JapanUmezawa, Yu; Toyoshima, Kanae; Saitoh, Yu; Takeda, Shigenobu; Tamura, Kei; Tamaya, Chiaki; Yamaguchi, Akira; Yoshimizu, Chikage; Tayasu, Ichiro; Kawamoto, Kazuaki
ENVIRONMENTAL POLLUTION
ELSEVIER SCI LTD
Long term monitoring of atmospheric wet and dry depositions and associated nutrients fluxes was conducted on the coast of Japan facing the East China Sea continuously for 1 year and 2 months, with the origin of air mass investigated based on isotope analyses (Sr, Nd, and NO3). During the same period, intensive observations of ocean conditions and the chemical composition of sinking particles collected using sediment traps were conducted to investigate the effects of atmospheric deposition-derived nutrients on phytoplankton blooms. Dry-deposition-derived nutrient inputs to the surface ocean were larger during autumn to spring than in summer due to the effect of continental air mass occasionally carrying Asian dust (yellow sand). However, these nutrients fluxes were limited (1.1-1.5 mg-N m(-2) day(-1) on average) and didn't appear to cause phytoplankton blooms through the year. Although average dissolved inorganic nitrogen (DIN) concentrations in rainwater were lower in oceanic air masses compared to continental air masses, wet-deposition-derived nutrient inputs to the surface ocean on rainy days during the summer (26.0 mg-N m(-2) day(-1) on average) were large due to higher precipitation from oceanic air masses. Wet-deposition-derived nutrients significantly increased nutrient concentrations in the surface ocean and seemed to cause phytoplankton blooms in the warm rainy season when nutrients in the surface were depleted due to increased stratification. The increase in phytoplankton biomass was reflected in increased particle sinking into the bottom layer, as well as changing chemical characteristics. The supply of flesh phytoplankton-derived labile organic matter into the bottom layer could be expected to promote rapid bacterial decomposition and contribute to the formation of hypoxic water masses in early summer when the ocean was strongly stratified. Atmospheric deposition-derived nutrients in East Asia will have important impacts on not only the oligotrophic outer ocean but also surrounding coastal areas in the warm rainy season.
2021年12月15日, 研究論文(学術雑誌), 共同, 291, 0269-7491,
DOI(公開)(r-map) Seasonal variation in terrestrial cellulose assimilation of benthic invertebrates inhabiting wetlands in Osaka Bay, Japan.
3. Liu W, Umezawa Y, Kato S and Matsuoka K
Laguna
2021年12月, 研究論文(学術雑誌), 共同, 28, 37, 53
Geographic Variation of Particle Size Distribution in the Kuroshio Region: Possible Causes in the Upper Water ColumnYamada Y., Fukuda H., Umezawa Y, Nagata T.
Frontiers in Marine Science
2021年11月, 研究論文(学術雑誌), 共同,
DOI(公開)(r-map) Nitrogen burden from atmospheric deposition process in East Asian oceans in 2010 based on the high-resolution regional numerical modeling5. Itahashi, S., Hayashi, K., Takeda, S., Umezawa Y, Matsuda, K., Sakurai, T., and Uno, I.
Environmental Pollution
2021年10月, 研究論文(学術雑誌), 共同,
DOI(公開)(r-map) Potential oxygen consumption and community composition of sediment bacteria in a seasonally hypoxic enclosed bay4. Mori F, Umezawa Y, Kondo R, GN, Nishihara, Wada M
PeerJ
2021年08月, 研究論文(学術雑誌), 共同,
DOI(公開)(r-map) Estimation of spatiotemporal variations in nutrient fluxes from sediments in the seasonally hypoxic Omura Bay, JapanMuta, Naoki; Umezawa, Yu; Yamaguchi, Akira; Suzaki, Hirokazu; Wada, Minoru; Nakata, Hideaki; Kawamoto, Kazuaki; Matsuoka, Kazumi
LIMNOLOGY
SPRINGER JAPAN KK
In the seasonally hypoxic semi-enclosed Omura Bay, Japan, regression equations estimating cast(year as numeric)-round nutrient [NO3 + NO2, NH4, PO4, Si(OH)(4)] concentrations in pore water were successfully constructed based on water temperature and the concentration of biogenic elements in surface sediments, except for NH(4)and PO(4)concentrations in summer when the hypoxic water mass develops. Core incubation studies revealed that pore water NH(4)and PO(4)concentrations under anaerobic conditions increased 1.4-2.2 and 1.8-2.1 times, respectively, above levels estimated with the regression equations. These were in good agreement with the values observed in the field during summer. The gradient in nutrient concentrations between the measured values in the overlying water column and the estimated values in the pore water revealed that spatial fluctuations in nutrient fluxes at the sediment-water interface across the Omura Bay ranged from 1.5 to 2 times, reaching up to 3-4 times in the summer. Annual nutrient fluxes from the sediment (690-780 ton-N year(-1)for DIN, 77-85 ton-P year(-1)for DIP, and c.a. 4700 ton-Si year(-1)for DSi) were comparable to those from terrestrial areas. Accurate estimation of internal loadings is essential to properly evaluate residual nutrients and organic matter in the water column and their effect on aquatic ecosystems.
2020年08月, 研究論文(学術雑誌), 共同, 21, 3, 1439-8621,
DOI(公開)(r-map), 341, 356
Macroalgal metabolism and lateral carbon flows can create significant carbon sinksWatanabe, Kenta; Yoshida, Goro; Hori, Masakazu; Umezawa, Yu; Moki, Hirotada; Kuwae, Tomohiro
BIOGEOSCIENCES
COPERNICUS GESELLSCHAFT MBH
Macroalgal beds have drawn attention as one of the vegetated coastal ecosystems that act as atmospheric CO2 sinks. Although macroalgal metabolism as well as inorganic and organic carbon flows are important pathways for CO2 uptake by macroalgal beds, the relationships between macroalgal metabolism and associated carbon flows are still poorly understood. In the present study, we investigated carbon flows, including air-water CO2 exchange and budgets of dissolved inorganic carbon, total alkalinity, and dissolved organic carbon (DOC), in a temperate macroalgal bed during the productive months of the year. To assess the key mechanisms responsible for atmospheric CO2 uptake by the macroalgal bed, we estimated macroalgal metabolism and lateral carbon flows (i.e., carbon exchanges between the macroalgal bed and the offshore area) by using field measurements of carbon species, a field-bag method, a degradation experiment, and mass-balance modeling in a temperate Sargassum bed over a diurnal cycle. Our results showed that macroalgal metabolism and lateral carbon flows driven by water exchange affected air-water CO2 exchange in the macroalgal bed and the surrounding waters. Macroalgal metabolism caused overlying waters to contain low concentrations of CO2 and high concentrations of DOC that were efficiently exported offshore from the macroalgal bed. These results indicate that the exported water can potentially lower CO2 concentrations in the offshore surface water and enhance atmospheric CO2 uptake. Furthermore, the Sargassum bed exported 6 %-35% of the macroalgal net commu-nity production (NCP; 302-1378 mmolCm(-2) d(-1)) as DOC to the offshore area. The results of degradation experiments showed that 56 %-78% of macroalgal DOC was refractory DOC (RDOC) that persisted for 150 d; thus, the Sargassum bed exported 5 %-20% of the macroalgal NCP as RDOC. Our findings suggest that macroalgal beds in habitats associated with high water exchange rates can create significant CO2 sinks around them and export a substantial amount of DOC to offshore areas.
2020年05月05日, 研究論文(学術雑誌), 共同, 17, 9, 1726-4170,
DOI(公開)(r-map), 2425, 2440
Estimation of spatiotemporal variations in nutrient fluxes from sediments in the seasonally hypoxic Omura Bay, JapanMuta N, Umezawa Y*, Yamaguchi A, Suzaki H, Wada M, Nakata H, Kawamoto K, and Matsuoka K
Limnology
2019年09月24日, 研究論文(学術雑誌), 共同, 21, 3,
DOI(公開)(r-map), 341, 356
浅海生態系における年間二酸化炭素吸収量の全国推計桑江朝比呂・吉田吾郎・堀正和・渡辺謙太・棚谷灯子・岡田知也・梅澤有・佐々木 淳
土木学会論文集B2(海岸工学)
2019年06月20日, 研究論文(学術雑誌), 共同, 75, 1, 1884-2399,
DOI(公開)(r-map), 10, 20
Feeding habits estimated from weight-related isotope variations of mesopelagic fish larvae in the Kuroshio waters of the northeastern East China SeaMei, Weiping; Umezawa, Yu; Wan, Xin; Yuan, Jinghan; Sassa, Chiyuki
ICES JOURNAL OF MARINE SCIENCE
OXFORD UNIV PRESS
Bulk carbon and nitrogen stable isotope (SI) ratios (delta C-13 and delta N-15) were analysed to investigate the feeding habits of six taxa of mesopelagic fish larvae inhabiting the Kuroshio waters of the northeastern East China Sea. Large variation in tissue SI during early larval periods suggested maternal effects from parent fishes, and non-selective feeding on a variety of plankton species due to poor swimming ability. The similarity between SI ratios measured in larval tissues and those estimated for eggs of an ”income breeder” in the spawning area support an ” income breeder” strategy in Diaphus slender type and Vinciguerria nimbaria, while Lipolagus ochotensis seemed to show ”capital breeder”-like characteristics. SI ratios of the fish larvae studied became relatively constant at species-specific body dry-weights (0.5-1.0 mg), probably due to the commencement of selective feeding, meaning SI ratios during late larval periods could be used for trophic position analysis. There was great overlap (44.6-76.5%) in trophic niche among the larval fishes within the same taxonomic family of Myctophidae. Even if principal diet components cannot be identified with gut contents analyses, diet information from other fish species occupying a similar isotopic niche can thus improve our understanding of the diets of larval fishes.
2019年05月, 研究論文(学術雑誌), 共同, 76, 3, 1054-3139,
DOI(公開)(r-map), 639, 648
Hypoxic water mass in the highly turbid well-mixed macrotidal Rokkaku River Estuary, Ariake Sea, JapanHayami, Yuichi; Wada, Minoru; Umezawa, Yu; Fujii, Naoki; Nakamura, Akito; Mori, Fumiaki
ESTUARINE COASTAL AND SHELF SCIENCE
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Hypoxic water masses are usually formed in the bottom layer of stratified water columns. However, we found that hypoxia was formed throughout the water column in a well-mixed macrotidal estuary, the Rokkaku River Estuary, Japan. There was a spring-neap variation in the dissolved oxygen (DO) concentration where hypoxia developed during spring tides. Minimum DO concentration was observed 1 or a few days after the spring tide. When hypoxia developed, all the water column from bottom to surface became hypoxic ( < 2 mg l(-1) or < 30% saturation). The hypoxic water mass was associated with the estuarine turbidity maximum (ETM). Oxygen demand of water in this area was very large ( > 2 mg l(-1) day(-1)). Potential oxygen consumption by microorganisms was positively correlated with turbidity. Concentration of suspended solid (SS) at the ETM exceeded 1000 mg l-1. Furthermore, particulate organic carbon (POC) concentration in the estuary increased in spring tides. C/N ratio and delta C-13 of organic matter suggested that POC was transported from the sea into the estuary. These results suggest that the active resuspension of organic matter caused by the strong tidal current during spring tides enhanced the respiratory activity of microorganisms and the main source of the organic matter was detrital material from the sea. Such a large amount of organic matter should fuel microbial respiration effectively. Since microbial oxygen consumption was larger than the oxygen supply from the water surface even in the well mixed condition, a hypoxic water mass was formed in this estuary.
2019年04月05日, 研究論文(学術雑誌), 共同, 219, 0272-7714,
DOI(公開)(r-map), 210, 222
Using segmental isotope analysis of teleost fish vertebrae to estimate trophic discrimination factors of bone collagenMatsubayashi, Jun; Umezawa, Yu; Matsuyama, Michiya; Kawabe, Ryo; Mei, Weiping; Wan, Xin; Shimomae, Atsushi; Tayasu, Ichiro
LIMNOLOGY AND OCEANOGRAPHY-METHODS
WILEY
We conducted feeding experiments with sardine (Sardinops melanostictus) and Japanese flounder (Paralichthys olivaceus) to investigate trophic discrimination factors (TDFs) in bone collagen using retrospective isotope analysis. Sardines and Japanese flounder were fed a single diet for 9 months and 4 months, respectively. At the end of the experiments, we extracted vertebral centra from six sardines and seven Japanese flounder and subdivided them into multiple sections. We extracted bone collagen from each section, and measured the delta C-13 and delta N-15 of each vertebral section and food source. In all fish samples, the delta C-13 and delta N-15 values of bone collagen increased from the centers of vertebrae to the marginal sections. This trend was consistent with the predicted isotopic shift in the diets of these fishes. The TDFs for sardines were estimated at 5.58 +/- 0.25 parts per thousand (mean +/- SD) for delta C-13 and -0.70 +/- 0.25 parts per thousand for delta N-15; those for Japanese flounder were 3.89 +/- 0.14 parts per thousand for delta C-13 and 1.18 +/- 0.35 parts per thousand for delta N-15. Our results show that segmental analysis of vertebrae can reconstruct delta C-13 and delta N-15 values for multiple life-stages of both fish species and is useful for estimating TDFs and turnover times of fish bone collagen.
2019年02月, 研究論文(学術雑誌), 共同, 17, 2, 1541-5856,
DOI(公開)(r-map), 87, 96
Factors controlling spatiotemporal variations in stable nitrogen isotopes of Trachurus japonicus larvae and juveniles in the East China SeaMei, Weiping; Umezawa, Yu; Wan, Xin; Sassa, Chiyuki; Takahashi, Motomitsu
FISHERIES SCIENCE
SPRINGER JAPAN KK
To clarify the factors that affect spatiotemporal isotopic variations in fishes, we examined stable carbon and nitrogen isotope ratios (C-13 and N-15) of Japanese jack mackerel Trachurus japonicus larvae and juveniles sampled in the shelf break region of the East China Sea (ECS) in April during six consecutive surveys (2005-2010). The C-13 values in fish tissues were similar between northern and southern ECS, while N-15 values were higher in the southern ECS, probably because of lower nitrogen fixation and the presence of fish with larger body size occupying a higher trophic level. Interannual variations in N-15 of T. japonicus juveniles might be mainly contributed by the variation in the abundance of the main diet such as Oncaeidae copepodites and Corycaeus. The isotopic overlaps between epipelagic T. japonicus larvae and other dominant mesopelagic fish larvae were negligible, suggesting lesser competition for food resources. Knowledge regarding spatiotemporal variation in stable isotope ratios of T. japonicus can be applied to understand the feeding habits and migrations of fishes in the ECS.
2019年01月, 研究論文(学術雑誌), 共同, 85, 1, 0919-9268,
DOI(公開)(r-map), 71, 80
Dynamics of Sulfate-Reducing Bacteria Community Structure in Surface Sediment of a Seasonally Hypoxic Enclosed BayMori, Fumiaki; Umezawa, Yu; Kondo, Ryuji; Wada, Minoru
MICROBES AND ENVIRONMENTS
JAPANESE SOC MICROBIAL ECOLOGY, DEPT BIORESOURCE SCIENCE
We herein report on the dynamics of a sulfate-reducing bacteria (SRB) community structure in the surface sediment of a seasonally hypoxic enclosed bay for two consecutive years (2012 and 2013). The uppermost (0-5 mm) and subsurface (5-10 mm) layers of sediment were examined with a terminal-restriction fragment length polymorphism (T-RFLP) analysis based on the dissimilatory sulfite reductase (dsrA) gene. The SRB community significantly differed between the two sediment layers over the sampling period. This difference was mainly attributed to operational taxonomic units (OTUs) that were unique to either of the sediment layers. However, nearly 70% of total OTUs were shared between the two layers, with a few predominating. Therefore, no significant shift was observed in the SRB community structure under varying dissolved oxygen (DO) conditions in bottom water overlying the sediment surface. An additional analysis of 16S rRNA gene amplicon sequences, conducted for three uppermost sediment samples (July, August, and September in 2012), revealed that Desulfococcus, a member of SRB with high tolerance to oxygen, was the predominant Deltaproteobacteria across the uppermost sediment samples. Based on the predominance of shared OTUs across the SRB community in the sediment (0-10 mm) regardless of bottom-water DO, some SRB that are physiologically tolerant of a wide range of DO conditions may have dominated and masked changes in responsive SRB to DO concentrations. These results suggest that the SRB community structure in the enclosed bay became stable under repeated cycles of seasonal hypoxia, but may be compromised if the severity of hypoxia increases in the future.
2018年12月28日, 研究論文(学術雑誌), 共同, 33, 4, 1342-6311,
DOI(公開)(r-map), 378, 384
Temporal dynamics of dissolved organic carbon (DOC) produced in a microcosm with red tide forming algae Chattonella marina and its associated bacteriaWada, Minoru; Takano, Yukiko; Nagae, Saki; Ohtake, Yuka; Umezawa, Yu; Nakamura, Shinichi; Yoshida, Makoto; Matsuyama, Yukihiko; Iwataki, Mitsunori; Takeshita, Satoshi; Oda, Tatsuya
JOURNAL OF OCEANOGRAPHY
SPRINGER
Acute and severe hypoxia associated with harmful algal bloom has become one of the major causes for the environmental deterioration of coastal areas. Although it is generally thought that a large part of the dissolved oxygen consumption at a bloom site is initiated by heterotrophic bacteria that attack organic matter derived from dead or dying algal cells, precise microbial processes leading to the hypoxia are yet to be examined. Here we show temporal dynamics of extracellular dissolved organic carbon (DOC) of the red tide forming raphidophyte Chattonella marina and bacterial populations associating with the algae under laboratory conditions. During the growth of non-axenic strains of C.marina, we monitored abundance of algae, associated bacteria, and DOC in the culture media. Bacterial cell abundance increased in response to the increase in DOC both at the beginning and the late log phase of the algal growth. Flow cytometric analysis revealed that transient increase in the percentage of respiratory-active bacterial cells also coincided with the timing of the increase in bacterial abundance and DOC. These results strongly suggest that DOC released from growing C.marina fuels respiration and growth of planktonic bacteria surrounding the algae. This has implications for the role of DOC released from C.marina bloom before the collapse in mediating interactions between neighboring algae and bacterial assemblage which may eventually lead to algal bloom-associated hypoxia.
2018年12月, 研究論文(学術雑誌), 共同, 74, 6, 0916-8370,
DOI(公開)(r-map), 587, 593
Diurnal and seasonal variation of particle and dissolved organic matter release by the coral Acropora tenuisKurihara, Haruko; Ikeda, Nao; Umezawa, Yu
PEERJ
PEERJ INC
Release rates of particulate organic carbon and nitrogen (POC and PON) and dissolved organic carbon (DOC) from the scleractinian coral Acropora tenuis were measured during the day and night in summer and winter seasons. Physiological parameters including calcification, photosynthesis and respiration rates were also measured simultaneously. The release rate of both POC and DOC was significantly higher in summer compared to winter and higher during the day compared to the night. The daily release rate of total organic carbon (POC + DOC) was 1,094 and 219 mu mol C cm(-2) d(-1) for summer and winter, respectively, being 4.9 times higher in summer. The POC:PON ratios of the particulate organic matter released during daytime in both seasons (summer: 12.8 +/- 5.7, winter: 12.0 +/- 4.1) were significantly higher than those during nighttime (summer: 6.1 +/- 2.5, winter: 2.2 +/- 1.8). The DOC:POC ratio was 0.5 +/- 0.03 during summer and 0.32 +/- 0.98 during winter, suggesting higher mucus release in particulate form. Daily net production was estimated to be 199 and 158 mu g C cm(-2) d(-1) for summer and winter, respectively, with the amount of carbon released as mucus accounting for 6.5% and 1.6% of the net carbon fixation, respectively. The study reveals diurnal and seasonal changes in the quantity and quality of mucus released from this coral species. Since coral mucus is used as a food source by reef macro-organisms, and can also serve as an energy source for micro-organisms, the observed changes in mucus release rates are expected to influence the seasonal dynamics of organic carbon and nitrogen cycling over coral reefs.
2018年11月07日, 研究論文(学術雑誌), 共同, 6, 2167-8359,
DOI(公開)(r-map) Effects of bottom-water hypoxia on sediment bacterial community composition in a seasonally hypoxic enclosed bay (Omura Bay, West Kyushu, Japan)Mori, Fumiaki; Umezawa, Yu; Kondo, Ryuji; Wada, Minoru
FEMS MICROBIOLOGY ECOLOGY
OXFORD UNIV PRESS
The bacterial community strongly drives carbon and other biogeochemical cycles in marine sediment. However, little is known about the impact of dissolved oxygen (DO) availability on bacterial community composition. To fill this gap, we examined diversity, richness and structure of the bacterial population for three consecutive years (2011-2013) in the uppermost (0-5 and 0-7 mm depth) and the subsurface layers (5-10 and 7-14 mm depth) of Omura Bay, Kyushu, Japan, a seasonally hypoxic enclosed bay. Automated ribosomal intergenic spacer analysis revealed a unimodal pattern of diversity indices with DO, peaking at the suboxic (11 mu MO2) condition. Shifts in the bacterial communities were also evident in response to the availability of DO. Changes in the operational taxonomic units (OTUs) that were less abundant accounted for a large part of the community dissimilarity. It was further demonstrated that the relative abundance of OTUs affiliated with Gammaproteobacteria was correlated positively with DO, while that with Deltaproteobacteria was inversely correlated with DO. These results strongly suggest that DO availability of bottom water plays a fundamental role in shaping the bacterial community in sediment surfaces of shallow coastal areas.
2018年05月, 研究論文(学術雑誌), 共同, 94, 5, 0168-6496,
DOI(公開)(r-map) Phytoplankton as a principal diet for callianassid shrimp larvae in coastal waters, estimated from laboratory rearing and stable isotope analysisUmezawa, Yu; Tamaki, Akio; Suzuki, Toshikazu; Takeuchi, Seiji; Yoshimizu, Chikage; Tayasu, Ichiro
MARINE ECOLOGY PROGRESS SERIES
INTER-RESEARCH
The field diet of meroplanktonic decapod crustacean larvae is poorly known, despite standard use of microzooplankton as food in laboratory culture. Using callianassid shrimp Nihonotrypaea harmandi larvae collected from a 65 m deep inner-shelf location off mid-western Kyushu, Japan, between June and August 2012 and 2013 and mass-reared in the laboratory, a phytoplankton-based diet through larval development (zoeae I-VI to decapodid) was demonstrated. When the pure-cultured diatom Chaetoceros gracilis was fed to zoeae, survival rate to decapodids was 3.4 to 3.9% in 26 to 40 d at 22 degrees C, which was comparable to previous rearing results for zoeae fed microzooplankton. Trophic enrichment factors (TEFs) from stable isotope (SI) analysis of zoeal whole-body tissue in the laboratory were 2.0 parts per thousand for delta C-13 and 1.9 parts per thousand for delta N-15. In the field water column, diatoms dominated the nano-to micro-sized plankton, accounting for 38 to 81% of the biovolume, followed by heterotrophic protists. The trophic position (TP) estimated from amino acid-specific delta N-15 values for the field-collected zoeae VI was 2.1 (TPGlu/Phe) or 2.7 (TPAla/Phe), suggesting that those zoeae fed on mixtures of phytoplankton and heterotrophs including protists. Bulk SI analyses were performed for particulate organic matter (POM; proxy for phytoplankton), microzooplankton (mainly calanoid copepods), and shrimp zoeae to elucidate the diet of larvae in the water column. A shift in SI from fresh to degraded POM was determined through the incubation of field-collected POM. Based on this shift during degradation and larval TEFs, phytoplankton and their sinking detritus with heterotrophic protists were estimated to be the principal diet for those larvae residing mostly below the chlorophyll maximum layer.
2018年03月29日, 研究論文(学術雑誌), 共同, 592, 0171-8630,
DOI(公開)(r-map), 141, 158
Highly heterogeneous diazotroph communities in the Kuroshio Current and the Tokara Strait, JapanCheung Shunyan, Suzuki Koji, Saito Hiroaki, Umezawa Yu, Xia Xiaomin, Liu Hongbin
PLOS ONE
2017年10月23日, 共同, 12, 10, 1932-6203,
DOI(公開)(r-map) Evidence of chronic anthropogenic nutrient within coastal lagoon reefs adjacent to urban and tourism centers, Kenya: A stable isotope approachMwaura Jelvas, Umezawa Yu, Nakamura Takashi, Kamau Joseph
MARINE POLLUTION BULLETIN
2017年06月30日, 共同, 119, 2, 0025-326X,
DOI(公開)(r-map), 74, 86
Spatial dietary shift in bivalves from embayment with river discharge and mariculture activities to outer seagrass beds in northwestern PhilippinesMorimoto Naoko, Umezawa Yu, Diego-McGlone Maria Lourdes San, Watanabe Atsushi, Siringan Fernando P., Tanaka Yoshiyuki, Regino Genevieve L., Miyajima Toshihiro
MARINE BIOLOGY
2017年04月, 共同, 164, 4, 0025-3162,
DOI(公開)(r-map) Variation in oxygen isotope ratio of dissolved orthophosphate induced by uptake process in natural coral holobiontsFerrera Charissa M., Miyajima Toshihiro, Watanabe Atsushi, Umezawa Yu, Morimoto Naoko, Lourdes San Diego-McGlone Maria, Nadaoka Kazuo
CORAL REEFS
2016年06月, 35, 2, 0722-4028,
DOI(公開)(r-map), 655, 668
Phosphorus as a driver of nitrogen limitation and sustained eutrophic conditions in Bolinao and Anda, Philippines, a mariculture-impacted tropical coastal areaFerrera Charissa M., Watanabe Atsushi, Miyajima Toshihiro, San Diego-McGlone Maria Lourdes, Morimoto Naoko, Umezawa Yu, Herrera Eugene, Tsuchiya Takumi, Yoshikai Masaya, Nadaoka Kazuo
MARINE POLLUTION BULLETIN
2016年04月15日, 105, 1, 0025-326X,
DOI(公開)(r-map), 237, 248
大村湾の貧酸素水塊形成期における堆積物微生物群集呼吸の動態
森郁晃・近藤竜二・梅澤有・松岡數充・須崎寛和・中田英昭・和田実
沿岸海洋研究
2015年08月, 87, 95
Potential contribution of microalgal intracellular phosphorus to phosphorus distribution in tidal flat sediments during winter
Yamaguchi Akira, Umezawa Yu, Wada Minoru, Sayama Mikio
PLANKTON & BENTHOS RESEARCH
2015年03月, 10, 1, 1880-8247, 1, 10
Distribution of large benthic foraminifers around a populated reef island: Fongafale Island, Funafuti Atoll, TuvaluFujita Kazuhiko, Nagamine Sakie, Ide Yoichi, Umezawa Yu, Hosono Takashi, Kayanne Hajime, Yamano Hiroya
MARINE MICROPALEONTOLOGY
2014年12月, 113, 0377-8398,
DOI(公開)(r-map), 1, 9
Seasonal shifts in the contributions of the Changjiang River and the Kuroshio Current to nitrate dynamics in the continental shelf of the northern East China Sea based on a nitrate dual isotopic composition approach
Umezawa Y, Yamaguchi, A., Ishizaka, J., Hasegawa, T., Yoshimizu, C., Tayasu, I., Yoshimura, H., Morii, Y., Aoshima, T., and Yamawaki, N.
Biogeosciences
2014年, 11, 1297, 1317
有明海西岸域への地下水由来の栄養塩供給量の評価
塩川麻保, 山口聖, 梅澤有
沿岸海洋研究
2013年02月, 50, 85, 95
Microbial community respiration and structure of dead zone sediments of Omura Bay, JapanWada Minoru, Suzuki Shotaro, Nara Tadashi, Umezawa Yu, Shimanaga Motohiro, Matsuoka Kazumi, Nakata Hideaki
JOURNAL OF OCEANOGRAPHY
2012年12月, 68, 6, 0916-8370,
DOI(公開)(r-map), 857, 867
Groundwater Dynamics of Fongafale Islet, Funafuti Atoll, TuvaluNakada Satoshi, Umezawa Yu, Taniguchi Makoto, Yamano Hiroya
GROUND WATER
2012年07月, 50, 4, 0017-467X,
DOI(公開)(r-map), 639, 644
I-1. Evaluation of nitrogen sources and denitrification activity based on stable isotopesYu Umezawa
Nippon Suisan Gakkaishi (Japanese Edition)
2012年01月01日, 78, 00215392,
DOI(公開)(r-map), 275
Food habits of the farmer damselfish Stegastes nigricans inferred by stomach content, stable isotope, and fatty acid composition analysesHata Hiroki, Umezawa Yu
ECOLOGICAL RESEARCH
2011年07月, 26, 4, 0912-3814,
DOI(公開)(r-map), 809, 818
Decline in heavy metal contamination in marine sediments in Jakarta Bay, Indonesia due to increasing environmental regulationsHosono Takahiro, Su Chih-Chieh, Delinom Robert, Umezawa Yu, Toyota Tomoyo, Kaneko Shinji, Taniguchi Makoto
ESTUARINE COASTAL AND SHELF SCIENCE
2011年04月10日, 92, 2, 0272-7714,
DOI(公開)(r-map), 297, 306
Multiple isotope (H, O, N, S and Sr) approach elucidates complex pollution causes in the shallow groundwaters of the Taipei urban areaHosono Takahiro, Wang Chung-Ho, Umezawa Yu, Nakano Takanori, Onodera Shin-ichi, Nagata Toshi, Yoshimizu Chikage, Tayasu Ichiro, Taniguchi Makoto
JOURNAL OF HYDROLOGY
2011年01月24日, 397, 1-2, 0022-1694,
DOI(公開)(r-map), 23, 36
Human impacts on large benthic foraminifers near a densely populated area of Majuro Atoll, Marshall IslandsOsawa Yoko, Fujita Kazuhiko, Umezawa Yu, Kayanne Hajime, Ide Yoichi, Nagaoka Tatsutoshi, Miyajima Toshihiro, Yamano Hiroya
MARINE POLLUTION BULLETIN
2010年08月, 60, 8, 0025-326X,
DOI(公開)(r-map), 1279, 1287
Application of multi-isotope ratios to study the source and quality of urban groundwater in Metro Manila, PhilippinesHosono Takahiro, Siringan Fernando, Yamanaka Tsutomu, Umezawa Yu, Onodera Shin-ichi, Nakano Takanori, Taniguchi Makoto
APPLIED GEOCHEMISTRY
2010年06月, 25, 6, 0883-2927,
DOI(公開)(r-map), 900, 909
比抵抗法による環礁州島における帯水層の塩水化評価
中田聡史, 山野博哉, 梅澤有, 藤田昌史, 渡邊真砂夫, 谷口真人
日本リモートセンシング学会誌
2010年02月, 30, 317, 330
Investigation of submarine groundwater discharge using several methods in the inter-tidal zone
Ishitobi T., Taniguchi M.,Umezawa Y., Kasahara S., Onodera S., Hayashi M., Miyaoka K., Hayashi M., & Miyake K
IAHS publication
2010年, 312, 60, 67
Investigation of submarine groundwater discharge using several methods in the inter-tidal zone
Ishitobi T., Taniguchi M.,Umezawa Y., Kasahara S., Onodera S., Hayashi M., Miyaoka K., Hayashi M., & Miyake K
IAHS publication
2010年, 312, 60, 67
From Headwaters to the Ocean: Hydrological Changes and Watershed Management - Proceedings of the International Conference on Hydrological Changes and Management from Headwaters to the Ocean, HYDROCHANGE 2008: Preface
Makoto Taniguchi, William C. Burnett, Yoshihiro Fukushima, Martin Haigh, Yu Umezawa
From Headwaters to the Ocean: Hydrological Changes and Watershed Management - Proceedings of the International Conference on Hydrological Changes and Management from Headwaters to the Ocean, HYDROCH
2009年12月01日
Cause of groundwater contamination in Jakarta alluvium volcanic fan deduced by sulfate and strontium isotope ratios.
Hosono T, Delinom R, Onodera S, Umezawa Y, Nakano T, Taniguchi M.
IAHS publication
Sulfate and strontium isotope ratios were analysed in groundwater, river water, and spring water samples in order to examine the groundwater quality under the Jakarta volcanic fan watershed. On the basis of sulfate isotopic comparison with possible source materials, it is suggested that anthropogenic materials such as chemical fertilizers are responsible for the pollution of groundwater. Moreover, strontium isotopic signatures with ions concentrations data clearly suggest that the groundwater nitrate pollution is occurring in an area where aquifer sediments originated from volcanic rocks other than the sedimentary rocks. This study demonstrates the usefulness of sulfate and strontium isotopes in understanding the cause of groundwater deterioration under the Jakarta volcanic fan watershed. Detailed pollution status and deterioration mechanisms with sufficient water samples need to be investigated in future research. Copyright © 2009 IAHS Press.
2009年12月01日, 329, 01447815, 201, 206
Net release of dissolved organic matter by the scleractinian coral Acropora pulchraTanaka Yasuaki, Miyajima Toshihiro, Umezawa Yu, Hayashibara Takeshi, Ogawa Hiroshi, Koike Isao
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY
2009年09月01日, 377, 2, 0022-0981,
DOI(公開)(r-map), 101, 106
Physical and topographic factors affecting suspended particulate matter composition in a shallow tropical estuaryUmezawa Yu, Komatsu Teruhisa, Yamamuro Masumi, Koike Isao
MARINE ENVIRONMENTAL RESEARCH
2009年08月, 68, 2, 0141-1136,
DOI(公開)(r-map), 59, 70
Sources of nitrate and ammonium contamination in groundwater under developing Asian megacities (vol 404, pg 361, 2008)Umezawa Yu, Hosono Takahiro, Onodera Shin-ichi, Siringan Fernando, Buapeng Somkid, Delinom Robert, Yoshimizu Chikage, Tayasu Ichiro, Nagata Toshi, Taniguchi Makoto
SCIENCE OF THE TOTAL ENVIRONMENT
2009年04月15日, 407, 9, 0048-9697,
DOI(公開)(r-map), 3218, 3231
Effects of intensive urbanization on the intrusion of shallow groundwater into deep groundwater: Examples from Bangkok and Jakarta (vol 404, pg 401, 2008)Onodera Shin-ichi, Saito Mitsuyo, Sawano Misa, Hosono Takahiro, Taniguchi Makoto, Shimada Jun, Umezawa Yu, Lubis Rachmat Fajar, Buapeng Somkid, Delinom Robert
SCIENCE OF THE TOTAL ENVIRONMENT
2009年04月15日, 407, 9, 0048-9697,
DOI(公開)(r-map), 3208, 3217
Underground sources of nutrient contamination to surface waters in Bangkok, ThailandBurnett William C., Chanyotha Supitcha, Wattayakorn Gullaya, Taniguchi Makoto, Umezawa Yu, Ishitobi Tomotoshi
SCIENCE OF THE TOTAL ENVIRONMENT
2009年04月15日, 407, 9, 0048-9697,
DOI(公開)(r-map), 3198, 3207
Stable Nitrogen Isotope Composition in Sedimentary Organic Matter as a Potential Proxy of Nitrogen Sources for Primary Producers at a Fringing Coral ReefUmezawa Yu, Miyajima Toshihiro, Koike Isao
JOURNAL OF OCEANOGRAPHY
2008年12月, 64, 6, 0916-8370,
DOI(公開)(r-map), 899, 909
Effects of intensive urbanization on the intrusion of shallow groundwater into deep groundwater: Examples from Bangkok and JakartaOnodera Shin-ichi, Saito Mitsuyo, Sawano Misa, Hosono Takahiro, Taniguchi Makoto, Shimada Jun, Umezawa Yu, Lubis Rachmat Fajar, Buapeng Somkid, Delinom Robert
SCIENCE OF THE TOTAL ENVIRONMENT
2008年10月15日, 404, 2-3, 0048-9697,
DOI(公開)(r-map), 401, 410
Sources of nitrate and ammonium contamination in groundwater under developing Asian megacitiesUmezawa Yu, Hosono Takahiro, Onodera Shin-ichi, Siringan Fernando, Buapeng Somkid, Delinom Robert, Yoshimizu Chikage, Tayasu Ichiro, Nagata Toshi, Taniguchi Makoto
SCIENCE OF THE TOTAL ENVIRONMENT
2008年10月15日, 404, 2-3, 0048-9697,
DOI(公開)(r-map), 361, 376
Specific growth rate as a determinant of the carbon isotope composition of the temperate seagrass Zostera marinaTanaka Yoshiyuki, Miyajima Toshihiro, Yamada Katsumasa, Hori Masakazu, Hasegawa Natsuki, Umezawa Yu, Koike Isao
AQUATIC BOTANY
2008年10月, 89, 3, 0304-3770,
DOI(公開)(r-map), 331, 336
Role of GIS working group - the progress in 2007 and future plan
Umezawa Y.
Progress Report ”Human Impacts on Urban Subsurface Environments”
2008年, 1, 104, 108
Degradation of subsurface environmental in Asian coastal cities
Taniguchi M., Shimada J., Fukuda Y., Onodera S., Yamano M., Yoshikoshi A., Kaneko S., Umezawa Y, Ihitobi T., K.A.B. Jago-on
Proceedings of HydroChange 2008
2008年, 1, 605, 610
Impact of terrestrial nutrients through submarine groundwater discharge (SGD) on macroalgal bloom at fringing reef ecosystem
Umezawa Y, Herzfeld I, Colgrove C, Smith CM
Proceedings of HydroChange 2008
2008年, 1, 619, 624
Characteristics of major ion concentrations in natural water at Southeast Asian mega cities (Seoul, Taipei, Bangkok, Jakarta, and Manila)
Hosono T., Umezawa Y, Onodera S, Wang C-H, Siringan F, Buapeng S, Delinom R, Nakano T, and Taniguchi M.
Proceedings of HydroChange 2008
2008年, 1, 295, 300
Degradation of subsurface environmental in Asian coastal cities
Taniguchi M., Shimada J., Fukuda Y., Onodera S., Yamano M., Yoshikoshi A., Kaneko S., Umezawa Y, Ihitobi T., K.A.B. Jago-on
Proceedings of HydroChange 2008
2008年, 1, 605, 610
Impact of terrestrial nutrients through submarine groundwater discharge (SGD) on macroalgal bloom at fringing reef ecosystem
Umezawa Y, Herzfeld I, Colgrove C, Smith CM
Proceedings of HydroChange 2008
2008年, 1, 619, 624
Characteristics of major ion concentrations in natural water at Southeast Asian mega cities (Seoul, Taipei, Bangkok, Jakarta, and Manila)
Hosono T., Umezawa Y, Onodera S, Wang C-H, Siringan F, Buapeng S, Delinom R, Nakano T, and Taniguchi M.
Proceedings of HydroChange 2008
2008年, 1, 295, 300
Role of GIS working group - the progress in 2007 and future plan
Umezawa Y.
Progress Report ”Human Impacts on Urban Subsurface Environments”
2008年, 1, 104, 108
Degradation of subsurface environmental in Asian coastal cities
Taniguchi M., Shimada J., Fukuda Y., Onodera S., Yamano M., Yoshikoshi A., Kaneko S., Umezawa Y, Ihitobi T., K.A.B. Jago-on
Proceedings of HydroChange 2008
2008年, 1, 605, 610
Impact of terrestrial nutrients through submarine groundwater discharge (SGD) on macroalgal bloom at fringing reef ecosystem
Umezawa Y, Herzfeld I, Colgrove C, Smith CM
Proceedings of HydroChange 2008
2008年, 1, 619, 624
Characteristics of major ion concentrations in natural water at Southeast Asian mega cities (Seoul, Taipei, Bangkok, Jakarta, and Manila)
Hosono T., Umezawa Y, Onodera S, Wang C-H, Siringan F, Buapeng S, Delinom R, Nakano T, and Taniguchi M.
Proceedings of HydroChange 2008
2008年, 1, 295, 300
Degradation of subsurface environmental in Asian coastal cities
Taniguchi M., Shimada J., Fukuda Y., Onodera S., Yamano M., Yoshikoshi A., Kaneko S., Umezawa Y, Ihitobi T., K.A.B. Jago-on
Proceedings of HydroChange 2008
2008年, 1, 605, 610
Impact of terrestrial nutrients through submarine groundwater discharge (SGD) on macroalgal bloom at fringing reef ecosystem
Umezawa Y, Herzfeld I, Colgrove C, Smith CM
Proceedings of HydroChange 2008
2008年, 1, 619, 624
Characteristics of major ion concentrations in natural water at Southeast Asian mega cities (Seoul, Taipei, Bangkok, Jakarta, and Manila)
Hosono T., Umezawa Y, Onodera S, Wang C-H, Siringan F, Buapeng S, Delinom R, Nakano T, and Taniguchi M.
Proceedings of HydroChange 2008
2008年, 1, 295, 300
Evaluation of fresh groundwater contributions to the nutrient dynamics at shallow subtidal areas adjacent to Metro-Bangkok
Yu Umezawa, Tomotoshi Ishitobi, Sompop Rungsupa, Sinichi Onodera, Tsutomu Yamanaka, Chikage Yosimizu, Chikage Yosimizu, Ichiro Tayasu, Toshi Nagata, Gullaya Wattayakorn, Gullaya Wattayakorn, Makoto Taniguchi
IAHS-AISH Publication
Both submarine groundwater discharge (SGD) and the Chao Phraya River are major agents of nutrient supply into the Gulf of Thailand. With the development of the city of Bangkok, however, lowered groundwater levels due to over-pumping suggests a decrease of the fresh groundwater flux into the sea. In this study, time-series resistivity monitoring under the seabed adjacent to Bangkok city did not actually show any evidence of fresh groundwater fluxes, and σD and σ18O signatures in porewater also followed this phenomenon. Consequently, the observed upward water flux can be mainly attributed to recirculation of the overlying water. σ15N and σ18O values in nitrate suggested that nitrate was mainly supplied via the river, and rapidly reduced in the surface suboxic sediment, while re-mineralized ammonium and phosphate were substantially released into the overlying water. River water-derived nutrient could be still important as original sources of organic matter, even at the area where high amounts of SGD is observed. Copyright © 2007 IAHS Press.
2007年12月01日, 01447815, 169, 179
Variation in internal delta N-15 and delta C-13 distributions and their bulk values in the brown macroalga Padina australis growing in subtropical oligotrophic watersUmezawa Yu, Miyajima Toshihiro, Tanaka Yasuaki, Koike Isao
JOURNAL OF PHYCOLOGY
2007年06月, 43, 3, 0022-3646,
DOI(公開)(r-map), 437, 448
Distribution and partitioning of nitrogen and phosphorus in a fringing reef lagoon of Ishigaki Island, northwestern PacificMiyajima Toshihiro, Hata Hiroshi, Umezawa Yu, Kayanne Hajime, Koike Isao
MARINE ECOLOGY PROGRESS SERIES
2007年, 341, 0171-8630,
DOI(公開)(r-map), 45, 57
Fresh groundwater contributions to the nutrient dynamics at shallow subtidal areas adjacent to a mega city, Bangkok.
Umezawa Y., T. Ishitobi, S. Rungsupa, S. Onodera, T. Yamanaka, C. Yoshimizu, I. Tayasu, T. Nagata and M. Taniguchi Y
IAHS publication
2007年, 312, 169, 179
Fresh groundwater contributions to the nutrient dynamics at shallow subtidal areas adjacent to a mega city, Bangkok.
Umezawa Y., T. Ishitobi, S. Rungsupa, S. Onodera, T. Yamanaka, C. Yoshimizu, I. Tayasu, T. Nagata and M. Taniguchi Y
IAHS publication
2007年, 312, 169, 179
Temporal variability of stable carbon and nitrogen isotopic composition of size-fractionated particulate organic matter in the hypertrophic Sumida River Estuary of Tokyo Bay
Sato T., T. Miyajima*, H. Ogawa, Umezawa Y, I. Koike
Estuarine Coastal and Shelf Science
2006年12月, 68, 245, 258
Effects of nitrate enrichment on release of dissolved organic carbon and nitrogen from zooxanthellate coral, Acropora pulchra and Porites cylindrica.
Tanaka Y., T. Miyajima, Y. Umezawa, H. Fukuda, I. Koike, H. Ogawa and T. Hayashibara
Proceedings of 10th International Coral Reef Symposium
2006年, 925, 931
Effects of nitrate enrichment on release of dissolved organic carbon and nitrogen from zooxanthellate coral, Acropora pulchra and Porites cylindrica.
Tanaka Y., T. Miyajima, Y. Umezawa, H. Fukuda, I. Koike, H. Ogawa and T. Hayashibara
Proceedings of 10th International Coral Reef Symposium
2006年, 925, 931
Nutrients dynamics at seagrass beds in tropical and subtropical ecosystems
Koike I. and Y. Umezawa
Monthly Kaiyo
2005年, 37, 139, 147
海草藻場生態系における物質循環-特に熱帯域に注目して-
小池勲夫、梅澤有
月刊海洋
2005年, 37, 139, 147
Water flow and sediment in Enhalus acoroides and other seagrass beds in the Andaman Sea, off Khao Bae Na, Thailand.
Komatsu T., Umezawa Y, M.Nakaoka, C.Supanwanid and Z.Kanamoto
Coastal Marine Science
2004年08月, 29, 63, 68
Internal variation of nutrients and C stable isotope ratios in the leaves of the seagrass Enhalus acoroides (L.f) Royle.
Yamamuro M., Umezawa Y and I. Koike
Aquatic Botany
2004年07月, 21, 95, 102
Significance of groundwater nitrogen discharge into coral reefs at Ishigaki Island, southwest of Japan
Umezawa Y., T.Miyajima, I. Koike and H. Kayanne
Coral Reefs
2002年12月, 21, 346, 356
Fine scale mapping of land-derived nitrogen in coral reefs, by d15N values in macroalgae.
Umezawa Y., T.Miyajima, M.Yamamuro, H. Kayanne and I. Koike
Limnology and Oceanography
2002年10月, 47, 1405, 1416
Cycling of phosphorus maintains the production of microphytobenthic communities in carbonate sediments of a coral reef.
Suzumura M., T.Miyajima, H.Hata, Y. Umezawa and H.Kayanne, I. Koike
Limnology and Oceanography
2002年08月, 47, 771, 781
Seasonality in nutrient concentrations and stable isotope ratios of Halophila ovalis growing on the intertidal flat of SW Thailand
Yamamuro M., Y. Umezawa and I. Koike
Limnology
2001年11月, 2, 199, 205
Microbiological nitrogen transformation in carbonate sediments of a coral-reef lagoon and associated seagrass beds
Miyajima T., M. Suzumura, Y. Umezawa and I. Koike
Marine Ecology Progress Series
2001年05月, 21, 273, 286
Analysis of influential area of land-derived nitrogen in tropic and subtropic area.-usefulness of 15N values in macroalgae-
Umezawa Y., T.Miyajima, M.Yamamuro, H.Kayanne, I.Koike
Monthly Kaiyo
2001年, 33, 472, 476
熱帯・亜熱帯沿岸域における陸源窒素影響域の解析-底生大型藻類のd15Nの利用梅澤 有, 宮島利宏, 山室真澄, 茅根創, 小池 勲夫
月刊海洋
2001年, (MISC)総説・解説(学術雑誌), 33,
DOI(公開)(r-map), 472, 476