Article信州大学理学部附属諏訪臨湖実験所報告 9: 43-45(1995)departmental bulletin pape

Yamada,  Yoshihiro

English

Yamada  Yoshihiro

Shinshu University Institutional Repository

Rep. Su",a il}'drobioL, g' 43'v45 (199"proceedings of the 7th Jnternatienal Symposiutnon River and Lake Environments, l994. MatsttmotoCharacteristics of Lake Biwa from Stable Isotopic Viewpoints43Yoshihiro Yamada1: Cent¢r for Ecological Research, Kyoto University , Shimosakarrioto 4-1-23,  Japan, Fax: 81-775-79-8457Otsu,Shiga 520-Ol,XNTRODUCTION Nitrogen is the most importaiit biophilic element ancl consists of two stable isotopes: '`N andi5N. Although both physicochemical nature is quite simllar ,more precisely i`N and i5N undergofraedonation in every physical and chemical processes. Consequently, eacli Ritrogen bearingsubstance has its own inherent isotopic composition depending upon its position in inaterialcyclings in nature [1], I2], [3]. It has becn recognized that 6i5N of an animai is an useful indicatorof its trophic level, while its carbon isotope ratio reflects 6'3C of the food base and is an availablesource indicator of its carbon[4], [5]. [Iherefore, theSI ratio('SNIi`N) can be possible indicator totrace transport of organic matter and to reconstruct a foed web strt!cture of natural ecosystems [6],[7], [81, [9]. Ii} this paper, prelirniiiary surveys wer¢ performed on the distributien of nitrogeRisotope ratio among biogenic substaiices involving nitrate, POM plankton and pisoes in LakeBiwa, Japan, with emphasis on the construction of a possible isotopic geochernical structure of the1ake ecosystem.MATE]RIALS AND METHODSStudy area Lake Biwa is the largest 1ake locates in the eentral part of Honshu Islaiid, Japan. Its surface areais 647 km2. 'lhe lake is separated into two pans: t!ie north basin and south basiB. The north basinoccupies the major parts of the 1ake with maximum depth of 108m and a water volume of 27theusand mitlion tonnages. In contrast, the south basin is small with average deptli of 4in andwater volume of 2 hundred miHion toimages. 'Ihe lake water is supplied from the surroundingmountaiii areas. An estimated exchange rate of the lakewateT is around 10 years[10]. Tke lake ismonomictic and the depth of a tiiermocline in the north basin becomes deeper during spring throughautumn from 15m to 40m. 'Ilhe tliermoc1ine disappears coinmonly in January.Analytieal method  POM, phytoplankton, zooplanktoR and fishes were collected frem Aprll through August in1993, together witii nitrate at the deepest points(wateT depths ef 70 and 90m) iii tl}e north basin inAugust. Zooplankton samples were collected by horizontal towing a Ret (150 pt n} mesh size) alldwere sorted under a stereoscopic inicroscope into each species. Phytopiaiikton samples werecoliected by various kinds of nets, of which mesh sizes were 70, 40, 20 g m, respectlvely. POM44 were collected on GFID(2.7 pt m) and GF!F(1.2 pt m) glass fiber fllters precembusted at 450℃ for 2 hours. Collected samples on the filter was washed with O.05N hydrockloric acid and dried at 6G OC. Sampies for nitrogen isotope anaiysis were combusted by the sealed quartz tube metltod to N, gas[111. 1 to 10mg ef dry sample materials weresealed into an evacuated quartz tube witli 1.0g ofcopper oxide, and O.5gof copper and silv¢r wires. 'llie tube was heated up to 5000C for30 minutes and at 8500C fer2hours and then cooled down ovemight in the famace. N,gas was separated and purified cryogenicatly by using liquid nirogen and dry ioe-ethanol traps. Purified gases weye introduced into a Delta-S inass spectromcter foT ratiometry. Isotope ratio was expressed as paim!l deviatien from a standard as follows:  6i5N(%o)x(R,a,n,i,IRalr"1)×leOO, wkere R donates iSN/i`N. L-alanin¢ was used as a running standarcl for the isotope measurement.RESVLT AND DXSCVSSgON Silurtis biwaensis, Plecogiassus altiveiis altivelis, zooplankton, phyteplankton, and POM kadvery high 6i5N vaiues so far examined in the present lake. 6i5N value of POM and phytoplanktoltraiiged 6 to 9%o. Eodiaptomus j'aponicus exhibited 6i5N value ef 10 to 15%o. Ternporalvariatien of 6iSN in E. laponicus showed similar with those of POM, and phytoplankton of whichmesh size was from 2.7(GFIP) to 70 pt m. Fishes exhibited iather high 6iSN value. Forexample, Plecoglassus altivelis altivelis had 6iSN values of 13 to 18%e and Silunis biwaensis,ca. 19%o. A relationship between an average 6i5N value ef each organism collected during Aprit to                                                 'August in 1993 and its correspollding trophic level was summarized in Fig 1. Astepwise inerease2e   ge   Z'   n lo   ua     70-4eLttn    (82 E$e )40-20pva,sedifnefit    (7.8%o )oSitms bi,vaensis 18.9ElboPiecogtasstts aitivetis attivelis (15.6Sbe )Eodiaptomus japenicus (l2.096v2oimi-G{leil %,llIili l,1ltlllll1l1lllllIlIIllllI11 2 3 4Trophic levelFig. I A relatioRship between 615N of an organism aRd its corresponding trophic      level. The straight line was obtained using the 6i5N value of POM aRd                                                                                45of iSN was cleariy demonstrated aiong a food chain in the following mamer: phytoplankton aiidPOM, E. J'(tponicus, Plecogiassus altivelis altivelis, and Siluras biwaensis. 'lhe fact stronglysuggested that the stepwise ei tricimeHt of 6iSN was also confimied in Lake Biwa with a en!ictmentfacter of 3.3%oll".L.. 'Iherefere, the 6i5N could be a very clear indicatoy of trophic level of anorganisin as has been showll in Lake Suwa, the estuaries, and iiiarine enviroaments[2], [4], [5], [8]. Rather high 6iSN value of the whole food web in Lake Biwa(Fig. 1) celncided with high6i5N vaiue of nitrate(5 to 6%o) in spite of the supply of nitrate with low Si5N(O to 2 %e) throughprecipitation onto the surroullding meuBtaiii areas.  ln Lake Biwa, less of ca.40% of nitrate was reported from a mass balaiice calculation ofnitrogen[12]. If high 6i5N value is caused by denitrificatlon, the occurrence of denitrificatioR withrathcr ltigh fractiollation factor of 1.009 was strongly suggested in Lake Biwa.]R.]EFERENCES1.Wada, E.,1976: Measureinent and availabthty of i5N using massspectroscopy.      Radioisotope,25:1088-89.(in Japanese)2. Minagawa, M and Wadeg E,1984: Stepwise enrlciment of i5N alofig food chains: fu!ther      evideRce and the reiation between 6i5N and animal age. Geockemica et Cosmochimlea      Acta., 48:1135-1140.3.Wada, E. and Hattori, A.,1991: Nitrogen iii the sea; Forrns, Abundaiices and Rate Process. CRC      press, F16rida, USA.4.Wada, E. et al.,1987: iSN and i3C abundaiices in the Ai2tarctic Ocean with emphasis on the      biogeoch¢rnical structure of the food web. Deep-sea Res., 34:829-841.5.Wada, E. et al.,1993: Stable isotopic str't!cture of aquatic ecesystem. J.Biosci., 18:483-499.6.Yoshioka, T. et al.,1988a: Aiialysis of lacustirine foecl web with natural carboR and nitrogeR      isotope fatios. Intemationale Vereinigung fur theoretische und angewandte Limnologie,      Verhandiunegen, 23:573-578.7.Yoshioka, T. et al., 1988b: Isotope Chairacterization of Lake Kizaki afid Suwa. JpR. J.      LimBol.,49:119-128.8.Yoskioka, T.,1991: AssessmeRt of prirriary production iii a eutrophic 1ake from carboR and      nitregefi isotope ratios of camivoreus fish(a pond smek). Mass Spectroscopy, 39:277-278.9.Yoshioka, T et al.,1994: Astable isotope study on seasoma1 foed web dynamics in a eutrophic      lake.Ecology, 75:835-846.10.0kamato, I.,1992: Tke Circulation ofwater in Lake Biwa. Symposium of Biwa science, News      latter No.3.11.Minagawa M. et al.,1984: CoinparisoR ef Kjeldahl and combustion methods foimeasllrement      of nitrogen isotope ratios in organic matter.Anal. Chem., 56:1859.12.Miyazima, T., 1994: Mud water fiuxes of inorganic nitrogen and mangaiiese in the pelagic      region Lake Biwa: Seasonai dyBarnics aRd i!npact on the hypokmetic metabolism.Arch.      HydrobioL, (in press)

Characteristics of Lake Biwa from stable isotopic viewpoints

46947

Rep. Su",a il}'drobioL, g' 43'v45 (199"proceedings of the 7th Jnternatienal Symposiutnon River and Lake Environments, l994. MatsttmotoCharacteristics of Lake Biwa from Stable Isotopic Viewpoints43Yoshihiro Yamada1: Cent¢r for Ecological Research, Kyoto University , Shimosakarrioto 4-1-23,  Japan, Fax: 81-775-79-8457Otsu,Shiga 520-Ol,XNTRODUCTION Nitrogen is the most importaiit biophilic element ancl consists of two stable isotopes: '`N andi5N. Although both physicochemical nature is quite simllar ,more precisely i`N and i5N undergofraedonation in every physical and chemical processes. Consequently, eacli Ritrogen bearingsubstance has its own inherent isotopic composition depending upon its position in inaterialcyclings in nature [1], I2], [3]. It has becn recognized that 6i5N of an animai is an useful indicatorof its trophic level, while its carbon isotope ratio reflects 6'3C of the food base and is an availablesource indicator of its carbon[4], [5]. [Iherefore, theSI ratio('SNIi`N) can be possible indicator totrace transport of organic matter and to reconstruct a foed web strt!cture of natural ecosystems [6],[7], [81, [9]. Ii} this paper, prelirniiiary surveys wer¢ performed on the distributien of nitrogeRisotope ratio among biogenic substaiices involving nitrate, POM plankton and pisoes in LakeBiwa, Japan, with emphasis on the construction of a possible isotopic geochernical structure of the1ake ecosystem.MATE]RIALS AND METHODSStudy area Lake Biwa is the largest 1ake locates in the eentral part of Honshu Islaiid, Japan. Its surface areais 647 km2. 'lhe lake is separated into two pans: t!ie north basin and south basiB. The north basinoccupies the major parts of the 1ake with maximum depth of 108m and a water volume of 27theusand mitlion tonnages. In contrast, the south basin is small with average deptli of 4in andwater volume of 2 hundred miHion toimages. 'Ihe lake water is supplied from the surroundingmountaiii areas. An estimated exchange rate of the lakewateT is around 10 years[10]. Tke lake ismonomictic and the depth of a tiiermocline in the north basin becomes deeper during spring throughautumn from 15m to 40m. 'Ilhe tliermoc1ine disappears coinmonly in January.Analytieal method  POM, phytoplankton, zooplanktoR and fishes were collected frem Aprll through August in1993, together witii nitrate at the deepest points(wateT depths ef 70 and 90m) iii tl}e north basin inAugust. Zooplankton samples were collected by horizontal towing a Ret (150 pt n} mesh size) alldwere sorted under a stereoscopic inicroscope into each species. Phytopiaiikton samples werecoliected by various kinds of nets, of which mesh sizes were 70, 40, 20 g m, respectlvely. POM44 were collected on GFID(2.7 pt m) and GF!F(1.2 pt m) glass fiber fllters precembusted at 450℃ for 2 hours. Collected samples on the filter was washed with O.05N hydrockloric acid and dried at 6G OC. Sampies for nitrogen isotope anaiysis were combusted by the sealed quartz tube metltod to N, gas[111. 1 to 10mg ef dry sample materials weresealed into an evacuated quartz tube witli 1.0g ofcopper oxide, and O.5gof copper and silv¢r wires. 'llie tube was heated up to 5000C for30 minutes and at 8500C fer2hours and then cooled down ovemight in the famace. N,gas was separated and purified cryogenicatly by using liquid nirogen and dry ioe-ethanol traps. Purified gases weye introduced into a Delta-S inass spectromcter foT ratiometry. Isotope ratio was expressed as paim!l deviatien from a standard as follows:  6i5N(%o)x(R,a,n,i,IRalr"1)×leOO, wkere R donates iSN/i`N. L-alanin¢ was used as a running standarcl for the isotope measurement.RESVLT AND DXSCVSSgON Silurtis biwaensis, Plecogiassus altiveiis altivelis, zooplankton, phyteplankton, and POM kadvery high 6i5N vaiues so far examined in the present lake. 6i5N value of POM and phytoplanktoltraiiged 6 to 9%o. Eodiaptomus j' aponicus exhibited 6i5N value ef 10 to 15%o. Ternporalvariatien of 6iSN in E. laponicus showed similar with those of POM, and phytoplankton of whichmesh size was from 2.7(GFIP) to 70 pt m. Fishes exhibited iather high 6iSN value. Forexample, Plecoglassus altivelis altivelis had 6iSN values of 13 to 18%e and Silunis biwaensis,ca. 19%o. A relationship between an average 6i5N value ef each organism collected during Aprit to                                                 'August in 1993 and its correspollding trophic level was summarized in Fig 1. Astepwise inerease2e   ge   Z'   n lo   ua     70-4eLttn    (82 E$e )40-20pva,sedifnefit    (7.8%o )oSitms bi,vaensis 18.9ElboPiecogtasstts aitivetis attivelis (15.6Sbe )Eodiaptomus japenicus (l2.096v2oimi-G {leil %, llIili l,1ltlllll1l1lllllIlIIllllI11 2 3 4Trophic levelFig. I A relatioRship between 615N of an organism aRd its corresponding trophic      level. The straight line was obtained using the 6i5N value of POM aRd                                                                                45of iSN was cleariy demonstrated aiong a food chain in the following mamer: phytoplankton aiidPOM, E. J'(tponicus, Plecogiassus altivelis altivelis, and Siluras biwaensis. 'lhe fact stronglysuggested that the stepwise ei tricimeHt of 6iSN was also confimied in Lake Biwa with a en!ictmentfacter of 3.3%oll".L.. 'Iherefere, the 6i5N could be a very clear indicatoy of trophic level of anorganisin as has been showll in Lake Suwa, the estuaries, and iiiarine enviroaments[2], [4], [5], [8]. Rather high 6iSN value of the whole food web in Lake Biwa(Fig. 1) celncided with high6i5N vaiue of nitrate(5 to 6%o) in spite of the supply of nitrate with low Si5N(O to 2 %e) throughprecipitation onto the surroullding meuBtaiii areas.  ln Lake Biwa, less of ca.40% of nitrate was reported from a mass balaiice calculation ofnitrogen[12]. If high 6i5N value is caused by denitrificatlon, the occurrence of denitrificatioR withrathcr ltigh fractiollation factor of 1.009 was strongly suggested in Lake Biwa.]R.]EFERENCES1.Wada, E.,1976: Measureinent and availabthty of i5N using massspectroscopy.      Radioisotope,25:1088-89.(in Japanese)2. Minagawa, M and Wadeg E,1984: Stepwise enrlciment of i5N alofig food chains: fu!ther      evideRce and the reiation between 6i5N and animal age. Geockemica et Cosmochimlea      Acta., 48:1135-1140.3.Wada, E. and Hattori, A.,1991: Nitrogen iii the sea; Forrns, Abundaiices and Rate Process. CRC      press, F16rida, USA.4.Wada, E. et al.,1987: iSN and i3C abundaiices in the Ai2tarctic Ocean with emphasis on the      biogeoch¢rnical structure of the food web. Deep-sea Res., 34:829-841.5.Wada, E. et al.,1993: Stable isotopic str't!cture of aquatic ecesystem. J.Biosci., 18:483-499.6.Yoshioka, T. et al.,1988a: Aiialysis of lacustirine foecl web with natural carboR and nitrogeR      isotope fatios. Intemationale Vereinigung fur theoretische und angewandte Limnologie,      Verhandiunegen, 23:573-578.7.Yoshioka, T. et al., 1988b: Isotope Chairacterization of Lake Kizaki afid Suwa. JpR. J.      LimBol.,49:119-128.8.Yoskioka, T.,1991: AssessmeRt of prirriary production iii a eutrophic 1ake from carboR and      nitregefi isotope ratios of camivoreus fish(a pond smek). Mass Spectroscopy, 39:277-278.9.Yoshioka, T et al.,1994: Astable isotope study on seasoma1 foed web dynamics in a eutrophic      lake.Ecology, 75:835-846.10.0kamato, I.,1992: Tke Circulation ofwater in Lake Biwa. Symposium of Biwa science, News      latter No.3.11.Minagawa M. et al.,1984: CoinparisoR ef Kjeldahl and combustion methods foimeasllrement      of nitrogen isotope ratios in organic matter.Anal. Chem., 56:1859.12.Miyazima, T., 1994: Mud water fiuxes of inorganic nitrogen and mangaiiese in the pelagic      region Lake Biwa: Seasonai dyBarnics aRd i!npact on the hypokmetic metabolism.Arch.      HydrobioL, (in press)

https://soar-ir.repo.nii.ac.jp/record/16415/files/Suwa09-07.pdf

Characteristics of Lake Biwa from stable isotopic viewpoints

Abstract

Similar works

Full text

Available Versions

Shinshu University Institutional Repository

Shinshu University Institutional Repository