Yokouchi Y.,Japan National Institute of Environmental Studies |
Nojiri Y.,Japan National Institute of Environmental Studies |
Toom-Sauntry D.,Environment Canada |
Fraser P.,CSIRO |
And 5 more authors.
Geophysical Research Letters | Year: 2012
It has been suggested that the emissions of volatile organic compounds (VOCs) from the ocean could be affected by global warming, with feedback effects on the climate. In order to detect changes in their emissions as a response to global environmental change, long-term observations are required. Here we report for the first time long-term variations of atmospheric methyl iodide (CH 3I), the most abundant iodine-containing compound predominantly emitted from the ocean. We monitored its concentration periodically at five remote sites covering 82.5N-40.4S and over the western and northern Pacific Ocean from the late 1990s to 2011. At most observation sites, CH3I increased from 2003/2004 to 2009/2010 by several tens of per cent, with a decreasing trend before 2003. The inter-annual variation pattern is well approximated by a sine curve with a period of 11years and showed a good correlation with the Pacific Decadal Oscillation (PDO), suggesting that CH 3I emissions are affected by global-scale, sea surface temperature (SST)-related, decadal anomalies. The influence of natural oscillations or environmental change on trace gas emissions from the ocean may be greater than has been thought previously, and these emissions may thus be sensitive to future climate change. © 2012. American Geophysical Union.
Amemura-Maekawa J.,Japan National Institute of Infectious Diseases |
Kikukawa K.,Saitama Prefectural University |
Helbig J.H.,TU Dresden |
Helbig J.H.,Nippon Medical School |
And 14 more authors.
Applied and Environmental Microbiology | Year: 2012
Legionella pneumophila serogroup (SG) 1 is the most frequent cause of legionellosis. This study analyzed environmental isolates of L. pneumophila SG 1 in Japan using monoclonal antibody (MAb) typing and sequence-based typing (SBT). Samples were analyzed from bathwater (BW; n=50), cooling tower water (CT; n=50), and soil (SO; n=35). The distribution of MAb types varied by source, with the most prevalent types being Bellingham (42%), Oxford (72%), and OLDA (51%) in BW, CT, and SO, respectively. The ratios of MAb 3/1 positive isolates were 26, 2, and 14% from BW, CT, and SO, respectively. The environmental isolates from BW, CT, and SO were divided into 34 sequence types (STs; index of discrimination [IOD]=0.973), 8 STs (IOD= 0.448), and 11 STs (IOD=0.879), respectively. Genetic variation among CT isolates was smaller than seen in BW and SO. ST1 accounted for 74% of the CT isolates. The only common STs between (i) BW and CT, (ii) BW and SO, and (iii) CT and SO were ST1, ST129, and ST48, respectively, suggesting that each environment constitutes an independent habitat. © 2012, American Society for Microbiology.
Yokoyama E.,Chiba Prefectural Institute of Public Health |
Etoh Y.,Fukuoka Institute of Health Environmental |
Ichihara S.,Fukuoka Institute of Health Environmental |
Horikawa K.,Fukuoka Institute of Health Environmental |
And 7 more authors.
Journal of Food Protection | Year: 2011
Enterohemorrhagic Escherichia coli serovar O157 (O157) strains with highly similar pulsed-field gel electrophoresis (PFGE) patterns were isolated in Japan during 2007 and 2008. Several genetic features related to O157 evolution were investigated to indicate whether homoplasy might have contributed to the highly similar PFGE patterns in these strains. The O157 strains were classified in lineage I/II, as defined by a lineage-specific polymorphism assay-6 with an atypical allele in Z5935 (code: 231111). Analysis of the insertion sites of stx 2 phage in these strains showed that the sites were "occupied" in yehV and "intact" in wrbA, indicating that the strains were derived from "Cluster 1" of "Subgroup C." When a specific single-nucleotide polymorphism in ECs2357 in clade 8 strains was investigated, all of the strains in the present study were confirmed to be clade 8 strains. These results indicated that the O157 strains in this study had common genetic features, suggesting that the highly similar PFGE patterns of these strains were not due to homoplasy. Because no common source of these strains could be identified in 2007 to 2008 in Japan, these strains may have emerged from a unique O157 clade 8 clone and then spread by dissemination in Japan. © International Association for Food Protection.
Liu X.,University of Tokyo |
Liu X.,Changzhou University |
Kondo Y.,University of Tokyo |
Ram K.,University of Tokyo |
And 10 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2013
The emission of black carbon (BC) from East Asia and its long-range transport strongly influence the mass concentration of BC (MBC) over the western Pacific. However, reliable and long-term BC data are still limited in this region, especially at elevated altitudes. In this study, we present accurate measurements of MBC using a continuous soot monitoring system at Happo, a remote mountain site at an altitude of about 1.8 km in Japan, from August 2007 to August 2009. The annual average MBC at Happo was about 0.260.18 (1s) mgm3. The monthly average MBC values exhibited similar seasonal variations during both years, with minimum values in winter. Around 40% of the air sampled at the site was of free tropospheric (FT) origin, with about 10% originating in North China (NC) origin, respectively. The MBC values for FT (0.24 mgm3) and NC (0.23 mgm3) air were representative of the MBC values (0.26 mgm3) at 1.8 km height in the western Pacific, which are strongly influenced by BC emissions in North China. The MBC values calculated using a regional-scale model reproduced well the MBC observed at Happo. The model predicted that BC transported from northern China alone contributed ~53% to the measured MBC, consistent with trajectory analysis. The comparison of model-calculated and observed MBC values indicates that the minimum values of MBC in winter were caused by the suppressed upward transport of BC over the Asian continent. Biomass burning in Siberia substantially increased MBC in the spring of 2008. © 2013. American Geophysical Union. All Rights Reserved.
Genetic analyses of GII.17 norovirus strains in diarrheal disease outbreaks from december 2014 to march 2015 in Japan reveal a novel polymerase sequence and amino acid substitutions in the capsid region
Matsushima Y.,Kawasaki City Institute for Public Health |
Matsushima Y.,Yokohama City University |
Ishikawa M.,Kawasaki City Institute for Public Health |
Shimizu T.,Kawasaki City Institute for Public Health |
And 11 more authors.
Eurosurveillance | Year: 2015
A novel GII.P17-GII.17 variant norovirus emerged as a major cause of norovirus outbreaks from December 2014 to March 2015 in Japan. Named Hu/GII/JP/2014/GII.P17-GII.17, this variant has a newly identified GII. P17 type RNA-dependent RNA polymerase, while the capsid sequence displays amino acid substitutions around histo-blood group antigen (HBGA) binding sites. Several variants caused by mutations in the capsid region have previously been observed in the GII.4 genotype. Monitoring the GII.17 variant’s geographical spread and evolution is important. © 2015, European Centre for Disease Prevention and Control (ECDC). All Rights Reserved.
Noh N.-J.,Gifu University |
Kuribayashi M.,Gifu University |
Kuribayashi M.,Nagano Environmental Conservation Research Institute |
Saitoh T.M.,Gifu University |
And 4 more authors.
Ecosystems | Year: 2015
How global warming will affect soil respiration (RS) and its source components is poorly understood despite its importance for accurate prediction of global carbon (C) cycles. We examined the responses of RS, heterotrophic respiration (RH), autotrophic respiration (RA), nitrogen (N) availability, and fine-root biomass to increased temperature in an open-field soil warming experiment. The experiment was conducted in a cool-temperate deciduous forest ecosystem in northern Japan. As this forest is subjected to strong temporal variation in temperature, on scales ranging from daily to seasonal, we also investigated the temporal variation in the effects of soil warming on RS, RH, and RA. Soil temperature was continuously elevated by about 4.0°C from 2007 to 2014 using heating wires buried in the soil, and we measured soil respiratory processes in all four seasons from 2012 to 2014. Soil warming increased annual RS by 32–45%, but the magnitude of the increase was different between the components: RH and RA were also stimulated, and increased by 39–41 and 17–18%, respectively. Soil N availability during the growing season and fine-root biomass were not remarkably affected by the warming treatment. We found that the warming effects varied seasonally. RH increased significantly throughout the year, but the warming effect showed remarkable seasonal differences, with the maximum stimulation in the spring. This suggests that warmer spring temperature will produce a greater increase in CO2 release than warmer summer temperatures. In addition, we found that soil warming reduced the temperature sensitivity (Q10) of RS. Although the Q10 of both RH and RA tended to be reduced, the decrease in the Q10 of RS was caused mainly by a decrease in the response of RA to warming. These long-term results indicate that a balance between the rapid and large response of soil microbes and the acclimation of plant roots both play important roles in determining the response of RS to soil warming, and must be carefully considered to predict the responses of soil C dynamics under future temperature conditions. © 2015 Springer Science+Business Media New York
Yamamoto S.,Japan National Research Institute of Fisheries Science |
Kitano S.,Nagano Environmental Conservation Research Institute |
Sakano H.,Japan National Research Institute of Fisheries Science |
Yagyu M.,Japan National Research Institute of Fisheries Science
Fisheries Science | Year: 2010
Brown trout Salmo trutta were first introduced into Japan in 1892, and they currently naturally reproduce in several rivers in Honshu and Hokkaido, Japan. Although negative impacts of brown trout introductions on native salmonid fishes have been documented in some Hokkaido rivers, studies of ecological interactions between brown trout and native salmonid fishes on Honshu are limited. In this study, we describe the longitudinal distribution patterns of introduced brown trout, white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou in a 4 km stretch of a stream in central Honshu. Underwater observations were conducted in all pools within upstream, middle and downstream sections (190-400 m in length) of this stretch in order to estimate the densities of these species. Only white-spotted charr was observed in the upstream section, while brown trout and masu salmon were observed in the middle and downstream sections. Masu salmon densities, however, were much lower than brown trout densities. In the downstream section, white-spotted charr was absent. These results are consistent with results from previous studies of Hokkaido rivers, where it was found that white-spotted charr in low-gradient areas tend to be displaced by brown trout. © The Japanese Society of Fisheries Science 2010.
Fukui S.,Hokkaido University |
May-McNally S.L.,University of British Columbia |
Katahira H.,Hokkaido University |
Kitano S.,Nagano Environmental Conservation Research Institute |
Koizumi I.,Hokkaido University
Hydrobiologia | Year: 2016
Introductions of non-native species have caused various negative impacts on native species and their ecosystems. Hybridization is particularly prevalent among closely related species, and can result in displacement, hybrid swarms, or the disruption of a locally adapted gene complex. Although hybridization between native and non-native species is widespread, long-term monitoring is generally lacking. In this study, we compared the distribution and composition of native white-spotted charr (Salvelinus leucomaenis), introduced brook trout (Salvelinus fontinalis), and their hybrids in the upper Sorachi River, Hokkaido, Japan in 2003 and 2013, especially focusing on (1) if genetic introgression or hybrid swarm has occurred and (2) if white-spotted charr have declined, since a previous study indicated a potentially harmful asymmetric hybridization with the mothers of hybrids being all white-spotted charr. We found no evidence of decline in native white-spotted charr; rather, the distribution and abundance of introduced brook trout had decreased. Of 142 charr (i.e., genus Salvelinus) collected, 18 individuals (13%) were hybrids but no unidirectional hybridization was observed. However, most of the hybrids were post-F1 individuals with biased mating with white-spotted charr. The effects of long-term introgression on native white-spotted charr should be further examined. © 2016 Springer International Publishing Switzerland
Shimatani Y.,Hokkaido University |
Fukue Y.,Wildlife Community Institute |
Kishimoto R.,Nagano Environmental Conservation Research Institute |
Masuda R.,Hokkaido University
Mammal Study | Year: 2010
The American mink (Neovison vison) as invasive alien species has spread along the Chikuma River in Nagano Prefecture, central Honshu, Japan, through naturalization of animals escaped from fur farms in the past. To clarify genetic structures of the naturalized populations, we genotyped ten microsatellite loci on 126 wild-caught animals from this region. Consequently, the genetic variations of American minks in Nagano were relatively low, and no correlations between genetic distances and geographical distances were observed. Based on the genotype data, animals examined were divided to four genetically different clusters. The results suggest that the genetic characters of the American mink populations around the Chikuma River were not formed after naturalization, but during or before breeding in fur farms. In addition, the present study indicated their migration between localities which may bring gene flow and promote random mating, resulting in genetic structure change in the future populations. © the Mammalogical Society of Japan.
Kitano S.,Nagano Environmental Conservation Research Institute |
Ohdachi S.,Hokkaido University |
Koizumi I.,Hokkaido University |
Hasegawa K.,Hokkaido University |
Hasegawa K.,Hokkaido National Fisheries Research Institute
Ichthyological Research | Year: 2014
Invasion status and impacts of nonnative brook trout (Salvelinus fontinalis) in a Hokkaido stream were investigated with field surveys and genetic analyses. Nonnative brook trout was detected in nine (41 %) of the 22 sampled reaches in three tributaries of the Sorachi River, Hokkaido, Japan. Based on the external pigmentation, twelve putative hybrids between brook trout and native white-spotted charr (Salvelinus leucomaenis) were collected in two reaches. Microsatellite and mitochondrial DNA data established that 58% of these hybrids were first-generation (F1) progenies between male brook trout and female white-spotted charr. Our results suggest potential negative impacts of nonnative brook trout on native charr populations in Hokkaido through interspecific interactions. © 2013 The Ichthyological Society of Japan.