Negoro, Kenichiro

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RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:Some Remarkable Changes in thePlankton of Lake Biwa in RecentYearsNegoro, KenichiroNegoro, Kenichiro. Some Remarkable Changes in the Plankton of Lake Biwa in RecentYears. Memoirs of the College of Science, University of Kyoto. Series B 1960, 27(2): 145-1501960-11-20http://hdl.handle.net/2433/258184MEMolRsOF THE COLLEGE    Vol. XXVII,OF SCIENCE,No. 2, ArticleifNIVERSXTY 8 (Bielogy),oyi I<YOTO, 1960SERIES B,SemeRemarkable Changes izi  in Recentthe PIanktolt ofYearsLal<e Biwa                         By                Ken-ichire NEGORoOtsu SydrobSological Station, College of Science,              (ReÅëeived September 20, 196e)University of Kyoto                                  1.   The planl<ton community of any great lake iR a prime or all old age is saidto have kept an equilibrium in its constit"tion as well as its seasoRal periodicity,but it seldom loses its balance.  That no great change has occuryed in tlte plankton of Lake Biwa for the pasttimes, at least during the last severcal thousands years, was demonstrated by mymicrofossil ana}yses of the core samples of bottom deposits wkich were takenfrom the profuRdal zone of this lake (K. NEGoRo, 1954b, '58). It seems, how-ever, probable that the changes of secondary importance in tlte plaRkton ofLake Biwa took place occassiomally in the past, even if they happened veryrerely.   So far as I have known, these changes of the so-called secondary importancein the plankton of Lake Biwa have beeR observed in the following threeoccasions, one of which was only experienced by me:   1) Prof. Em. 'ii'amiji KAwApti(uRA, who was the director of our Station,noticed in about 1925 a considerable multiplicaÅíion of Ceratium hirundinella, bywhich the lake water showed a brown colour.   2) Mr. Yasuji KoNDo, a forrner member of our Station, observed a rerr}ark-able phenomenon in about 1932, at which the lake water showedastronglyalkaline reaction due to the enormous occurrence of Nodularia sp. in the sogth-ern shallower part (the so-called auxMary basin) of Lake Biwa.   3) Early in Octobei' of 1958 an enormous multiplicatioR of a single species,Botryococctes Braunii, was foundt by me in the main basin of Lal<e Biwa, thewhole water of which had become deeply muddy coleur due te tlte attackingof the typkoon on August 25th of tlie same year.                                  z.    In the recent years the remarkable changes of plankton components werek6 Ken-ichiyo NEGoRotwice observecl in the wlto!e basin of Lake Biwa. I should like to report herethose changes.   1. An expgosive ?nultipgicatio•n of Closterium acicuiare T. WEsT var. sub-pronum W. et G. S. WEsT.   Closterium aciculare Tuffeg WEsT var. subpronum W. et G. S. WEsT (W.and G. S. WEsT, 1902, '04) is ever a member of the plankton in the main basinof Lake Biwa (K. NEGoRo, 1954a, '56). Itis a slender, straight form, curvingslightly only near the encls; breadth 4.5-7pt, breadth of apices 1-1.5L{; length450-650pt, about one hundred times loRger tkan diameter. Cell-wall smooth andcolourless, chloroplasts with 5 to 14 pyrenoids, each of terminai vacuoles coR-taiiting one moving grangle. In Lake Biwa tltis planktonic desmid appearsusually in spring (Feb.-May) and autumn (SeptrNov.), being tlte most abuxxdantfrom April to May.   From February of 1958 this desmid showed a tendency to increase slightly,and from the end of January of the next year it began active multiplicatioB.During the two months or so of the spring, from the end of March to the endof May of 1959, it reached a maximum mukiplicatioR; the individual Rumberper litre of water was ten or moi'e times as that of a normal year. Then to-ward tke summer of the same year the alga decreased gradually and from themlddle of October began to increase again. Even at the end of December itoccurred in a considerable quaRtity, continulng to the end of Aprll of 1960.Thereafter the alga diminished rapidly its number.   Durin.g the kigltest multiplication period of this desmid, it was strikingthat a white plankton-net was soon coloured green by filtration of lake waterand the decayed algal cells fell like dust over the leaves of submerged plants.The fibre or textile maRufactories by the lal<e had some trouble in usi#g thelake water; moreover, the watef-works eÅí Kyoto city met witk a diMcultyto filter the water conducted from Lake Biwa.   Mr. Mitsugi OisHi, an univeursity student under rny leadership, made in1959 a study on tke plankton oÅí the Seta-gawa Rivef, the Gnly natural ouÅíletof Lake Biwa (M. Oism, MS.). According to hi$ calculation, the lndlvldgalnumber of Closter'iuin aciculare var. subPronum per litre of water at the startingpoint of the ontlet kas been clianged with the progress of months, as showRin the followlng table (Table 1).   From the results of my study on a great number of plankton materialcellected in 1950 from the whole littoral regions of the main basiR of Lake Biwa,I have come to a concluslon that the centre of the occurrence of Ciosteriwnacicitlare var. subPronum may be located in the Rorthernmost region oS the Iake(K. NEGoRo, 1954a). At the beginning of July of l959, I had fortunately anopportunity to make a limnological survey of this region (off the TsuzuraoPeninsgla) and was able to ascertain my supposition. I ltave observed theyean astonishing multipl2catien of the desmid, whick I have never met with else-where. The result of this observation is as follows (Table 2).    Some Remarl<ab}e Changes in the PlanktonTable 1. The individual number of Closteritmt   in l litre water of tlae Seta-gawa River, theof Lake BiwaacictcSare var. only naturalin Recent YearssubPronu?n containedoutlet oÅí Lake Biwa.147Date  Statien A(The right banl<[Otsu city side)  Statien B(The left banl<Seta town side)1958. }} )r1959. )f Il IJ ll le tt rr )p t) 11 r7 tr IJXII. 13XII. 20XII. 27  I. 3  I. 10  I. 17  I. 24  I. 30 II. 7 II. 21III. 7III. 21 IV. 4 IV. 18 IV. 25 V. 2 V. 18  2.2  7.8 30.6  34.1  12.1  65.7 203.7 186.3 222.0 190.4 322.1 446.0 221.0 676.5 g6o.e2869.02121.5  2.0  1,9  32D  47.6  80.2 113.5 106.8 119.6  10.6 130.24814.0 487.5 670.51434.0 804.0 3e7.ol D.t, kTiet?;g.nvOhntbAa.in{Th2`afg.Eo,n             IOtSU CitY Si           de)l eta townBbankside)iililliIiIillI'll1959. Ir 71 tt }s lt lt }1 !I 1) lt )e 7} lr lt 11 t)  V. 25 VI. 1 VI. 8 VI. 15 VI. 29VII. I3VII. 27VIII. 10VIII. 2•4 IX. 28  X. 14 XI. 20 XI. 18 XI. 26XII. 3XII. 10XII. 26'l2319.0 462.5 334.e  55.5  15.0  19.0   1.0   o.o  35.0   s.e  37.0  48.0 156.0 663.0 280.5 835.51431.5l 846.5371.0121.0  2.0 32.0  1.0  1.5 13.0 48.5 46.0178.0518.0226.0275.5776.5Table 2. The   Biwa at a   CleSteriuntresult of a limnological observation in the northernmost region of Lake depth of 65 rn off Tsuzurao Peninsula and the vertical distribution ofaciculare var. subProntim (number per litre of lake water).       July 7th, 1959; 13h. Cloudy weather.       Atmospheric temperature 28.0"C.Depth (m)o510l5203e40se6063Temperature  of water    (eC)Ill26.023.920.817.516.111.510.1 9.8 9.5 9.0pH7.87.97.67.37.l6.96.96.96.956.9 02(cc/l)ilIiIlj5.975.776.746.646.276.376.436.596.516.53 02(o/o)lEIi103.8 96.5106.6 98a4 90.2 83.1 81.2 82.7 81.2 80.5The individua! numberof Ctosterium aciculare   var. subProm4m  }]-N}]]}}••••••••• 130584••••••••• 42087•••J••••• 16835••••••••+ 6839••••••••+ 1964------t--148 Ken-ichiro NEGoRo   The zone of 0-5m deep coRtaiRed as many as 130 thousands individualsof the desmld in 1 litre water, but 40-60m zone only ca.2 thousands. Thematerials from the zone below 5m comprised a great number of feded cells ofthls alga.   2. A sudden occw"re•nce of Daphnia galeata G. O. SAits.   OR October 4th, 1958, Mr. Hisanao YAMAGucw, a member of the .otaff of ottrStation, discovered a daphnid with a pointed head abottt 2.5mm long, whichhad never beexx found in this lake, ln the piaRkton material collected at a stationof 3m deep in the main basin of Lake Biwa off Hikone city. This crustaceanwas identified by Prof. M. UENo as a peculiar race of DaPl?,nia galeata G. O.SARs. Afterwards this daphnid was also seen in the southern or auxiliayy basinuRtil She middle of December. In the next year, too, this planktonid aRimalappeared in the auxillary basiR on September 26th and disappeared entirely onDecember IOth.   According to Oism's study (M. Oisffi, MS.), DaPhnia ga,ieata was Åíound atthe starting point of the outlet Seta-gawa in the following number (Table 3) :        Table 3. The individua} number of DaPli•nia galeata contained in 1 litre           water oÅí the Seta-gawa River, the only natural outlet of I.ake Biwa.Date1958. )s1959. I} 71 7t tt lsXII.XII.XLXI.XI.XII.XILXII.132010182632026  g't'a"{i6T.nd'i'wu'---_.(The right bankOtsu city side)lI  Station(The leftSeta town'1"ww'---v.ww.banl{side)o.oo.oo.o2.0o.o2.eo.oo.o 1.0 o.o 2.024.0 2.011.053.5 o.o   This planktonic animal is not so abundantmaximum occurreRce, but it is impressible withoccurrence in such a warm-water as Lake Biwa.even duriltg theits peculiar shapeperiod of itsand the rare                                  3.   By what these chaRges of the so-ca}led secondary importaRce have beencaused in the plankton of Lalge Blwa? The causes of the first and secoRdchaRges stated above are unknown. It is, however, evident that the third-mentioned change experienced by me was cattsed by the turbidity .of lake waterdue to the disturbance by typhoon. Just after that time tke physical andSomeRemarl<able Changes in the Plankton of Lake Biwa in Recent Years 149Table 4.   basinThe result ofof Lake Biwa October 4th, Atmospherica limnological observation in theat a depth of 70m off Omatsu.1953; 10h. Fine weather.temperature 2I.OOC.mainDepth (m)o510ll121520253040se6065Ternperature                                 02 Of e."c' ger i PH a (cc/})iif22.021.62!.521.52e.318.215.212.810.6 8.98.27.9 7.7l7.17.07.06.96.7zo6.86.96.66.76.66.66.5I6.206.076.085.845.575.766.366.556.466.776.656.5602(o/o)leo.397.497.4 93.6 87.386.689.887.9 825 835 80A78.8chemical condiSions measured in the main basin off Omatsu at the westerncoast were as fol!ows (Table 4).   The transparency of water measured with SEccm'$ white disc was only 90cm,wiiile it was several maetres at tke same season of a normal year. The lal<ewater was stroRgly Åíurbid and was a yellowish brown in colour due to suspend-ed muddy parSicle$. This turbldity of lake water spread in the whole basindid not disappear for ihree months after ehe disturbance by tke violent wind(the typhoon No. 13 of tkis year). I have never seen $uch thick turbidities inLake Biwa over Åíhe last ten years, with the exception of this occassion. Vhetwo plankton changes in recent years, i.e., aR explosive multiplication of Closte-riecm aciculare var. sttbPronum and a suddell occurrence of DaPJtnia galeata,$eem to agree in time. What changes of natural conditions in Lake Biwa havecaused such remarkable phenomena? According te the investigations by theFishery Experimental StatioR of Shiga Prefecture and by the Water-worksBureau of Kyoto City, no conspicuous changes are found in the temperatureof water as well as in the quantity of nutrients dissolved iR water (Fish. Exp.Stat. Shiga Pref. 1958, '59, '60; WaSer-worl<s Bureatt of Kyoto City, 1957, '58,'59). However, so far as the radioactivity measurement$ of lal<e water are con-cerned, there is fognd a marked ckange of yadioactivity in recent years (Water-works Bureau of Kyoto City, 1957, '58, '59). It has become extraordinarilyhigher for cabout ten months, from July of 1958 to May of the next year; it150 Ken-ichiro !slEGopto(in average) was 8.6:hrl.7 c.p.m./l*' in February, 1959, 9.7Å}-1.6 c.p.m./l in April,while it was 2.0=i 1.4 and 1.7Å}1.6 c.p.m./l respectively ill the correspondingmonths ef 1958.    I suppose that the two reraarkable chakges in the plankton of Lake Biwain recent years would have any relation with the chaRge iR radioactlvity ofthe lake water. It may be safe to say that tke unusual development of plankton,iR particuiar of tlte algal planl<ton under cofisideration here, was caused by theminute change in quantity of any rare but indlspensable minor constltuent,which might possibly have arisen from the alteration of radioactivity in thewater.    I wish to express my hearty thanks to Prof. Dr. M. UENo for his kindnessin feading the manuscript and to Prof. Dr. M. IcffiKAwA, director of the OtsuHydrobiological Station, for his enceuragement.                                 ReferencesFIsl{ERy EXPERIIve[ENTAL STATIoN oF SmGA ?REI?EcTuRE, 1958, '59, '60. Regular limnolo-       gical observations in Lal<e Biwa. Sci. Rep. Fish. Exp. Stat. Shiga Pref., NDs. 9, 10, 11.       (In Japanese.)NEGoRo, K. 1954a. The planl<ton of Åíake Biwa. Sci. Rep. Fish. Exp. Stat. Shiga Pref., Spec.       Publ. in 1954. Pp. 1-40, 10 plates with 101 figures, 2 tables. (In JapaRese.)--•--  l954b. The diatom shells in the deposits of the profundal zone of Lake Biwa. Kagaku,       24: 527-528. (In Japanese.)".....t..t..t..tt. 1956. The phytoplankton of the main basin of Lal{e Biwa-ko. Jap. J. Limnol., 18 : 37-47.       (In Japanese, with English summary.)rm 1958. An analytical study of diatom shells in the bottom deposlts oÅí Lake Biwa-ko.       Ibid., 19: 77-84. (In Japanese, with English summary.)Oism, M., MS. Studies on the p;anl<ton of the Seta-gawa River, the only Ratural outiet of       Lake Biwa.WAcER-woRi<s BuREAv oF Kyo'yo CITy, 1957, '58, '59. Report on the results of scientlfic       test of the drinking water. Nos. of 1957, 1958 and 1959. (In Japanese.)WEsT, W., & G. S. WEsT, 1902. A contribution to the freshwater algae of the north of       Ireland. Transact. Roy. Irish Acad., 32, B, L      & -------- 1904. A menograph ef the British Desmidiaceae. Vol. I. London.Figs.Fig.Fig.                  Exp}amation ef Mate g 1 and 2. 'I'he plankton of Ciosteritem aciculare T. WEsl' var. sscbpront.cm W.   et G. S. WEsT at a period ef its enormous multiplication, accompanied   with few individuals of Ceratiecm hirundinegga and staz4rastrum paradoxtt?n.3. DaPhnia galeata G. O. SARs.4. A pointed head of Daph?tia ga{eata G. O. SApNs.*) 23 c.p.mVi are equivalent to 10m7 lx Curie peg ml.Mem. Coll. Sci., Univ. Kyoto, Ser. B, Vol. XXVII, No. 2. PL I.--'il .'t:•,:t   l/    lt*3x,x x  h-

Some Remarkable Changes in the Plankton of Lake Biwa in Recent Years

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Some Remarkable Changes in the Plankton of Lake Biwa in Recent Years

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