Algae Volume 21(3): , 2006 [Note] 유해성적조생물, Cochlodinium polykrikoides Margalef (Dinophyceae) 성장에영향을미치는광량과파장 오석진 1 윤양호 2 * 김대일 3 崎 ( 1 일본미

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1 Algae Volume 21(3): , 2006 [Note] 유해성적조생물, Cochlodinium polykrikoides Margalef (Dinophyceae) 성장에영향을미치는광량과파장 오석진 1 윤양호 2 * 김대일 3 崎 ( 1 일본미에현산업지원센타 (MIESC), 2 전남대학교해양기술학부, 3 해양경찰청해양오염관리국, 4 일본큐슈대학농학연구원 ) Effects of Light Quantity and Quality on the Growth of the Harmful Dinoflagellate, Cochlodinium polykrikoides Margalef (Dinophyceae) Seok Jin Oh 1, Yang Ho Yoon 2 *, Dae-Il Kim 3, Yohei Shimasaki 4, Yuji Oshima 4 and Tsuneo Honjo 4 1 Mie Industrial Enterprise Support Center (MIESC), Sakaecho, Tsu , Japan 2 Faculty of Marine Technology, Chonnam National University, Yeosu , Korea 3 Marine Pollution Control Bureau, Korea Coast Guard, Incheon , Korea 4 Laboratory of Marine Environmental Science, Faculty of Aquaculture, Kyushu University, Fukuoka , Japan The effects of light quality and irradiance on the growth of Cochlodinium polykrikoides were investigated in the laboratory. At 25 C and 30 psu the irradiance-growth curve was described as µ = 0.34 (I-9.76)/(I+12.5), (r=0.98). This suggests half-saturation photon flux density (PFD) (K s ) of 32.0 µmol photons m 2 s 1, and a compensation PFD (I c ) of 9.76 µmol photons m 2 s 1. Because the I c equates to a depth of ca m, these responses suggest that irradiance at the depth around and below the thermocline in Yeosuhae Bay would provide favorable conditions for C. polykrikoides. Photoinhibition did not occur at 300 µmol photons m 2 s 1, which was the maximum irradiance used in this study. Blue (450 nm), yellow (590 nm) and red (650 nm) light had different effects on the growth of C. polykrikoides: it grew well under blue light, but not under yellow light. This implies that C. polykrikoides is more likely to cause an outbreak of red tide in the open sea where blue-green wavelengths predominate, rather than in enclosed water bodies where suspended particles absorb most of the blue wavelengths, and yellow-orange wavelengths predominate. Key Words: Cochlodinium polykrikoides, growth, harmful dinoflagellate, irradiance, light quality 서론해양의기초생산자인식물플랑크톤은태양에너지를이용하여무기물로부터유기물을합성한다. 식물플랑크톤의광합성과성장은빛의성질에따라크게영향을받게되며, 특히빛의파장과조성은광합성생물및비광합성생물의신진대사에까지영향을미친다 (Sànchez-Saavedra and Voltolina 1994). 특히, 와편모조류를포함하는식물성편모조류는미약하지만운동능력을보유하고있어, 광학적으로성장할수있는심도까지내려가저층에풍부한영양염을섭 *Corresponding author (yoonyh@chonnam.ac.kr) 취하여성장할수있다 (Honjo et al. 1989). 따라서보다낮은광조건에서도성장할수있는종은유영심도가더욱깊어져다른종보다유리한생존전략을가진다. 또한, 수심에따라빛의파장은크게다르기때문에여러파장대빛을이용할수있는종이보다효율적으로성장할수있다. 한편 1995년이후매년남해안과동해안에서대규모로적조를발생시켜막대한경제적손실과해양생태계의황폐화를초래하고있는유해성와편모조류 (NFRDI 1999, 2000), Cochlodinium polykrikoides Margalef는 Caribbean Sea에위치하는 Puerto Rico에서처음으로명명되었다 (Margalef 1961). 더욱이 C. polykrikoides에의한적조는우리나라에만국한되지않고, 2005년에는일본 Tottori현 ( 동해에위치한현 ) 에서이종에따른적조로대량의어패류폐사가있었다. 이곳의

2 312 Algae Vol. 21(3), 2006 적조발생에대하여일본의일부연구자들은한국남해에서발생한적조일부가 Tsushima 난류를타고동해로유입되어발생하였다고주장하고있다 ( 口, ). 반면 Matsuoka and Iwataki(2004) 은 Tottori현적조는 Kyushu 지방의 Yatsushiro해적조가 Tsushima 난류를타고운반되었을가능성에대해서도보고하고있어, 동해에위치하는일본연안해역적조원인을명확히하기위해서는이들적조의발생기작을분명하게하여야할것이다. 본연구는이러한발생기작을알기위한시도로서 C. polykrikoides의성장에미치는광조건및파장을실내실험을통하여살펴보았다. 재료및방법 Cochlodinium polykrikoides의분리와배양 Cochlodinium polykrikoides의세포는 2005년 3월일본 Kyushu에있는Inokushi 만입구에서채수한해수로부터 pasteur pipette(ca. ø µm) 를이용하여분리하였다. 분리된세포는여과해수 (Sterivex-GS, 0.22 µm filter unit with a filling bell; Millipore, Billerica MA US) 에 4-5회세척한후배양튜브 (TB-2800, Tokyo Japan) 에이식하였다. 사용된배지는 Kuroshio 해수를바탕으로한 f/2(guillard and Ryther 1962) 로 selenium(h 2 SeO 3 ) 을최종농도가 µm 되게첨가하였다. 배양온도와염분의조건은현장수온과염분에상응하는조건 (17 C, 30 psu) 으로, 광량은약 100 µmol photons m 2 s 1 (12L:12D; cool-white fluorescent lamp) 에서실시하였다. 분리되어진 C. polykrikoides에대한무균화처리는수행하지않았지만, 2차생물학적오염을막기위해모든실험기구는 autoclave(202 kpa, 20 min) 또는건조멸균 (185 C, 1hr) 하여사용하였고, 모든실험은 clean bench에서수행하였다. 광조건에따른성장속도변화수온 17 C, 염분 30 psu 그리고광량 100 µmol photons m 2 s 1 (12L:12D; cool-white fluorescent lamp) 의조건에서유지배양을한 Cochlodinium polykrikoides를 Kim et al.(2004a) 에언급되어진최적수온과염분조건하 ( 수온 25 C 와염분30 psu) 에서실험을하기위해서하루에 1 C씩상승시켜 8일후25 C에도달하도록한다음, 신선배지에이식하여전배양을실시하였다. 배양액중세포밀도를약 3.0 x 10 3 cells ml 1 까지증식시킨후, 60 ml 배양튜브 (25 x 150 mm) 에 f/2 배지 20 ml를주입하여, 최종세포밀도는약 100 cells ml 1 되도록접종하였다. 광조건은가시광선차단필름을이용하여 10, 20, 50, 75, 100, 200, 300 µmol photons m 2 s 1 (QSL-2100, Biospherical Instrument Inc., San Diego CA USA) 의 7단계로조절하였다. 매일 1회오전10시에 0.5 ml 의배양액을채취하여도립현미경 (Type-210, Nikon, Tokyo Japan) 을이용하여세포수를관찰하였다. 성장속도는대수성장 (exponential growth) 을보이는기간동안의세포수를이용하여다음 (1) 식에의해계산하였다. 1 N t µ = ln (1) t N 0 N 0, N t : 대수성장기에서초기와 t시간 (day) 후의세포수 (cells ml 1 ) t: 대수성장기의배양시간 (day) 각각의광조건실험은 triplicate로수행하였으며, 성장속도는이들의평균값으로나타냈었다 ( 단, triplicate 중명백히오류로판명된값은평균시제외함 ). 성장속도와광량의관계는 Lederman and Tett(1981) 의모델을개량한다음 (2) 식을이용하여계산하였다. I I c µ = µ m (2) (Ks I c ) + (I I c ) µ: 성장속도 (specific growth rate; day 1 ) I: 광량 (irradiance; µmol photons m 2 s 1 ) I c : 보상광량 (compensation photon flux density (PFD); µmol photons m 2 s 1 ) µ m : 최대성장속도 (maximum specific growth rate; day 1 ) K s : 반포화광량 (half-saturation light intensity; µmol photons m 2 s 1 ) 파장에따른 Cochlodinium polykrikoides의성장특성가시광선중대표적인 3개파장의빛 ( 청색, 적색, 황색 ) 을선택하여 Cochlodinium polykrikoides의성장실험을실시하였다. 이때청색은 450 nm, 적색은 650 nm, 황색은 590 nm의파장에해당한다. 이들파장은발광다이오도 (light emission diode, LED) 를이용하여주사하였으며, 명암주기는 12L: 12D hr, 광량은 70 µmol photons m 2 s 1 이었다. C. polykrikoides은 70 ml culture flask에 (Easy Flask, Nunc., Roskide Denmark) 최종세포수가 10 cells ml 1 이되게20 ml f/2 배지에접종한후, 매일 1회오전10시에도립현미경을이용하여세포수를관찰하였다. 이실험또한 triplicate로수행하였으며, 성장속도는전술의 (1) 식에따라계산하였다.

3 Oh et al.: Effects of Light on the Growth of the Dinoflagelate, C. polykrikoides 313 결과및고찰 Cochlodinium polykrikoides의세포밀도는 10 µmol photons m 2 s 1 에서초기세포밀도와거의유사한약 10 2 cells ml 1 로변화가없었으나, 20 µmol photons m 2 s 1 에서는약 500 cells ml 1 로증가하였으며 µmol photons m 2 s 1 에서는약 1,000 cells ml 1 까지증가하였다 (Fig. 1a). 성장속도는 10 µmol photons m 2 s 1 조건에서는성장하지않았지만, µmol photons m 2 s 1 조건에서는광량의증가에따라성장속도가증가하였다 ( day 1 ) µmol photons m 2 s 1 광조건에서는성장속도가 0.31 day 1 로 100 µmol photons m 2 s 1 광조건에서성장속도와유사하였다 (Fig. 1b). 광조건에의해유도된성장식은 µ = 0.34 (I 9.76)/(I ), (r = 0.98)(Fig. 1b) 로, µ m 은 0.34 day 1, I c 는 9.76 µmol photons m 2 s 1, K s 는 32.0 µmol photons m 2 s 1 로나타났다. Cochlodinium polykrikoides는배양에사용된최대광량인 300 µmol photons m 2 s 1 에서일부식물플랑크톤에서보고되는광저해현상 (photoinhibition) 은나타나지않았다 (Fig. 1b). 이와같은결과는통영연안 ( 최대 7500 lux; Lee et al. 2001) 과일본 Furue만 ( 최대 230 µmol photons m 2 s 1 ; Kim et al. 2004a) 에서분리한 strain으로부터광저해현상이발견되지않았다는내용과유사한내용이다. 다만실제자연환경은보다높은광조건을나타내기에 ( 여름표층은 2000 µmol photons m 2 s 1 이상 ), 실험실조건만으로광저해현상을단정할수는없으며보다높은광조건실험이필요하다. 한편일본 Inokushi만산C. polykrikoides의 I c 는약9.76 µmol photons m 2 s 1 로일본Furue만 strain의 10.4 µmol photons m 2 s 1 와비슷한결과를보여 (Kim et al. 2004a), 비교적약한광조건에서도충분한성장이가능할것으로판단되었다. 또한연안해역에서적조를형성하여수산업에심각한영향을미치는주요유해성편모조류의보상광량 (I c ) 과비교하면, 한국남해안에서 C. polykrikoides이발생시출현을보이는 Gymnodinium catenatum( 여수해만에서분리한 strain) 이 10.0 µmol photons m 2 s 1 (Oh and Yoon 2004), 양식어패류를폐사시키는침편모조류인 Chattonella antiqua와 C. marina는 10.3 µmol photons m 2 s 1 (Yamaguchi et al. 1991) 로 C. polykrikoides과유사한광생리적인특성을보였다. 그리고 Karenia mikimotoi( 일본 Hiroshima 만에서분리한 strain) 에서 0.7 µmol photons m 2 s 1 (Yamaguchi and Honjo 1989), 침편모조류인 Heterosigama akashiwos는 1.0 µmol photons m 2 s 1 로낮았다 (Takahashi and Hara 1989). 반면에이른봄진해만에서이매패류독화원인종인 Alexandrium tamarense( 일본 Hiroshima 만에서분리한 Cell density (cells ml -1 ) Specific growth rate (day -1 ) µmol photons m -2 s Time (day) 0.05 µ=0.34(i-9.76)/(i+12.5) r=0.98 (b) Irradiance (µmol photons m -2 s -1 ) (a) Fig. 1. (a) Growth curves of Cochlodinium polykrikoides under various light intensities. Temperature 25 C, salinity 30 psu, and ph 8.0. (b) Specific growth rates of Cochlodinium polykrikoides as a function of light intensity. Growth rate was calculated from the exponential growth phase in batch culture incubation. strain) 는 µmol photons m 2 s 1 (Yamamoto and Tarutani 1997) 로 C. polykrikoides보다높아종에따른차이가크게나타났다. Cochlodinium polykrikoides의초기적조발생지역인여수해만에서 Ic에해당하는수심을 Lambert-beer식 (I z = I 0 e kz ; I z 은수심z에서의광량, I 0 는해면에서광량, z은수심, k는빛의소산계수 ) 에대입하여간접적으로계산할수있다. 이때소산계수는 7월여수해만의평균소산계수인 0.299(Yoon, unpublished data), I 0 는하계의평균광량인 2,000 µmol photons m 2 s 1 에서해수면으로입사할때 50% 가감소한다고고려하여 1,000 µmol photons m 2 s 1 을대입하였다. 계산결과, C. polykrikoides의성장에필요한 I c 에해당하는수심은약15.4m가계산되었다. 이수심은여수해만같은경우중 저층까지해당되며, 남해안외양역의경우수온약층보다깊은수심으로 C. polykrikoides의광이용만을고려하면남

4 314 Algae Vol. 21(3), 2006 Cell density (cells ml -1 ) Growth rate (day -1 ) Blue light Red light Yellow light Time (Day) (a) (b) Blue light Red light Yellow light Light color Fig. 2. Growth of Cochlodinium polykrikoides under different wavelengths (blue, yellow and red light). (a) growth curves, (b) Specific growth rates. 해연안해역어디에서도이종의유영세포가발견될수있다. 특히, Kim et al.(2004b) 에따르면 C. polykrikoides의유영속도는최대 3.6 m hr 1 로대표적인유해적조플랑크톤 G. catenatum의 1.2 m hr 1 (Baba et al. 2001), K. mikimotoi의 2.2 hr 1 (Koizumi et al. 1996), C. antique의 0.8 m hr 1 (Watanabe et al. 1995) 보다높았다. 따라서 C. polykrikoides 는무기형태영양염뿐만아니라용존태유기영양염또한흡수가능한것으로밝혀져 (Kim et al. submitted), 표층에영양염류가고갈되어있을경우이종의비교적빠른유형능력과낮은 I c 에기인해저층에풍부한영양염을섭취할수있을것이다. 한편빛의파장은식물플랑크톤의광합성을조절하는중요한요인이기에 (Sánchez-Saavedra and Voltolina 1994), 식물플랑크톤의종천이및수직 수평분포에크게영향을미친다. 일반적으로해양은청녹색파장 ( 약 480 nm) 이주로우점하며, 식물플랑크톤은이파장에노출되어있지만 (Wallen and Geen 1971), 부유물질이많은내만및연안해 역과같은경우현탁입자에청녹색파장이흡수되어황색파장이우점한다 (Faust et al. 1982). 더욱이적색파장은해수물분자또는해염에의해극표층에서흡수된다. 따라서청녹색파장을주로흡수하고낮은 I c 를가지는종은부유물질이많은연안 내만해역에서성장을유지하기힘들며, 반대로황색파장을주로이용하는종은외양역에서우점되기힘들다. Cochlodinium polykrikoides는청색파장에서최종세포수가약 200 cells ml 1 까지증가하였으며, 적색파장은약 20 cells ml 1 에그쳤다. 그리고황색파장에서는세포수의변동이없었다 (Fig. 2a). 청색파장의성장속도는 0.21 day 1 로, 접종세포수의차이때문에복수파장을이용한광조건실험 ( 형광등 ; Fig. 1b) 과비교하기는어렵지만, 복수파장의 70 µmol photons m 2 s 1 와유사한성장속도를보였다 (0.25 day 1 ). 적색파장에서성장속도는 0.11 day 1 로청색파장의절반수준이었으며, 황색파장에서는성장하지못하였다 (Fig. 2b). 청색광의경우, 일부미세조류의엽록소의함유량과성장속도를증가시키는경향을보이지만 (Jeffrey and Vesk 1977), 홍조류에서는반대의작용이보고되기도한다 (Mercado et al. 2002). Figueroa et al.(1995) 는 Chlorophyceae, Pheophyceae 와 Rhodophyceae의성장이청색파장에서증가하는것을분명히하였고, 규조류 Thalassiosira gravida, Chaetoceros sp., Phaeodactylum tricornutum와 Cyclotella caspia 또한청색파장에서잘성장한다는것이알려져있다 (Jeffrey and Vesk 1977; Holdsworth 1985; Aidar et al. 1994; Sánchez- Saavedra and Voltolina 1994). 하지만와편모조류, Heterocapsa pygmaea (Nelson and Prézelin 1990) 와규조류 Skeletonema costatum (Tremblin et al. 2000) 그리고일부저서성규조류 (Correa-Reyes et al. 2001) 는청색파장에서성장이증가되지않았다. 이와같이단일파장에서도종에따라다른성장을보이는기질특이성을나타낸다고볼수있다. Cochlodinium polykrikoides는낮은i c 와청색파장을잘이용하며다른파장의이용성이낮은것으로보아청색파장이도달하는해역, 즉부유물질이많은내만해역보다연안및외양해역에서잘성장할수있을것으로판단된다. 이와같은결과는 C. polykrikoides 적조가다른적조원인생물과는달리, 왜내만해역보다연안 / 외양해역에서보다광범위하게발생하는가에대한의문을풀기위한중요한단서가될수있는것으로판단된다. 감사의글본연구의일부는일본미에현산업지원센타 (Mie Industry and Enterprise Support Center; MIESC) 의 Collaboration of Regional Entities for the Advancement Technological Excellence(CREATE) 프로그램일환으로수

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19(4)-07(43).fm

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