Microsoft PowerPoint - ilec2007.ppt

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1 Long-Term Change of Biomass of Phytoplankton in Lake BIWA ( ) 琵琶湖における植物プランクトンの現存量の変遷について ( ) 滋賀県立衛生環境センター水嶋清嗣伊藤貢一瀬諭藤原直樹若林徹哉 Shiga Prefectural Institute of Public Health and Environmental Science Satoshi ICHISE *,Naoki FUJIWARA,Tetsuya WAKABAYASHI, Kiyoshi MIZUSHIMA * and Mitsugu ITO *

2 琵琶湖におけるにおける植物植物プランクトンプランクトンの現存量現存量の変遷について ( ) Long-Term Change of Biomass of Phytoplankton in Lake BIWA( ) 要約琵琶湖におけるPhytoplankton 相の長期的変化について知るため種類毎の平均細胞容積から積算してPhytoplankton 現存量を求めた結果 Phytoplankton 優占種は1990 年以降明らかに変化してきていることが明らかとなったまた各月における平均細胞容積量は春季に小型種が多く秋季に大型種が多くなる事も明らかとなった過去から現在にかけての琵琶湖のPlankton 現存量の変動を調べた結果富栄養化防止条例制定以降 Phytoplankton 量は少なくなったがその後横ばいとなり 1995 年以降は徐々に増加傾向にあること等も明らかとなった

3 Long-Term Change of Biomass of Phytoplankton in Lake BIWA ( ) We determined the long-term change of biomass of phytoplankton in Lake Biwa using mean cell volume determined by us. It became apparent that plankton community of Lake Biwa experienced a major change from 1990 in terms of total cell number as well as total biomass. In addition, biomasses of months averaged over study years tend to be small in spring and large in autumn. Inspecting the variation of plankton biomass from past till present, the biomasses decreased temporary after the enactment of the ordinance against the eutrophication, however it became obvious that they tend to increase gradually after 1995.

4 The background and the aim Analysis on the relationship between physicochemical data and numerical data of planktons in Lake Biwa Both large species (10,000( 10,000μm 3 )and small species(1 (1μm 3 ) have been enumerated with unit of particles. Shift in species of phytoplankton occurred in the lake from past to today were evaluated on the basis of biomass.

5 Method Mean cell volume of 156 species of phytoplankton which found at the central point of the northern basin during April,1994~March,1995 were calculated. Biomass of phytoplankton were calculated using these mean cell volumes.the results was presented at the meeting of the Japan water environment society. Mean cell volume of ca.400 species of Phytoplankton were determined this time. Changes of biomass of phytoplankton in Lake Biwa in these 23 years were assessed.

6 Cell volumes of planktons found in Lake Biwa μm 3

7 Formula for cell volumes(v) of each types of cell shapes A-type cylinder,elliptic cylinder π a:long axis cell volume(v)= a b h b:short axis 4 h:height B-type sphere,ellipsoid π cell volume(v)= a b 2 a:long axis 6 b:short axis C-type cube,rectangular parallelepiped a:length Cell volume(v)= a b h b:breadth h:height

8 Sampling Point (Sta.1)

9 Dominant species as the measure of cell number 1~3 4~6 7~9 10~ ~ ~1990

10 Dominant species as the measure of cell number 1991~2000 1~3 4~6 7~9 10~12

11 Dominant species as the measure 1987~1985 of biomass 1~3 4~6 7~9 10~ ~1990

12 Dominant species as the measure of biomass 1991~2000 1~3 4~6 7~9 10~12

13 2.00E E E +04 Annual change of total cell number of phytoplankton E E E E E E E E

14 Annual change of biomass 3.E E μm 3 ml -1 2.E E E E E

15 Annual change of concentration of chlorophyll a Chlorophyll a Annual change of concentration of chlorophyll a 今津沖中央におけるクロロフィル _a 量の変動 ( )l Chlorophyll a concentration(μg ml ー 1 )

16 Monthly change of total cell number of phytoplankton 6.E+03 T otal cell num ber(cells cells/m l) E+03 4.E+03 3.E+03 2.E+03 1.E+03 0.E+00 Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec. M onthly change of total cell num ber averaged

17 Monthly change of total cell volume total cell volum e(μ m 3 ) 7.E+06 6.E+06 5.E+06 4.E+06 3.E+06 2.E+06 1.E E+00 Jan. Feb. M ar. A pr. M ay. Jun. Jul. A ug. S ep. O ct. N ov. D ec. Monthly change of total cell volume,averaged

18 Monthly change of chlorophyll a concentration Ch lo ro ph yll a c o n c e n tratio n ( μg/ L) Jan. Fe b. Mar. Apr. May. Ju n. Ju l. Au g. Sep. Oc t. Monthly change of chlorophyll a concentration (1979 年 ~2000 年 ) 7.9 Nov. De c.

19 Relationship between total cell volume and total cell number 3.E+07 3.E+07 T o t a l c e l l v o lu m e ( μ m 3 ) 2.E+07 2.E+07 1.E+07 5.E+06 0.E ,000 4,000 6,000 8,000 10,000 total cell num (cells/ml ml)

20 Relationships between chlorophyll a concentration and total cell number or total cell volumes of phytoplankton 2.E E E+ 0 7 Totall cell number (cells/ml) 2.E+04 1.E+04 To tal c e ll vo lu m e (μ m 3 ) 2.0 E E E E E E Chlorophyll l l a concentrationti on(μg/l) 0.0 E Ch lo ro ph yll a c o n c e n tratio n ( μg/ l) R=0.41 R=0.77

21 Annual change of total cell number of phytoplankton(log10) 1.E+00 1.E+00 1.E+00 1.E+00 2.E+00 2.E+00 2.E+00 2.E+00 3.E+00 3.E+00 3.E+00 3.E+00 4.E+00 4.E+00 4.E+00 4.E+00 5.E+00 5.E+00 5.E+00 5.E

22 Annual change of total cell volume of phytoplankton(log10) μm 3 m l -1 (logarism ic scale)

23 Changes of ratio of total cell volume to total cell number 1.8E E E E E E E E E E

24 Ratio of total cell volume to total cell number(average cell volume) A verage cell volum e e(μ m3/ ml) Jan. Feb. M ar. A pr. M ay. Jun Jul. A ug. S ep. O ct. N ov. D ec. Monthly change of average cell volume( )

25 E+07 1.E+06 1.E+05 1.E+04 1.E+03 1.E+02 1.E+01 1.E+00 Annual change of total cell volume of CYANOPHYCEAE CYANOPHYCEAE 2000 Annual change of total cell volume of CYANOPHYCEAE CELL VOLUME (μm 3 )

26 Summary Annual changes of phytoplankton biomass in these 23 years were calculated and phase of phytoplankton in years before 1989 are apparently differ from that after 1990.Phytoplankton in recent years were thought to be experiencing changes. Total biomass of phytoplankton decreased in the years when unusual growth of picophytoplankton took place.it increased gradually in subsequent years. Total cell volumes averaged over study years tended to be minimal in springs and maximal in falls. The variations of chlorophyll a concentration were ensured to agreed well with those of total cell volume than total cell numbers. The relationships were recognized to present that total cell volumes were small when total cell numbers were large and when total cell volumes were large total cell number were large.

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