Effects of the megamega-earthquake
and tsunami on rocky shore
ecosystems on theh Sanriku
Sik Coast,CJapan
Hideki Takami
Takami,, Tomohiko Kawamura,, Daisuke Muraoka,
Muraoka,Nam--Il Won, Hiroshi Nakaie
NamBackground• Massive tsunami generated by a mega
mega-earthquake
earthquake hit awide area of the Pacific coast of northeast Japan.
• Fisheries are one of the important industries in the coastal
area impacted by the tsunami.
• Rapid assessments are needed to evaluate the effects of thetsunami on coastal ecosystems and populations of fisheryorganisms for the future fishery and stock management.
• The abalone Haliotis discus hannai and the sea urchin
Strongylocentrotus nudus are valuable fisheries resourcesin this area, and also play important roles in the rocky shore
ecosys e .
ecosystem.

Study Aim
OtsuchiIwaisaki

Before the quake,
quantitative analyses on
the populations ofabalone and sea urchinwere regularly carriedout.

Tomarihama⊗
Epicenter of quake
Fukushima I

To assess the impacts of
the quake and tsunami,
the survey using thesame method before theeventt were carried.
i dMain study site: Tomarihama on Oshika
Penins la Miyagi
Peninsula,Mi agi• This study site is 130 km away fromtheh epicenter.
i• Run up height of 15 m waves hit
aroundd theh studyd site.
iTTomarihamaih⊗
Epicenter of quake
Fukushima I

Study site includes three algal communities
CCrustose
C
Coralline Algae(CCA)
5~7 m
Lithophylum yessoensis

Algal Turf(AT)

4~5 m

2~4 m

G lidiGelidium
eleganslKelp Bed(KB)
Eisenia bicyclis

100 mChanges in algal communities betweenb fbeforeandd after
ft theth ttsunamii
Kelp Beds (KB)
Remaining holdfasts of brownalgae that lost their fronds wereobserved (not many)many).
June 2011
Kelp
p biomass (kgg wtw/m2)

15
1.5

b f
before

after

10.5

0Jul. 2010

Jun. 2011

The biomass of brown algae was
not significantly different.

Changes in algal communities between before andafter the tsunami
November 2010

beforeJune 2011

afterAlgalg Turf (AT)( ) and
Crustose Coralline Algae (CCA)
Heavy sedimentation of mud andsilt covered the bed rocks
Many of the large rocks werecracked and turned over on thesea floor. Urchin density
extremely
tl reduced.
d dbeforeafter

Young recruits of large brownalgae were observed.
afterDensities of urchin and abalone
Methods
CCAATKB• Urchins
U hi andd abaloneb lwere sampled
l d usingiquantitative quadrats (2 m × 2 m).
m).
• In each algal community (KB, AT, andCCA) 3 replicate
CCA),
liquadrats
dwere haphazardly
h hdl
located.
• All animals in the quadrats were collected byh dhand.
• Densities
D iti were comparedd between
b tb fbefore(Jul 20102010-Feb 2011) and after (Jun 2011).

Changes in urchin density between before
and after the tsunami
CCA
Nov 2010

Jun 2011

ATKB

Sea urchinn density ((inds m-2)

30
Jul 2010
Nov 201020

Jun 2011

100.2

0
KB

0.1

NDAT

CCA

Changes in urchin density between before
and after the tsunami
Jun 2011

Nov 2010

Jun 2011

CCA: grazer resistant,dominating under high grazingpressure of urchins.
After the tsunami, previously
unrecordedd d recruitment
itt off
juvenile macroalgae wereobserved on CCA due to largelargescale removal
remo al of urchinsrchinsSea urchinn density ((inds m-2)

30
Jul 2010
Nov 2010
20Jun 2011

100.2

0KB

0.1

ND
AT

CCA

Changes in abalone density between before
andafterthetsunami
CCAATKB

Abalone density (indAds m-2)

76

Jul 2010
Nov 2010

5Feb 2011
Jun 2011

432
10KB

ATCCA

40

Jul 2010
n=573020
10040

01020304050

60708090100 110

Changes in size distribution ofabalone between before andafter the tsunami

Nov 2010
n=613020•

Abalone collected by the quadrat
sampling from CCA, AT, KB
were pooled for size distribution
datadata.

•The juvenile abalone <5050 mm SL
were not collected after thetsunami.

•The juveniles are more
vulnerable to the impact of thetsunami than adults.

10040

01020304050607080

90

100 110FFebb 2011
n=90

3020
10040
30

01020304050607080

90

100 110Jun 2011
n=23201000 0 10 10 20 20 30 30 40 4050 50 60 60 70 70 80 80 90 90100100110110120

Shell length (mm)Impact of tsunami on survival of 00-1 year
year--oldjuveniles -Methods
Methods-• Continuous monitoringg of jjuvenile
densities have been carried out since2009.
• Density of juveniles was difficult toestimate by quadrat (patchy and cryptic).
cryptic)
The abundance was monitored byintensive visual searching.
searching• The relative abundance was expressed ascatcht h per unit
it effort
ff t (CPUE) accounting
tifor the number of collected juveniles persearching
hi timei ini hours.
hSeasonal changes in CPUE of 0-1 year-old abalone
2009202009 Jan

151055020051015202530

May1520105551015202530

Aug1510502051015

202530Oct1509 YC

105051015

20

2508 YC

30

02015

2011302011 Feb

10 YC

10AT

09 YC

05101520

CCA

20251510020

2010 Jan09 YC

151007 YC

08 YC

2010

2030
May

20

51015

202530JunAdults inhabited in KB, butjuveniles <30 mm SL were not
50 observed in KB.
20151051015202530
Jul5151015202530AugFrom winterFi t tot spring,i0-year00 old CPUEs were high in CCA.
051015202530
51015202530
2020↓
DecNov
10 YC
1515
10 From spring to summer,
1011 YC
55CPUEsin CCA were00
51015202530
51015
202530decreased,
Shell length (mm) while increased in AT
1010

55In autumn and winter, thenext year class occurred inCCA

Impact of the tsunami on 0-1 year-old abalone
2009
202009 Jan

151055020051015202530May152010 Jan09 YC

1508 YC

20

51015

20

25

1530
May

20

55515202530

Aug

150
20

51015

20

25

1530
Jul

0
20

10105

5520

51015202530

Oct1509 YC

515

1010 YC

15

2025

30
Nov

20

10

10

5

5

5

1015

20

25

30

2530
Jun

51015

202530Aug

51015

202530Dec

202530After thetsunami

2011 Feb

11 YC

00
5

20

15

100

15

00
20

1015

100

5

15
1010CCA
AT09 YC

01052011 Feb

10 YC

1010020

2011

30
20

1007 YC

08 YC

2010

20

51015202530

Shell length (mm)510152011 Junz Dramatic reduction of 2010 YC after the tsunami was caused by catastrophic wave action.
z New
N recruit
it afterft theth tsunamiti (2011 YC) was negatively
ti l affected
ff t d byb theth sedimentation
dit ticovering their nursery ground, CCA.

Impacts of the tsunami on rocky shore
ecosystem at three sites on Sanriku coast

Otsuchi
Dec.2010 vsJul 2011

Iwaisaki

Kelpbiomass

Densityof adultabalone

CPUE of Density
juvenile of sea
abalone urchinNotsignificant

Not
significant

Significant

Significant

Not
significant

Not
significant

Significant

Significant

Not
significant

Significant

Significant

Significant

Feb 2011 vsJun 2011

Tomarihama
Feb 2011 vs Jun 2011

Conclusion 1• TheTh iimpact off tsunamii was more profoundfd in
i AT andd CCA
than in KB. In KB, the turbulent flow induced by the tsunamimight
i ht havehbeenbattenuatedttt d byb theth presence off theth algall l canopy.
DeeperCCA

ShallowerAT

Large reduction of juvenile
abalone and sea urchin

KB

Adult abalonesurvived
Kelp biomass
did not change

Conclusion 2• Juvenile abalone and sea urchins largely decreased after thetsunami. Most of these animals inhabited AT and CCA.

CCAAT

Large reduction of juvenile
abalone and sea urchin

KB

Adult abalone
survived
Kelp biomass
did not change

Conclusion 3• Juvenile macroalgae were observed in CCA after thetsunami. Decreased grazing pressure by largelarge-scale removal of sea
urchins. Tsunami affects the succession of algal species indirectly
through the changes in the grazing pressure of herbivores.

CCAAT

Large reduction of urchin andgdense recruit of macroalgae

KB

Adult abalone
survived
Kelp biomass
did not change

Conclusion 4• Theh youngest year classl off abaloneb l
was seriously
i ldamaged by the tsunami. Since the age at first capture ofabalone is 4 to 5 year olds, the future commercial catch may decreaseat least after 3 to 4 years from the tsunami.

CCAATR
Recruitment
itt failuref il
off juveniles
jilDisturbance by catastrophic wave action
Sedimentation covering nursery ground, CCAKB

AdultAd
lt abaloneb lsurvived
Kelp biomass
nott changedhd

Further studies
to digdi iinto deeperdto understanddd theh iimpacts off theh hhuge didisaster• Conducting the continuous monitoring tounderstand the recovering process of abalone
and urchin populations
populations.
• Analyzing the data of before/ after
comparisons of other benthic organisms tofully understand the effects on rocky shore
ecosystems.

Thank you for your attention.
We also thank PICES members for your praying
and support after the Japanese megamega-earthquakeand tsunami.
ARIGATOU!!

This study was partly supported by the Coastal Ecosystem Complex ofMinistry of Education, Culture, Sports, Science and Technology Japan.