Rikunomizu（Limnology in Tokai Region of Japan）74 : 13 - 21（2016）

ReportAutumn and winter periphyton biomass in the Ohtakigawa River watershed
1 year after the 2014 eruption of Mount Ontake, central Japan
Kentaro NOZAKI 1), 2)
Abstract
To understand the effect of the 2014 Mount Ontake eruption on the river periphyton community in
the Ohtakigawa River watershed and its recovery processes, several parameters associated with water
quality and chlorophyll-a amounts on stones reflecting the biomass of epilithic algae were investigatedbetween September 2015 and February 2016. The adjoining Nigorigawa and Shimokurosawa rivers aretributaries of the Ohtakigawa. Erupted materials from Mount Ontake accumulated in the Nigorigawa
riverbed. The pH and electrical conductivity of the Ohtakigawa changed drastically after the junction with
the Nigorigawa, indicating that the Nigorigawa strongly affected the water quality of the Ohtakigawa.
Periphyton biomass, quantified as chlorophyll-a amount in the Nigorigawa was low at 0.02-0.06 mg Chl.
a m-2. Chlorophyll-a in the Shimokurosawa was also low at 0.3 mg Chl.a m-2 in September and October,however, a rapid increase to 26 mg Chl.a m-2 was observed in November in the absence of the shading
effects of riparian vegetation. Propagation of the filamentous green alga Stigeoclonium lubricum and theunicellular diatom Gomphonema was observed. Chlorophyll-a amounts at the Ohtakigawa 1 station ranged
from 35 to 74 mg Chl.a m-2 with propagation of the large filamentous green alga, Cladophora. However,these values dropped sharply at the Ohtakigawa 2 station after the junction with the Nigorigawa, and themarkedly low biomass was maintained during the investigation period. The periphyton community was
not established at the Nigorigawa and Ohtakigawa 2 stations, which received the flow of erupted materials
during the investigation period, within 12-16 months after the eruption. The physical disturbance of theriverbed and the chemical components of the river water, acidified by volcanic activity, are presumed tohave had a negative effect on periphyton biomass accumulation and algal growth in the Nigorigwa Riverand at Ohtakigawa 2 station.
Key words: periphyton biomass, Ohtakigawa River watershed, Mount Ontake, volcanic eruption(Received: 28 July 2016; Accepted: 20 August 2016)
the Japanese Islands (National Astronomical Observatory,2016), the influence of volcanic eruption on the periphytoncommunity and its subsequent recovery processes have yet
to investigated. Mount Ontake (elevation 3067 m), an active
volcano located in the central part of the Japanese Islands,
suddenly erupted on September 27 in 2014 (Oikawa etal., 2015; Kaneko et al., 2016; Maeno et al., 2016). Largeamounts of erupted materials fell on the mountainside, andIntroduction
Volcanic eruption results in a remarkable disruption to
the freshwater periphyton habitat through the physicaldestruction of the community, changes in water quality, andvolcanic ash accumulation on substrates (Ward et al., 1983;
Rushforth et al., 1986; Steinman and Lamberti, 1988).
Although active volcanoes are widely distributed throughout
1)

School of Education, Sugiyama Jogakuen University, Hoshigaoka Moto-machi 17-3, Chikusa-ku, Nagoya, Aichi, 464-8662 Japan(E-mail: ken@sugiyama-u.ac.jp)
2)
Mount Ontake Volcanic Eruption Research Group of the Tokai Branch of the Japanese Society of Limnology (with Drs. Takashi
TASHIRO, Tomomasa TANIGUCHI and Yukio ONODA)

13

Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

Kentaro NOZAKI

the ash flowed into the Ohtakigawa River. To understandthe effect of the disturbance caused by the eruption of
the volcano on the river periphyton community and its
recovery processes, the present study investigated several
parameters indicative of water quality and chlorophyll-aamounts on stones, as indicators of the biomass of epilithic
algae, between September 2015 and February 2016 in the
Ohtakigawa River watershed.

2016), at the headwaters of the Nigorigawa. Thus, finesediments such as volcanic ash accumulated in the riverbedof the Nigorigawa (Fig. 2B). In contrast, the Shimokurosawa
runs through dense deciduous forests (Fig. 2C). For thisstudy, a control station was established in the KurokawaRiver, a branch of the Kisogawa River flowing from the
Kaidakogen highland at the foot of Mount Ontake (Fig. 2D).
To investigate the ecological effects of the erupted materials
on periphytic algae, two sampling stations were establishedin the Ohtakigawa River. Ohtakigawa 1 station was locatedbefore the junction with the Nigorigawa (Fig. 2E), andOhtakigawa 2 station was established after the junction withthat river (Fig. 2F). All stations were located on sections orriver with gravel riverbeds.
Field surveys were conducted four times on September
6-8, October 8-10 and November 29-30 in 2015, andFebruary 27-28 in 2016. Water temperature (using an
alcohol thermometer), pH (WAK-pH/WAK-BCG Pack
Test, Kyoritsu Rikagaku Company), electrical conductivity(CM21P electrical conductivity meter, TOA-DDK
Company) and water turbidity (WA1 water analyzer, Nippon
Denshoku Company) were measured at each samplingstation. Water samples were transferred to glass fiber filters(GF-75, Advantec Company) in preparation for analyses
of water color and nutrient concentrations. Water color
was measured with a water analyzer (WA1 water analyzer,
Nippon Denshoku Company). Nutrient analyses were
performed by measuring NH4+-N, NO2--N, NO3--N, PO43--Pand SiO2 concentrations.
Three gravel clasts were collected at each station for
periphyton sampling. The surface area of the stones growing
periphytic algae was calculated as simple geometric shapes
such as triangle, quadrangle, trapezoid and ellipse. Largefilamentous green algae, such as Cladophora, were gently
removed from the stones. Other periphytic algae werecollected using a steel brush. Each sample was filteredusing a glass fiber filter (GF-75, Advantec Company).
Filters collecting periphyton were used for analyses ofchlorophyll-a (UNESCO method) and dry weight. The dryweight of the periphyton was measured after drying for
48 hours at 50℃. Periphytic algae were observed underan optical microscope (BX-51, Olympus Company), andphotomicrographs were acquired using a digital camera(Camedia C-5060, Olympus Company). Nutrient analysis,
periphyton collection, and chlorophyll-a and dry weightmeasurements were performed according to the Tokai
Branch of the Japanese Society of Limnology (2014).

Table 1. Geographical information for each sampling station.
Values were taken from the GSI (Geospatial Information
Authority of Japan) web site.
Sampling station

LatitudeLongitude

Nigorigawa

N35˚48'12"

E137˚28'54"

Elevationm
1035

Shimokurosawa

N35˚48'42"

E137˚28'17"

1031

Kurokawa
Ohtakigawa 1
Ohtakigawa 2

N35˚52'32"
N35˚47'56"
N35˚47'54"

E137˚40'31"
E137˚28'59"
E137˚29'05"

844
1019
1013

Shimokurosawa
1300
1100 m

1200
Nigorigawa

1400
1300

1200 1100 m

Ohtakigawa 1

Ohtakigawa 2
0

300 m

Fig. 1. A map of the locations of each sampling station in the
Ohtakigawa watershed.

Methods
Geographical information of each sampling station is listed
in Table 1. Latitude, longitude and elevation values wereobtained from the web site of the Geospatial Information
Authority (GSI) of Japan. Figure 1 shows a map of thelocations of each sampling station in the Ohtakigawa
watershed. Location of the Kurokawa shows in Onoda
and Kayaba (2016). The adjoining Nigorigawa andShimokurosawa rivers both flow from the top of Mount
Ontake, and are tributaries of the Ohtakigawa River. The
Nigorigawa was open environment (Fig, 2A）. Erupted
materials from a vent on Mount Ontake flowed along the
Jogokudani Valley (Oikawa et al., 2015; Kaneko et al.,Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

14Periphyton biomass in the Ohtakigawa

A

B

C

D

E

F

Fig. 2. Photographs of sampling stations. 2A: Nigorigawa (October 10, 2015), 2B: Accumulation of volcanic ash in theriverbed of the Nigorigawa (October 10, 2015), 2C: Shimokurosawa (October 8, 2015), 2D: Kurokawa (October 9, 2015), 2E:
Ohtakigawa 1 (November 29, 2015) and 2F: Ohtakigawa 2 after the junction with the Nigorigawa (November 29, 2015).

15

Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

Kentaro NOZAKI
Table 2. Parameters of water quality at each sampling station. E. C. is electrical conductivity. W. T. is water temperature.
Date

Time

Weather

W.T.
℃

E.C.
mS m-1pH

Turbidity

Color

7 September 20158 October
9 October
10 October
29 November
30 November
28 February 2016
Shimokurosawa

10:40
16:35
17:15
13:55
13:30
8:45
15:20

rain
fine
fine
cloud
fine
fine
fine

13.8
9.9
10.7
11.4
7.5
5.6
6.8

27.30
34.40
34.70
34.80
36.30
36.80
39.00

5.0
5.2
5.3
5.3
5.2
5.1
5.0

139.6
7.6
3.6
3.4
4.0
4.8
3.3

0.0
0.2
0.2
0.8
0.0
0.0
0.0

6 September 2015
7 September
8 October
30 November
27 February 2016
Kurokawa

14:30
13:15
14:00
13:15
13:40

rain
rain
fine
fine
snow

11.9
13.1
10.6
7.6
2.0

5.26
2.24
3.60
2.61
3.32

6.5
7.0
6.5
6.3
6.5

0.4
39.7
0.7
4.6
3.2

0.0
0.0
2.0
3.1
3.0

8 September 2015
9 October
29 November
27 February 2016
Ohtakigawa 1

9:15
9:45
10:30
10:55

rain
fine
fine
cloud

12.6
9.6
6.1
3.0

3.41
5.08
4.65
5.07

6.5
6.2
6.2
6.2

1.2
0.4
0.2
0.3

0.2
1.1
0.8
0.0

10 October 2015
29 November
28 February 2016
Ohtakigawa 2

13:20
14:30
16:10

cloud
fine
fine

12.8
8.1
5.0

2.76
3.48
2.88

6.8
6.8
6.8

0.9
1.0
1.9

4.3
1.7
1.3

10 October 2015
29 November
28 February 2016

14:15
15:10
16:30

cloud
fine
fine

11.7
7.4
5.6

28.50
22.40
18.53

5.4
5.4
5.4

2.8
3.0
3.9

0.4
0.8
1.8

Nigorigawa

40Electrical Conductivity (mS m-1)

▲ Nigorigawa

Results and Discussion△ Shimokurosawa

30

Parameters of water quality
General information of water quality at each samplingstation is listed in Table 2. At the Nigorigawa andOhtakigawa 2 stations, electrical conductivity was higher
and pH was lower than at the other stations. Tanaka et al.
(1984) measured the pH in the Ohtakigawa watershed on
November 13-15 and December 22 in 1979, and on March
10-11 in 1980, after the Mount Ontake eruption on October
28 in 1979. Values in the upper reaches of the Nigorigawa
and the Shimokurosawa were 3.1 and 7.3-7.6, respectively,
and pH in the Ohtakigawa was 4.9 after the junction with
the Nigorigawa. Tomatsu et al. (1994) reported pH values
8 years after a large-scale landslide caused by the Western
Nagano Prefecture Earthquake in 1984. Values in the lower
reaches of the Nigorigawa and at the Ohtakigawa after the◆ Kurokawa

inflow
20● Ohtakigawa 1○ Ohtakigawa 2

10

0
5.0

5.5

6.0
pH

6.5

7.0

Fig. 3. Relationship between pH and electrical conductivity ateach sampling station. The pH and electrical conductivity of
the Ohtakigawa changed drastically after the junction with the
Nigorigawa, indicating that the Nigorigawa strongly affected thewater quality of the Ohtakigawa.

Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

16Periphyton biomass in the Ohtakigawa
Table 3. Nutrient concentrations in the river water at each sampling station (N.D. = not detected).
NH4+-Nμg L-1NO2--Nμg L-1

NO3--Nμg L-1

PO43--P
μg L-1

SiO2
mg L-17 September 20158 October
9 October
10 October
29 November
30 November
28 February 2016
Shimokurosawa

28.1
23.8
7.4
5.6
2.3
7.1
12.8

4.5
0.5
N.D.
N.D.
N.D.
N.D.
N.D.

77.9
47.1
45.3
46.2
42.7
50.8
72.4

7.6
9.0
9.8
6.8
0.9
0.9
1.2

3.4
4.4
4.3
4.8
33.3
33.6
33.1

6 September 20158 October
30 November
27 February 2016
Kurokawa

4.9
16.5
N.D.
9.0

N.D.
N.D.
N.D.
N.D.

43.6
40.9
32.0
117.0

19.4
9.8
2.3
4.1

15.2
10.7
9.7
9.0

8 September 2015
9 October
29 November
27 February 2016
Ohtakigawa 1

4.0
15.6
1.4
9.0

0.1
9.2
N.D.
N.D.

149.0
113.2
102.6
99.1

10.6
6.8
5.3
4.1

9.1
10.8
11.0
10.9

10 October 2015
29 November
28 February 2016
Ohtakigawa 2

11.0
7.1
N.D.

13.2
N.D.
N.D.

34.6
41.8
58.1

2.3
0.9
1.2

9.2
11.6
10.3

10 October 2015
29 November
28 February 2016

2.9
0.6
3.7

N.D.
N.D.
N.D.

41.8
48.1
48.5

9.0
2.3
2.7

4.5
20.6
19.2

Date
Nigorigawa

40junction with the Nigorigawa were 4.4 and 4.5 in July, 6.4
and 6.4 in September, and 6.8 and 6.8 in October 1992,
respectively. Figure 3 shows the relationship between pH
and electrical conductivity at each station. The values for
the Ohtakigawa changed drastically after the junction with
the Nigorigawa, indicating that the Nigorigawa strongly
affected the water quality of the Ohtakigawa.
The Nigorigawa water became white and turbid during
the investigation period. Suspended particles such as
volcanic ash appeared to be the cause of the turbidity,
because water color measurements using filtered samples
showed almost clear values (Table 2). On November 30 in2015 and February 27 in 2016, the turbidity values at the
Shimokurosawa were similar to those at the Nigorigawa.
Water color increased in parallel, suggesting that dissolved
organic matter such as humic substances resulted inincreased turbidity.

▲ Nigorigawa

Chlorophyll-a (mg m-2)

△ Shimokurosawa

30◆ Kurokawa

26

20
14

10
5
2

0

5

0 Sep.30.5 Oct.61 Nov.91.5Dec.122 Jan.
152.5Feb.
2016
2015

Fig. 4. Temporal changes in chloropyll-a amounts at samplingstations in the Nigorigawa and Shimokurosawa rivers as
tributaries of the Ohtakigawa River, and at the Kurokawa Riveras control. Error bars show the SD (n=3).

17

Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

Kentaro NOZAKI

Nutrient concentrations are listed in Table 3. The
concentrations of dissolved inorganic nitrogen andphosphorus did not differ significantly among thestations. The analyses showed nitrogen- and phosphoruspoor conditions at all stations. SiO2 concentrations werecomparable to those measured in July, September andOctober 1992 by Tomatsu et al. (1994), except for the values
recorded in the Nigorigawa in September and October 2015.
The cause of the low SiO2 concentrations remains unclear.

biomass, on the Nigorigawa riverbed, where the erupted
materials accumulated, were low at 0.02-0.06 mg Chl.a m-2.
The values were also low in the adjacent Shimokurosawa
in September and October 0.3 mg Chl.a m-2, however,a rapid increase in biomass was observed in November.
Propagation of the filamentous green alga Stigeoclonium
lubricum and the unicellular diatom Gomphonema wasobserved (Fig. 5). Chlorophyll-a amounts in the Kurokawa
showed a tendency to increase toward February (Fig. 4).
Previous field studies performed in Japan reported that the
periphyton biomass in the upper and middle reaches ofrivers with stony and gravel riverbeds is often high fromlate autumn to winter (Tominaga and Ichimura, 1966;
Nakanishi and Yamamura, 1984; Nozaki, 2004; Nozaki,

Periphyton biomass
Changes in periphytic chlorophyll-a amounts in the
Nigorigawa, Shimokurosawa and Kurokawa are shown in
Figure 4. Chlorophyll-a amounts, indicating periphyton

160● Ohtakigawa 1

Chlorophyll-a (mg m-2)

○ Ohtakigawa 2

120

80

40

0

74

37

35

0 Oct. 30.5 Nov. 61 Dec.91.5 Jan. 122 Feb.
2016
2015

Fig. 5. Photomicrograph of a periphytic algal community
collected from the Shimokurosawa on November30, 2015
(maginification 200× ).

Fig. 7. Temporal changes in chlorophyll-a amounts at stations 1
and 2 on the Ohtakugawa River. Error bars show the SD (n=3).

Fig. 6. Shimokurosawa on November 30, 2015.

Fig. 8. Photomicrograph of a periphytic algal community
collected from the Ohtakigawa 1 station on October 10, 2015
(maginification 200× ).

Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

18Periphyton biomass in the Ohtakigawa

2013; Nozaki and Shimura, 2013).
Light availability, nutrient concentration, and watertemperature have a significant effect on the growth ofriver periphyton by affecting photosynthetic activity andrespiration, and the periphyton biomass is regulated byphysical disturbances such as floods, and grazing (Biggs,
1996). Along the Shimokurosawa (Fig. 6), the periphyton
biomass showed a rapid increase in November despite low
water temperatures and nitrogen- and phosphorus-poor
conditions. This suggests that the periphytic algae were not
restricted by the shading effects of riparian vegetation after
leaf fall (Sumner and Fisher, 1979; Allan, 1995, p. 89-90).
Hill et al. (1995) reported that leaf canopies can intercept 95% or more incident radiation in some small streams.
Chlorophyll-a amounts at stations along the Ohtakigawa
are shown in Figure 7. The average values of periphytic
algal biomass at the Ohtakigawa 1 station ranged from 35
to 74 mg Chl.a m-2. Propagation of the large filamentous
green alga Cladophora was detected at each sampling date(Fig. 8), however, periphyton biomass decreased sharply at
Ohtakigawa 2 station after the junction with the Nigorigawa,and a remarkably low biomass was maintained during theinvestigation period. The extremely low chlorophyll-aamounts at the Nigorigawa and Ohtakigawa 2 stations in theabsence of canopy shading could be attributed to unstableriverbed conditions caused by the inflow of sediments
transported from the large landslide zone of the upper
reaches of the Nigorigawa (Ashida and Egashira, 1986;
Inokuchi and Yagi, 2014). The effect of natural physicaldisturbances on riverbed stability is a major factor regulating
periphytic algal biomass (Uehlinger, 1991; Biggs, 2000).
In fact, the main channel of both rivers was covered with
newly accumulated sediment and driftwood (Fig.2A and F).
Although acidification resulting from volcanic emissions
is another possible explanation of inhibiting algal growth,
the complete disappearance of periphytic algal vegetation
does not occur at a pH of 5 (Planas, 1996). When theWestern Nagano Prefecture Earthquake occurred in 1984,
an acidic hot spring (pH 5.4), the Nigorigawa-onsen, locatedin the middle reaches of the Nigorigawa was buried by adebris flow (Inokuchi and Yagi, 2014). Kokubu et al., (1977)
reported that hot spring water collected on June 29 in 1975
contained abundant dissolved inorganic matter such as Na+(735 mg L-1), Cl- (760 mg L-1), SO42- (645 mg L-1), Fe2+
(9.1 mg L-1), Fe3+ (14.5 mg L-1), Al3+ (5.4 mg L-1) and SiO2
(229 mg L-1). This chemical composition strongly suggeststhat the hot springs were influenced by volcanic emissions

160▲ Nigorigawa

Chlorophyll-a (mg m-2)

△ Shimokurosawa

120◆ Kurokawa● Ohtakigawa 1○ Ohtakigawa 2

80

40

0
0

20

40

60

80

100

Dry Weight (g m-2)

Fig. 9. Relationships between periphyton dry weight andchlorophyll-a amounts at each sampling station. Error bars show
the SD (n=3).

(Yoshiike, 2003; Sanada et al., 2013). The present-day
Nigorigawa water is acidic (pH 5) and shows higher
electrical conductivity indicating an abundance of dissolved
inorganic matter (Fig. 3). Thus, the volcanic activity at
Mount Ontake affects the water quality of the Nigorigawa
via hot springs welling up from vents. The present study did
not investigate the inhibiting effect of dissolved inorganic
matter derived from acid hot springs (especially certain
metals such as iron and aluminum) on periphyton growth(Planas, 1996). Therefore physiological activities such as
photosynthesis and respiration in the periphyton collectedfrom the Ohtakigawa 1 station should be measured byincubation in the Nigorigawa water in future studies todetermine the influence of water chemistry on such activity.
Recovery of periphyton community
Periphyton communities were not established at the
Nigorigawa and Ohtakigawa 2 stations (which received theflow of erupted materials) during the investigation period
within 12-16 months after the eruption. Ward et al. (1983)
reported the recovery of many different species of algae atvarious aquatic habitats in the blast zone within 3-4 months
after the May 18, 1980 eruption of Mount St. Helens.
Rushforth et al. (1986) also reported that algal communities
were established throughout the blast impact area within 15
months or less of the eruption.
Ash derived from volcanic eruptions accumulates on
periphytic algal communities on colonized substrates(Rushforth et al., 1986). Ash sediments appear to regulate

19

Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

Kentaro NOZAKI

algal growth through a shading effect. Figure 9 shows therelationship between the dry weight and chlorophyll-aamounts of the periphyton at each sampling station. If
the erupted materials accumulated, dry weight would be
increasing. In actual, a tendency towards an increase in dry
weight on stones was not observed, indicating that algal
growth was not inhibited by shading due to volcanic ash
accumulation.
As discussed above, physical disturbance of the riverbed
and the chemical components of volcanically acidified
river water are presumed to have had a negative effect on
periphyton biomass accumulation and algal growth at the
Nigorigwa and Ohtakigawa 2 stations. These factors will
be investigated further in future studies. Steinman andLamberti (1988) found that species richness and diversity
index values of periphytic algae tended to be lowest at themost heavily disturbed sites in the Mount St. Helens region
6 years after its eruption. Therefore, long-term studies areneeded to understand the recovery processes of periphytic
algal communities after the Mount Ontake 2014 eruption in
the Ohtakigawa watershed.

31-56. Academic Press, San Diego.
Biggs, B. J. F. (2000): Eutrophication of streams and rivers:
dissolved nutrient-chlorophyll relationships for benthic
algae. Journal of North American Benthological Society,19: 17-31.
Hill, W. R., M. G. Ryon and E. M. Schilling (1995): Lightlimitation in a stream ecosystem: Responses by primary
producers and consumers. Ecology, 76: 1297-1309.
Inokuchi, T. and H. Yagi (2014): Mount Ontake landslidecaused by the Nagano-ken Seibu earthquake in 1984.
Journal of Japan Landslide Society, 51 (3): 113-115 (inJapanese).
Kaneko, T., F. Maeno and S. Nakada (2016): 2014 Mount
Ontake eruption: characteristics of the phreatic eruption
as inferred from aerial observations. Earth, Planets andSpace, 68: 72-82.
Kokubu, N., A. Yamasaki, M. Kinoshita and A. Fujitsuka(1977): Chemical study of hot springs in Mt. Kiso-Ontake
region 1. Journal of Hot Spring Sciences, 28 (2): 53-64 (inJapanese).
Maeno, F., S. Nakada, T. Oikawa, M. Yoshimoto, J. Komori,Y. Ishizuka, Y. Takeshita, T. Shimano, T. Kaneko and M.
Nagai (2016): Reconstruction of a phreatic eruption on
27 September 2014 at Ontake volcano, central Japan,
based on proximal pyroclastic density current and fallout
deposits. Earth, Planets and Space, 68: 82-101.
Nakanishi, M. and N. Yamamura (1984): Seasonal changes
in the primary production and chlorophyll a amount ofsessile algal community in a small mountain stream,
Chigonosawa. Memoirs of the Faculty of Science, Kyoto
University, Series of Biology, 9: 41-55.
Nozaki, K. (2004): Development of large filamentous green
algal community in the middle region of the Yahagi River.
Advances in River Engineering, Japan Society of Civil
Engineers, 10: 49-52 (in Japanese with English abstract).
Nozaki, K. (2013): 3.1. Periphytic Algae. In River Ecology,
Nakamura, F. (ed.): 72-88. Kohdansya, Tokyo (inJapanese).
Nozaki, K. and C. Shimura (2013): Seasonal changes inchlorophyll-a amounts of periphytic algal communities
and nutrient concentrations in the middle region of the
Yahagigawa River and the Tokigawa River. Report of
Yahagi River Institute, 17: 101-105 (in Japanese).
National Astronomical Observatory (2016): Rika Nenpyo(Chronological Scientific Tables), Maruzen, Tokyo (inJapanese).
Oikawa, T., K. Yamaoka, M. Yoshimoto, S. Nakada, Y.

Acknowledgments
The author thanks his colleagues participating in this study,
Drs. Takashi TASHIRO of Nagoya University, Tomomasa
TANIGUCHI of Mie University and Yukio ONODA of the Aqua
Restoration Research Center for their help in field surveys
and for providing suggestions. Thanks are also due to Ms.
Machiko YAMADA of the Kiso Biological Station, Kyoto
University, the Ohtaki Village Board of Education, andthe Makio Dam Operation and Management Office for
their valuable information. This research was supported
by a Grant from the Water Resources Environment Center(No.2015-04) to Kentaro NOZAKI.

References
Allan, J. D. (1995): Stream Ecology, Structure and functionof running waters. Kluwer Academic Publishers,
Dordrecht.
Ashida, K. and S. Egashira (1986): Running-out processesof the debris associated with the Ontake land slide.
Natural Disaster Science, 8 (2): 63-79.
Biggs, B. J. F. (1996): Patterns in benthic algae of streams.
In Algal Ecology, Freshwater Benthic Ecosystems,
Stevenson, R. J., M. L. Bothwell and R. L. Lowe (eds.):Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology

20Periphyton biomass in the Ohtakigawa

Takeshita, F. Maeno, Y. Ishizuka, J. Komori, T. Shimanoand S. Nakano (2015): The 2014 Eruption of Ontake
Volcano, Central Japan. Bulletin of the VolcanologicalSociety of Japan, 60: 411-415 (in Japanese, 9 color
photographs with English captions).
Onoda, Y. and Y. Kayaba (2016): Evaluation of impacts ofa volcanic eruption on fish distribution by fish census instreams near Mt. Ontake. Rikunomizu (Limnology in TokaiRegion of Japan), 47: 23-28.
Planas, D. (1996): Acidification effects. In Algal Ecology,
Freshwater Benthic Ecosystems, Stevenson, R. J., M.
L. Bothwell and R. L. Lowe (eds.): 497-530. Academic
Press, San Diego.
Rushforth, S. R., L. E. Squires and C. E. Cushing (1986):
Algal communities of springs and streams in the Mt. St.
Helens region, Washington, U.S.A. following the May
1980 eruption. Journal of Phycology, 22: 129-137.
Sanada, T., G. I. Matsumoto and H. Nagashima (2013):
Geochemical characteristics and Chemical Components
in Dake and Takayu Hot Springs, Fukushima Prefecture
in Japan. Journal of Hot Spring Sciences, 63: 28-43 (inJapanese with English abstract).
Steinman, A. D. and G. A. Lamberti (1988): Lotic algal
communities in the Mt. St. Helens region six years
following the eruption. Journal of Phycology, 24: 482-489.
Sumner, W. T. and S. G. Fisher (1979): Periphyton
production in Fort River, Massachusetts. Freshwater
Biology, 9: 205-212.
Tanaka Y., M. Churei and Y. Sawada (1984): Investigationon the techniques for volcanic activity surveillance.
Technical Reports of the Meteorological ResearchInstitute, 12: 172-178 (in Japanese with English abstract).
Tokai Branch of Japanese Society of Limnology (2014):
Mijika Na Mizu No Kankyokagaku (Methods forEnvironmental Studies of Inland Waters). Asakura
Publishing, Tokyo (in Japanese).
Tomatsu, O., C. Takenaka and J. Wakamatsu (1994): Water
qualities of natural water in Ohtaki Village. Journal ofJapan Landslide Society, 31 (3): 43-46 (in Japanese withEnglish abstract).
Tominaga, H. and S. Ichimura (1966): Ecological studies
on the organic matter production in a mountain river
ecosystem. Botanical Magazine, Tokyo, 79: 815-829.
Uhelinger, U. (1991): Spatial and temporal variability ofthe periphyton biomass in a prealpine river (Necker,
Switzerland). Archiv für Hydrobiologie, 123: 219-237.
Ward, A. K., J. A. Baross, C. N. Dahm, M. D. Lilley and J. R.

Sedell (1983): Qualitative and quantitative observations
on aquatic algal communities and recolonization within
the blast zone of Mt. St. Helens, 1980 and 1981. Journalof Phycology, 19: 238-247.
Yoshiike, Y. (2003): Variation in the chemical compositionof Obuki Spring, Tamagawa Hot Springs (1951-2000).
Geochemical Journal, 37: 649-662.
GSI (Geospatial Information Authority of Japan) Map :http://maps.gsi.go.jp/#5/35.362222/138.731389/&base=
std&ls=std&disp=1&vs=c1j0l0u0f0 (accessed June 27,2016).
(Editor: Dr. Yuichi KAYABA, Aqua Restoration Research Center)摘要2014年の御嶽山噴火から1年後の王滝川水系における秋と冬の付着藻現存量
野崎健太郎
2014年9月27日に発生した御嶽山（長野県，海抜3067 m）
噴火が河川の付着藻群集に及ぼすかく乱および回復過程を理解するために，2015年9月～2016年2月に水質とクロロフィ
ル a 量の調査を王滝川水系で行った。隣接した濁川と下黒沢
川は王滝川の支流となる。火山噴出物は濁川の河原に堆積していた。王滝川の水質は，濁川が流入した後に大きく変化
し，濁川が王滝川の水質形成に強く影響していることが明らかになった。クロロフィル a 量で示した濁川の付着藻現存量は0.02～0.06 mg Chl.a m-2であり，常に低かった。下黒沢川の現存量は9月と10月の調査では0.3 mg Chl.a m-2で低かったが，11月には河畔林の遮光が解消され26 mg Chl.a m-2の急激な上昇を示し，糸状緑藻 Stigeoclonium lubricm や単細胞の珪藻 Gomphonema 属の繁茂が観察された。濁川が流入する前の王滝川地点1のクロロフィル a 量は35～74 mg Chl.a m-2であり，大型糸状緑藻の Cladophora 属が繁茂していた。しかしながら，濁川が流入した後の王滝川地点2では，クロロフィ
ル a 量は激減した。本研究の期間中に，御嶽山からの噴出物が流入した濁川と王滝川地点2では，付着藻群集の形成は観察できなかった。この原因は，河床の物理的かく乱と火山性の酸性河川水であると考えられた。
キーワード：付着藻現存量，王滝川水系，御嶽山，火山噴火（〒464-8662 愛知県名古屋市千種区星ヶ丘元町17-3，椙山女
学園大学教育学部，E-mail：ken@sugiyama-u.ac.jp）

21

Ⓒ2016

The Tokai Branch of the Japanese Society of Limnology