Dynamics of planktonic communities in Lake Shumarinai

Shuji HINO, Diasuke SATOH,Akiko OKAMURA, Sachiko KIKUCHI,

Yamagata University

Yasushi ISHIKAWA, Hidetoshi MIKAMI, Seiki IGARASHI,

Hokkaido Institute of Environmental Science

and

Keishi TAKANO, Hokkaido Institute of Public Health

Hino et al. [b]

(l)Bacterioplankton and picophytoplankton

Fig.1 shows horizontal distribution of bacterioplankton (comparison with surface layer at

sta.1-6) and vertical distribution (sta. 1 and 2). Bacterioplankton density in surface layer

varied from 8.71 x 106 cell/ml (Sta5) to 1.32x108 cell/ml (Sta.6), and its mean value was

6.83x107 cell/ml. The density increased in summer with water temperature. The vertical

distribution showed higher level in metalimnion and hypolimnion than in surface layer .. In

general, the cell density is high in eutrophic level. Although Lake Shumarinai is not in

eutrophic level, bacterioplankton cell size was smaller and was higher than that in other

eutrophic lake (106-107 cells/ml).

Horizontal (cells/ ml)

May

15•10. f 1.0x10 8

5.0x107 11 I

0.0 -·-·

Jul.

1.5x10 8 ~

::::.:: [111 I I I Aug.

Oct.

1.5x10

8

f 1.0x10 8

5 .0x10~:11 •••• 1-0 2- 0 3-0 4-0 5-0 6- 0

Vertical

Sta.1 Sta.2 (cells/ ml)

1.5x10 8 - - 0 1.5x10 8 -0

1~~ 20 30

0 10 20 30

0 1.5x10 8

0

0 1.5x10 8

1~~ 20 30

2~~ 0 1.5x10 8

1~~ 20~

0 1.5x10 8

1~~ 20 ..

Fig.1 Bacterial density of horizontal and vertical distribution in Lake Shumarinai (2002)

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Picophytoplanton was separated red type from orange type when those were measured by

fluorescent microscope. In surface layer, the total cell density varied from 5.22x103 cell/ml

(Sta.2) to 1.llx105 cell/ml (Sta.5), and mean value was 3.76x104 cell/ml. The cell density

increased in summer similar to bacterioplankton. In vertical distribution, red type and orange

type plankton mainly distributed in surface layer and in deep layer, respectively.

(2)Changes in species compositions and abundance of phytoplankton

The species compositions and abundance of phytoplankton were investigated m Lake

Shumarinai. Fig.2 shows fluctuation in cell density of phytoplankton as mean value of surface

layer in all stations on May, June, August and October in 2002 and 2003. Diatoms dominated

in May. The dominant phytoplankton species was Diatoma sp., and the cell density 4500

cells/ml as mean value of surface layer in all stations. This dominant species was replaced by

Stephanodiscus astraea and by Aulacoseira ambigua in June, and by several flagellates in

August.

(cell 11! -I )

Diam ms 0 100 200 3000 100 200 3000 100 200 3000 100 200 300

Altuio11s//a formosa

All/accssira ambigua -.Diatoma sp. ... Ntz.schia sp.

Stspha11odisws astrasa D llm

Tabsl/ariafa1111strala Fr::! l003

Ma)I June August October

(cell 11! - 1 )

FbgellaR• 0 100 200 3004Xl.500 100200 3004XJ 500 100200 300400.500 100200 3004){) 500

Oyptomo11Qs sp.

Euglsna sp.

G]mnodi11ium sp

S,nura sp.

Trachs/omo11Qs spp.

Uroglsna am1ricana ......,.__ __ .....J

Ma)I June August October

Fig.2 Cell density of phytoplankton in Lake Shumarinai (2002-2003)

(Mean value of surface layer in Sta. 1-6)

Anabaena planktonica did not appear abundantly in June and August in 2002, 2003 and

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2005. In contrast, it increased in summer on 2002 and 2004 and formed the dense water

bloom. In autumn, diatoms slightly appeared and mixotrophic phytoplankton appeared instead

of diatoms. Uroglena americana, Gymnodinium sp., and Synura sp. showed a high cell

density from June to October. Uroglena Americana was most dominant species and its

maximum cell density was 12900 cells/ml in 2002, and 2300 cells/ml in 2003 although its

density varied markedly (Fig.3). Although water bloom of Anabaena planktonica did not

appear, dense Gymnodinium sp. appeared in 5 m layer(S±0.3 m) at Sta.2 in 2005.

Characteristic of this lake for phytoplankton is that much mixotrophic phytoplankton

appeared from summer to autumn. As phosphorus is lacking in this lake at the same time,

mixotrophic phytoplankton might increase to obtain phosphorus etc from bacteria and

picoplankton by predation. However, water bloom of Anabaena planktonica appeared in July

and August in 2002 and 2003. In this time, this phytoplankton must uptake phosphorus by

method except for predation. It is unclear for the reason that Anabaena and mixotrophic

phytoplankton coexist in the same time in 2002. The low temperature or shortage of water

may be also one of the reasons for the difference of dominant species and abundance of

phytoplankton and zooplankton between 2002 and 2003.

-e "' E 0

8 ~ ~ 8

Anabaena planktonica

October

2 3 4

Station

0 2002

11 2003

5 6

Uroglena americana 1a--~~~~~~~~~~

10 May

10

1ct 1d

- HT

0 2002

11 2003

e ~ 10 __ ~~~~~~~~~~~~~ 0 u 10

1d HT 10 ,.,._.-........... --......... _

2 3 4

Station 5 6

Fig.3 Seasonal variation of filamentus and cell density Anabaena planktonica and

Uroglena americana in Lake Shumarinai

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(3) Changes in species compositions and abundance of zooplankton

Fig.4 shows fluctuation in individual density of zooplankton as mean value of surface layer

in all stations. Maximum individual density in each station was 178 inds./l (Aug. 2003; Sta. 6),

and minimum was 0.0 inds./l (Oct. 2003; Sta. 1, 4, and 5). In Lake Shumarinai, Copepoda

slightly appeared in all stations, and Eurotatorea was relatively dominant. The dominant

zooplankton species are Asplanchna priodonta, Polyarthra vulgaris, and Keratella cochrearis

throughout a year. Filinia longiseta and Holopedium gibberum are also abundant in 2002 and

2003, respectively. In Lake Shumarinai, zooplankton was not abundant in May 2002 and

October 2003. This phenomenon might be due to low water temperature because of late

spring or early winter. Low water temperature introduced decreasing of phytoplankton

activity and biomass, and lacking of food for zooplanktons.

Copepoda Cyclops c~~wm I 2002/05/21 I 2002/07/24 I 2002/08/27 I 2002/10/28

naupf 1us I I. I. • Clado cera Alona sp,

I ~ ~ ~ Bonj na corefoD 1 10111 na ongiros r1 l 011 1 nops6sP~~'1eW

~ ~ ' I 0i1p~arso~a ~rachu ru1 0 mo~~~agL nmT Ro I i fer . t . I I I A Am~mus~11~m

erac!~onus ffl~c1~ orus I ~ ~ I ol~1e a ~nf 1 nata

~c aois 1 i ata!a 1 1n1a ong1se a ca 1 '!Yr h~V'ovus Ke~a e coc 3a Is [ r c. c-era e IM~aer: ~

Noth~lca s~r1a~a oeso a s . Polyar~ ra vufgar~s r

~ F r rr1mWH !C: Trichocerca eP c1na

Trtcbo~erca cyf ln~rT I r1c ocerca e ooga a I I I r11chgc,rca IO~f'Sf a I r 1t o r 1 a e ac 1 s I I I

0 5 ID 15 10 25 30 0 5 I 0 15 20 25 30 0 5 I 0 15 20 25 30 0 5 I 0 15 20 25 30

Copepoda Cyclop\~t~enm , 2003/05/26 I 2003/06/30 ~ 2003/08/14 2003/10/07

nMY1us • I -Cladocera Alona sp , I ~ I 8oujna coreyoo1 ~0111na ongro1 r1s on1nops~s e1 ers1 I ,. ~

Oiap~Tso~e AM~!u1fli ~ ~ I o ope 1 u1 g~ 3ruf R .

1 eptodora 1n 111

o t 1 er I I I As~Ymmuif f ~~m

~ ~ r BracTyus fflYCI y or rs o ~re a ~nf1na a ~c ao1s i itata

c 'l'"'a 1gnrset1 as pus 1opus ~ ~ ~ Keiate!Yt1tOC~ aar15 era e rem/: ~ r I I I Noth~lca str i a~• oeso a sp . .... ... = I Po l yar~ rahvuf§ar1s Tr1mc:~ca :~ : ~ I ~ I Tr~chocerca fag~cina

Trtc .ocerca cy I rica r I ~hocerca e OOfill

Tf lC gcerca long1 ea I I I"" I ric otr1a tetract1s

0 5 I 0 15 20 25 30 0 5 10 15 20 25 30 0 5 I 0 15 20 25 30 0 5 10 15 20 25 30

Fig.4. List of zooplankton in Lake Shumarinai (2002-2003).

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( 4) Interaction of microbial community

Fig. 5 shows interaction of microbial community in Lake Shumarinai. Fluctuation in cell

density or individual density of bacterioplankton, picophytoplankton, phytoplankton, and

zooplankton was due to feeding together besides water temperature and light intensity etc.

Rotifer (Eurotatorea) highly related to Crysophyta and red type picophytoplankton. Although

diatoms highly related to Chlorophyta (positive correlation) and bacterioplankton (negative

correlation), it did not related to other zooplankton community.

Zooplankton

Copepoda

Phytoplankton

Cyanophyta

Picophytoplankton

Bacteria

Bacteria

Significance 5%

1%

- 0.1%

Fig.5 Interaction of microbial community in Lake Shumarinai.

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