102
1
Introduction
The Great East Japan Earthquake 2011 (2011
Tohoku-Oki Earthquake) occurred on the 11th of
March 2011. After the earthquake, tsunami waves
washed over the Pacifi c side of the Tohoku area –
the northern part of the main island of Japan.
Tsunamis destroyed many coastal towns, even
those protected by seawalls of 10 m in height,
and damaged and disabled a nuclear power plant
as well. The Japanese government directed efforts
to help the area recover from earthquake and
tsunami damage, and several programs were
conducted in terrestrial areas. During this time,
surveys of marine ecosystems were conducted
separately.
An initiative called the Tohoku EcosystemAssociated Marine Science (TEAMS) project
was launched at the end of the fi scal year 2011
with the support of the Ministry of Education,
Culture, Sports, Science and Technology. The
TEAMS project is required to contribute to the
following in the ocean areas off Tohoku: (a) elucidate the effects of earthquakes and tsunamis;
(b) with a view to assessing recovery, reveal the
dynamics of organisms and their environment;
(c) suggest fi sheries that could be sustainably
exploited; and (d) assess the safety of such products in terms of anthropogenic chemical compound content. As part of this project,
multidisciplinary surveys of the environmental
conditions and state of the ecosystem have been
conducted from coastal areas to the continental
slope, where fi sheries are conducted, in order to
assess the effect of earthquakes and tsunamis.
Previous research suggested heavy damage by
the earthquake and tsunami in coastal and shallow ocean areas. Large amounts of sedimentation
(Goto et al. 2012 ), increases in marine debris
(Shibata et al. 2013 ), decrease in ground level/
seafl oor depth (Ozawa et al. 2011 ), and changes
in the distribution of benthic organisms (Seike
et al. 2013 ; Urabe et al. 2013 ) are considered to
be the main changes in the ecosystem. Although
extensive research and cleanup activities have
been conducted in shallow waters, research
results from deep-sea areas are scarce. A few
reports, some sedimentation studies, suggested
diffi culty in identifying the effects of the earthquake and the tsunami event in the upper part of
the deep sea (such as shallower than 750 m)
because of bioturbation (Arai et al. 2013 ).
Nonetheless, marine debris is expected to have
either positive or negative effects in deep-sea
areas (Goto 2012 ; Ramirez-Llodra et al. 2011 ).
In the present paper, we introduce preliminary
results on the distribution of debris in the datasets
collected from deep-sea surveys by TEAMSrelated cruises and from archived data from other
studies. We focus in particular on the spatial distribution of marine debris and the types of marine
debris to assess the positive or negative effects of
marine debris originating from the earthquake on
ecosystems in the upper part of the deep sea.
2
Methods
2.1
Study Area
The Tohoku offi ng is located on the northern
Pacifi c side of the main island of Japan and is
well-known as a frontal area where the warm,
northward-fl owing Kuroshio current encounters
the cold, southward-fl owing Oyashio current.
Since 2011, we have surveyed the deep-sea area
using a side-scan sonar, deep-tow submergible
cameras, and an ROV (remotely operated vehicle) system. The target region for the TEAMS
surveys encompassed the area from the coast to
the continental slope, and this study focused on
the offshore region of Miyagi and Iwate
Prefectures. The survey areas and sites are plotted in Fig. 1 .
2.2
Data Collection
We examined the data from fi ve different surveys
to evaluate quantitatively the occurrence of
marine debris in each survey area or along each
survey transect. Details of each survey are as follows: towed camera surveys by the 4KC (4,000 m
camera deep-tow camera) and YKDT (Yokosuka
deep-tow camera) were conducted from May 16
T. Yamakita et al.
1
Introduction
The Great East Japan Earthquake 2011 (2011
Tohoku-Oki Earthquake) occurred on the 11th of
March 2011. After the earthquake, tsunami waves
washed over the Pacifi c side of the Tohoku area –
the northern part of the main island of Japan.
Tsunamis destroyed many coastal towns, even
those protected by seawalls of 10 m in height,
and damaged and disabled a nuclear power plant
as well. The Japanese government directed efforts
to help the area recover from earthquake and
tsunami damage, and several programs were
conducted in terrestrial areas. During this time,
surveys of marine ecosystems were conducted
separately.
An initiative called the Tohoku EcosystemAssociated Marine Science (TEAMS) project
was launched at the end of the fi scal year 2011
with the support of the Ministry of Education,
Culture, Sports, Science and Technology. The
TEAMS project is required to contribute to the
following in the ocean areas off Tohoku: (a) elucidate the effects of earthquakes and tsunamis;
(b) with a view to assessing recovery, reveal the
dynamics of organisms and their environment;
(c) suggest fi sheries that could be sustainably
exploited; and (d) assess the safety of such products in terms of anthropogenic chemical compound content. As part of this project,
multidisciplinary surveys of the environmental
conditions and state of the ecosystem have been
conducted from coastal areas to the continental
slope, where fi sheries are conducted, in order to
assess the effect of earthquakes and tsunamis.
Previous research suggested heavy damage by
the earthquake and tsunami in coastal and shallow ocean areas. Large amounts of sedimentation
(Goto et al. 2012 ), increases in marine debris
(Shibata et al. 2013 ), decrease in ground level/
seafl oor depth (Ozawa et al. 2011 ), and changes
in the distribution of benthic organisms (Seike
et al. 2013 ; Urabe et al. 2013 ) are considered to
be the main changes in the ecosystem. Although
extensive research and cleanup activities have
been conducted in shallow waters, research
results from deep-sea areas are scarce. A few
reports, some sedimentation studies, suggested
diffi culty in identifying the effects of the earthquake and the tsunami event in the upper part of
the deep sea (such as shallower than 750 m)
because of bioturbation (Arai et al. 2013 ).
Nonetheless, marine debris is expected to have
either positive or negative effects in deep-sea
areas (Goto 2012 ; Ramirez-Llodra et al. 2011 ).
In the present paper, we introduce preliminary
results on the distribution of debris in the datasets
collected from deep-sea surveys by TEAMSrelated cruises and from archived data from other
studies. We focus in particular on the spatial distribution of marine debris and the types of marine
debris to assess the positive or negative effects of
marine debris originating from the earthquake on
ecosystems in the upper part of the deep sea.
2
Methods
2.1
Study Area
The Tohoku offi ng is located on the northern
Pacifi c side of the main island of Japan and is
well-known as a frontal area where the warm,
northward-fl owing Kuroshio current encounters
the cold, southward-fl owing Oyashio current.
Since 2011, we have surveyed the deep-sea area
using a side-scan sonar, deep-tow submergible
cameras, and an ROV (remotely operated vehicle) system. The target region for the TEAMS
surveys encompassed the area from the coast to
the continental slope, and this study focused on
the offshore region of Miyagi and Iwate
Prefectures. The survey areas and sites are plotted in Fig. 1 .
2.2
Data Collection
We examined the data from fi ve different surveys
to evaluate quantitatively the occurrence of
marine debris in each survey area or along each
survey transect. Details of each survey are as follows: towed camera surveys by the 4KC (4,000 m
camera deep-tow camera) and YKDT (Yokosuka
deep-tow camera) were conducted from May 16
T. Yamakita et al.