研究者詳細 - 藤村　弘行

論文 - 藤村　弘行

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Bacterial enhancement of bleaching and physiological impacts on the coral Montipora digitata

Higuchi T, Agostini A, Casareto BE, Yoshinaga K, Suzuk T, Nakano Y, Fujimura H and Suzuki Y

Journal of Experimental Marine Biology and Ecology ( その他の出版社 ) 440 54 - 60 2013年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Multiple effects of hydrogen peroxide and temperature on antioxidants and bleaching

Higuchi,T, Suzuki,Y, Fujimura H

Proceedings of the 12th International Coral Reef Symposium 4C_3 2012年06月 [ 査読有り ]

掲載種別: 研究論文（国際会議プロシーディングス）

Biological and Chemical Characteristics of the Coral Gastric Cavity

Agostini S, Suzuki Y, Higuchi T, Casareto BE, Yoshinaga K, Nakano Y and Fujimura H

Coral Reefs ( International Coral Reef Society ) 31 ( 1 ) 147 - 156 2012年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

All corals have a common structure: two tissue layers enclose a lumen, which forms the gastric cavity. Few studies have described the processes occurring inside the gastric cavity and its chemical and biological characteristics. Here, we show that the coral gastric cavity has distinct chemical characteristics with respect to dissolved O-2, pH, alkalinity, and nutrients (vitamin B-12, nitrate, nitrite, ammonium, and phosphate) and also harbors a distinct bacterial community. From these results, the gastric cavity can be described as a semi-closed sub-environment within the coral. Dissolved O-2 shows very low constant concentrations in the deepest parts of the cavity, creating a compartmentalized, anoxic environment. The pH is lower in the cavity than in the surrounding water and, like alkalinity, shows day/night variations different from those of the surrounding water. Nutrient concentrations in the cavity are greater than the concentrations found in reef waters, especially for phosphate and vitamin B-12. The source of these nutrients may be internal production by symbiotic bacteria and/or the remineralization of organic matter ingested or produced by the corals. The importance of the bacteria inhabiting the gastric cavity is supported by the finding of a high bacterial abundance and a specific bacterial community with affiliation to bacteria found in other corals and in the guts of other organisms. The findings presented here open a new area of research that may help us to understand the processes that maintain coral health.

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Distribution and Potential Effects of Novel Antifouling Herbicide Diuron on Coral Reefs

Sheikh MA, Oomori T, Fujimura H, Higuchi T, Imo T, Akamatsu A, Miyagi T, Yokota T, Yasumura S

■■■ 2012年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Extracellular matrix protein in calcified endoskeleton: a potential additive for crystal growth and design

Rahman MA, Fujimura H, Shinjo R and Oomori T

Journal of Crystal Growth ( その他の出版社 ) 324 ( 1 ) 177 - 183 2011年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

In this study, we demonstrate a key function of extracellular matrix proteins (ECMPs) on seed crystals, which are isolated from calcified endoskeletons of soft coral and contain only CaCO3 without any living cells. This is the first report that an ECMP protein extracted from a marine organism could potentially influence in modifying the surface of a substrate for designing materials via crystallization. We previously studied with the ECMPs from a different type of soft coral (Sinularia polydactyla) without introducing any seed crystals in the process, which showed different results. Thus, crystallization on the seed in the presence of ECMPs of present species is an important first step toward linking function to individual proteins from soft coral. For understanding this interesting phenomenon, in vitro crystallization was initiated in a supersaturated solution on seed particles of calcite (I 0 4) with and without ECMPs. No change in the crystal growth shape occurred without ECMPs present during the crystallization process. However, with ECMPs, the morphology and phase of the crystals in the crystallization process changed dramatically. Upon completion of crystallization with ECMPs, an attractive crystal morphology was found. Scanning electron microscopy (SEM) was utilized to observe the crystal morphologies on the seeds surface. The mineral phases of crystals nucleated by ECMPs on the seeds surface were examined by Raman spectroscopy. Although 50 mM Mg2+ is influential in making aragonite in the crystallization process, the ECMPs significantly made calcite crystals even when 50 mM Mg2+ was present in the process. Crystallization with the ECMP additive seems to be a technically attractive strategy to generate assembled micro crystals that could be used in crystals growth and design in the Pharmaceutical and biotechnology industries. (C) 2011 Elsevier B.V. All rights reserved.

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Seawater temperature proxies based on DSr, DMg, and DU from culture experiments using the branching coral Porites cylindrica

Armid A, Asami R, Fahmiati T, Sheikh, MA, Fujimura H, Higuchi T, Taira E, Shinjo R and Oomori T

Geochimica et Cosmochimica Acta ( その他の出版社 ) 75 ( 15 ) 4273 - 4285 2011年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

In order to investigate the incorporation of Sr, Mg, and U into coral skeletons and its temperature dependency, we performed a culture experiment in which specimens of the branching coral (Porites cylindrica) were grown for 1 month at three seawater temperatures (22, 26, and 30 degrees C). The results of this study showed that the linear extension rate of P. cylindrica has little effect on the skeletal Sr/Ca, Mg/Ca, and U/Ca ratios. The following temperature equations were derived: Sr/Ca (mmol/mol) = 10.214(+/- 0.229) 0.0642(+/- 0.00897) x T (degrees C) (r(2) = 0.59, p < 0.05); Mg/Ca (mmol/mol) = 1.973(+/- 0.302) + 0.1002 (+/- 0.0118) x T (degrees C) (r(2) = 0.67, p < 0.05); and U/Ca (mu mol/mol) = 1.488(+/- 0.0484) - 0.0212(+/- 0.00189) x T (degrees C) (r(2) = 0.78, p < 0.05). We calculated the distribution coefficient (D) of Sr, Mg, and U relative to seawater temperature and compared the results with previous data from massive Porites corals. The seawater temperature proxies based on D calibrations of P. cylindrica established in this study are generally similar to those for massive Porites corals, despite a difference in the slope of D-U calibration. The calibration sensitivity of D-Sr, D-Mg, and D-U to seawater temperature change during the experiment was 0.64%/degrees C, 1.93%/degrees C, and 1.97%/degrees C, respectively. These results suggest that the skeletal Sr/Ca ratio (and possibly the Mg/Ca and/or U/Ca ratio) of the branching coral P. cylindrica can be used as a potential paleothermometer. (C) 2011 Elsevier Ltd. All rights reserved.

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CNP budgets of a coral-dominated fringing reef at La Re´union, France: coupling of oceanic phosphate and groundwater nitrate

Cuet P, Atkinson MJ, Blanchot J, Casareto BE, Cordier E, Falter J, Frouin P, Fujimura H, Pierret C, Susuki Y and Tourrand C

Coral Reefs ( International Coral Reef Society ) 30 ( S.I. Suppl.1 ) 45 - 55 2011年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Productivity, nutrient input, nutrient uptake, and release rates were determined for a coral-dominated reef flat at La R,union, France, to assess the influence of groundwater nitrogen on carbon and nutrient budgets. Water samples were collected offshore in the ocean, at the reef crest and back reef for nutrients, picoplankton, pH, and total alkalinity. Volume transport of ocean water across the reef flat was measured using both current meters and drogues. Groundwater advected onto the reef flat and mixed with incoming ocean water. Metabolic rates for the reef community were determined to be: gross primary production = 1,000 mmol C m(-2) d(-1), community respiration = 960 mmol C m(-2) d(-1), and community calcification = 210 mmol C m(-2) d(-1). Across the reef flat, silicate behaved conservatively, there was net uptake of phosphate (0.06 mmol P m(-2) d(-1)) and net release of nitrate, ammonia, dissolved and particulate organic nitrogen (total 7.0 mmol N m(-2) d(-1)). Groundwater nitrate contributed 37% of the increase in nitrate plus ammonia. The first-order mass transfer coefficient of phosphate was 3.3 m d(-1), and for nitrate plus ammonia, 5.9 m d(-1). Gross N and P uptake from estimates of mass transfer and uptake of particles were 0.37 mmol P m(-2) d(-1) and 7.2 mmol N m(-2) d(-1), respectively giving an N:P uptake ratio of 20:1. Thus, the elevation of nitrogen across the reef flat maintains a high N:P flux, enhancing algal growth downstream of the transect. We conclude that net community production (40 mmol C m(-2) d(-1)) was sustained by net uptake of phosphate from the ocean and net uptake of new nitrogen from groundwater.

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Photochemical Formation of Hydroxyl Radicals in Tissue Extracts of the Coral Galaxea fascicularis

Higuchi T, Fujimura H, Hitomi Y, Arakaki T, Oomori T and Suzuki Y

Photochemistry and Photobiology ( その他の出版社 ) 86 ( 6 ) 1421 - 1426 2010年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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サンゴ礁での石灰化と陸域の風化作用による島喚系の二酸化炭素収支

津留見　遼太,小林　秀星,樋口　富彦,大森　保,タカギ　キンバリー K.,新垣　誠司,土屋, 誠,

COE報告書（平成20年度） ( 琉球大学21世紀COEプログラム ) 2009年04月

掲載種別: 研究論文（その他学術会議資料等）

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Effects of carbon dioxide on the coccolithophorid Pleurochrysis carterae in incubation experiments

Casareto BE, Niraula MP, Fujimura H and Suzuki Y

Aquatic Biology ( その他の出版社 ) 7 ( 1-2 ) 59 - 70 2009年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Production (abundance and biomass) and net calcification rates of the coccolithophorid Pleurochrysis carterae under different partial pressures of CO2 (pCO(2)) were examined using short (15, 24 and 39 h), long (7 d) and dark (7 d) incubation experiments. Short incubations were conducted at ambient, 500 and 820 ppm pCO(2) levels in natural seawater that was enriched with nutrients and inoculated with P. carterae. Long incubations were conducted at ambient and 1200 ppm pCO(2) levels in natural seawater (0.2 mu m filtered as well as unfiltered) that was enriched with nutrients and inoculated with P. carterae. Dark incubations were conducted at ambient and 1200 ppm pCO(2) in unfiltered seawater that was inoculated with P. carterae. The abundance and biomass of coccolithophorids increased with pCO(2) and time. The abundance and biomass of most noncalcifying phytoplankton also increased, and were hardly affected by CO2 inputs. Net calcification rates were negative in short incubations during the pre-bloom phase regardless of pCO(2) levels, indicating dissolution of calcium carbonate. Further, the negative values of net calcification in short incubations became less negative with time. Net calcification rates were positive in long incubations during blooms regardless of pCO(2) level, and the rate of calcification increased with pCO(2). Our results show that P. carterae may adapt to increased (similar to 1200 ppm) pCO(2) level with time, and such increase has little effect on the ecology of noncalcifying groups and hence in ecosystem dynamics. In dark incubations, net calcification rates were negative, with the magnitude being dependent on pCO(2) levels.