Tracking the direct impact of rainfall on groundwater at Mt. Fuji by multiple analyses including microbial DNA

A total of 2 to 3 million tons of spring water flushes out from the foot of Mt. Fuji, the largest volcanic mountain in Japan. Based on the concept of piston flow transport, residence time of stored groundwater at Mt. Fuji was estimated at  ∼ 15–30 years by the 36Cl∕Cl ratio (Tosaki et al., 2011). This range, however, represents the average residence time of groundwater that was mixed before it flushed out. To elucidate the route of groundwater in a given system, we determined signatures of direct impacts of rainfall on groundwater, using microbial, stable isotopic (δ18O), and chemical analyses (concentration of silica). Chemical analysis of the groundwater gave an average value of the water, which was already mixed with waters from various sources and routes in the subsurface environment. The microbial analysis suggested locations of water origin and paths.In situ observation during four rainfall events revealed that the stable oxygen isotopic signature obtained from spring water (at 726ma.s.l., site SP-0m) and shallow groundwater (at 150ma.s.l., site GW-42m), where the average recharge height from rainfall was 1700–1800m, became greater than values observed prior to a torrential rain producing more than 300mm of precipitation. The concentration of silica decreased after this event. In addition, the abundance of Bacteria in spring water increased, suggesting the influence of heavy rain. Such changes did not appear when rainfall was less than 100mm per event. The above findings indicate a rapid flow of rain through the shallow part of the aquifer, which appeared within a few weeks of torrential rain extracting abundant microbes from soil in the studied geologic setting. Interestingly, we found that after the torrential rain, the abundance of Archaea increased in the deep groundwater at site GW-550m,  ∼ 12km downstream of SP-0m. However, chemical parameters did not show any change after the event. This suggests that strengthened piston flow caused by the heavy rain transported archaeal particles from the geologic layer along the groundwater route. This finding was supported by changes in constituents of Archaea, dominated by Halobacteriales and Methanobacteriales, which were not seen from other observations. Those two groups of Archaea are believed to be relatively tightly embedded in the geologic layer and were extracted from the environment to the examined groundwater through enforced piston flow. Microbial DNA can thus give information about the groundwater route, which may not be shown by analysis of chemical materials dissolved in the groundwater

2-17 Understanding microbial ecology in a subsurface environment

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Deep Terrestrial Subsurface Bacterial Unique Distribution Constrained by Geological Setting

出版者版タイトル：Unique distribution of deep groundwater bacteria constrained by geological setting出版者版著者名：Kato, Kenji : Nagaosa, Kazuyo : Kimura, Hiroyuki : Katsuyama, Chie : Hama, Katsuhiro : Kunimaru, Takanori : Tsunogai, Urumu : Aoki, Kazuhiroautho

Planktonic Bacterial Population Dynamics with Environmental Changes in Coastal Areas of Suruga Bay

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Subsurface bacterial growth and grazing impact revealed by an in situ experiment in a shallow aquifer

出版者版タイトル：Active Bacterial Populations and Grazing Impact Revealed by an In Situ Experiment in a Shallow Aquiferautho

Denitrification Activity and Relevant Bacteria Revealed by Nitrite Reductase Gene Fragments in Soil of Temperate Mixed Forest

Erratumは同誌Vol.24,No.1,Page76に掲載されたもの（著者コメント）「日本微生物生態学会2009年度論文賞」受賞2009-07-13 18:02:34+09publishe

Population Dynamics of Crenarchaeota and Euryarchaeota in the Mixing Front of River and Marine Waters

A transect from the Tomoe River Mouth through Shimizu Port to Suruga Bay, Japan, was examined between 2005 and 2009 to reveal the population dynamics of Crenarchaeota and Euryarchaeota in an estuary environment. Crenarchaeota tended to increase in abundance in waters deeper than 100 m compared with Euryarchaeota, and comprised 11% of total direct counts. Archaeal abundance was highest in the Tomoe River Mouth, with a strong negative correlation between surface euryarchaeal abundance and salinity (P<0.001). The diversity index for the phylotypic archaeal community in the mouth was three times higher than that at sites St1-1m and St1-10m in the estuary, and OTUs represented most of the OTU groups at the sites. Three of the seven total OTUs, which comprised 83.6% of the 140 sequenced clones in the estuary, were related to the OTUs in the mouth with similarities higher than 97%. A significant proportion of the archaeal community appears to be derived from the Tomoe River. The two dominant phylotypes of the archaeal community in Shimizu Port, belonging to MGI and MGII, occurred ubiquitously.publishe