Journal of Plant Research

, Volume 127, Issue 1, pp 23–42 | Cite as

Radioactive cesium accumulation in seaweeds by the Fukushima 1 Nuclear Power Plant accident—two years’ monitoring at Iwaki and its vicinity

  • Hiroshi Kawai
  • Akira Kitamura
  • Mari Mimura
  • Tetsuro Mimura
  • Tomoya Tahara
  • Daiki Aida
  • Kenji Sato
  • Hideaki Sasaki
Open Access
JPR Symposium Current status and future control of cesium contamination in plants and algae in Fukushima

Abstract

Accumulations of radionuclides in marine macroalgae (seaweeds) resulting from the Fukushima 1 Nuclear Power Plant (F1NPP) accident in March 2011 have been monitored for two years using high-purity germanium detectors. Algal specimens were collected seasonally by snorkeling at Nagasaki, Iwaki, Fukushima Prefecture (Pref.), Japan, ca. 50 km perimeter from the F1NPP. Additional collections were done at Soma, Hironocho, Hisanohama and Shioyazaki in Fukushima Pref. as well as at Chiba Pref. and Hyogo Pref. as controls. In May 2011, specimens of most macroalgal species showed 137Cs levels greater than 3,000 Bq kg−1 at Shioyazaki and Nagasaki. The highest 137Cs level recorded 7371.20 ± 173.95 Bq kg−1 in Undariapinnatifida (Harvey) Suringar on 2 May 2011, whereas seawater collected at the same time at Shioyazaki and Nagasaki measured 8.41 ± 3.21 and 9.74 ± 3.43 Bq L−1, respectively. The concentration factor of marine macroalgae was estimated to be ca. 8–50, depending on taxa and considering a weight ratio of wet/dry samples of ca. 10. 137Cs level declined remarkably during the following 5–6 months. In contrast, the 137Cs level remained rather stable during the following 12–16 months, and maintained the range of 10–110 Bq kg−1. Contamination was still detectable in many samples in March 2013, 24 months after the most significant pollution.

Keywords

134Cs 137Cs F1NPP 40Radionuclide accumulation Seaweeds 

Introduction

Radioactive contamination of the coastal seawater following the Fukushima 1 Nuclear Power Plant (F1NPP) accident was the most significant artificial radioactive liquid release into the sea ever known, on a short time and space scale basis (Buesseler et al. 2011; Linsley et al. 2005). The amount of radionuclides discharged from the F1NPP immediate after the accident was estimated to be 5–10 PBq to the atmosphere and 3–6 PBq to the sea, the latter being caused by direct leakages of the contaminated cooling water (Estournel et al. 2012; Kawamura et al. 2011; Miyazawa et al. 2012; Tsumune et al. 2012).

The seawater contamination has become severe by (1) a deposition from an atmospheric contamination plume, (2) direct, artificial releases of highly contaminated waters into the sea, and (3) the transport of radiopollutants into the sea by surface water leaching through contaminated soil or by river systems. The first case was most serious during mid-March 2011, and the second from late March to early April 2011. The contaminated seawater may be diluted or has been transported offshore by currents. Along the coast, however, a significant portion of the radioactive Cs and other radioactive substances are believed to have been absorbed by coastal organisms or bound to suspended particles, causing a deposition of radiopolluted sediments on the sea bottom. The concentration of radionuclides reached the maximum in mid-April 2011, but it thereafter declined exponentially. However, in addition to the inflow through the river systems, artificial release of radionuclides from F1NPP is reported to have continued at least until 2012 (Kanda 2013).

Among the radionuclides discharged by the accident, the effects of 134Cs and 137Cs are most serious because of their high levels and long decay periods. These radionuclides are considered to most substantially contribute to the contamination of marine organisms due to the contaminated seawater. Marine macroalgae (so-called seaweeds) grow by absorbing nutrient salts and other minerals directly from seawater at the surface of their thalli. Cs+ is soluble in seawater, and algal cells are thought to absorb Cs+ through certain K+ transporters (Kanter et al. 2010; Zhu and Smolders 2000), resulting in Cs+ accumulation within the cells.

The concentration factors (CFs) of marine macroalgae for 137Cs were reported to vary considerably from species to species (Coughtrey and Thorne 1983; Pentreath 1976; Tateda and Koyanagi 1994), but IAEA (2004) recommended the value of 50. Marine macroalgae may also capture the ions in phycocolloids such as alginate, fucan, agar, and carrageenan, although the affinity of Cs+ for these phycocolloids is not well-established (Morris et al. 1980). Marine macroalgae are primary producers in coastal ecosystems, and diverse benthic animals as well as fishes feed on them. Therefore, the radioactive contamination of marine macroalgae will be transferred to consumer animals through the food chain, and may become concentrated by biological accumulation.

Prior to the accident, the concentrations of 137Cs in the surface water of the Pacific Ocean were in the range of 1–4 Bq m−3 (Ikeuchi 2003; Nakanishi et al. 2010; Povinec et al. 2004), which mainly resulted from global fallout due to atmospheric nuclear weapon tests. Tateda and Koyanagi (1994) have reported the background concentrations of 137Cs in representative green, red and brown marine macroalgae, e.g. Ulvapertusa Kjellman, Neodilseayendoana Tokida, Saccharinareligiosa (Miyabe) C.E. Lane, C. Mayes, Druehl & G.W. Saunders (=Laminariareligiosa Miyabe), Sargassumhorneri (Turner) C. Agardh, S. thunbergii (Mertens ex Roth) Kuntze, in the range of ca. 0.03–037 Bq kg wet weight−1. Later, Morita et al. (2010) have compared the level of 90Sr and 137Cs in Undariapinnatifida collected from three representative areas (Nagasaki Pref., Kanagawa Pref. and Niigata Pref.) in Japan and in Saccharinalongissima (Miyabe) C.E. Lane, C. Mayes, Druehl & G.W. Saunders (=Laminarialongissima Miyabe) from Hokkaido during a 1998–2008 period and reported 137Cs levels of 0.03–0.08 and 0.05–0.09 Bq kg wet weight−1 for U. pinnatifida and S. longissima, respectively. Morita et al. (2010) also compared concentrations of 90Sr and 137Cs in some additional kelp and Sargassum species and reported 137Cs concentrations of 0.02–0.34 kg wet weight−1.

Several agencies have conducted investigations to measure the radioactive quantities of major fishery organisms after the F1NPP accident. Some algal taxa have been included in the target species, e.g., Pyropia (Porphyra), Saccharina (Laminaria), Eisenia, Gloiopeltis, Monostroma, but the number of species was rather limited, and rather biased in respect to phylogenetic diversity, habitat, and life history (e.g., intertidal vs. subtidal, annual vs. perennial). In addition, measurement protocols were not standardized among the investigations, and the detection levels were sometimes rather high (e.g., > 20 Bq kg−1 for fresh specimens: http://www.jfa.maff.go.jp/e/inspection/index.html) depending on the available facilities. Therefore, it was difficult to compare the data to clarify the general fate of radioactive contamination in marine macroalgae, and to discuss the differences in the CFs for radionuclides among the taxa.

In the present study, we aimed to monitor the level of radionuclides including 134Cs, 137Cs and 40K based on a standardized protocol using high-purity germanium detectors and to undertake multi-seasonal sampling as much as possible.

Materials and methods

Specimens were seasonally collected by snorkeling at Nagasaki, Fukushima Pref., ca. 50 km distant from the F1NPP (Fig. 1). Additional specimens were collected at the following localities: Hironocho, Hisanohama, Shioyazaki and Soma (Fukushima Pref.); Iwanuma (Miyagi Pref.); Kamogawa and Katsuura (Chiba Pref.); and Iwaya (Hyogo Pref.) (Fig. 1). The list of the specimens is shown in Table 1 (measurements made at Kobe University) and Table 2 (measurements made at Iwaki Meisei University).
Fig. 1

Locations of the collection sites of the specimens investigated in the present study

Table 1

List of samples examined at Kobe University, and the results of 134Cs, 137Cs and 40K measurements for dried samples when not specially noted

Sample code

Collection date

Taxonomy

Locality

Note (sample preparation and nature of samples)

134Cs

137Cs

40K

Class

Order

Species

Bq kg−1

Error

Detect. limit

Bq kg−1

Error

Detect. limit

Bq kg−1

Error

Detect. limit

k001

9 July 2011

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Fertile thalli, directly dried

320.57

16.07

0.012

346.14

22.70

0.009

1,132.70

310.81

0.282

k002

2 May 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Shioyazaki, Iwaki, Fukushima

Frozen

5,406.70

68.22

0.029

5557.90

93.10

0.020

2,494.30

375.95

0.309

k003

2 May 2011

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Frozen

3,009.50

97.10

0.054

2897.80

122.56

0.042

2,780.80

1013.30

0.942

k004

9 July 2011

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

487.54

58.31

0.051

567.83

74.20

0.046

n.d.

n.d.

1.381

k005

2 May 2011

Phaeophyceae

Fucales

Sargassumthunbergii

Shioyazaki, Iwaki, Fukushima

Frozen

4,151.90

60.11

0.026

4239.90

81.19

0.020

2,507.50

384.80

0.315

k006

2 May 2011

Phaeophyceae

Ectocarpales s.l.

Scytosiphonlomentaria

Shioyazaki, Iwaki, Fukushima

Frozen

5,417.10

131.01

0.073

5672.50

172.27

0.041

n.d.

n.d.

1.013

k007

6 May 2011

Phaeophyceae

Ectocarpales s.l.

Scytosiphonlomentaria

Nagasaki, Iwaki, Fukushima

Frozen

4,544.90

69.54

0.031

4616.00

93.95

0.021

n.d.

n.d.

0.376

k008

2 May 2011

Phaeophyceae

Fucales

Sargassummuticum

Shioyazaki, Iwaki, Fukushima

Frozen

3,991.30

98.26

0.049

4282.40

132.04

0.038

1,981.80

808.57

0.760

k009

2 May 2011

Ulvophyceae

Ulvales

Ulvapertusa

Shioyazaki, Iwaki, Fukushima

Frozen

4,231.90

138.52

0.070

4340.20

182.55

0.062

n.d.

n.d.

1.409

k010

2 May 2011

Phaeophyceae

Laminariales

Undariapinnatifida

Shioyazaki, Iwaki, Fukushima

Frozen

7,433.50

133.33

0.060

7371.20

173.95

0.047

1,152.20

799.52

0.800

k011

9 July 2011

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Juvenile thalli, directly dried

529.92

48.56

0.160

569.08

60.43

0.142

n.d.

n.d.

3.396

k012

9 July 2011

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Basal portion, directly dried

457.65

22.24

0.053

501.06

29.90

0.044

2,867.30

411.99

1.061

k013

2 May 2011

Ulvophyceae

Ulvales

Ulvalinza

Shioyazaki, Iwaki, Fukushima

Frozen

5,516.50

128.99

0.073

5433.80

165.31

0.038

n.d.

n.d.

0.944

k014

6 May 2011

Rhodophyceae

Gigartinales

Gloiopeltisfurcata

Nagasaki, Iwaki, Fukushima

Frozen

691.86

23.50

0.015

767.37

32.90

0.012

371.85

260.95

0.257

k015

6 May 2011

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Frozen

4,690.00

71.89

0.031

4810.30

96.65

0.023

2,957.80

462.11

0.383

k016

9 July 2011

Rhodophyceae

Gigartinales

Grateloupialanceolata

Nagasaki, Iwaki, Fukushima

Directly dried

318.48

28.83

0.106

352.40

36.17

0.090

n.d.

n.d.

2.073

k017

9 July 2011

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Frozen

606.50

66.73

0.200

576.93

85.96

0.199

n.d.

n.d.

5.182

k018

9 July 2011

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Tip portion, directly dried

340.77

21.65

0.018

321.15

26.71

0.016

4,783.70

525.79

1.280

k019

9 July 2011

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

426.87

37.52

0.136

425.32

45.34

0.097

n.d.

n.d.

2.638

k020

9 July 2011

Phaeophyceae

Fucales

Sargassumyamadae

Nagasaki, Iwaki, Fukushima

Directly dried

499.62

25.71

0.064

498.74

33.71

0.061

1,871.40

446.75

1.295

k023

9 July 2011

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Fertile thalli, frozen

278.38

16.89

0.045

292.40

21.88

0.038

1,987.90

355.52

0.976

k024

17 May 2011

Phaeophyceae

Fucales

Sargassummuticum

Iwaya, Awaji Isl., Hyogo

Directly dried

n.d.

0.00

0.002

n.d.

0.00

0.003

2,768.80

25.04

k025

17 May 2011

Phaeophyceae

Laminariales

Undariapinnatifida

Iwaya, Awaji Isl., Hyogo

Directly dried

n.d.

0.00

0.001

n.d.

0.00

0.001

1,841.80

34.15

0.029

k026

31 May 2011

Phaeophyceae

Ectocarpales s.l.

Colpomeniasinuosa

Iwaya, Awaji Isl., Hyogo

Directly dried

n.d.

0.00

0.001

n.d.

0.00

0.001

496.50

45.30

0.042

k027

31 May 2011

Ulvophyceae

Ulvales

Ulvapertusa

Iwaya, Awaji Isl., Hyogo

Directly dried

n.d.

0.00

0.001

n.d.

0.00

0.001

1,147.60

42.53

0.037

k028

30 May 2011

Phaeophyceae

Ectocarpales s.l.

Scytosiphonlomentaria

Iwaya, Awaji Isl., Hyogo

Directly dried

n.d.

0.00

0.007

n.d.

0.00

0.005

1,955.90

188.09

0.176

k029

6 September 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Directly dried

681.86

20.68

0.043

773.22

30.83

0.034

2,115.40

278.58

0.703

k030

6 September 2011

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.220

202.85

43.48

0.158

n.d.

n.d.

4.519

k031

6 September 2011

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Juvenile thallus, directly dried

193.70

25.07

0.097

230.31

36.71

0.086

4,214.10

860.98

2.389

k032

6 September 2011

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Old sporophyll, directly dried

255.02

31.38

0.121

224.34

36.26

0.108

n.d.

n.d.

2.716

k035

14 October 2011

Rhodophyceae

Gigartinales

Hypneaasiatica

Nagasaki, Iwaki, Fukushima

Directly dried

114.04

28.88

0.045

161.96

28.91

0.039

2,423.00

1144.60

1.108

k036

14 October 2011

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

36.56

4.75

0.006

43.05

6.67

0.007

1,013.10

194.79

0.177

k037

14 October 2011

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

57.64

4.20

0.005

67.41

6.09

0.005

1,120.30

158.44

0.137

k038

14 October 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Directly dried

51.42

9.67

0.014

64.29

10.74

0.013

1,380.30

372.98

0.348

k039

14 October 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Mature thalli, directly dried

105.99

4.78

0.004

114.00

6.66

0.004

995.04

126.90

0.109

k040

14 October 2011

Rhodophyceae

Gigartinales

Neodilseayendoana

Nagasaki, Iwaki, Fukushima

Directly dried

53.92

6.21

0.009

68.46

8.43

0.007

1,550.90

264.19

0.233

k041

14 October 2011

Phaeophyceae

Fucales

Sargassumyamadae

Nagasaki, Iwaki, Fukushima

Directly dried

200.17

14.01

0.013

229.20

17.54

0.012

1,522.60

401.82

0.380

k042

14 October 2011

Rhodophyceae

Gigartinales

Ahnfeltiopsisparadoxa

Nagasaki, Iwaki, Fukushima

Directly dried

59.91

5.33

0.007

86.65

7.68

0.006

761.02

184.22

0.170

k043

14 October 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Juvenile thalli, directly dried

59.57

6.33

0.008

69.15

8.25

0.008

1,742.10

259.79

0.226

k045

14 October 2011

Rhodophyceae

Ceramiales

Chondriacrassicaulis

Nagasaki, Iwaki, Fukushima

Directly dried

121.40

7.23

0.006

111.81

9.18

0.008

2,772.70

244.74

0.192

k046

2 May 2011

Seawater

Shioyazaki, Iwaki, Fukushima

Seawater

9.54

2.25

0.004

8.41

3.21

0.003

n.d.

n.d.

0.096

k047

2 May 2011

Seawater

Nagasaki, Iwaki, Fukushima

Seawater

11.27

2.15

0.003

9.74

3.43

0.003

n.d.

n.d.

0.094

k048

9 July 2011

Meltwater (dripping)

Nagasaki, Iwaki, Fukushima

From Undariapinnatifida

39.48

3.10

0.003

42.21

4.05

0.003

340.45

97.78

0.091

k049

9 July 2011

Meltwater (dripping)

Nagasaki, Iwaki, Fukushima

From Scytosiphonlomentaria

344.71

8.63

0.005

383.09

12.01

0.005

n.d.

n.d.

0.120

k050

9 July 2011

Meltwater (dripping)

Shioyazaki, Iwaki, Fukushima

From Sargassumthunbergii

402.97

8.86

0.005

436.72

12.14

0.004

502.65

116.14

0.108

k051

9 July 2011

Meltwater (dripping)

Shioyazaki, Iwaki, Fukushima

From Eiseniabicyclis

697.87

11.19

0.006

809.50

16.20

0.005

440.83

113.32

0.106

k052

5 December 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Juvenile thalli, directly dried

54.38

7.13

0.009

69.84

12.27

0.009

2,512.00

310.20

0.232

k053

5 December 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Mature thalli, directly dried

96.84

8.52

0.007

106.11

12.00

0.010

2,258.50

275.40

0.210

k054

5 December 2011

Rhodophyceae

Gigartinales

Neodilseayendoana

Nagasaki, Iwaki, Fukushima

Directly dried

45.30

7.30

0.010

40.58

13.32

0.012

1,082.40

281.80

0.249

k056

5 December 2011

Rhodophyceae

Corallinales

Calliarthron sp.

Nagasaki, Iwaki, Fukushima

Directly dried

25.56

5.17

0.007

34.10

8.95

0.007

n.d.

n.d.

0.197

k057

5 December 2011

Rhodophyceae

Ceramiales

Dasyasessilis

Nagasaki, Iwaki, Fukushima

Directly dried

219.43

22.28

0.022

234.59

29.33

0.021

4,101.20

705.21

0.592

k058

5 December 2011

Phaeophyceae

Fucales

Sargassumyamadae

Nagasaki, Iwaki, Fukushima

Directly dried

70.49

7.93

0.007

82.22

11.74

0.010

2,037.50

297.70

0.234

k059

5 December 2011

Rhodophyceae

Gigartinales

Ahnfeltiopsisparadoxa

Nagasaki, Iwaki, Fukushima

Directly dried

100.85

9.72

0.010

92.07

11.75

0.009

468.71

261.31

0.248

k060

5 December 2011

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

67.14

7.07

0.007

78.82

10.21

0.008

1,793.10

259.95

0.209

k061

5 December 2011

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

57.12

8.51

0.011

59.34

13.53

0.011

2,279.10

351.17

0.283

k062

5 December 2011

Phaeophyceae

Ralfsiales

Analipusjaponicus

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.048

197.20

41.70

0.042

n.d.

n.d.

1.285

k063

5 December 2011

Rhodophyceae

Gigartinales

Gloiopeltisfurcata

Nagasaki, Iwaki, Fukushima

Directly dried

51.77

10.06

0.008

53.65

11.71

0.011

592.87

309.57

0.296

k064

7 March 2012

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Directly dried

133.87

23.47

0.031

187.58

30.54

0.023

2,015.00

856.60

0.831

k065

7 March 2012

Rhodophyceae

Bangiales

Bangiafuscopurpurea

Nagasaki, Iwaki, Fukushima

Directly dried

160.51

8.98

0.009

226.22

13.80

0.009

936.70

256.60

0.240

k066

7 March 2012

Ulvophyceae

Ulvales

Ulvalinza

Nagasaki, Iwaki, Fukushima

Directly dried

66.25

10.30

0.016

85.16

14.60

0.015

1,865.00

443.30

0.408

k067

7 March 2012

Phaeophyceae

Fucales

Sargassumthunbergii

Nagasaki, Iwaki, Fukushima

Directly dried

106.37

6.40

0.007

137.03

9.24

0.006

1,654.00

208.10

0.178

k068

7 March 2012

Phaeophyceae

Ectocarpales s.l.

Scytosiphonlomentaria

Nagasaki, Iwaki, Fukushima

Directly dried

82.48

7.86

0.008

115.59

10.55

0.009

2,442.00

285.50

0.237

k069

7 March 2012

Rhodophyceae

Bangiales

Pyropiayezoensis

Nagasaki, Iwaki, Fukushima

Directly dried

24.47

4.78

0.008

51.06

9.61

0.008

1,195.00

252.30

0.230

k070

7 March 2012

Phaeophyceae

Ectocarpales s.l.

Petaloniafascia

Nagasaki, Iwaki, Fukushima

Directly dried

53.68

8.59

0.013

84.37

12.50

0.014

3,159.00

446.90

0.381

k071

7 March 2012

Ulvophyceae

Ulvales

Monostromanitidum

Nagasaki, Iwaki, Fukushima

Directly dried

46.99

9.58

0.017

69.71

10.99

0.013

1,614.00

412.70

0.400

k072

7 March 2012

Phaeophyceae

Ralfsiales

Analipusjaponicus

Nagasaki, Iwaki, Fukushima

Directly dried

76.48

5.71

0.006

105.77

8.00

0.005

1,064.00

184.90

0.164

k073

7 March 2012

Phaeophyceae

Ralfsiales

Analipusjaponicus

Nagasaki, Iwaki, Fukushima

Directly dried

93.27

6.47

0.008

101.18

8.32

0.008

1,512.00

258.00

0.243

k074

7 March 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Directly dried

33.69

4.58

0.005

62.91

6.44

0.005

1,642.00

178.60

0.148

k075

7 March 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Directly dried

26.96

3.95

0.005

37.92

5.43

0.005

2,999.00

193.90

0.140

k076

9 April 2012

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Directly dried

17.43

2.09

0.003

21.75

2.40

0.003

1,996.70

101.66

0.082

k077

9 April 2012

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

42.63

4.35

0.006

60.71

5.65

0.006

862.87

172.48

0.164

k078

9 April 2012

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Directly dried

21.71

1.83

0.002

28.45

2.48

0.002

1,588.50

89.13

0.073

k079

9 April 2012

Phaeophyceae

Fucales

Sargassumthunbergii

Nagasaki, Iwaki, Fukushima

Directly dried

67.57

2.97

0.003

90.22

4.19

0.003

1,293.00

1016.60

0.088

k080

9 April 2012

Phaeophyceae

Desmarestiales

Desmarestialigulata

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.007

n.d.

0.00

0.007

1,743.30

203.49

0.186

k081

9 April 2012

Phaeophyceae

Ectocarpales s.l.

Scytosiphonlomentaria

Nagasaki, Iwaki, Fukushima

Directly dried

48.66

2.99

0.003

71.76

4.17

0.003

1,603.20

115.51

0.099

k082

9 April 2012

Rhodophyceae

Rhodymeniales

Lomentariahakodatensis

Nagasaki, Iwaki, Fukushima

Directly dried

157.82

3.96

0.003

221.71

6.00

0.003

897.33

95.59

0.086

k083

9 April 2012

Rhodophyceae

Bangiales

Pyropiayezoensis

Nagasaki, Iwaki, Fukushima

Directly dried

38.64

3.26

0.004

49.65

3.92

0.004

967.23

130.02

0.120

k084

9 April 2012

Rhodophyceae

Ceramiales

Pterosiphoniapinnulata

Nagasaki, Iwaki, Fukushima

Directly dried

253.76

7.22

0.007

360.95

10.61

0.006

2,149.90

190.20

0.169

k085

9 April 2012

Rhodophyceae

Gigartinales

Ahnfeltiopsisparadoxa

Nagasaki, Iwaki, Fukushima

Directly dried

29.80

2.24

0.003

44.04

2.91

0.002

982.30

87.27

0.077

k086

9 April 2012

Phaeophyceae

Ectocarpales s.l.

Colpomeniasinuosa

Nagasaki, Iwaki, Fukushima

Directly dried

29.86

2.60

0.004

41.46

3.64

0.004

649.33

113.44

0.107

k087

9 April 2012

Phaeophyceae

Ectocarpales s.l.

Colpomeniasinuosa

Nagasaki, Iwaki, Fukushima

Directly dried

222.63

9.12

0.010

302.99

12.39

0.009

3,865.90

282.48

0.243

k088

9 April 2012

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

10.05

1.89

0.003

15.28

2.59

0.003

1,988.00

103.71

0.084

k089

9 April 2012

Phaeophyceae

Ralfsiales

Analipusjaponicus

Nagasaki, Iwaki, Fukushima

Directly dried

53.89

2.75

0.003

77.91

3.90

0.003

983.29

95.03

0.085

k090

9 April 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Directly dried

7.84

1.17

0.002

8.58

1.53

0.002

1,051.40

76.61

0.007

k091

9 April 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Juvenile thalli, directly dried

8.30

2.89

0.005

18.21

2.96

0.004

1,905.00

142.12

0.123

k092

9 April 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Sporophyll, directly dried

16.73

1.98

0.003

22.49

2.54

0.003

2,767.40

104.09

0.077

k093

10 April 2012

Phaeophyceae

Fucales

Sargassumyamadae

Yoshio, Katsuura, Chiba

Directly dried

n.d.

0.00

0.003

n.d.

0.00

0.003

1,184.00

102.98

0.091

k094

10 April 2012

Phaeophyceae

Laminariales

Eiseniabicyclis

Yoshio, Katsuura, Chiba

Directly dried

n.d.

0.00

0.002

n.d.

0.00

0.002

1,745.10

93.14

0.076

k095

10 April 2012

Phaeophyceae

Dictyotales

Padinaarborescens

Yoshio, Katsuura, Chiba

Directly dried

n.d.

0.00

0.006

n.d.

0.00

0.006

1,579.40

183.42

0.166

k096

10 April 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Yoshio, Katsuura, Chiba

Directly dried

n.d.

0.00

0.003

n.d.

0.00

0.003

1,991.10

94.59

0.075

k097

10 April 2012

Phaeophyceae

Laminariales

Eiseniabicyclis

Kamogawa, Chiba

Directly dried

n.d.

0.00

0.003

n.d.

0.00

0.003

1,652.30

95.39

0.079

k098

10 April 2012

Phaeophyceae

Laminariales

Eckloniacava

Kamogawa, Chiba

Directly dried

n.d.

0.00

0.003

n.d.

0.00

0.003

2,714.60

119.12

0.092

k099

10 April 2012

Phaeophyceae

Fucales

Sargassumfusiforme

Kamogawa, Chiba

Directly dried

n.d.

0.00

0.002

n.d.

0.00

0.002

3,236.60

91.82

0.061

k100

10 April 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Kamogawa, Chiba

Directly dried

n.d.

0.00

0.003

n.d.

0.00

0.003

1,922.90

103.42

0.084

k101

23 May 2012

Phaeophyceae

Fucales

Sargassumhorneri

Terashima, Iwanuma, Miyagi

Directly dried

67.12

26.24

0.029

76.05

23.03

0.022

1,701.70

723.22

0.711

k102

23 May 2012

Ulvophyceae

Ulvales

Ulvaprolifera

Terashima, Iwanuma, Miyagi

Directly dried

370.13

20.46

0.023

485.87

27.16

0.022

1,268.70

663.95

0.655

k103

23 May 2012

Phaeophyceae

Fucales

Sargassumhorneri

Matsukawaura, Soma, Fukushima

Directly dried

55.55

2.55

0.003

81.23

3.75

0.003

1,619.50

97.97

0.081

k104

23 May 2012

Ulvophyceae

Ulvales

Ulvapertusa

Soma Port, Soma, Fukushima

Directly dried

n.d.

0.00

0.012

n.d.

0.00

0.011

449.78

329.17

0.329

k105

23 May 2012

Ulvophyceae

Ulvales

Ulvapertusa

Matsukawaura, Soma, Fukushima

Directly dried

21.80

3.16

0.004

26.03

3.99

0.004

1,015.10

157.70

0.148

k106

23 May 2012

Phaeophyceae

Desmarestiales

Desmarestialigulata

Soma Port, Soma, Fukushima

Directly dried

n.d.

0.00

0.005

6.25

5.01

0.005

1,261.70

154.20

0.141

k107

23 May 2012

Phaeophyceae

Fucales

Sargassummuticum

Soma Port, Soma, Fukushima

Directly dried

n.d.

0.00

0.009

13.29

8.60

0.008

2,181.51

287.91

0.260

k108

23 May 2012

Rhodophyceae

Ceramiales

Delesseriaserrulata

Soma Port, Soma, Fukushima

Directly dried

14.26

4.03

0.005

25.17

4.34

0.004

1,723.80

145.10

0.128

k109

9 April 2012

Ulvophyceae

Ulvales

Monostromanitidum

Nagasaki, Iwaki, Fukushima

Directly dried

25.73

3.51

0.007

27.32

5.02

0.006

703.11

180.50

0.173

k110

23 May 2012

Rhodophyceae

Gigartinales

Grateloupialanceolata

Matsukawaura, Soma, Fukushima

Directly dried

12.96

3.27

0.006

n.d.

0.00

0.005

825.74

168.62

0.160

k111

23 May 2012

Rhodophyceae

Gigartinales

Schizymeniadubyi

Matsukawaura, Soma, Fukushima

Directly dried

n.d.

0.00

0.004

n.d.

0.00

0.003

721.71

108.01

0.101

k112

23 May 2012

Rhodophyceae

Gigartinales

Schizymeniadubyi

Matsukawaura, Soma, Fukushima

Directly dried

19.68

6.73

0.007

17.97

7.14

0.007

882.64

216.67

0.210

k113

23 May 2012

Rhodophyceae

Corallinales

Gelidiumelegans

Matsukawaura, Soma, Fukushima

Directly dried

60.91

4.66

0.006

90.92

6.23

0.006

1,165.70

177.93

0.167

k115

23 May 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Matsukawaura, Soma, Fukushima

Directly dried

49.35

2.50

0.003

54.70

3.31

0.003

1,428.50

99.27

0.008

k116

9 December 2012

Ulvophyceae

Ulvales

Ulvapertusa

Hirono, Futaba, Fukushima

Directly dried

36.73

3.03

0.004

54.46

4.98

0.004

0.00

0.00

0.209

k117

9 December 2012

Rhodophyceae

Gigartinales

Chondrusgiganteus

Hirono, Futaba, Fukushima

Directly dried

13.61

1.84

0.002

22.89

2.22

0.002

0.00

0.00

0.132

k118

9 December 2012

Phaeophyceae

Ectocarpales s.l.

Petaloniafascia

Hirono, Futaba, Fukushima

Directly dried

33.09

2.67

0.003

48.98

3.81

0.004

0.00

0.00

0.200

k119

9 December 2012

Rhodophyceae

Gigartinales

Neodilsealongissima

Hirono, Futaba, Fukushima

Directly dried

13.66

2.15

0.002

n.d.

0.00

0.00

0.00

0.139

k122

10 December 2012

Phaeophyceae

Fucales

Sargassumyamadae

Nagasaki, Iwaki, Fukushima

Directly dried

17.05

1.79

0.002

22.02

2.63

0.003

1,299.00

88.13

0.075

k123

10 December 2012

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.007

26.19

6.81

0.006

769.50

208.60

0.202

k124

10 December 2012

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.003

10.49

3.04

0.003

1,996.00

106.00

0.086

k125

10 December 2012

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Directly dried

19.62

3.96

0.004

21.56

4.08

0.005

2,457.00

160.10

0.135

k128

10 December 2012

Phaeophyceae

Dictyotales

Spatoglossumpacificum

Nagasaki, Iwaki, Fukushima

Directly dried

41.53

2.92

0.004

68.91

5.62

0.004

2,484.00

147.10

0.121

k130

10 December 2012

Rhodophyceae

Bangiales

Pyropiayezoensis

Nagasaki, Iwaki, Fukushima

Directly dried

12.21

2.80

0.004

26.86

3.84

0.005

657.28

148.70

0.143

k131

10 December 2012

Ulvophyceae

Ulvales

Ulvaprolifera

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.008

8.04

7.58

0.008

848.51

236.56

0.229

k132

10 December 2012

Ulvophyceae

Cladophorales

Chaetomorphamoniligera

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.007

n.d.

0.00

3,770.30

247.20

0.214

k133

10 December 2012

Rhodophyceae

Gigartinales

Chondrusocellatus

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.003

6.68

3.58

0.004

677.03

112.57

0.106

k134

10 December 2012

Rhodophyceae

Gigartinales

Grateloupiaturuturu

Nagasaki, Iwaki, Fukushima

Directly dried

10.32

2.49

0.003

9.46

4.22

0.004

1,163.40

128.02

0.116

k135

10 December 2012

Rhodophyceae

Gigartinales

Ahnfeltiopsisparadoxa

Nagasaki, Iwaki, Fukushima

Directly dried

10.64

2.14

0.002

9.84

1.87

0.003

604.94

81.66

0.076

k138

10 December 2012

Rhodophyceae

Gigartinales

Gloiopeltisfurcata

Nagasaki, Iwaki, Fukushima

Directly dried

64.95

8.00

0.014

92.33

12.25

0.013

5,190.10

427.40

0.376

k139

10 December 2012

Rhodophyceae

Gigartinales

Grateloupialanceolata

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.007

8.51

6.27

0.006

688.58

198.65

0.193

k140

10 December 2012

Rhodophyceae

Gigartinales

Plocamiumcartilagineum

Nagasaki, Iwaki, Fukushima

Directly dried

22.16

3.92

0.007

59.69

6.30

0.006

514.62

206.47

0.204

k141

10 December 2012

Rhodophyceae

Ceramiales

Chondriacrassicaulis

Nagasaki, Iwaki, Fukushima

Directly dried

41.82

4.62

0.005

47.81

5.45

0.006

3,859.40

213.11

0.174

k142

9 December 2012

Phaeophyceae

Fucales

Sargassumthunbergii

Hisanohama, Iwaki, Fukushima

Directly dried

345.96

5.95

0.004

592.67

98.32

0.004

1,401.50

112.60

0.098

k143

9 December 2012

Rhodophyceae

Gigartinales

Chondrusgiganteus

Hisanohama, Iwaki, Fukushima

Directly dried

38.55

2.44

0.003

59.74

3.62

0.003

1,149.10

97.59

0.086

k144

9 December 2012

Rhodophyceae

Gigartinales

Chondrusgiganteus

Hisanohama, Iwaki, Fukushima

Directly dried

18.33

3.51

0.004

36.82

3.47

0.004

1,257.70

122.81

0.110

k145

9 December 2012

Phaeophyceae

Fucales

Sargassummuticum

Hisanohama, Iwaki, Fukushima

Directly dried

123.97

4.21

0.004

209.89

6.76

0.004

1,503.30

1290.70

0.113

k146

9 December 2012

Phaeophyceae

Fucales

Sargassumfusiforme

Hisanohama, Iwaki, Fukushima

Directly dried

21.49

1.86

0.003

34.70

3.37

0.003

4,206.90

116.52

0.078

k147

9 December 2012

Phaeophyceae

Ectocarpales s.l.

Colpomeniasinuosa

Hisanohama, Iwaki, Fukushima

Directly dried

219.97

4.88

0.004

363.65

7.70

0.003

3,025.40

122.48

0.093

k148

9 December 2012

Phaeophyceae

Laminariales

Saccharinajaponica

Hisanohama, Iwaki, Fukushima

Directly dried

33.55

2.71

0.003

60.87

35.82

0.003

3,479.60

118.90

0.086

k149

9 December 2012

Phaeophyceae

Laminariales

Saccharinajaponica

Hisanohama, Iwaki, Fukushima

Directly dried

34.03

2.82

0.003

54.74

3.61

0.003

3,218.60

122.46

0.091

k150

9 December 2012

Rhodophyceae

Ceramiales

Chondriacrassicaulis

Hisanohama, Iwaki, Fukushima

Directly dried

42.05

4.27

0.005

58.60

6.18

0.005

3,937.10

186.64

0.147

k151

16 March 2013

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.003

10.64

3.11

0.003

2,250.80

108.28

0.085

k152

16 March 2013

Phaeophyceae

Fucales

Sargassumyamadae

Nagasaki, Iwaki, Fukushima

Directly dried

9.69

2.30

0.005

7.91

4.56

0.004

840.94

140.74

0.132

k153

16 March 2013

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

9.79

1.87

0.003

19.12

3.24

0.003

1,453.10

117.82

0.103

k154

16 March 2013

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

 

7.18

1.84

0.003

1,274.50

91.32

0.079

k155

16 March 2013

Phaeophyceae

Fucales

Sargassumthunbergii

Nagasaki, Iwaki, Fukushima

Directly dried

13.92

2.35

0.003

20.90

2.88

0.003

1,738.20

124.22

0.106

k156

16 March 2013

Rhodophyceae

Gigartinales

Ahnfeltiopsisflabelliformis

Nagasaki, Iwaki, Fukushima

Directly dried

16.71

3.77

0.008

22.80

7.53

0.007

1,349.40

230.51

0.217

k158

16 March 2013

Rhodophyceae

Rhodymeniales

Lomentariahakodatensis

Nagasaki, Iwaki, Fukushima

Directly dried

34.77

3.08

0.004

60.47

4.43

0.004

993.42

130.86

0.121

k159

16 March 2013

Phaeophyceae

Dictyotales

Pachydictyoncoriaceum

Nagasaki, Iwaki, Fukushima

Directly dried

26.23

4.94

0.007

38.11

5.35

0.007

1,494.50

229.91

0.216

k160

16 March 2013

Ulvophyceae

Cladophorales

Cladophora sp.

Nagasaki, Iwaki, Fukushima

Directly dried

50.88

5.23

0.006

75.11

6.10

0.006

1,029.20

190.05

0.179

k161

16 March 2013

Ulvophyceae

Ulvales

Ulvaprolifera

Nagasaki, Iwaki, Fukushima

Directly dried

44.66

4.58

0.006

67.05

5.66

0.006

1,218.00

182.82

0.172

k162

16 March 2013

Ulvophyceae

Cladophorales

Chaetomorphamoniligera

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.004

10.23

3.07

0.004

3,397.30

168.28

0.134

k164

16 March 2013

Rhodophyceae

Gigartinales

Ahnfeltiopsisparadoxa

Nagasaki, Iwaki, Fukushima

Directly dried

11.31

2.13

0.002

16.85

2.18

0.002

902.53

85.45

0.076

k165

16 March 2013

Rhodophyceae

Gigartinales

Gloiopeltisfurcata

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.003

n.d.

0.00

0.003

534.66

105.28

0.100

k166

16 March 2013

Rhodophyceae

Gigartinales

Grateloupialanceolata

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.004

n.d.

0.00

0.004

601.26

125.92

0.120

k167

16 March 2013

Rhodophyceae

Gigartinales

Grateloupialanceolata

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.003

7.42

1.97

0.003

503.27

85.20

0.081

k169

16 March 2013

Rhodophyceae

Gigartinales

Polyopesaffinis

Nagasaki, Iwaki, Fukushima

Directly dried

27.53

4.41

0.004

48.01

4.06

0.004

533.00

133.37

0.128

k170

16 March 2013

Rhodophyceae

Gigartinales

Polyopesaffinis

Nagasaki, Iwaki, Fukushima

Directly dried

12.20

2.42

0.004

13.51

3.60

0.003

377.65

107.94

0.105

k171

16 March 2013

Phaeophyceae

Ralfsiales

Analipusjaponicus

Nagasaki, Iwaki, Fukushima

Directly dried

13.12

2.58

0.006

36.35

5.03

0.005

931.90

180.17

0.172

k173

16 March 2013

Rhodophyceae

Ceramiales

Chondriacrassicaulis

Nagasaki, Iwaki, Fukushima

Directly dried

12.14

2.48

0.004

15.77

3.92

0.004

4,277.60

152.07

0.110

k174

16 March 2013

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Directly dried

6.70

2.11

0.003

n.d.

0.00

0.029

1,352.80

100.01

0.086

k175

16 March 2013

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Directly dried

5.29

2.10

0.003

11.27

2.96

0.003

1,808.80

102.71

0.084

k176

16 March 2013

Ulvophyceae

Cladophorales

Cladophoraalbida

Nagasaki, Iwaki, Fukushima

Directly dried

62.13

5.30

0.006

113.19

8.75

0.006

1,573.60

205.12

0.190

k177

16 March 2013

Rhodophyceae

Gigartinales

Mazzaellajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0.00

0.004

8.24

2.33

0.004

771.82

109.99

0.103

k178

16 March 2013

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

32.05

3.56

0.005

60.48

5.13

0.005

1,362.20

161.87

0.148

k179

16 March 2013

Ulvophyceae

Ulvales

Ulvapertusa

Hirono, Futaba, Fukushima

Directly dried

26.06

4.60

0.007

58.17

5.74

0.006

1,016.70

201.46

0.192

k180

16 March 2013

Rhodophyceae

Gigartinales

Chondrusgiganteus

Hirono, Futaba, Fukushima

Directly dried

8.03

2.00

0.003

13.81

3.09

0.003

537.88

90.53

0.086

k183

16 March 2013

Rhodophyceae

Bangiales

Pyropiayezoensis

Hirono, Futaba, Fukushima

Directly dried

n.d.

0.00

0.005

11.26

2.88

0.004

759.90

146.33

0.139

k184

16 March 2013

Ulvophyceae

Ulvales

Ulvaprolifera

Hirono, Futaba, Fukushima

Directly dried

78.64

6.22

0.008

139.62

8.75

0.007

828.08

230.72

0.224

k185

16 March 2013

Phaeophyceae

Ectocarpales s.l.

Petaloniafascia

Hirono, Futaba, Fukushima

Directly dried

n.d.

0.00

0.005

21.69

3.26

0.004

1,394.70

138.48

0.125

k186

16 March 2013

Rhodophyceae

Gigartinales

Neodilsealongissima

Hirono, Futaba, Fukushima

Directly dried

7.08

2.59

0.003

14.36

3.25

0.003

1,756.70

113.02

0.096

k187

16 March 2013

Rhodophyceae

Gigartinales

Gloiopeltisfurcata

Hirono, Futaba, Fukushima

Directly dried

14.63

2.89

0.005

18.17

3.36

0.005

437.27

148.11

0.145

k188

16 March 2013

Rhodophyceae

Gigartinales

Gloiopeltisfurcata

Hirono, Futaba, Fukushima

Directly dried

9.04

2.42

0.005

24.57

3.71

0.005

542.12

143.03

0.138

k189

16 March 2013

Phaeophyceae

Ralfsiales

Analipusjaponicus

Hirono, Futaba, Fukushima

Directly dried

22.10

2.30

0.003

36.36

3.02

0.003

1,113.90

1017.40

0.910

k190

16 March 2013

Rhodophyceae

Ceramiales

Chondriacrassicaulis

Hirono, Futaba, Fukushima

Directly dried

29.82

2.84

0.003

49.95

4.25

0.003

3,051.80

126.98

0.097

k191

16 March 2013

Phaeophyceae

Laminariales

Undariapinnatifida

Hirono, Futaba, Fukushima

Directly dried

n.d.

0.00

0.003

11.93

2.67

0.002

1,313.60

89.82

0.077

Values of detection limit in Bq kg−1. n.d. means not detectable (blow the detection limit). Error means overall error estimated by the analyzing software from systematic errors in the system together with the standard deviation of the counting

Table 2

List of samples examined at Iwaki Meisei University, and the results of 134Cs and 137Cs measurements

Sample code

Collection date

Taxonomy

Locality

Note (sample preparation and nature of samples)

134Cs

137Cs

Class

Order

Species

Bq kg−1

Error

Detect. limit

Bq kg−1

Error

Detect. limit

IMU001

2 May 2011

Phaeophyceae

Dictyotales

Spatoglossumpacificum

Shioyazaki, Iwaki, Fukushima

Frozen

5,200

138

156

9,430

179

133

IMU002

2 May 2011

Phaeophyceae

Fucales

Sargassumyamadae

Shioyazaki, Iwaki, Fukushima

Frozen

1,210

25.2

25.8

1,980

31.5

19.9

IMU003

6 May 2011

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Frozen

3,910

116

144

6,020

138

108

IMU004

6 May 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Frozen

3,670

96.5

107

5,980

119

89.2

IMU005

6 May 2011

Rhodophyceae

Gigartinales

Grateloupialanceolata

Nagasaki, Iwaki, Fukushima

Frozen

2,920

123

159

4,390

146

144

IMU006

9 July 2011

Phaeophyceae

Dictyotales

Dictyotadichotoma

Nagasaki, Iwaki, Fukushima

Frozen

556

72.1

167

1,130

88.2

148

IMU007

9 July 2011

Phaeophyceae

Ectocarpales s.l.

Colpomeniasinuosa

Nagasaki, Iwaki, Fukushima

Frozen

720

163

446

1,390

189

434

IMU008

9 July 2011

Phaeophyceae

Ectocarpales s.l.

Scytosiphonlomentaria

Nagasaki, Iwaki, Fukushima

Frozen

590

53.4

98.5

1,080

68.3

101

IMU009

9 July 2011

Phaeophyceae

Desmarestiales

Desmarestialigulata

Nagasaki, Iwaki, Fukushima

Frozen

154

7.70

11.3

255

9.98

11.5

IMU010

9 July 2011

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Frozen

676

16.0

21.0

1,240

21.1

17.5

IMU011

9 July 2011

Rhodophyceae

Gigartinales

Chondrusocellatus

Nagasaki, Iwaki, Fukushima

Frozen

288

64.1

174

333

63.7

164

IMU012

9 July 2011

Rhodophyceae

Gigartinales

Grateloupiasparsa

Nagasaki, Iwaki, Fukushima

Frozen

569

50.0

102

1,030

58.8

81.1

IMU013

9 July 2011

Rhodophyceae

Gigartinales

Ahnfeltiopsisparadoxa

Nagasaki, Iwaki, Fukushima

Frozen

174

13.2

23.3

339

17.4

22.9

IMU014

9 July 2011

Rhodophyceae

Rhodymeniales

Gastrocloniumpacificum

Nagasaki, Iwaki, Fukushima

Frozen

733

43.8

70.2

1,190

53.1

64.5

IMU015

14 October 2011

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Frozen

267

62.3

172

470

66.2

147

IMU016

4 July 2012

Phaeophyceae

Ralfsiales

Analipusjaponicus

Nagasaki, Iwaki, Fukushima

Directly dried

54.2

6.30

13.8

87.8

7.52

13.7

IMU017

4 July 2012

Phaeophyceae

Dictyotales

Dictyotadichotoma

Nagasaki, Iwaki, Fukushima

Directly dried

113

8.20

14.8

150

9.31

14.7

IMU018

4 July 2012

Phaeophyceae

Ectocarpales s.l.

Leathesiadifformis

Nagasaki, Iwaki, Fukushima

Directly dried

128

10.4

20.7

213

12.2

18.5

IMU019

4 July 2012

Phaeophyceae

Ectocarpales s.l.

Scytosiphonlomentaria

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0

51.0

56.3

15.8

45.7

IMU020

4 July 2012

Phaeophyceae

Ectocarpales s.l.

Tinocladiacrassa

Nagasaki, Iwaki, Fukushima

Directly dried

27.3

8.31

24.4

38.7

9.62

27.0

IMU021

4 July 2012

Phaeophyceae

Fucales

Sargassumconfusum

Nagasaki, Iwaki, Fukushima

Directly dried

15.5

3.80

10.6

30.0

4.20

9.20

IMU022

4 July 2012

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Directly dried

17.7

3.75

10.3

37.4

4.75

11.1

IMU023

4 July 2012

Phaeophyceae

Fucales

Sargassumthunbergii

Nagasaki, Iwaki, Fukushima

Directly dried

14.3

2.81

7.59

31.3

3.60

8.00

IMU024

4 July 2012

Phaeophyceae

Laminariales

Undariapinnatifida

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0

10.8

23.0

4.25

11.2

IMU025

4 July 2012

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0

10.8

23.7

3.92

9.39

IMU026

4 July 2012

Phaeophyceae

Laminariales

Eiseniabicyclis

Nagasaki, Iwaki, Fukushima

Directly dried

14.8

3.23

8.69

19.0

3.67

9.52

IMU027

4 July 2012

Ulvophyceae

Ulvales

Ulvapertusa

Nagasaki, Iwaki, Fukushima

Directly dried

15.3

3.76

10.5

23.7

4.32

11.0

IMU028

4 July 2012

Ulvophyceae

Cladophorales

Chaetomorphamoniligera

Nagasaki, Iwaki, Fukushima

Directly dried

17.1

3.99

11.0

26.5

4.93

12.7

IMU029

4 July 2012

Ulvophyceae

Codiales

Codiumlucasii

Nagasaki, Iwaki, Fukushima

Directly dried

n.d.

0

48.0

109

18.3

4.50

IMU030

4 July 2012

Ulvophyceae

Bryopsidales

Bryopsisplumosa

Nagasaki, Iwaki, Fukushima

Directly dried

72.4

8.32

19.0

86.7

8.96

19.5

IMU031

4 July 2012

Rhodophyceae

Corallinales

Corallinapilulifera

Nagasaki, Iwaki, Fukushima

Directly dried

36.2

3.56

7.29

63.9

4.63

7.87

IMU032

4 July 2012

Rhodophyceae

Corallinales

Calliarthronyessoense

Nagasaki, Iwaki, Fukushima

Directly dried

14.7

3.53

9.82

22.1

3.83

9.45

IMU033

4 July 2012

Rhodophyceae

Gigartinales

Chondracanthusintermedius

Nagasaki, Iwaki, Fukushima

Directly dried

38.9

6.04

14.9

54.2

6.64

14.7

IMU034

4 July 2012

Rhodophyceae

Gigartinales

Chondrusocellatus

Nagasaki, Iwaki, Fukushima

Directly dried

23.2

4.07

10.3

40.6

4.87

10.4

IMU035

4 July 2012

Rhodophyceae

Gigartinales

Ahnfeltiopsisparadoxa

Nagasaki, Iwaki, Fukushima

Directly dried

27.9

35.9

8.22

47.0

4.54

9.15

IMU036

4 July 2012

Rhodophyceae

Ceramiales

Chondriacrassicaulis

Nagasaki, Iwaki, Fukushima

Directly dried

69.0

7.69

16.4

105

8.81

15.4

IMU037

4 July 2012

Rhodophyceae

Ceramiales

Laurenciaokamurae

Nagasaki, Iwaki, Fukushima

Directly dried

129

7.29

11.3

239

9.59

9.84

IMU038

10 December 2012

Phaeophyceae

Fucales

Sargassumhorneri

Nagasaki, Iwaki, Fukushima

Directly dried

16.3

4.69

13.6

n.d.

0

16.0

IMU039

10 December 2012

Phaeophyceae

Fucales

Sargassumsiliquastrum

Nagasaki, Iwaki, Fukushima

Directly dried

60.5

7.04

16.2

118

8.37

13.1

IMU040

10 December 2012

Phaeophyceae

Laminariales

Saccharinajaponica

Nagasaki, Iwaki, Fukushima

Directly dried

26.2

5.23

13.8

47.5

6.22

13.9

Values of detection limit in Bq kg−1. n.d. means not detectable (blow the detection limit). Error means overall error estimated by the analyzing software from systematic errors in the system together with the standard deviation of the counting

For the measurements at Kobe University, sorted specimens were identified based on their morphology, preliminarily air-dried overnight using a fan at room temperature, and then dried in an oven at 90–100 °C for 8 h. The weight ratios of wet/dry samples were roughly 10, and this value was used in the comparisons of literature data based on wet samples, and concentration factors. Dried specimens were preliminarily broken into fragments manually, and powdered using a blender (Waring J-SPEC 7011BUJ, Conair Corp., Stamford, CT, USA). Powdered specimens were packed in U-8 sample cups (56 mm ø and 68 mm high) and used for measurement. The protocol of radioactivity measurements is described in Mimura et al. (2014). In Tables 1 and 2, “Error” is the overall error estimated by the analyzing software from systematic errors in the system together with the standard deviation of the counting. Seawaters collected at the coasts of Nagasaki and Shioyazaki in May 2011 were filled in U-8 sample cups and used for measurements without evaporation.

For the measurements at Iwaki Meisei University, sorted specimens were identified based on their morphology, washed with fresh water and pre-dried at room temperature. Dried specimens were desiccated in an oven at 60 °C for 48 h, powdered using a blender, and packed in U-8 sample cups. 134Cs and 137Cs were measured using a GEM40P4-76 germanium detector (Seiko EG & G, Tokyo, Japan) following the manufacturer’s instructions.

The first collections (May 2011) of the macroalgal specimens were kept frozen at −20 °C until drying. However, this protocol resulted in some loss of radioactivity in meltwater (dripping). Accordingly, in order to assess the loss of radioactivity during thawing, some specimens (collected in July 2011) were either frozen before drying or directly dried, and the radioactivity was compared between these drying protocols. In addition, the radioactivity of the meltwater obtained from the thawed specimens was also measured.

Statistical problems

In some radioactivity measurements, such as for macroalgal samples, we could not obtain a sufficient amount of samples that allow us to ensure statistical reliance of the measurement. There was also a limitation in the total running time on a germanium detector. In other cases, the total volume of collected samples was not large enough to fill the U-8 sample cup, resulting in rather low detection signals. For all these experiments, only data are presented with notification that the precision of data was not statistically tested.

Results

The 134Cs:137Cs ratios of examined specimens were plotted according to time series (Fig. 2). The ratio reduced to ca. 0.6 after two years, which agreed well with the expected value by natural decay (0.79 after one year, and 0.64 after two years).
Fig. 2

Evolution of 134Cs/137Cs ratio of the specimens examined. Dotted line indicates the theoretical expected value by the spontaneous decay of 134Cs and 137Cs

Results of the measurements at Kobe University (134Cs, 137Cs and 40K) and Iwaki Meisei University (134Cs and 137Cs) are listed in Table 1 and Table 2, respectively. On 2 May and 6 May 2011 (Shioyazaki and Nagasaki, about 50 km from F1NPP), specimens of most macroalgal species, i.e., Ulvapertusa, U. linza Linnaeus, Scytosiphonlomentaria (Lyngbye) Link, Eiseniabicyclis (Kjellman) Setchell, Undariapinnatifida, Sargassummuticum (Yendo) Fensholt, and S. thunbergii, showed 137Cs levels greater than 3,000 Bq kg−1 (Figs. 3, 4). The highest 137Cs level was 7,371.20 ± 173.95 Bq kg−1 in Undariapinnatifida (Fig. 3; sample code k010 in Table 1). The 134Cs:137Cs ratio was ca. 0.97. Exceptionally, Gloiopeltisfurcata (Postels & Ruprecht) J. Agardh showed a relatively lower value of 767.37 ± 32.90 Bq kg−1 (Fig. 4; sample code k014 in Table 1). Seawater collected on May 2 at Shioyazaki (Fig. 3) and Nagasaki (Fig. 4) measured 8.41 ± 3.21 and 9.74 ± 3.43 Bq L−1, respectively. In control samples from Awaji Island in May 2011, 137Cs levels were below the detectable level of 0.001–0.002 in Undariapinnatifida, Sargassummuticum, and Ulvapertusa (Table 1).
Fig. 3

Quantities of 134Cs and 137Cs of diverse marine macroalgae and seawater collected in May 2011 at Shioyazaki, Iwaki, Fukushima Pref., Japan. Measurement unit for seawater is Bq kg−1 (wet weight). Asterisks show data by the measurement at Iwaki Meisei University

Fig. 4

Quantities of 134Cs and 137Cs of diverse marine macroalgae and seawater collected in May 2011 at Nagasaki, Iwaki, Fukushima Pref., Japan. Measurement unit for seawater is Bq kg−1 (wet weight). Asterisks show data by the measurement at Iwaki Meisei University

137Cs levels remarkably declined at Nagasaki within the following 5–6 months. In July 2011, 137Cs ranged from ca. 300–600 Bq kg−1 (Fig. 5), declined to 40–200 Bq kg−1 in October 2011 (Fig. 6) and became lower than 100 Bq kg−1 in most samples in July 2012 (Fig. 7) and December 2012 (Fig. 8). However, 137Cs was still detectable in the range of 10–100 Bq kg−1 in many samples in March 2013, 24 months after the date of highest records (Fig. 9).
Fig. 5

Quantities of 134Cs and 137Cs of diverse marine macroalgae collected in July 2011 at Nagasaki, Iwaki, Fukushima Pref., Japan. Asterisks show data by the measurement at Iwaki Meisei University

Fig. 6

Quantities of 134Cs and 137Cs of diverse marine macroalgae collected in October 2011 at Nagasaki, Iwaki, Fukushima Pref., Japan. Asterisks show data by the measurement at Iwaki Meisei University

Fig. 7

Quantities of 134Cs and 137Cs of diverse marine macroalgae collected in July 2012 at Nagasaki, Iwaki, Fukushima Pref., Japan. Asterisks show data by the measurement at Iwaki Meisei University

Fig. 8

Quantities of 134Cs and 137Cs of diverse marine macroalgae and seawater collected in December 2012 at Nagasaki, Iwaki, Fukushima Pref., Japan. Asterisks show data by the measurement at Iwaki Meisei University

Fig. 9

Quantities of 134Cs and 137Cs of diverse marine macroalgae and seawater collected in March 2013 at Nagasaki, Iwaki, Fukushima Pref., Japan

The progression of 137Cs levels differed in different taxa. In the green alga Ulvapertusa, which has very short lifetime (ephemeral species), 137Cs levels clearly declined during the summer of 2011, but remained in the range of 10–110 Bq kg−1 from winter 2011 to spring 2013 (Fig. 10). 40K was somewhat higher in May 2011 samples, but was rather constant in the other samples (ca. 1,000–1,500 Bq kg−1). The annual brown algae Undariapinnatifida (Fig. 11) and Sargassumhorneri (data not shown) showed similar patterns of 137Cs progression: they showed rapid decline in the first year, and continuously declined until March 2013. The 40K level of Undariapinnatifida of the specimens from Chiba Pref. and Hyogo Pref. were 1,840–1,990 Bq kg−1 (Fig. 11).
Fig. 10

Evolution of 134Cs, 137Cs and 40K quantities in the annual green alga Ulvapertusa at Nagasaki, Iwaki, Fukushima Pref., Japan

Fig. 11

Evolution of 134Cs, 137Cs and 40K quantities in the annual brown alga Undariapinnatifida at Nagasaki, Iwaki, Fukushima Pref., Japan

Perennial brown algae such as Eiseniabicyclis (Fig. 12) and Sargassumyamadae (Fig. 13), which are important elements of algal beds in the area, also showed similar progressions in 137Cs levels, although the level of 40K (ca. 1,500–2,000 Bq kg−1) was generally higher than in Ulvapertusa (Fig. 11). The 40K levels of Eiseniabicyclis and Sargassumyamadae of the specimens from Chiba Pref. were 1,650–1,750 and 1,180 Bq kg−1, respectively, and were comparable to those in Fukushima Pref. (Figs. 12, 13). Unfortunately, there were few species of red algae that could be collected seasonally. Ahnfeltiopsisparadoxa (Suringar) Masuda (Fig. 14) showed a clear decrease in 137Cs levels in 2011, but it was also still in a detectable range of ca. 10 Bq kg−1 in March 2013. 40K levels were in the range of 800–1,000 Bq kg−1, which was comparable to Ulva (green alga) and considerably lower than Undaria, Eisenia and Sargassum) (brown algae).
Fig. 12

Evolution of 134Cs, 137Cs and 40K quantities in the perennial brown alga Eiseniabicyclis at Nagasaki, Iwaki, Fukushima Pref., Japan

Fig. 13

Evolution of 134Cs, 137Cs and 40K quantities in the perennial brown alga Sargassumyamadae at Nagasaki, Iwaki, Fukushima Pref., Japan

Fig. 14

Evolution of 134Cs, 137Cs and 40K quantities in the perennial red alga Ahnfeltiopsisparadoxa at Nagasaki, Iwaki, Fukushima Pref., Japan

Discussion

137Cs concentrations in seawater off the eastern Japan coast prior to the accident were in the same order of magnitude as other surface oceanic waters, between 1 and 3 Bq m−3 for 137Cs (Nakanishi et al. 2010). After the accident, measured concentrations in a 30 km perimeter around the plant exceeded 10 Bq L−1 (or 10,000,000 Bq m−3) (Bailly du Bois et al. 2012).

The 137Cs levels in seawater at the coast of Iwaki (Shioyazaki and Nagasaki) one month after the mass discharge of high concentration contaminated water in April measured ca. 8–10 Bq L−1 in our own measurements (Fig. 4). These values agree well with the report of Bailly du Bois et al. (2012). The coast around Shioyazaki and Nagasaki was estimated to have been exposed up to ca. 60 Bq L−1 for about two weeks (15 April–1 May 2011) according to the estimated geographical distribution of the 137Cs in Bailly du Bois et al. (2012).

The influence of the radioactive liquid effluents escaping directly from the nuclear power plant was particularly significant from 26 March to 8 April 2011 in the vicinity of the plant. Concentrations measured after 10 April 2011 declined in the vicinity of the plant. The perennial brown alga Eiseniabicyclis also showed a similar pattern, but in the red alga Ahnfeltiopsisparadoxa the levels stayed about the same during December 2012 and March 2013. In contrast, the concentration of 40K was relatively stable throughout the period, in accordance with the assumption that it is not of anthropogenic origin because the levels were comparable to those of the specimens from Chiba Pref. and Hyogo Pref.

Given that the seawater 137Cs levels were in the range of 10–60 Bq L−1 at Shioyazaki and Nagasaki in April 2011 [according to our data and those by Bailly du Bois et al. (2012)], and that seaweeds collected in May 2011 contained an average 137Cs level of ca. 5,000 Bq kg−1, the seaweeds are considered to have accumulated 137Cs in their tissues by 8–50 folds compared to their environment (80–500 folds in dry samples, given the wet/dry mass ratio of 10). These CF values must be certainly underestimated because some part (or a large part) of the algal tissue of the specimens collected in early May 2011 (2 May and 6 May 2011) had already been grown up before the exposure to the highly radiopolluted seawater. In general, the growth rate of seaweeds differs depending on the species; even in rather fast growing species, such as Ulva spp. and Undariapinnatifida, their growth period is longer than one month; and many species grow up in 3–4 months.

The above CF values of ca. 8–50 agree well with the known CF values of ca. 30–50 in marine macroalgae (IAEA 2004). Considering the underestimation in our data as mentioned above, macroalgal CF may be somewhat higher than the IAEA standard. This could be caused if the local concentration of 137Cs in polluted seawater during the seaweed growth period (e.g., during later April 2011) were higher than that on the collection dates after May 2011.

The 137Cs levels of the specimens directly dried after collection (air-dried and then heated; e.g., k001, k004 in Table 1), and those frozen before drying (frozen, thawed, air-dried and then heated; e.g., k017, k023) were roughly comparable. Meltwater from the frozen algal tissues (k048–k051) contained significantly higher concentrations of 137Cs compared to the thawed tissue, although the levels were rather variable depending on the taxa (ca. 40 Bq L−1 in Undariapinnatifida to ca. 800 Bq L−1 in Eiseniabicyclis). The 137Cs concentrations in meltwater was much higher than that in ambient seawater, which was below the detection level of ca. 1 Bq L−1 in early July 2011, and was comparable to that in fresh algal tissues, which was estimated from the present measurements of directly dried specimens. Thus, we concluded that the measurements based on dried specimens after the freezing process may underestimate the 137Cs concentrations in fresh algal tissues.

We showed that the radioactive Cs levels in marine macroalgae decline rather rapidly during the summer of 2011. This may be ascribed to the fact that the marine macroalgae grow and turnover rapidly during this period. The growth periods of a number of annual taxa [e.g., Scytosiphonlomentaria, Monostromanitidum Wittrock, Ulva spp., Pyropia (Porphyra) spp.] are less than six months irrespective of their life history patterns (see below; Fig. 15). Many taxa have life histories with alternation of heteromorphic sporophytes and gametophytes [e.g., Undariapinnatifida, Scytosiphonlomentaria, Monostromanitidum, Pyropiayezoensis (Roth) C. Agardh] and their macroscopic generations disappear during summer and autumn (Bold and Wynne 1985; Graham and Wilcox 2000; Hori 1993, 1994). In these cases, even though the thallus tissues had absorbed a large amount of radionuclides during development (i.e., late March–April 2011), they were replaced by new tissues, resulting in lower or null radionuclide concentrations before summer and autumn 2011.
Fig. 15

Schematic presentation of growth period (phenology) of representative marine macroalgae at Iwaki and its vicinity

Some of the taxa with heteromorphic life history have perennial macroscopic thalli, and these thalli persist during summer (e.g., Eiseniabicyclis, Saccharinajaponica). However, they show intercalary growth with a growth zone in the transitional zone between blade and stipe, and the older parts of the thalli (blade) become gradually lost from the tip within several months (Bold and Wynne 1985). Many others, e.g., Ulva spp., Dictyotadichotoma (Hudson) J.V. Lamouroux, Spatoglossumcrissum J. Tanaka, Chondrus spp., Gloiopeltisfurcate, and Ahnfeltiopsisparadoxa, have life histories with alternation between isomorphic macroscopic generations. However, the growth period of a generation is generally less than 6 months as mentioned above.

A few taxa, e.g., Codium spp. and Sargassum spp., lack alternation of generations in their life history. Among them, Sargassumhorneri is a winter-spring annual, and S. yamadae is a perennial species growing during a spring–summer term. Therefore, most of the macroalgae (and the tissues constituting their thalli) collected later than autumn 2011 grew by absorbing ambient nutrients including Cs after a rapid decline of the radionuclide concentrations in seawater. However, it is noteworthy that the levels of 134Cs as well as 137Cs have remained more or less stable since winter 2012, and were still detectable in spring 2013 in most marine macroalgae (ca. 8–140 Bq kg−1 for 137Cs in dried specimens). Considering the CF values of Cs in marine macroalgae, i.e., 8–50 in our study and 50 in the IAEA report, the 137Cs level in ambient seawater of marine macroalgae habitats was considered to have retained at the minimum the level of ca. 0.02–0.3 Bq L−1 (based on CF 50). The detection limit of 134Cs and 137Cs in seawater differs remarkably depending on analytical facilities: ca. 0.0008 Bq L−1, http://www1.kaiho.mlit.go.jp/KANKYO/press/press20121106.pdf; 0.025 Bq L−1, http://www.env.go.jp/guide/budget/h25/h25-gaiyo/011.pdf; and 1.2 Bq L−1, http://radioactivity.nsr.go.jp/ja/contents/8000/7638/24/278_i_0531.pdf. The concentration in seawater (0.02–0.3 Bq L−1) is critical for the direct detection of radionuclides in some analytical facilities.

It has been suggested that marine macroalgal metal loads can be used as markers to track the geographical distributions of the metal concentrations in coastal seawaters, e.g., Ulva spp. (Caliceti et al. 2002; Haritonidis and Malea1999), Undariapinnatifida (Yamada et al. 2007). Similarly, the bio-monitoring of coastal 137Cs using seaweeds must be very useful because marine macroalgae in general are shown to avidly accumulate 137Cs in their tissues (CF = ca. 8–50), whereas they grow rather rapidly and, hence, turnover rapidly, so that they exert no influence of bioconcentration through the food chain.

Notes

Acknowledgments

We are grateful to E.C. Henry (Reed Mariculture) for his valuable comments on the manuscript, Chiyo Komiyama and Tomoko Kotani (Kobe University) for technical support in the measurements of radionuclides and data analyses, Toshiaki Wada, Tadashi Iwasaki, Naoto Hirakawa (Fukushima Prefectural Fisheries Experimental Station), Masataka Ohta (Marine Ecology Research Institute) and Norio Kikuchi (Natural History Museum and Institute, Chiba) for assistance in the field collections. The project was supported by the research grant of Organization of Advanced Science and Technology, Kobe University.

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Copyright information

© The Botanical Society of Japan and Springer Japan 2013

Authors and Affiliations

  • Hiroshi Kawai
    • 1
  • Akira Kitamura
    • 2
  • Mari Mimura
    • 3
  • Tetsuro Mimura
    • 3
  • Tomoya Tahara
    • 4
  • Daiki Aida
    • 5
  • Kenji Sato
    • 5
  • Hideaki Sasaki
    • 5
  1. 1.Kobe University Research Center for Inland SeasKobeJapan
  2. 2.Graduate School of Maritime ScienceKobeJapan
  3. 3.Graduate School of Science, Kobe University RokkodaiKobeJapan
  4. 4.Iwaki Community Reconstruction CenterIwaki Meisei UniversityIwakiJapan
  5. 5.Faculty of Science and TechnologyIwaki Meisei UniversityIwakiJapan

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