Abstract
The 2011 Tohoku tsunami had a serious impact, such as an increase in harmful substances and salinity over a large area. Herein, we evaluated transitions in bacterial communities in agricultural fields in the four years after the 2011 Tohoku tsunami. Bacterial communities were compared across four different types of soil—unflooded field (UF) soil, soil flooded for a short term (ST), soil flooded for the long term (LT), soil flooded long term and cultivated fields (LTC), and marine environmental materials (bay sediment, sea sand and sea water), using a polymerase chain reaction (PCR) and pyrosequencing of 16S ribosomal RNA genes. In the soil bacterial communities that were flooded by the 2011 Tohoku tsunami, these effects were not seen after 2013. Although the difference in bacterial communities between LT and UF became smaller during the four years, the bacterial communities in LT were different from those in UF in several ways, such as a higher tendency frequency of sulfur-oxidizing bacteria (SOB) and the presence of halotolerant SOB. Therefore, it is thought that the Tohoku tsunami affected the microbial communities in the soil for more than four years. Especially genus Halothiobacillus, which is Halotolerant SOB in flooded soils, was detected neither in unflooded soil nor in the marine environment. Therefore, it is thought that inundation by a tsunami produces a unique environment with bacterial communities to form in soil. Further, SOB structure, especially halotolerant, might serve as a good indicators of the impacts of inundation on bacterial communities in agricultural fields over the long term.
Highlights
The 2011 Great East Japan Earthquake was one of the most powerful earthquakes ever recorded, and this event triggered a tsunami (2011 Tohoku tsunami), which had a serious impact on a large area [1,2]
Soil samples were taken from unflooded field (UF; Field 1 (UF1)), fields flooded for two weeks (short term, ST; Field 2 (ST2)) and fields flooded for two months (long term, LT; Field 3 (LT3)), the same as in our previous study [7]
We conclude that inundation by a tsunami produces a unique environment with bacterial communities to form in soil
Summary
The 2011 Great East Japan Earthquake was one of the most powerful earthquakes ever recorded, and this event triggered a tsunami (2011 Tohoku tsunami), which had a serious impact on a large area [1,2]. Agriculture is one of the major industries in the area, and agricultural fields were seriously contaminated by seawater and marine sediment [3]. Seawater inundation by tsunami causes an increase in harmful substances (such as arsenic) and salinity in agricultural fields, which directly affects plant growth [4,5,6]. Inundation greatly affects the soil microbial communities. This effect was evaluated using molecular biological techniques [7]. A year after the Tohoku tsunami, the phyla Acidobacteria and Proteobacteria were dominant in unflooded and flooded soil, respectively
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