Masahiro Suzumura - Academia.edu (original) (raw)

Papers by Masahiro Suzumura

Marine Chemistry, 2001

... Direct measurement of phospholipid-P has been accomplished using: (1) planar TLC with colorim... more ... Direct measurement of phospholipid-P has been accomplished using: (1) planar TLC with colorimetric detection and densitometric quantification (Gustavsson, 1986); (2) high-performance liquid chromatography (HPLC) with total P analysis (Kaitaranta and Bessman, 1981). ...

Oceanography in Japan, 2003

Journal of Oceanography, 2016

Marine Pollution Bulletin, Sep 30, 2004

Bulk suspended particulate matter (SPM), chlorophyll a (Chl a), ignition loss, particulate organi... more Bulk suspended particulate matter (SPM), chlorophyll a (Chl a), ignition loss, particulate organic carbon (POC), organic nitrogen, inorganic phosphorus (PIP), and organic phosphorus were investigated in the heavily eutrophic Arakawa River estuary, Japan. Chl a was high (approximately 35 microg l(-1)) in summer and low (approximately 6.7 microg l(-1)) in winter and autumn. POC from living phytoplankton accounted for approximately 34% and approximately 70% of total POC during low- and high-biomass seasons, respectively. During the low-biomass season, detrital POC distribution was conservative, and less reactive, land-derived materials mainly composed particulate organic materials (POM), but complex mixing of land-derived POM and autochthonous planktonic detritus caused nonconservative detrital POC behavior during the high-biomass season. PIP concentration in SPM decreased with increasing salinity, likely by desorption of soluble orthophosphate (ortho-P). The ortho-P released from SPM, 56% of the ortho-P input from the Arakawa River to the bay, was a significant potential source of biologically available phosphorus causing eutrophication of coastal environments.

Agu Fall Meeting Abstracts, Dec 1, 2010

Phosphorus is an essential nutrient for marine organisms. In oligotrophic environments, concentra... more Phosphorus is an essential nutrient for marine organisms. In oligotrophic environments, concentrations of dissolved inorganic phosphate (SRP), the most bioavailable form of phosphorus, are low and have been hypothesized to constrain the primary productivity. Evidence has been found that dissolved organic phosphorus (DOP) supports a significant fraction of primary production through hydrolytic remineralization of DOP to SRP by alkaline phosphatase (APA). In this study, DOP biogeochemistry was investigated at three locations of the open-ocean environment in the Kuroshio region and at a semi-eutrophic coastal site of the western North Pacific. Concentrations of SRP, DOP and hydrolyzable ester-P were measured in the euphotic zone. Kinetic parameters of APA were determined using a fluorogenic substrate, including potential maximum velocity (Vmax), apparent Michaelis-Menten half-saturation constant (Km), and turnover time (TA) of APA hydrolyzable DOP. SRP concentrations were quite low (≤ 10 nM) in the surface seawater and rapidly increased below the chlorophyll a maximum layer (CML). DOP concentration ranged from 29 to 223 nM. Above the CML, DOP composed a major fraction accounting for 60-100% of dissolved total P. A significant linear relationship was found between the concentrations of SRP and hydrolyzable ester-P (R2 = 0.83, P < 0.01). This suggests active utilization of ester-P under phosphate-depleted conditions. In the Kuroshio region, Vmax of APA exhibited the highest value at the surface water (0 m) and decreased rapidly with depth, while at the coastal site the peak value was found at CML. TA of hydrolyzable DOP was quite variable among the locations and increased with depth especially below CML. The estimated values of in situ hydrolysis rate were much lower (2-34%) than the potential Vmax which was determined with the addition of an excess amount of the substrate. The results suggest that marine microbes can efficiently and rapidly utilize hydrolyzable DOP under phosphate-depleted conditions and that there is still room in the in situ APA activity. Utilization of DOP, however, is likely regulated by the ambient concentrations of hydrolyzable ester-P lower than the apparent Km.

Marine Ecology Progress Series, 2001

Journal of Oceanography, Mar 25, 2010

We have investigated the effects of seawater acidification on the activities of leucine aminopept... more We have investigated the effects of seawater acidification on the activities of leucine aminopeptidase (LAPase), β-glucosidase (BGase), phosphatase (P-ase), α-glucosidase (AGase), and lipase (L-ase), which are important promoters of degradation of marine organic matter, including proteins, carbohydrates, organic phosphorus compounds, and lipids. Seawater samples were collected from a eutrophic coastal area, from Tokyo Bay, and from oligotrophic pelagic waters outside

Biogeochemistry, 2003

The chemical compositions of ground water and organic matter in sediments were investigated at a ... more The chemical compositions of ground water and organic matter in sediments were investigated at a sandy shore of Tokyo Bay, Japan to determine the fate of ground water NO 3 − . On the basis of Cl − distribution in ground water, the beach was classified into freshwater (FR)-, transition (TR)-, and seawater (SW)-zones from the land toward the shoreline. The NO 3 − and N 2 O did not behave conservatively with respect to Cl − during subsurface mixing of freshwater and seawater, suggesting NO 3 − consumption and N 2 O production in the TR-zone. Absence of beach vegetation indicated that NO 3 − assimilation by higher plants was not as important as NO 3 − sink. Low NH 4 + concentrations in ground water revealed little reduction of NO 3 − to NH 4 + . These facts implied that microbial denitrification and assimilation were the likely sinks for ground water NO 3 − . The potential activity and number of denitrifiers in water-saturated sediment were highest in the low-chlorinity part of the TR-zone. The location of the highest potential denitrification activity (DN-zone) overlapped with that of the highest NO 3 − concentration. The C/N ratio and carbon isotope ratio (␦ 13 C) of organic matter in sediment (< 100 -m) varied from 12.0 to 22.5 and from −22.5 to −25.5‰, respectively. The ␦ 13 C value was inversely related to the C/N ratio (r 2 = 0.968, n = 11), which was explained by the mixing of organic matters of terrestrial and marine origins. In the DN-zone, the fine sediments were rich in organic matters with high C/N ratios and low ␦ 13 C values, implying that dissolved organic matters of terrestrial origin might have been immobilized under slightly saline conditions. A concurrent supply of NO 3 − and organic matter to the TRzone by ground water discharge probably generates favorable conditions for denitrifiers. Ground water NO 3 − discharged to the beach is thus partially denitrified and fixed as microbial biomass before it enters the sea. Further studies are necessary to determine the relative contribution of these processes for NO 3 − removal.

J Oceanogr, 2010

ABSTRACT We investigated the effects of seawater acidification induced by ocean CO2 sequestration... more ABSTRACT We investigated the effects of seawater acidification induced by ocean CO2 sequestration on bathypelagic prokaryotes. We simulated acidification conditions by bubbling high-CO2 air or adding chemical buffer solutions to seawater samples in order to examine changes in total cell counts, heterotrophic production rate, direct viable cell count, and relative abundance of Bacteria and Archaea. Considerable suppression of prokaryotic activities was observed at pH 7.0 or lower, especially in samples enriched with organic matter. The relative abundance of Archaea increased with increasing CO2 concentration. We found that seawater acidification can potentially alter heterotrophic activities and community structure of bathypelagic prokaryotes. KeywordsOcean CO2 -sequestration-seawater acidification-prokaryotes- Bacteria - Archaea

Geochimica Et Cosmochimica Acta, May 1, 1993

Inositol hexaphosphate (IP 6) was isolated from Tokyo Bay sediments and studied by a combined tec... more Inositol hexaphosphate (IP 6) was isolated from Tokyo Bay sediments and studied by a combined technique of hypobromite oxidation, anion-exchange chromatography. 1H nuclear magnetic resonance, and gas chromatography. The concentrations of IP 6 in surface sediments (0-2.5 cm) range from 0.06 to 0.20 μmol · P/g, and average 0.12 μmol · P/g, a small portion of the total organic phosphorus (<2.2%). Three types of IP 6 isomers were identified: myo-≫ scyllo-> chiro-IP 6 in order of their abundance, similar to that reported for soils. It was confirmed by laboratory experiments that IP 6 is susceptible to biological degradation and disappears quickly before and during burial under marine conditions. This result strongly supports the low concentrations of IP 6 observed in Tokyo Bay sediments and suggests that IP 6 is not a significant component of refractory organic-P in marine sediments.

Journal of Japan Society on Water Environment

Ecological Engineering, 2015

Limnology and Oceanography, 1995

In order to clarify the origin and the fate of inositol hcxaphosphate (IP,) in coastal sediments ... more In order to clarify the origin and the fate of inositol hcxaphosphate (IP,) in coastal sediments from Tokyo Bay, we determined IP, in several potential source materials, such as plankton, soil, riverine, and estuarine samples. IP, was not found in zoo-and phytoplankton samples, thus eliminating these as a source to the sediments. Soils collected from the catchment areas of major rivers flowing into the bay contained high concentrations of IP6 (0.25-5.65 pmol P g-l). Samples of suspended solids and estuarine sediments from the rivers also had significant amounts of IP,. The distribution pattern of IP, in Tokyo Bay sediments exhibited relatively high concentrations in the estuarine areas, decreasing gradually toward the mouth of the bay. The IP, in coastal sediments was composed of three isomers in the same order of abundance as those found in the terrestrial and riverine samples: myo-B scyllo-> chiro-. From these results, IP, in Tokyo Bay sediments was ascribed to soils transported by rivers from land into the bay. The IP6 concentration ranged from 0.0 1 to 0.10 pm01 P g I in surface sediments (O-2.5 cm), accounting for < 1.2% of the total organic P; it was completely decomposed in the subsurface. Consequently, this compound is quite ephemeral in coastal marine environments.

Energy Procedia, 2014

Among in-situ microbes within depleted oil-gas reservoir, there are special species those produce... more Among in-situ microbes within depleted oil-gas reservoir, there are special species those produce much more methane gas in CO 2 rich environment than in CO 2 poor environment. CO 2 acts as a catalyst in the reaction. If we maintain preferable conditions for methanogenesis archaea during geological CCS, we will be able to abate greenhouse gas emission and produce natural gas as one of natural energy resources at the same time. We named the technological concept as 'Bio-CCS'. In Bio-CCS, CO 2 will be injected from a well for two purposes: to abate greenhouse gas emission and to cultivate methanogenic geo-microbes. CH 4 gas will be produced later using other wells. The procedure is similar to the Enhanced Oil/Gas Recovery (EOR/EGR) operation, but in Bio-CCS, the target is generation and production of methane out of depleted oil/gas reservoir during CO 2 abatement. We are evaluating the basic practicability of Bio-CCS that cultivate methanogenic geo-microbes within depleted oil/gas reservoirs for geological CCS, and produce methane gas as fuel resources on the course of CO 2 abatement for GHG control. While biologists are identifying the most effective cultivating conditions for methanogenic archaea, geologists, environmental scientists and system scientists are evaluating feasibilities of the technology concept. In this paper, we will introduce methodologies and interim results of our feasibility study on Bio-CCS.

To understand how the dissolution rate of calcium carbonate changes, laboratory experiments were ... more To understand how the dissolution rate of calcium carbonate changes, laboratory experiments were conducted under high pressure and high pCO2 condition. As a result, rapid dissolution was observed at above 5000 ppm of pCO2. The initial dissolution rates of the well correlated with initial concentration of dissolved inorganic carbon. Dissolution rate were generally decreased with time. Dissolution of calcium carbonate increased dissolved inorganic carbon and total alkalinity in the seawater. Then, degrees of undersaturation and dissolution rate of calcite in the seawater were decreased with time. Dissolution rates normalized with apparent surface area were well fit to the rate law in the empirical kinetic showed in previous studies. Using the function of dissolution rate of calcite, we constructed 3-D map of Omega and dissolution rate of calcite in the western North Pacific.

The ocean sequestration of carbon dioxide (CO2), direct injection of CO2 into bathypelagic layers... more The ocean sequestration of carbon dioxide (CO2), direct injection of CO2 into bathypelagic layers, is one of the climate change mitigation options. It is essential to assess the potential environmental impacts on the marine ecosystem. In bathypelagic layers, bacteria are dominant organisms and play significant roles in oceanic carbon cycling through utilization and transformation of organic matter. We performed laboratory experiments by acidifying bathypelagic seawater with CO2 gas or buffer solutions to examine the impact on bacterial activities (abundance, production rate, and proportion of viable cells). In the laboratory experiments, we observed some potential effects by artificial changes in CO2 concentration, pH, or both, on bacterial activities. It was suggested that trophic conditions of bacterial assemblage strongly influence the magnitude of the impacts on bacterial activities and metabolisms by CO2 sequestration.

Ocean CO2 storage that actively utilizes the ocean potential to dissolve extremely large amounts ... more Ocean CO2 storage that actively utilizes the ocean potential to dissolve extremely large amounts of CO2 is a useful option with the intent of diminishing atmospheric CO2 concentration. CO2 storage into sub-seabed geological formations is also considered as the option which has been already put to practical reconnaissance in some projects. Direct release of CO2 in the ocean storage and potential CO2 leakage from geological formations into the bottom water can alter carbonate system as well as pH of seawater. It is essential to examine to what direction and extent chemistry change of seawater induced by CO2 can affect the marine environments. Previous studies have shown direct and acute effects by increasing CO2 concentrations on physiology of marine organisms. It is also a serious concern that chemistry change can affect the rates of chemical, biochemical and microbial processes in seawater resulting in significant influences on marine biogeochemical cycles of the bioelements includi...