What happened to the marine environments after Great East Japan Earthquake？
TEAMS International Conference, March 2016
The succession of microbial populations in Otsuchi Bay and Tohoku coastal area
Reiko Fujimura, Ryo Kaneko, Kazuhiro Kogure*
Atmosphere and Ocean Research Institute, the University of Tokyo
5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
Key word: bacteria, community structure, next generation sequencer, Otsuchi
【Background】
What are marine bacteria?
Bacteria are tiny (0.5-1.0m) organisms that
can be seen only under microscopy. They
distribute almost any part of this planet. In
marine
environments,
there
are
approximately one million cells in surface
water, and at least one thousand cells even in
deep ocean. Any organic matter or pollutants
introduced into the sea are finally degraded
into CO2 and water by bacteria. Therefore,
their functions are essential to keep marine
environment clean and sustain our biospheres.
By the development of recent molecular
technique, it is now possible to extract DNA
directly from seawater, analyze their base
sequences by so called next generation
sequencer (NGS). The sequences tell us what
kind of bacteria are present and what kind of
functions they may exert in the sea.
Microorganisms play major roles in material
cycles in marine environments. The earthquake and
tsunami on March 11 caused disturbance of coastal
ecosystem, leading to the change of chemical
components in the environments. In addition, various
chemical substances, including toxic ones, might be
introduced to the sea from terrestrial environments.
These environmental changes might affect biomass,
community structure, physiology and functions of
microorganisms. We hypothesized that the
earthquake and tsunami caused at least temporal
changes of numbers and community structures of
microorganisms in the marine environment.
【Aim】
To see the change of the numbers and community
structures of bacterial populations in Otsuchi Bay and
adjacent area.
【What we found】
By analyzing the gene sequences obtained from
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100%
80%
60%
40%
20%
0%
【Conclusion】
1. The numbers and community structures of bacteria
in Otsuchi Bay and adjacent area returned to their
original level and structures by October 2012.
2. There were particular bacterial groups that
appeared only in the bay and outside of the bay.
Therefore unique bacterial populations are present
in each environment thoughout the period of the
distance.
3.
Fig. 1. Phylogenetic tree of 16S rDNA sequences obtained.
【How we investigated】
From 2012 June to 2015 March, we had 10
cruises by R/V Shinsei Maru (JAMSTEC) in Tohoku
area. Temperature, salinity, oxygen, depth profiles
were measured by CTD on board. Seawater,
*Corresponding:
Kazuhiro Kogure
e-mail: kogure@aori.u-tokyo.ac.jp
Tel: +81-4-7136-6160
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・Komatsu, T., Ohtaki, T., Sakamoto, S., Sawayama,
S., Hamana, Y., Shibata, M., Shibata, K. and Sasa,
S. (2015) Tsunami on seagrass and seaweed beds
in Otsuchi Bay, Sanriku Coast, Japan. In “Marine
productivity: perturbations and resilience of
socio-ecosystems ”
(eds. Ceccaldi, H.J.,
Hénocque, Y., Koike, Y., Komatsu, T., Stora, G. and
Tusseau-Vuillemin, M.-H.), Springer International
Publishing Switzerland, Cham, pp. 43-53.
・R/V Shinsei maru Research vessel was built as a
part of TEAMS. Please visit the web site for details;
http://www.jamstec.go.jp/e/about/equipment/ships/
shinseimaru.html
・Some cruise data are available at the followings;
http://www.jamstec.go.jp/teams/e/data.html
http://157.82.133.112/~database/oceandb/cruise.
cgi
sediment and plankton samples were obtained by
Niskin water sampler, multiple corer and Norpac net,
respectively, DNA and RNA were extracted from
water and sediment samples. All samples were
treated on board and carried back to AORI for further
analyses. Sequences of DNA and RNA were obtained
by the next generation sequencer (454 GS Junior).
【Further readings and information】
・Kawamura, T., Takami, H., Hayakawa, J, Won, N.-I.,
Muraoka, D. and Kurita, Y. (2014) Changes in
abalone and sea urchin populations in rocky reef
ecosystems on Sanriku Coast damaged by the
massive tsunami and other environmental changes
associated with the Great East Japan Earthquake
in 2011. Global Environmental Research, 18,
47-56.
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