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Tanaka S.,Kansai Electric Power Co. | Ikeda K.,The General Environmental Technos Co. | Ikeda K.,Okayama Institute of Science and Technology | Miyasaka H.,Kansai Electric Power Co. | And 7 more authors.
Journal of Bioscience and Bioengineering | Year: 2011

Methyl viologen (MV) causes severe oxidative stress by generating superoxide in the photosystem. The marine Chlamydomonas strain W80 is highly tolerant to MV (inhibitory concentration 50% [IC 50]=110μM), and another marine Chlamydomonas strain HS5 shows also relatively a high tolerance (IC 50=12μM). These two marine strains and a freshwater Chlamydomonas reinhardtii, which is highly sensitive to MV (IC 50=0.03μM), were compared with respect to their reactive oxygen species (ROS) eliminating enzymes (superoxide dismutase, catalase, glutathione peroxidase, and ascorbate peroxidase), intracellular free amino acids, and antioxidant activities of the cell extracts. The marked difference between the marine Chlamydomonas strains and C. reinhardtii is the much higher (more than 5 fold) ascorbate peroxidase (APX) activity in the marine strains. The marine strains also kept the high APX activities (more than 100% of non-stressed condition) under the MV stressed condition, while the APX activity in C. reinhardtii was significantly decreased (36% of non-stressed condition) under the stressed condition, indicating that APX activity potentially contributes to the oxidative stress tolerance in Chlamydomonas. In addition, the levels of intracellular free proline, which is supposed to ameliorate oxidative stress, were several tens of times higher in the marine Chlamydomonas strains than in C. reinhardtii. © 2011 The Society for Biotechnology, Japan. Source


Shigemitsu M.,Hokkaido University | Yamanaka Y.,Hokkaido University | Yamanaka Y.,Japan Science and Technology Agency | Watanabe Y.W.,Hokkaido University | And 2 more authors.
Earth and Planetary Science Letters | Year: 2010

We used moored time-series sediment traps to collect settling particles at station KNOT (44°N, 155°E; trap depth 770m) in the western subarctic Pacific (WSAP) from October 1999 to May 2006. Particulate nitrogen content (PN) and isotope ratios (δ15NPN) were measured in the samples collected. The general pattern of variation in δ15NPN results showed lower values during the spring bloom periods and summer, and higher values during winter. To interpret the processes controlling such variations quantitatively and reveal some implications for paleoceanographic use of δ15NPN, we developed an ecosystem model that included nitrogen isotopes. This model was validated with an observed data set and successfully reproduced the seasonal variations of δ15NPN. In simulations, the lower δ15NPN during the spring bloom period was caused mainly by the highest proportion of dead large phytoplankton (diatom) in PN within a year, the highest f-ratio of the year, and phytoplankton assimilation of nitrate with the lowest δ15N of the year. The lower δ15NPN in summer was due to the high relative proportion of dead non-diatom small phytoplankton and microzooplankton fecal pellet with the lowest δ15N values among all the PN components in our model. The higher δ15NPN in winter was mainly caused by the highest proportion of zooplankton components in PN, with higher δ15N values than phytoplankton components, and the enhanced δ15N values of ammonium induced by nitrification and its subsequent assimilation by phytoplankton. Our identification of nitrification as one cause of higher δ15NPN in winter is consistent with previous findings in a proximal marginal sea, the Okhotsk Sea, with an ecosystem model simpler than our model. This might indicate that the cause of higher δ15NPN in winter is common in the WSAP. In our model, we optimized the isotope effect of each process using our observational data of δ15NPN and δ15N of nitrate published elsewhere as constraints, and investigated the sensitivity of the annual flux-weighted mean of δ15NPN to the isotopic fractionation effects. As a result, we found that the isotope effects of nitrate assimilation appear to be different for non-diatom small phytoplankton and large diatom, and the annual flux-weighted mean of δ15NPN can be influenced to some extent by the isotope effect of nitrification. © 2010 Elsevier B.V. Source


Okuhata H.,Kansai Electric Power Co. | Ikeda K.,The General Environmental Technos Co. | Miyasaka H.,Kansai Electric Power Co. | Takahashi S.,Japan Institute for Environmental Sciences | And 4 more authors.
Journal of Bioscience and Bioengineering | Year: 2010

The removal of bisphenol A, an endocrine disruptor, by 25 different kinds of Salvia cultivars was examined with hydroculture experiments. All the Salvia cultivars showed a high BPA-eliminating ability, and 100% to 74% of BPA (50 μM) was eliminated after 3 days. © 2010. Source


Kita J.,Japan Research Institute of Innovative Technology for the Earth | Stahl H.,Scottish Association for Marine Science | Hayashi M.,The General Environmental Technos Co. | Green T.,Scottish Association for Marine Science | And 2 more authors.
International Journal of Greenhouse Gas Control | Year: 2015

In 2012, a controlled sub-seabed release of carbon dioxide (CO2) was conducted in Ardmucknish Bay, a shallow (12m) coastal bay on the west coast of Scotland. During the experiment, CO2 gas was released 12m below the seabed for 37 days, causing significant disruption to sediment and water carbonate chemistry as the gas passed up through the sediment and into the overlying water. One of the aims of the study was to investigate how the impacts caused by leakage from geological CO2 Capture and Storage (CCS) could be detected and quantified in the context of natural heterogeneity and dynamics. To do this underwater photography was used to analyze (i) the benthic megafaunal response to the CO2 release and (ii) the dynamics of the CO2 bubble streams, emerging from the seabed into the overlying water column. The frequently observed megafauna species in the study area were Virgularia mirabilis (Cnidaria), Turritella communis (Mollusca), Asterias rubens (Echinodermata), Pagurus bernhardus (Crustacea), Liocarcinus depurator (Crustacea), and Gadus morhua (Osteichthyes). No discernable abnormal behavior was observed for these megafauna, in any of the zones investigated, during or after the CO2 release. Time-lapse photography revealed that the intensity and presence of the CO2 bubble plume was affected by the tides, with the most active bubbling seen at low tides and the larger hydrostatic pressure at high tide suppressing CO2 bubbling from the seabed. © 2014 Elsevier Ltd. Source


Yamamoto M.,Hokkaido University | Shimamoto A.,The General Environmental Technos Co. | Fukuhara T.,The General Environmental Technos Co. | Tanaka Y.,Japan National Institute of Advanced Industrial Science and Technology | Ishizaka J.,Nagoya University
Organic Geochemistry | Year: 2012

Seasonal and depth variation in the flux of glycerol dialkyl glycerol tetraethers (GDGTs) and TEX86 (TEX86H and TEX86L) values in sinking particles was examined by conducting a 21month time-series sediment trap experiment at a mooring station (WCT-2, 39°N, 147°E) in the mid-latitude NW Pacific. The aim was to understand the sinking process of GDGTs in the water column and the preservation of the TEX86 signal in the water column and sediment surface. In the shallow trap, the sinking flux of GDGTs showed maxima from May 1998 to February 1999. The maximal peaks in sinking flux corresponded to peaks in the sinking flux of organic carbon, opal and lithogenic material. GDGT concentration in the total fine fraction and the caldarchaeol/crenarchaeol ratio at three depths (ca. 1300-4800m) varied synchronously, implying rapid vertical transport of GDGTs to deeper water with a sinking velocity >260mday-1 below ca. 1300m. The changes in TEX86-based temperature were different from those in contemporary sea surface temperature (SST). The former was lower than the SST from May to December and corresponded to the temperature at the thermocline, whereas it was higher than the SST from December to May. The annual average sinking flux of the GDGTs decreased with depth. The GDGT half-depth, the depth range over which half of the GDGT is lost, was calculated to be 3108-3349m, implying that GDGTs were well preserved during sinking. The flux-weighted average TEX86-based temperature was constant with depth and corresponded roughly to mean annual SST. The findings support a previous hypothesis that the GDGTs produced in surface water are preferentially delivered to the deeper water column via grazing and repackaging in larger particles. The constant TEX86 at different depths indicates that it was not affected by degradation in the water column. The preservation efficiency of GDGTs was 1.0-1.3% at the water-sediment interface. Despite significant GDGT degradation, there was a small difference in TEX86 values between sinking particles and surface sediment. © 2012 Elsevier Ltd. Source

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