Takami Morita

Fisheries Research Agency, Yokohama, Kanagawa, Japan

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Publications (16)50.19 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To clarify the level of contamination with radioactive cesium (radiocesium) discharged from Fukushima Dai-ichi Nuclear Power Plant (FDNPP), three fish species caught in the main harbor of FDNPP were subjected to gamma-ray analysis. The concentration of radiocesium in muscle differed among individual fish, even those of similar size of the same species, and showed little relation to the standard length of fish. The maximum concentration of radiocesium (202 kBq/kg-wet) was detected from fat greenling samples. Comparison with data from outside the port indicated that the level of radiocesium contamination inside the port was higher than that outside. We found that beta-rays were emitted from otoliths of fishes caught in the port of FDNPP. Beta-ray intensities were correlated with the concentrations of radiocesium in muscles of the three fish species. In Japanese rockfish, the beta-ray count rates from otoliths were significantly correlated with the concentration of radiocesium and 90Sr in whole body without internal organs of Japanese rockfish. However, no beta-rays were detected from brown hakeling samples collected around FDNPP, suggesting that the detection of beta-rays from otoliths may indicate living in the main harbor of FDNPP.
    Environmental Science & Technology 05/2015; 49(12). DOI:10.1021/es5051315 · 5.48 Impact Factor
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    ABSTRACT: Levels of radiocesium (134Cs + 137Cs) contamination in lake water, bottom sediment, plankton, and fish were investigated in three geographically separated lakes in Fukushima Prefecture (Lake Hayama, Lake Akimoto, and Lake Tagokura) between June 2012 and November 2013. Levels of contamination differed among the three lakes, with the highest levels of each measured component in Lake Hayama, followed by Lake Akimoto, and the least contamination in Lake Tagokura. Among the lakes, the magnitude of contamination decreased with distance from the Fukushima Dai-ichi Nuclear Power Plant. Mean radiocesium concentrations were higher in piscivorous fish than in other fish, possibly reflecting differences in trophic level. The radiocesium concentrations in some fish species decreased significantly by 33-65 % during the period between 2012 and 2013. Radiocesium concentrations of the lake water, bottom sediment, plankton, and fish were significantly correlated with surface soil radiocesium content near lake sites.
    Fisheries Science 01/2015; DOI:10.1007/s12562-015-0874-7 · 0.86 Impact Factor
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    ABSTRACT: We conducted a sequential chemical extraction experiment for radiocesium (134Cs + 137Cs) using 21 surface sediment samples and two sets of size-fractionated surface sediment samples collected offshore Fukushima. Our results support earlier reports in this area that organic substances in marine sediments have an apparently higher preference for radiocesium than mineral substances. Observations suggest that mineral and organic substances in the marine sediments offshore Fukushima have the same order of preference for radiocesium, primarily because of the existence of ionic competitors in seawater. The apparent preference of radiocesium for organic material is greater because of the partial coverage of sediment mineral surfaces by organic substances. By using these relationships, we created a 2-D map of radiocesium concentration in sediment organic fraction in offshore-Fukushima region. Combining our results with existing monitoring data of marine benthos in offshore-Fukushima sediments, we estimated a transfer coefficient of radiocesium from sediment organic materials to benthic polychaetes as less than 0.03–0.008.
    Geochemical journal GJ 01/2015; 49:219-227. DOI:10.2343/geochemj.2.0351 · 1.94 Impact Factor
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    ABSTRACT: Ayu Plecoglossus altivelis, a herbivorous fish, is an important fishery resource and key component of the foodweb in many Japanese streams. Radionuclide contamination of this species is likely transferred to higher trophic levels, include humans, in the food chain. After the Fukushima accident in March 2011, ayu were exposed to highly contaminated silt while feeding on algae attached to the riverbed stones. To understand the route by which herbivorous fish are exposed to radionuclides, the activity concentrations of sum of (134)Cs and (137)Cs (radiocesium) were analyzed in riverbed samples (algae and silt) and in the internal organs and the muscle of ayu in five river systems in the Fukushima Prefecture between summer 2011 and autumn 2013. Although there was a positive correlation between the radiocesium activity concentrations in the muscle and the internal organs of ayu, the median activity concentration in the muscle was much lower than those in the internal organs. The activity concentrations of radiocesium in the riverbed samples and the internal organs and the muscle of ayu were correlated with contamination levels in soil samples taken from the watershed upstream of the sample sites. The results of the generalized linear mixed models suggest that the activity concentrations in both the internal organs and the muscle of ayu declined over time. Additionally, the activity concentrations in the internal organs were correlated with those in the riverbed samples that were collected around the same time as the ayu. The activity concentrations in the muscle were correlated with ayu body size. Our results suggest that ayu ingest (134)Cs and (137)Cs while grazing silt and algae from the riverbed, and a part of the (134)Cs and (137)Cs is assimilated into the muscle of the fish. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Journal of Environmental Radioactivity 12/2014; 141C:32-37. DOI:10.1016/j.jenvrad.2014.11.012 · 3.57 Impact Factor
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    ABSTRACT: The Fukushima Dai-ichi nuclear power plant (FNPP) accident that followed the Great East Japan Earthquake in 2011 resulted in the release of enormous quantities of anthropogenic radionuclides, especially radioactive cesium (134Cs and 137Cs) into the ocean off the east coast of Japan. FNPP-derived radioactive Cs may have consequently accumulated within marine food webs via seawater intake and predator–prey interactions. We provide evidence of the temporal variability in 134Cs and 137Cs concentrations in seawater and zooplankton samples collected in coastal waters off Joban-Sanriku, in Sendai Bay, and in the Oyashio region between June 2011 and December 2013. In Sendai Bay, seawater 134Cs and 137Cs concentrations exceeded 1 Bq/kg in June 2011 and rapidly decreased during the study period. 134Cs and 137Cs concentrations in zooplankton were also high in June 2011, up to 23 Bq/kg-wet and also decreased during the study period, although at a slower rate than seawater 134Cs and 137Cs concentrations. Regarding 137Cs concentrations, the difference in the rate of decrease between seawater and zooplankton resulted in a high apparent concentration ratio (aCR) for zooplankton. The observed relation between 137Cs in seawater and the aCR of zooplankton were good indicators of the progress of 137Cs contamination in zooplankton from the beginning of the FNPP accident to the restoration phase.
    Fisheries Science 11/2014; 81(1). DOI:10.1007/s12562-014-0827-6 · 0.86 Impact Factor
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    ABSTRACT: We measured the radiocesium ((134)Cs and (137)Cs) contamination of 236 greenlings (Hexagrammos otakii) off the coast of Fukushima Prefecture in Japan, following the accident at the Fukushima Daiichi Nuclear Power Plant in March 2011. The radiocesium concentrations of greenlings caught approximately 40 km south of the power plant were significantly higher than those of greenlings caught approximately 50 km north of the power plant. The radiocesium concentrations of greenlings caught in southern waters were significantly higher in shallow than in deep waters. Meanwhile, two outlier specimens of greenlings with higher (137)Cs concentrations, 16,000 Bq/kg-wet on 1 August 2012 and 1,150 Bq/kg-wet on 8 May 2013, were caught approximately 20 km from the power plant. Our calculations suggest that the probability of two such outlier specimens being found off the coast of Fukushima is exceedingly low. By contrast, extremely contaminated greenlings were frequently caught in the power plant port (geometric mean of (137)Cs = 17,364 Bq/kg-wet). Our results suggest that the two outlier greenlings with higher (137)Cs concentrations migrated from the power plant port. Continued close monitoring of radiocesium concentrations in the area should be done to ensure the safety of food supplies.
    Scientific Reports 10/2014; 4:6851. DOI:10.1038/srep06851 · 5.58 Impact Factor
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    ABSTRACT: The spatial distributions of radiocesium concentration in sea sediment to a core depth of 14 cm were investigated in the offshore region from the Fukushima Prefecture to the northern part of the Ibaraki Prefecture in February and July 2012, at a spatial resolution of 5 min of latitude and longitude. The concentrations in the area south of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) were generally higher than those in the area north of it. In the southern area, a band of especially high concentration with a width about 20 km was present in the region shallower than 100 m, and a narrow minimal concentration band was found along the 200-m isobaths. In more than half of all cases, the vertical core profiles of radiocesium concentration generally showed an exponential decreasing trend with depth. However, in the area north of the FDNPP, where the radiocesium concentrations tended to be very low, radiocesium concentrations that had similar or larger magnitude compared with those of the most-surface layer were often found in deeper layers. Relatively good correlations were found between radiocesium concentrations and grain sizes of the most-surface sediment. The vertical profile of radiocesium concentration also had a relationship with grain size. In other case, the radiocesium concentration in the sediment seems to have had a dependence on the radiocesium concentration in bottom seawater, suggesting that the quantity of radiocesium supplied and the grain size were major factors determining the spatial distribution pattern of the radiocesium concentration after the FDNPP accident.
    Journal of Environmental Radioactivity 09/2014; 138:264–275. DOI:10.1016/j.jenvrad.2014.09.007 · 3.57 Impact Factor
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    ABSTRACT: Enormous quantities of radionuclides were released into the ocean via both atmospheric deposition and direct release as a result of the Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident. This study discusses the southward dispersion of FNPP-derived radioactive cesium (Cs) in subsurface waters. The southernmost point where we found the FNPP-derived (134)Cs (1.5-6.8 Bq m(-3)) was 18˚N, 135˚E, in September 2012. The potential density at the subsurface peaks of (134)Cs (100-500 m) and the increased water column inventories of (137)Cs between 0 and 500 m after the winter of 2011-2012 suggested that the main water mass containing FNPP-derived radioactive Cs was the North Pacific Subtropical Mode Water (NPSTMW), formed as a result of winter convection. We estimated the amount of (134)Cs in core waters of the western part of the NPSTMW to be 0.99 PBq (decay-corrected on 11 March 2011). This accounts for 9.0% of the (134)Cs released from the FNPP, with our estimation revealing that a considerable amount of FNPP-derived radioactive Cs has been transported to the subtropical region by the formation and circulation of the mode water.
    Environmental Science & Technology 02/2014; 48(6). DOI:10.1021/es403686v · 5.48 Impact Factor
  • 01/2011; 21(2):175-179. DOI:10.5985/jec.21.175
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    ABSTRACT: The anthropogenic radionuclides, (137)Cs, (90)Sr, (108m)Ag, (239+240)Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996-2007. There was no increase in the concentrations of these radionuclides and no large variation of the atom ratio of (240)Pu/(239)Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher atom ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentration of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentration of radionuclides with sampling depth would depend on the concentration in the seawater and diet.
    Marine Pollution Bulletin 10/2010; 60(12):2311-22. DOI:10.1016/j.marpolbul.2010.09.022 · 2.79 Impact Factor
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    ABSTRACT: (60)Co were detected in common octopus specimens collected in the East China Sea in 1996-2005. The source of (60)Co has remained unclear yet. Stable isotope analyses showed that there was no difference in stable Co concentrations between octopus samples with (60)Co and without (60)Co. This result showed that the stable Co in the digestive gland of octopus potentially did not include a trace amount of (60)Co and the source of (60)Co existed independently. Furthermore, investigations of octopus in other area and other species indicated that the origin of the source of (60)Co occurred locally in the restricted area in the East China Sea and not in the coastal area of Japan. Concentrations of (60)Co have annually decreased with shorter half-life than the physical half-life. This decrease tendency suggests that the sources of (60)Co were identical and were temporary dumped into the East China Sea as a solid waste.
    Marine Pollution Bulletin 08/2010; 60(8):1193-9. DOI:10.1016/j.marpolbul.2010.03.031 · 2.79 Impact Factor
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    ABSTRACT: Iodine-131 (physical half-life: 8.04 days) was detected in brown algae collected off the Japanese coast. Brown algae have been extensively used as bioindicators for radioiodine because of their ability to accumulate radionuclides in high concentration factors. The maximum measured specific activity of (131)I in brown algae was 0.37 + or - 0.010 Bq/kg-wet. Cesium-137 was also detected in all brown algal samples used in this study. There was no correlation between specific activities of (131)I and (137)Cs in these seaweeds. The specific activity of (137)Cs ranged from 0.0034 + or - 0.00075 to 0.090 + or - 0.014 Bq/kg-wet. Low specific activity and minimal variability of (137)Cs in brown algae indicated that past nuclear weapon tests were the source of (137)Cs. Although nuclear power stations and nuclear fuel reprocessing plants are known to be pollution sources of (131)I, there was no relationship between the sites where (131)I was detected and the locations of nuclear power facilities. Most of the sites where (131)I was detected were near big cities with large populations. Iodine-131 is frequently used in diagnostic and therapeutic nuclear medicine. On the basis of the results, we suggest that the likely pollution source of (131)I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.
    Science of The Total Environment 07/2010; 408(16):3443-7. DOI:10.1016/j.scitotenv.2010.04.001 · 4.10 Impact Factor
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    ABSTRACT: The anthropogenic radionuclides, 90Sr and 137Cs, were measured in two marine algal species, wakame seaweed (Undaria pinnatifida) and edible kelp (Laminaria longissima), collected in four coastal areas of Japan during 1998-2008. Although 90Sr and 137Cs could be detected at all sampling sites, the concentrations of 90Sr and 137Cs were at low levels and those in some samples were below the detection limit. These low concentrations and the small variation of both concentrations and the 137Cs/90Sr activity ratio indicate that the source of 90Sr and 137Cs detected in this study originated from the global fallout deposition following atmospheric nuclear-bomb tests in the past. There were no significant differences in both concentrations of 90Sr and 137Cs in wakame seaweed among three sampling sites. Although wakame seaweed is extensively distributed in southern and central Japan, it does not occur in northern areas and so edible kelp was monitored. The concentrations of 90Sr and 137Cs in edible kelp were significantly different from those in wakame seaweed in some sampling sites. These differences could be due to the difference in the concentrations of 90Sr and 137Cs in the surrounding seawater or the difference in species. The combined data with data from the previous report and the preexisting database showed that wakame seaweed incorporated 137Cs through a different pathway from that of 90Sr. The combined data also suggested that wakame seaweed responded differently to the source of 137Cs.
    Journal of Environmental Monitoring 05/2010; 12(5):1179-86. DOI:10.1039/B920173D · 2.11 Impact Factor
  • Takami Morita
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    ABSTRACT: The evolutionary adaptations of functional genes to life at high pressures are not well understood. To elucidate the mechanisms of protein adaptation to high pressures, we isolated two muscle protein-encoding cDNAs, alpha-actin and myosin heavy chain (MyHC), derived from skeletal muscles of two deep-sea fishes, Coryphaenoides yaquinae and C. armatus, and two non-deep-sea fishes, C. acrolepis and C. cinereus. The alpha-actins from two deep-sea fishes have three amino acid substitutions in comparison to those of non-deep-sea fishes. These substitutions enable the deep-sea fish actins to function even at 60 MPa. The MyHCs of the two deep-sea fishes have a proline residue in the loop-1 region and have a shorter loop-2 region than the non-deep-sea fishes. Additionally, the MyHCs of deep-sea fishes have biased amino acid substitutions at core positions within the coiled-coil structure of the rod region. The roles of these substitutions in the deep-sea fishes MyHCs, however, remain unclear.
    Annals of the New York Academy of Sciences 02/2010; 1189(1):91-4. DOI:10.1111/j.1749-6632.2009.05181.x · 4.31 Impact Factor
  • Marine Pollution Bulletin 09/2007; 54(8):1293-300. DOI:10.1016/j.marpolbul.2007.04.006 · 2.79 Impact Factor
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    Ken Fujimoto · Takami Morita
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    ABSTRACT: A novel strain of Halomonas (Tc-202), which has the capability of removing Tc(VII) from solid- and aqueous-phase material aerobically, was isolated from the marine environment. Tc-202 removed 55% of the total 99Tc in solutions at 15 degrees C by reducing Tc(VII) to Tc(V), but other Halomonas strains did not.
    Applied and Environmental Microbiology 01/2007; 72(12):7922-4. DOI:10.1128/AEM.00819-06 · 3.95 Impact Factor