Rikunomizu（Limnology in Tokai Region of Japan）70 : 51 - 54（2015）

ReportRecent trend in seasonal periodicity of phytoplankton community in a small
mountainous lake, Fukami-ike, Central Japan
Hiromi SUDA1), Masaaki TANAKA2), Maki OYAGI 2), Megumi NOBORI 1),
Akiko YOKOYAMA3) and Akihiko YAGI 1）
Abstract
In order to understand the present status of eutrophication of Lake Fukami-ike, seasonal periodicityof phytoplankton community was investigated from March 2013 to February 2014. Major species
were Cyclotella sp. (Bacillariophyceae) and Synedra rumpens (Bacillariophyceae) in spring,Aphanizomenon flos-aquae (Cyanophyceae) and Nitzschia sp. (Bacillariophyceae) in summer, Coelastrumsphaericum (Chlorophyceae) and Crucigenia tetrapedia (Chlorophyceae) in autumn and Synedra sp.
(Bacillariophyceae) in winter, respectively. The dominant species of the phytoplankton community
in 1978-1979 were Synedra acus (Bacillariophyceae) in spring to summer, and Aulacoseira ambigua(Bacillariophyceae) in autumn to winter. However, propagations of S. acus and A. ambigua were notobserved in this study. Furthermore, occurrence of cyanobacterial plankton was not seen in 1978-1979.
From the results of this study, seasonal periodicity of the phytoplankton community seemed to change
drastically in recent years. On the other hand, chlorophyll-a amounts in photic zone in 2013-2014 were
only slightly higher than those in 1978-1979. Thus, progression of the eutrophication of the Lake Fukamiike was not detected in this study.
Key words: Lake Fukami-ike, phytoplankton, seasonal periodicity(Received in 31 March 2015; Accepted in 9 August 2015)

Introduction
Lake Fukami-ike is a small monomictic and eutrophic lake,
located in southern Nagano Prefecture in Central Japan;
north latitude 35°32′55″77, east longitude 137°81′93″56,
which has a small diameter: 150 m, a long diameter: 300 m,area 2.1 ha, volume 1.0 × 105 m3 with a maximum depth of
7.8 m (Fig. 1). This lake has an outflow river and six inflow
rivers which have water from paddy fields, orchards andsurrounding house runoff into the lake. Circulation periods
were from November to March, and stagnation periods werefrom April to October; the dissolved oxygen concentration
was zero in about the 4 m to 5 m deeper layer in midsummer (Yagi, 2009, 2010). Investigations of Lake Fukamiike were begun from 1978, and are continuing roughlyFig. 1. Bathymetrical map of Lake Fukami-ike.

Fig. 470-0392,
1. Bathymetricalmap of Lake Fukami-ike.
Aichi Institute of Technology, 1247 Yachikusa, Yakusa-cho Toyota, Aichi
Japan
Yokkaichi University, 1200 Kayou-cho, Yokkaichi, Mie 512-8512, Japan
3)
Water Agency inc., 3-25 Higashigoken-cho, Shinjuku-ku, Tokyo 162-0813, Japan
1)

2)

51

Hiromi SUDA et al.

once a month (Yagi et al., 1983). High chlorophyll-aconcentration (357 μg L-1) and low transparency (35 cm)
were observed in the early 2000’s. This phenomenon
suggests that the lake environment is changing. The seasonal
periodicity of the dominant species of the phytoplankton
community is one of the signals indicating the state oflakes. However, information about the phytoplankton
community in Lake Fukami-ike is never been reported inrecent years. Thus, in order to understand the present statusof eutrophication of Lake Fukami-ike, seasonal periodicityof phytoplankton community was investigated.

at the deepest point with a hand-operation water pumpconnected to a polyvinylchloride tube from every 0.25 m
depth during the period of water stratification from April toOctober or from every 50 cm-1 m depth in other months.
A part of the water samples was filtered through a glass
fiber filter (Whatman, GF/F, 47 mm) immediately after thesampling. Chlorophyll-a concentrations were measured
by the fluorometric method (Holm-Hansen et al., 1965).
Chlorophyll-a amounts were calculated by multiplying theconcentration with the volume of the lake.

Results and Discussion

Methods

Dominant species of phytoplankton in 1978-1979(Tanaka, 1992) and 2013-2014 (this study) wereshown in Table 1. Major species in this study were
Cyclotella sp. (Bacillariophyceae) and Synedra rumpens(Bacillariophyceae) in spring, Aphanizomenon flos-aquae(Cyanophyceae) and Nitzschia sp. (Bacillariophyceae) insummer, Coelastrum sphaericum (Chlorophyceae) andCrucigenia tetrapedia (Chlorophyceae) in autumn andSynedra sp. (Bacillariophyceae) in winter, respectively. Thedominant species of the phytoplankton community in 19781979 were Synedra acus (Bacillariophyceae) in spring tosummer, and Aulacoseira ambigua (Bacillariophyceae) inautumn to winter. However, propagations of S. acus andSurveys were carried out from March 2013 to February
2014. Plankton samples were taken with a Van Dorn water
sampler (10L, Rigo Co., Ltd., Tokyo Japan) every 1 m fromthe upper to bottom layer. All samples were preserved in
1% formalin in the field immediately, then counted andidentified using an optical microscope (BX51, OLYMPUSOptical Co., Ltd., Tokyo, Japan) in the laboratory. The cellsof phytoplankton were counted using a ruled line glass slide.
The greatest number of species counted was as dominant
species, and the second most numerous of species was assubdominant species.
For chlorophyll-a analysis, lake water was collected

Table 1. Seasonal periodicity of phytoplankton in the Lake Fukami-ike.

Topthick lines: dominant species, thin lines: subdominant species
1978-1979: June 1978 – May 1979 (Tanaka, 1992).

Table 1. Seasonal periodicity of phytoplankton in the Lake Fukami-ike. thick lines: dominant species, thin lines: subdominantspecies 1978-1979: June 1978-May 1979 (Tanaka, 1992).

Bottom52

8Name : Hiromi Suda

Top
Recent trend in seasonal periodicity of phytoplankton community in a small mountainous lake, Fukami-ike, Central Japan1500
1978-1979
2013-2014

Chl.a(mgm㻙㻞-2㻕)㻯㼔㼘㻚㼍㻌㻌㻔㼙㼓㼙

1250
1000
750
500

250
04

5

6

7

8

9

10

11

12

1

23

Fig. 2. Seasonalvariations of Chlorophyll-a
the photiczone
zone inin1978-1979
Fig. 2. Seasonal variationsof Chlorophyll-aamountsamounts
in theinphotic
1978-1979 (Yagi,(Yagi, unpublished data) and 2013-2014.

unpublished data) and 2013-2014.
A. ambigua were not observed in this study. Furthermore,occurrence of cyanobacterial plankton was not seen in 19781979. From the results of this study, seasonal periodicity ofphytoplankton community seemed to change drastically inrecent years.
Seasonal variations of chlorophyll-a amounts in the photiczone in 1978-1979 (Yagi, unpublished data) and 20132014 (This study) were shown in Fig. 2. The value was lowin the stagnation period (spring-summer) and high in thecirculation period (autumn - winter). This trend was reported
in the previous study (Yagi et al., 1983). Total annual
amounts of chlorophyll-a were 4,401 mg m-2 in 2013-2014,
and 3,004 mg m-2 in 1978-1979. Chlorophyll-a amounts in
2013-2014 were only slightly higher than those in 19781979. Thus, progression of the eutrophication of the Lake
Fukami-ike was not detected in this study.
Major species of the phytoplankton community changed,
but chlorophyll-a amounts and the daily production rate
did not change in Lake Biwa, affected by TN/TP ratio,
trace elements, and noxious chemicals (Nakanishi et al.,2001). Sakamoto (2010) reported that only the species ofphytoplankton composition has changed, but chlorophyll-aamounts did not change in Lake Biwa. Kishimoto et al.
(2013) reported that phytoplankton biovolume decreased
about one fifth from 1980s to 2000s in long-term successionin Lake Biwa. The upward flux of nutrients was suppressedby global warming intensified thermal stratification andlimited light for phytoplankton growth by water mixing
in epilimnion. Cyanophyceae were characteristicallyin strongly competition for nutrients because they have9N 2 fixation typically. Homma et al. (2005) reported

Microcystis species which also belongs to Cyanophyceae
dominant in Lake Suwa under a NO3-N-limited condition.
Further analyses are required to elucidate changes of thephytoplankton community of Lake Fukami-ike about
environmental factors that influence the change.

Acknowledgements

BottomWe are grateful to the Anan-cho authorities in Shimoinagun, Nagano Prefecture, who generously provided
research facilities. We especially thank Ryota Nakagami,
Takuya Yokoyama and Hironori Goto of Aichi Institute ofTechnology students for their generous assistance in thefield.

Name : Hiromi Suda
Reference
Kishimoto, N., S. Ichise, K. Suzuki and C. Yamamoto(2013): Analysis of long-term variation in phytoplankton
biovolume in the northern basin of Lake Biwa. Limnology,
14: 117-128.
Holm-Hansen, O., et al. (1965): Fluorometric determinationof Chlorophyll. ICES Journal of Marine Science, 30:3-15.
Honma, T. and P. H-Dong (2005): Influences of Nitrateand Phosphate concentrations on Microcystis species
composition and Microcystin concentration in Lake Suwa.
Journal of Japan Society on Water Environment, 28: 373378 (in Japanese).
Nakanishi, M., K. Nozaki, M., Kagami, Y., Komatsu (2001):
Current status in Lake Biwa -phytoplankton community-.

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Hiromi SUDA et al.

Transactions of The Research Institute Oceanochemistry,
14 (2): 104-111 (in Japanese).
Sakamoto, M. (2010): Organisms in Lake Biwa. Lake Biwa,
Somiya Isao (ed.): 203-210. Gihodo Shuppan Co., Ltd,Tokyo (in Japanese).
Tanaka, M. (1992): Lake Fukami-ike. In the lakes of Japan:
417-421. The University of Nagoya Press, Nagoya (inJapanese).
Yagi, A. (2010): Biological manganese cycle in the oxicand anoxic layers of Lake Fukami-ike. Rikunomizu(Limnology in Tokai Region of Japan), 43: 51-60 (inJapanese).
Yagi, A., I. Shimodaira, H. Terai and Y. Saijo (1983): Seasonalchange of chlorophyll-a and bacteriochlorophyll-c in Lake
Fukami-ike. Japanese Journal of Limnology, 44: 283-292.
Yagi, A., N, Kai, M, Umemura, et al. (2009): Lake Fukamiike. Shimoina-shi: 328-346. Limnology Committee ofShimoina Kyoikukai, Nagano Prefecture (in Japanese).
(Editor: Dr. Kentaro NOZAKI,
School of Education, Sugiyama Jogakuen University)

摘学研究科2)

報学部3)〒162-0813 東京都新宿区東五軒町2-35，株式会社ウォー
ターエージェンシー

要

深見池における植物プランクトン群集の最近の傾向
須田ひろ実1)・田中正明2)・大八木麻希2)・登めぐみ1)・横山亜希子3)・八木明彦1)
深見池の富栄養化の現状を理解するために，植物プラ
ン ク ト ン 群 集 の 季 節 的 な 周 期 性 を2013年3月 か ら2014年2月にかけて調べた。主な植物プランクトンは，春季に珪藻 Cyclotella sp. と Synedra rumpens，夏季にシアノバクテリ
ア Aphanizomenon flos-aquae と 珪 藻 Nitzschia sp.， 秋 季 に 緑藻 Coelastrum sphaericum と Crucigenia tetrapedia， そ し て 冬季に珪藻 Synedra sp. であった。1978年から1979年の優占種
は，春季から夏季が珪藻 Synedra acus，秋季から冬季が珪藻 Aulacoseira ambigua であった。しかしながら，本研究では，これら2種類の珪藻の増殖は観察されなかった。加えて，1978～1979年にはシアノバクテリアの出現も見られなかった。本研究の結果からは，植物プランクトン群集の季節的な周期性が，近年，大きく変化しているであろうことが示唆された。一方で，有光層内のクロロフィル a 量は，1978～1979年の値よりわずかに高いのみであった。したがって，深見池の富栄養化の進行は，本研究では検出できなかった。
キーワード：深見池，植物プランクトン，季節的な周期性1)〒512-8512 三重県四日市市萱生町1200，四日市大学環境情〒470-0392 愛知県豊田市八草町八草1247，愛知工業大学工54