Fallen trees in the coastal forest immediately after the earthquake disaster
Arahama, Watari Town, Miyagi Prefecture April 2011WEB

The information gathered in this survey is published on the Ministry of theEnvironment, Biodiversity Center of Japan’s website“Shiokaze Natural Environment Log”

Larus crassirostris（Matsushima Bay）

Bulrush (Typha orientalis)

URL http://www.shiokaze.biodic.go.jp

Sanriku Fukko (reconstruction) National Park/Green Reconstrustion Project
The Ministry of the Environment is working on many programs in“Green Reconstruction
Project through Establishment of Sanriku Fukko (reconstruciton) National Park”aims at thereconstruction of the paciﬁc coastal regions in Tohoku. The national park, the axis of the project,
was established in May 2013, for the purpose of contributing to the reconstruction of the areas
damaged by the Great East Japan Earthquake.
The park stretches about 220 km from north to south, with magniﬁcent cliﬀs known as the“Marine Alps”in the north and elegant Rias coasts with intricate geographical features extending
towards the south. There are seabird breeding sites such as the black-tailed gull and streaked
shearwater along the coast where people can observe wildlife in close proximity. It also boasts ofseveral leading ﬁshing ports in Japan such as Hachinohe, Miyako, Kamaishi, Ofunato, Kesennuma
etc. where people can enjoy fresh seafood. In addition, many people from all around the nation
visit the area for eco-tourism.
The paciﬁc coastal regions in Tohoku are now on the road to recovery and the tourism industry
has also resumed.“Michinoku Coastal Trail,”which connects the nature and life, traces of theearthquake, visitors and local people in the regions, is available. Do come and visit Sanriku Fukko(reconstruction) National Park to experience culture, life and the natural blessings!!

Clam・Japanese littleneck clam (Ruditapes philippinarum)

Pickerel weed (Pontederia)

Impact of
the Great East Japan
Earthquake on
the Natural Environmentin Tohoku Coastal Regions

Green Reconstruction URL http://www.env.go.jp/jishin/park-sanriku/
Michinoku Coastal Trail URL http://www.tohoku-trail.go.jp/

Issued by

Nature Conservation Bureau, Ministry of the Environment

Crab (Helice tridens)

Biodiversity Center of Japan

Nature Conservation Bureau, Ministry of the Environment

5597-1, Kenmarubi, Kamiyoshida, Fujiyoshida-shi, Yamanashi 403-0005
TEL：+81-555-72-6033 FAX：+81-555-72-6035

Edited by

Biodiversity Center of Japan

Asia Air Survey Co., Ltd.
Published in November 2013
Bar-tailed Godwit (Limosa lapponica)

On March 11, 2011 at 2:46 p.m., a great earthquake of magnitude 9.0 occurred oﬀshore in Sanriku.
In Miyako City, Iwate Prefecture, tsunami waves measuring 40.5 meters high were recorded. The
wide area along the Paciﬁc Coast in the Tohoku region were assaulted by the tsunami, causing an
unprecedented disaster which is said to occur only once in a thousand years.

AomoriPrefecture
Sanriku Fukko (reconstruction) National Park

In 2011, the Ministry of the Environment started monitoring the coastal regions along the Paciﬁc
Coast from Aomori Prefecture to Chiba Prefecture where the natural environment has changed

Akita
Prefecture

drastically.

Iwate
Prefecture

Yamagata
Prefecture
Takatamatsubara, Rikuzentakata City, Iwate Prefecture

The vegetation changes before and after
the earthquake disaster were reported bycreating and overlaying the vegetation
maps in areas submerged by the tsunami
before and after the earthquake disaster.

MiyagiPrefecture

Sandy Beach Changes

Niigata
Prefecture
MinamisanrikuKinkasan
Quasi-National Park

Fukushima
Prefecture

Arahama, Sendai City, Miyagi Prefecture

Torinoumi, Watari Town, Miyagi Prefecture

Tokyo
Kanagawa
Prefecture

IbarakiPrefecture

Submerged areas due to the tsunami
Ecosystem Monitoring

Chiba
Prefecture

Tidal ﬂats with benthos: 16 sites
Zostera beds: 6 sites
Seaweed beds: 5 sites
Seabird breeding sites: 4 sites

Nakahama, Yamamoto Town, Miyagi Prefecture
Aerial photo: Taken by Asia Air Survey Co., Ltd.（March 2011）1

Idoura, August 2012

The sandy and muddy beaches within a rangeof about 100-500 meters inland from thecoastline in three diﬀerent periods ̶ the 1970s,
before the earthquake (2000s), and after theearthquake̶were interpreted to analyze thechanges in the beaches.

Change in the last
Hundred Years

Tochigi
Prefecture

SaitamaPrefecture

Vegetation Changes“Rivers”“lakes,and marshes”“wetlands”
,
“sand
,
dunes”, etc. were interpreted the Old Edition
from maps of the late Meiji Period (1903) tothe early Taisho Period (1918). We used
these information to identify the factors of
the ﬂooding and to plan the future land use.

Ecosystem Monitoring

Nakahama, Yamamoto town, May 2011

Hiroura, Natori City, 1907

Post-disaster surveys were carried out in 16
tidal ﬂats, 6 Zostera beds, 5 seaweed beds and
4 seabird breeding sites which were surveyed
previously before the earthquake to comparewith the situation before the earthquake.
Yamada Bay, October 20122

japonica

Vegetation Changes

e.g. Akasaki coast (Kesennuma City, Miyagi Prefecture)
Before the earthquake, sandy beach, sand dune vegetation and Black pine plantation could be seen along the shoreline while

In order to understand the changes in the vegetation in areas submerged by the tsunami along the Paciﬁc coastline

from Aomori Prefecture to Chiba Prefecture (about 576 km ), we created vegetation maps before and after the2earthquake (November 2012) and then overlayed them to compare the changes before and after the earthquake.
A scale of 1/10,000 was assumed for the plot accuracy up to a distance of about 500 meters inland. Thereafter, ascale of 1/25,000 was used further inland.

⓪No change

uncultivated ﬁeld areas and debris storage site.
After classifying the change patterns and vegetation damage status based on the maps before and after the earthquake, we
found that many of the coastal and river bank areas have been submerged or washed away, while many inland areas havebecome barren lands or have been transformed for artiﬁcial uses.

Example ⑩ Flowed out / sink

Before the earthquake*

Before the earthquake*

After the earthquake*（May 2011）(October 2006)

Paddy ﬁelds (light blue)

After the earthquake*（May 2011）

Inlands areas were mainly
cultivated as paddy ﬁelds.

Phragmitetea (sky blue)③Covered by Invasive alien tree species④Changed from natural and secondary vegetation
to other natural vegetation⑥Change from unvegetated area to natural vegetation⑦Change to barren land
⑧Changed to natural bare land

Legend⑨Changed for artiﬁcial use⑩Flowed out/Sink

Carpinus tschonoskiiCarpinus laxiﬂora community
Salix spp. shrub community⑪Change to Secondary grass ﬁeld

Pinus thunbergii community*Aerial Photos: Taken by Geospatial Information Authority of Japan

AomoriChanges in the Vegetation

Iwate
Miyagi

Iwate

Fukushima

Miyagi

Ibaraki

Fukushima

Chiba

Ibaraki
Chiba

0

0

20

0

20

0

20

20

40

60

40

40

40

40

60

60

60

60

Akasaki coast80

100（％）

After the earthquake

80“Changed to barren land”areas occupied
about 40%,“Flowed out/Sink”areas were also
100（％） seen in about 5% of the land.

Changed to barren land(orange)80“Changed to barren land”areas occupied
about 30%,“Flowed out/Sink”areas were also
100（％） seen in about 5% of the land.

20

0

20

80

40

40

60

80

“Changed to barren land”areas occupied about
40%,“Flowed out/Sink”areas were also seen in
100（％） about 5% of the land.

60

80

100（％）

80

Generally, areas showing“No change”occupied thegreatest share. However, in Sosa City and
Yokoshiba-Hikari Town,“Remained Forest”and100（％） “Lodging / Die back”areas occupied the greater share.

Based on all the areas in the six prefectures,“Changed to barren land”areas(where weeds grow abundantly in areas damaged by the tsunami) occupy thegreatest share at 30% of the total area. This is followed by“Changed for artiﬁcialuse”(e.g. developed lands and debris storage areas etc.) which occupies 10% of
100（％） the overall area. Due to the concern over the potential invasion by invasive alien
species in these areas, monitoring of the trends is thus required in future.

Pinus thunbergii plantation
Field weed communities
Paddy-ﬁeld weed communities
Urban and residential district
with many trees
Urban district with a few trees
Natural bare landBlack pine (Pinus thunbergii)
forests could be seen
behind the sandy beaches.
The Black pine forest of the
Akasaki coast have been
designated as a“Preserved
forest for tree genetic
resources”by the Forestry
Agency.

Newly-formed sandy
beaches (beige)（June 2011）

In paddy ﬁelds which havebecome uncultivated ﬁelds,
plants that thrive in wet
environments such as the
Typha latifolia have grown inabundance. Some of theseare observed to be rare
species facing the threat ofextinction. Future trends need
to be monitored carefully.

Vegetation speciﬁc to sandy
beaches such as the Carex
kobomugi and Calystegia
soldanella used to grow along
the beaches. The sceneryfrom the beach to thecoastal forest looks beautiful
and the beach has beenused by local people forrecreational activities for along time.

Coastal forests (green)*Geographical map: 1/25,000 map ofGeospatial Information Authority of Japan

Although the majority or about 60% of theareas showed“No change”,“Remained Forest”
areas also accounted for about 15% of the area.

Generally, areas showing“No change”occupied
the greatest share.
0

Phragmitetea
Sand dune vegetation
Cryptomeria japonica,Chamaecyparis obtusa,
Chamaecyparis pisifera plantation
Pinus densiﬂora plantation

Change in area

20

All the areas

0

Tsuya River

Reed (Phragmitetea) typical ofthe vegetation around rivers
were seen from the river
shores to the river mouth.

⑤Revegetated（Natural vegetation）

Aomori

Sand dune vegetation(light purple)（May 2001）

Example ① Remained Forest (50% or more remained)①Remained Forest（50% or more remained） （October 2006）②Lodging/Die back(less than 50% remained)

5

disappeared and the shoreline receded. In addition, the paddy ﬁelds and farmlands became vacant site covered in weeds,

Before the earthquake

Pattern of change due to the tsunami
Pattern of change

paddy ﬁelds and farmlands extended inland. After the earthquake, the sandy beaches, sand dune vegetation and coastal forests

Tsuya River
Akasaki coast

Although the vegetation isreturning along the sandy
beaches after theearthquake, invasion ofinvasive species has also
been observed at the sametime. The future trend needs
to be monitored.

Invasive species, Cakile edentula(Photo taken in August 2012)

Flowed out / Sink (Red)
Monochoria korsakowii (nearthreatened species)
Photo taken in September 2012

LegendNo change
Remained Forest(50% or more remained)
Lodging / Die back(less than 50% remained)
Revegetated (Natural vegetation)
Change from unvegetatedarea to natural vegetation

Change to barren land
Changed to natural bare land
Changed for artiﬁcial use
Flowed out / Sink

*Aerial Photos: Taken by
Geospatial Information
Authority of Japan

A large part of the coastal
forest and sand dune
vegetation have disappeared
from these ﬂooded areas. In
the Sanriku area that havebeen devastated, most of thevegetation in the sand dunes
were washed away together
with the sandy beaches.

6

Sandy Beach Changes

Changes in the last hundred years

In order to understand the changes in the sandy and muddy beaches along the Paciﬁc coastline from Aomori

From the Old Edition map of the Geospatial Information Authority of Japan which was surveyed about aPrefecture to Chiba Prefecture (about 680 km in total length) due to the tsunami, we compared the changes in thehundred years ago from 1903 to 1917,“old river channels”,“rivers”,“lakes and marshes”,“wetlands”,“sandthree periods using aerial and satellite photos taken in the 1970s, before (2000s) and after the earthquake disaster.

dunes”,“sandy beaches”were identiﬁed and converted to GIS. As shown in the following examples, the state

A scale of 1/10,000 was assumed for the plot accuracy and the survey range covered a width of 300-500 meters
for areas with wide sandy beaches and 100 meters for areas with narrow beaches.

Area change in from the 1970s until the earthquake
increased in all survey regions. Although the“sandy beach”area200

shrunk in Aomori Prefecture, the“coastal forest”area increased.

0

In Ibaraki and Miyagi Prefectures,“sand dune vegetation area”-200

was decreased.

-400

Area change before and after the earthquake

Iwate
Fukushima
Chiba

Aomori
Miyagi
Ibaraki

400“Coastal structures”such as harbours and ﬁshing facilities

August 2012

wetlands

Sandy Beach

Sand Dune
Vegetation

Coastal Forest

Coastal
Structures etc.

sand dunes

Othersandy beaches

Area change by prefecture
Idagawaura

Iwate
Fukushima
Chiba

Aomori
Miyagi
Ibaraki0“sand dune vegetation”and“coastal forest”in Miyagi Prefecture,-200

and“coastal forest”in Chiba Prefecture were changed to-400

Sandy Beach“Others”by almost the same extent in terms of the area.

Old Idagawaura

Sand Dune
Vegetation

Coastal Forest

Coastal
Structures etc.

Other

N

Idagawaura was once
covered in water.

The land reclaimed in 1929,
was used as a reclaimed
paddy ﬁeld.

2250

2000

1750

1500

1250

750

1000

500

250

800
600

Sandy Beach*Aerial Photos: Taken by Geospatial Information Authority of Japan

LegendBefore the earthquake

After the earthquake*

Abukuma River

Abukuma River（March 2003）

Abukuma River（September 2012）

old river channels
riverslakes and marshes
wetlands
sand dunes
sandy beaches

Torinoumi

May 2011

Torinoumi

Torinoumi

Other

2250

2000

1750

1500

1250

750

1000

Shoreline of 1970's

North

Distance in Coastal
Direction (m)

South

800

LegendCoastal Forest

400

Coastal Structures etc.
Other

200
2250

Shoreline of 1970's

Geographical map: 1/25,000 map of*Aerial Photos: Taken by Geospatial Information Authority of Japan
Geospatial Information Authority of JapanNN

A series of sand dunes(orange) used to extend
parallel to the coastline withthe areas in-between being
wetlands (yellow-green).

Areas which used to be sanddunes were turned into ﬁelds
while areas which used to bewetlands were turned into
paddy ﬁelds.

N

Sandy Beach
Sand Dune Vegetation

600

0Idagawaura, which was drained
and turned into paddy-ﬁeld,
was still submerged even one
year after the earthquake.

Coastal Structures etc.

200

2000

N

Due to the impact of the tsunami,
it returned to the water region
and wetlands that it used to beafter the earthquake.

Coastal Forest

400
0LegendSand Dune Vegetation

1750

2.3km
N

Distance in Coastal
Direction (m)

South

1500

N

North

1250

South

South
2.3km

Shoreline of 1970's

0

750

South

1907

Other

After the earthquake（May 2011）

UnosumaiRiver

Unosumai
River

2.3km

Surveyrange

Coastal Structures etc.

200

Ne.g. Torinoumi (Watari Town, Miyagi Prefecture)

Coastal Forest

400

1000

1km

600

500

Surveyrange

Sand Dune Vegetation

250

1km

800

LegendSandy Beach

Before the earthquake（February 2003）

Extension of Occupancy (m)Survey
range

South

500

1970s
shoreline

1970s
shoreline

Unosumai
River

7

North

North

1970s
shoreline

1km(May 2011)

0km

0km
North

After the earthquake*
※

North

250

The sandbar extending from the right bank disappeared due to the tsunami. A
V-shaped gulf section was formed and the shoreline receded by a maximum of
about 400 meters.

Extension of Occupancy (m)Before the earthquake disaster ‒ After the earthquake disaster

Extension of Occupancy (m)1970s until before the earthquake disaster

0km

Geographical map: 1/25,000 map ofGeospatial Information Authority of Japan

1970s

Sand dune vegetation grew in sandbars with a width of about 50 meters while
coastal forest extended towards the south. The estuary of the Unosumai River
moved towards the north comparing the changes of the two periods.

(February 2003)

Old IdagawauraNe.g. Nehama, Kamaishi City, Iwate Prefecture

Before the earthquake(April 2012)200

under“Others”).“Sand dune vegetation”in Aomori Prefecture,

1970s*

After the earthquake*lakes and marshes

400

man-made developments or changed into barren lands (included(September 2002)

rivers600

in all survey regions, and most were transformed through

Before the earthquake

1908
Legendold river channels

（ha）
800

“Sand dune vegetation”and“coastal forest”were vastly reduced

e.g. Idagawaura(Minamisoma City, Fukushima Prefecture)

Area change by prefecture

（ha）
600

that the land used to be is presumed to be reﬂected after the earthquake.

Distance in Coastal
Direction (m)Geographical map: 1/25,000 map ofGeospatial Information Authority of Japan

Although there were not big
changes in the areas which used tobe sand dunes after the earthquake,the ground of the areas which used
to be wetlands was weakened.

Ground of inland coastal
forests which used to bewetlands was lowered andsubmerged.

*Aerial Photos: Taken by Geospatial Information Authority of Japan

8

As Zostera forest are mainly located in the inner bay areas where the force of the tsunami is concentrated, the great
disturbance such as disappearance of the sea bed caused by the tsunami was observed.
●Hirota Bay
Before the earthquake, the largest Zostera
forest in the Sanriku area was formed here.
There was a clear demarcation between
Zostera marina in the shallow areas andZostera caulescens in the deeper areas.
However, the ground subsided by about
60-80 cm after the earthquake and the
distribution border became indistinguishable.

We monitored the seaweed beds, Zostera beds, seabird breeding sites and benthos living landscapein tidal ﬂats along the Paciﬁc coastal regions from Aomori Prefecture to Chiba Prefecture which arethought to be aﬀected by the earthquake especially.

Benthos in tidal ﬂats
There are various types of tidal ﬂats depending on the sites and geographical locations and the level of impact diﬀers for each area.
●Sanriku Coast
The disturbance was on a relatively large scale and thebenthos landscape has changed vastly together with changes inthe shape and submergence of the tidal ﬂats.

Many-formed cerith(Matsushima Bay)

●Aomori coast
The disturbance was on a relatively small
scale and no changes in the sea-bottom
living landscape were observed.

●Sendai Bay
Although the disturbance was on a relatively moderate scale, thebenthos landscape has changed together with the disappearance andwithering of Phragmitetea and deposition of sand on the sea bottom.
●Matsushima Bay
The disturbance at the entrance of the bay was on a relatively
moderate scale and the benthos landscape had changed. In the
inner bay, the disturbance was on a relatively small scale and thebenthos landscape hadn’t changed so much.

●Mangokuura
Although the impact of the tsunami wassmall, the disturbance was on a relatively
moderate scale; the previous appearanceof the tidal ﬂat at a low tide was lost due
to approximately 80 cm land subsidence.
The benthos landscape changed with that.
●The east coast of the
Boso peninsula
Although the disturbance was on arelatively moderate scale, the benthos
landscape changed together withchanges in the sea bottom.

Phyllospadix iwatensis (Inubosaki)●Yamada Bay
There was a large population of mixed Zostera
caespitosa and Zostera marina before the earthquake.
After the earthquake, the northern and central
areas of the bay were observed to be just as dense
even though the ground subsided by about 40 cm.

Ishinomaki City,e.g. Mangokuura,
Iwate Prefecture (lagoon)
Before the According to a survey of the west coast of Kuroshima
earthquake Island carried out near the center of the lagoon in
Dec 2006, Zostera was observed to be growing fromthe coast up to about 100 meters out at sea.
After the The ground was seen to have subsided by about 0.9
earthquake meters, becoming muddy as sludge accumulated.
The distribution area of the Zostera was drasticallyreduced. Zostera population reported in the survey
in 2006 was exterminated.

e.g. The estuary of Unosumai River, Kamaishi City, Iwate Prefecture (Sanriku coast)
Before the In tidal ﬂat areas with brackish water and relatively low salt content, many polychaete such
earthquake as Tylorrhynchus heterochaetus and crustacean such as Deiratonotus cristatus were observed.
After the Due to the tsunami, the sandbar disappeared and the estuary opened up directly into
earthquake the sea with the agricultural land on the left bank being turned into a tidal ﬂat. As aresult, organisms that live in brackish waters with relatively higher salt content such as Left bank of estuary of Unosumai
Nuttallia japonica, Laternula marilina, Ruditapes philippinarum and Mya arenaria oonogai moved River that has been turned into a new
tidal ﬂatin, resulting in changes to the ecosystem.

Seabird breeding sites

Calonectris leucomelas (Hide Island)●Hide Island (Miyako City, Iwate Prefecture)
Although the area was ﬂooded up to aheight of 20-40 meters, no soil runoﬀ due tothe tsunami or impact caused by the land
stripping were observed.

●Ashi Island(Onagawa Town, Miyagi Prefecture)
The impact of soil runoﬀ due to the tsunami
was minor and most of the vegetation and land
within the nesting range remained intact.

e.g. Ashi Island, Onagawa Town, Miyagi Prefecture
After the The tsunami was thought to have reached a height of about 15 meters as it
earthquake exceeded the height of the saddle in the center of the island (height about 15
meters). However, the land and vegetation remained in most areas and thus theimpact on the nest density of the Cerorhinca monocerata was thought to be minor.

9●OtsuchiSmall-scale Zostera beds used to dot the area
before the earthquake. After the earthquake, mostof it disappeared together with the seabed.
Although some Zostera was seen, the coverage
was almost 0%.

Mangokuura: Water Depth Gradient and Seaweed Algae Vertical Dis
Distribution Graph with 2006 and 2012 survey lines
1.5

Nutritional Plant Density 17 plants ／0.25m2

2006
2012

-2.0
-2.5

0

Legend102030Large sediment (boulders)

40

50

60

Small sediment (gravel)

Sargassum seaweed (Sargassum horneri)●Yamada Bay
Before the earthquake, it was a Laminariaceae
bed mainly consisted of Laminaria japonica
Areschoug and Costaria costata. After theearthquake, Laminaria japonica Areschoug wasseen.

Japanese kelp (Yamada Bay)

●Shizugawa Bay
Before the earthquake, the main population
seen was Eisenia bicyclis. No major changes in
the population landscape were seen
immediately after the earthquake but signiﬁcant
growth of Undaria pinnatifida was seen in 2012.

70

80

Oyster shells

Mud

Codium seaweed (Codium fragile)

90

100（m）

Eelgrass (Zostera marina)

Sea lettuce (Ulva pertusa)●Onagawa Bay
Before the earthquake, there were almost no large
algae species and several varieties of small red algae
were seen mostly. After the earthquake, Schizymenia
dubyi and Laminaria religiosa were seen mainly in theshallow areas while Undaria pinnatifida and Sargassum
horneri were seen mainly in the deeper areas.
●Kitaibaraki City area
Before the earthquake, it was mainly Undaria
pinnatifida and Sargassum beds. After theearthquake, it became a mixture of Eisenia
bicyclis, Undaria pinnatifida and Sargassum.

e.g. Onagawa Bay, Onagawa Town,

N

Miyagi Prefecture (Minamisanriku)

Before the Originally, the bed consisted of Undaria pinnatifida andearthquake Sargassum but is now dominated by several varieties ofsmall red algae dotted with Dictyota dichotoma, a large
brown algae (March 2007 survey).

Before the Ashi Island is the southern tip of the breeding grounds for Cerorhinca monocerata,
earthquake and Calonectris leucomelas also used to build their nests in the same area.

●Inubosaki
Before the earthquake, cold and warm
temperate and cold current algae and seaweed
used to grow in this area and no signiﬁcantchanges were seen after the earthquake.

Seaweed beds are mainly located at the mouth of the bay facing the open sea. While there has been some impact due to the sinking of theground caused by the tsunami, no large changes in the population landscape were observed. Also as this area is mainly used for growing
young algae such as Undaria pinnatifida and Laminariaceae bory, the impact on the population was thus thought to be relatively minor.

the land was stripped of its vegetation and litter ﬂowed out into the area together with the ﬂooding caused by the tsunami.

●Sangan Island(Kamaishi City, Iwate Prefecture)
The area was ﬂooded up to a height of about
20 meters and landslides shrunk the area
where storm petrels could build their nests.

●Matsushima Bay (Sabusawa Island)
One species of Zostera marina used to grow here
before the earthquake disaster. After the earthquake,the ground subsided by about 1 meter, and only asmall number at the mouth of the bay remained intact.

Seaweed beds

Although there was no direct impact on migratory seabirds since the earthquake occurred before they ﬂew here to breed,●Kabu Island(Hachinohe City, Aomori Prefecture)
The impact on the land slipping due to thetsunami was minor and the proportion ofvegetation such as Dactylis glomerata, Poaannua and Brassica napus increased.

●Mangokuura
Zostera was seen from the west coast of
Kuroshima Island to about 100 meters out
at sea before the earthquake disaster. Afterthe earthquake, the ground subsided byabout 90 cm, wiping out large areas of theZostera population.

Water depth（D.Lm）

Ecosystem Monitoring

Zostera beds

Laminaria religiosa（Onagawa Bay）

About 1m sinking
in the ground2012 Survey Point
2007 Survey Point

Nest area of the Larus crassirostrisat the northern end of Ashi Island

After the In the shallow areas, a red algae Schizymenia dubyi grows
Breakwater
broken byearthquake in abundance mixed with a large brown algae, Laminaria
tsunamireligiosa. In the deeper areas, it is mainly dominated by
Undaria pinnatifida
Sargassum horneri and Undaria pinnatifida (August 2012 （Onagawa Bay）
survey).
*Aerial Photos: Taken by Geospatial Information Authority of Japan

10