張 喆, 王曉紅, 鞏秀玉, 劉 永, 廖秀麗, 蔡文貴, 黃洪輝,*

1 中國(guó)水產(chǎn)科學(xué)研究院南海水產(chǎn)研究所, 廣州 510300 2 中山大學(xué)生命科學(xué)學(xué)院生物學(xué)實(shí)驗(yàn)教學(xué)中心, 廣州 510275 3 廣東省漁業(yè)生態(tài)環(huán)境重點(diǎn)實(shí)驗(yàn)室, 廣州 510300 4 農(nóng)業(yè)部南海漁業(yè)資源開(kāi)發(fā)利用重點(diǎn)實(shí)驗(yàn)室, 廣州 510300

南海北部海域春季浮游細(xì)菌和病毒空間分布及其影響因素

張 喆1,3,4, 王曉紅2, 鞏秀玉1,3,4, 劉 永1,3,4, 廖秀麗1,3,4, 蔡文貴1,3,4, 黃洪輝1,3,4,*

1 中國(guó)水產(chǎn)科學(xué)研究院南海水產(chǎn)研究所, 廣州 510300 2 中山大學(xué)生命科學(xué)學(xué)院生物學(xué)實(shí)驗(yàn)教學(xué)中心, 廣州 510275 3 廣東省漁業(yè)生態(tài)環(huán)境重點(diǎn)實(shí)驗(yàn)室, 廣州 510300 4 農(nóng)業(yè)部南海漁業(yè)資源開(kāi)發(fā)利用重點(diǎn)實(shí)驗(yàn)室, 廣州 510300

應(yīng)用流式細(xì)胞檢測(cè)技術(shù)測(cè)定了2014年春季南海北部海域浮游細(xì)菌和病毒豐度,研究了其水平和垂直分布特征并對(duì)其與環(huán)境因子的相關(guān)性進(jìn)行了分析。結(jié)果表明,調(diào)查海區(qū)浮游細(xì)菌和病毒豐度分別介于1.28×104—9.96×105個(gè)/mL和4.69×105—5.39×107個(gè)/mL之間,二者豐度隨水深的增加基本呈現(xiàn)逐漸下降的趨勢(shì),而水平分布趨勢(shì)不明顯。浮游細(xì)菌和病毒豐度與溫度、pH和溶解氧顯著正相關(guān),與水深、鹽度、活性磷酸鹽、硅酸鹽、硝酸鹽和總氮?jiǎng)t呈顯著負(fù)相關(guān)關(guān)系(P<0.01),說(shuō)明該海域細(xì)菌和病毒數(shù)量受到上述環(huán)境因子的共同調(diào)控。分析浮游細(xì)菌和病毒的相互關(guān)系發(fā)現(xiàn),VBR(Virus to bacteria ratio)平均32.23,最小值位于S11站位25m層,最大值則位于S7站位75m層,分別為4.80和264.63,VBR值小于100的站位占到調(diào)查站位總數(shù)的95.6%。VBR值除與細(xì)菌呈顯著負(fù)相關(guān)關(guān)系外(P<0.01),與其它環(huán)境因子相關(guān)性不明顯(P>0.05),說(shuō)明該海區(qū)細(xì)菌是病毒的主要寄主,病毒可能主要是以噬菌體的狀態(tài)存在。

微食物環(huán)；浮游病毒；浮游細(xì)菌；南海

Azam[1]1983年提出海洋微生物環(huán)(或微生物食物環(huán))的概念,引起國(guó)內(nèi)外學(xué)者的廣泛關(guān)注。研究表明,海洋浮游細(xì)菌和病毒不僅生物量巨大[2- 3],且在海洋生態(tài)系統(tǒng)能量流動(dòng)、物質(zhì)循環(huán)和維持海洋生物多樣性[4-6]中發(fā)揮著重要的作用。研究海洋浮游細(xì)菌和病毒的分布特征及其影響因素,對(duì)深入了解其在海洋生態(tài)系統(tǒng)中的功能具有重要意義[7]。南海(South China Sea, SCS)臨近西太平洋暖池區(qū),是世界第二大內(nèi)陸海和亞洲三大邊緣海之一,不僅蘊(yùn)藏著豐富的生物資源,而且具有重要的戰(zhàn)略地位[8-9]。因南海具有水溫高、貧營(yíng)養(yǎng)和浮游生物占主導(dǎo)地位等特點(diǎn),微生物環(huán)可能是促進(jìn)其碳循環(huán)和能量流動(dòng)的主要途徑[10],因此開(kāi)展南海微生物環(huán)的相關(guān)研究具有重要意義。目前有關(guān)南海微生物方面的研究,大多集中在沉積物微生物多樣性[11-12]和細(xì)菌生產(chǎn)力[13]等方面,圍繞南海北部海域浮游細(xì)菌和病毒生態(tài)分布特征的研究較少；其次研究區(qū)域大多位于南海北部上升流區(qū)域,而18°N線以南海域浮游病毒生態(tài)分布的大范圍調(diào)查研究尚未見(jiàn)公開(kāi)報(bào)道。本文通過(guò)分析2014年春季南海北部海域浮游細(xì)菌和病毒豐度及其與環(huán)境因子的關(guān)系,旨在對(duì)以下問(wèn)題進(jìn)行初步了解：(1)南海北部海域浮游細(xì)菌和病毒的水平及垂直分布特征如何？(2)上述分布特征受到何種因素的影響？(3)該分布特征及其影響因子與其他海域比較有何異同？通過(guò)對(duì)上述問(wèn)題的回答,為深入研究南海微食物環(huán)的功能提供理論依據(jù)。

圖1 采樣站位[14]Fig.1 Sampling Stations

1 材料與方法

1.1 調(diào)查區(qū)域概況

調(diào)查于2014年3—4月由中國(guó)水產(chǎn)科學(xué)研究院南海水產(chǎn)研究所“南鋒號(hào)”調(diào)查船執(zhí)行,調(diào)查海域?yàn)槟虾Ｖ形魃橙簫u及附近海域(12°30′—17°30′N(xiāo),110°0′—118°30′E),自北向南設(shè)置6個(gè)斷面,每個(gè)斷面2—6個(gè)站位,共計(jì)27個(gè)采樣站位(圖1),各站位水深介于222.0—4352.0 m之間。

1.2 研究方法

1.2.1 樣品采集

使用尼斯金采樣瓶(Niskin bottle)采集各站位水樣,采樣水層分別為5、25、75、150、200 m,樣品采集后經(jīng)0.45 μm孔徑、47 mm直徑的GF/F玻璃纖維濾膜過(guò)濾,取過(guò)濾后的水樣20 mL立即加入終濃度為0.5%戊二醛溶液,室溫條件下避光固定30 min后放入液氮速凍,后于-80℃冰箱保存直至分析。

1.2.2 樣品分析

應(yīng)用流式細(xì)胞儀對(duì)浮游細(xì)菌和病毒進(jìn)行計(jì)數(shù),具體方法參照文獻(xiàn)[15]進(jìn)行。樣品由-80℃冰箱取出后,于37℃水浴鍋中融化,將融化的水樣分別經(jīng)0.22 μm和0.02 μm濾膜過(guò)濾,將3份水樣進(jìn)行稀釋后,各取1 mL加入終濃度為1×10-5SYBR Green I(Sigma)后于80℃避光染色10 min,加入1.0 μm熒光微球(Polysciences)作為內(nèi)參,樣品于流式細(xì)胞儀進(jìn)行熒光信號(hào)采集分析(FACSCalibur,Becton-Dickson)。

采樣各水層溫度、鹽度由海鳥(niǎo)911型CTD(Sea-Bird Electronics)直接測(cè)出,pH、溶解氧、葉綠素a和營(yíng)養(yǎng)鹽數(shù)據(jù)由中國(guó)水產(chǎn)科學(xué)研究院南海水產(chǎn)研究所漁業(yè)環(huán)境研究室提供,測(cè)定方法參照《海洋調(diào)查規(guī)范》[16]。

1.3 數(shù)據(jù)處理與分析

運(yùn)用SPSS 13.0軟件Correlate程序?qū)Ω∮渭?xì)菌、病毒豐度與環(huán)境因子之間的相關(guān)性進(jìn)行分析；分別使用Surfer 8.0和Sigmaplot 11.0軟件對(duì)浮游細(xì)菌和病毒豐度的水平和垂直分布作圖；其他數(shù)據(jù)處理均通過(guò)Excel完成。

2 結(jié)果與分析

2.1 浮游細(xì)菌的水平和垂直分布

圖2所示為南海北部海域2014年春季不同水層浮游細(xì)菌豐度分布情況。本次調(diào)查海域浮游細(xì)菌豐度介于1.28×104—9.96×105個(gè)/mL,平均(4.86±7.23)×105個(gè)/mL。5 m層浮游細(xì)菌豐度在調(diào)查區(qū)域西部和東南部較高,北部較低,最高值和最低值分別為5.48×104個(gè)/mL和9.89×105個(gè)/mL,25 m和75 m水層浮游細(xì)菌分布與5 m水層相似,浮游細(xì)菌豐度均在S12站位達(dá)到最高,分別為9.96×105個(gè)/mL和1.09×106個(gè)/mL。150 m和200 m水層浮游細(xì)菌豐度分別介于1.72×104—3.93×105個(gè)/mL和1.29×104—1.55×105個(gè)/mL之間,200 m水層各站位浮游細(xì)菌豐度差別較小。

圖2 2014年春季南海北部浮游細(xì)菌豐度Fig.2 Bacterioplankton abundance in the north of South China Sea in the spring of 2014

調(diào)查海域5、25、75、150 m和200 m水層浮游細(xì)菌豐度平均值分別為2.83、2.59、2.53、1.45×105個(gè)/mL和0.76×105個(gè)/mL,200m水層浮游細(xì)菌豐度,25 m和75 m水層浮游細(xì)菌豐度較為接近,隨著水深增加,浮游細(xì)菌豐度呈現(xiàn)下降的趨勢(shì)。獨(dú)立樣本的均值t檢驗(yàn)結(jié)果顯示(表1),5 m層與150 m層浮游細(xì)菌豐度差異顯著(P<0.05),而與25 m和75 m層差異不顯著(P<0.05)；200 m層浮游細(xì)菌豐度與各采樣水層均存在極顯著差異(P<0.01)。

2.2 浮游病毒的水平和垂直分布

本次調(diào)查海域浮游病毒豐度介于4.69×105—5.39×107個(gè)/mL之間,平均值為(4.86±7.23)×106個(gè)/mL,最低值和最高值分別出現(xiàn)在S5站位的200 m層和S12站位的5 m層。5 m層浮游病毒豐度在調(diào)查范圍的中西沙海域出現(xiàn)高值區(qū),其中S12和S23站位浮游病毒豐度分別達(dá)到5.39×107個(gè)/mL和2.74×107個(gè)/mL,而在調(diào)查海域的西部浮游病毒豐度較低,其中S1和S24站位豐度僅為1.07×106個(gè)/mL和1.21×106個(gè)/mL,25 m和75 m層浮游病毒分布趨勢(shì)與5 m層相似。150 m水層浮游病毒豐度在調(diào)查區(qū)域東南部呈現(xiàn)高值區(qū),其中最高值和最低值分別出現(xiàn)在S23和S3站位,分別為3.64×106個(gè)/mL和5.76×105個(gè)/mL。200 m水層各站位浮游病毒豐度差異較小,在S27站位豐度最高,為3.51×106個(gè)/mL(圖3)。

表1 2014年春季南海浮游細(xì)菌豐度各水層間樣本均值t檢驗(yàn)

*顯著性差異(P<0.05),**極顯著性差異(P<0.01)

圖3 2014年春季南海浮游病毒豐度水平分布Fig.3 Horizontal distribution of virioplankton abundance in South China Sea in spring of 2014

調(diào)查區(qū)域5、25、75、150 m和200 m水層浮游病毒豐度平均值分別為8.22、7.12、5.02、2.49×106個(gè)/mL和1.46×106個(gè)/mL。隨著水深的增加,浮游病毒豐度呈現(xiàn)下降趨勢(shì)。獨(dú)立樣本的均值t檢驗(yàn)發(fā)現(xiàn)(表1),浮游病毒垂直分布與浮游細(xì)菌相似,75 m以上水層直接浮游病毒豐度差異不明顯(P<0.05)；150 m層浮游病毒豐度與其他水層均差異顯著,200 m層與各采樣水層均存在極顯著差異(P<0.01)。

表2 2014年春季南海浮游病毒豐度各水層間樣本均值t檢驗(yàn)

*顯著性差異(P<0.05),**極顯著性差異(P<0.01)

2.3 浮游細(xì)菌和病毒豐度與環(huán)境因子的相關(guān)性

圖4 不同水層VBR值Fig.4 Virus to bacteria ratio at water column

圖4所示為不同水層病毒和細(xì)菌豐度比值(virus to bacteria ratio, VBR)。由圖中可知,調(diào)查海域各站位VBR值介于4.80—264.63之間,平均32.23。VBR最小值位于S11站位25 m層,而最大值則位于S7站位75 m層,最大值是最小值的55.13倍。由垂直分布看,5、25、75、150 m和200 m水層VBR平均值分別為32.65、30.10、39.10、25.56和33.74,其中75 m層各站位VBR值相差較大。本次調(diào)查區(qū)域的大部分站位VBR值介于10—90之間,其中VBR值小于100的站位占到調(diào)查站位總數(shù)的95.56%。

表3 浮游細(xì)菌和病毒與環(huán)境因子的相關(guān)性分析

**P<0.01水平下非常顯著相關(guān)；*P<0.05水平下顯著相關(guān)；其他均為P>0.05,相關(guān)性不明顯

表3所示為浮游細(xì)菌和病毒豐度與環(huán)境因子相關(guān)性分析結(jié)果。由表中可知,浮游細(xì)菌和病毒豐度的分布受到多種環(huán)境因子的影響。其中,浮游病毒與溫度、pH和溶解氧呈正相關(guān),與水深、鹽度、磷酸鹽、硅酸鹽、硝酸鹽和總氮等營(yíng)養(yǎng)鹽呈顯著負(fù)相關(guān)關(guān)系(P<0.01),而與葉綠素a、亞硝酸鹽和銨鹽的相關(guān)性不明顯(P>0.05)。

3 討論

3.1 浮游細(xì)菌和病毒分布

南海是西太平洋的邊緣海,臨近西太平洋暖池區(qū),是我國(guó)面積最大的海域[11],研究南海浮游細(xì)菌和病毒的生態(tài)分布對(duì)了解其在南海海域的生態(tài)功能具有重要意義。本研究結(jié)果顯示,調(diào)查海域浮游細(xì)菌豐度介于1.28×104—9.96×105個(gè)/mL,與以往在南海西北部[8]、加拿大海盆海域[17]的調(diào)查數(shù)據(jù)接近,低于南海北部近岸[8]、珠江口[18]、大亞灣[19]和三亞灣海域[20]。南海屬于貧營(yíng)養(yǎng)海區(qū),其浮游細(xì)菌豐度較之高營(yíng)養(yǎng)水平海區(qū)要低[21]。本次調(diào)查結(jié)果顯示,調(diào)查區(qū)域表層浮游細(xì)菌數(shù)量低于同季節(jié)高緯度海區(qū)和河口、海灣等近岸海域,這一分布特征在以往的研究中也屢次被證實(shí)[20,22]。就本調(diào)查區(qū)域而言,同一水層浮游細(xì)菌豐度的水平分布并未呈現(xiàn)明顯的規(guī)律。

海洋水環(huán)境中浮游病毒的含量通常在105—108個(gè)/mL,高生產(chǎn)力和營(yíng)養(yǎng)狀況較高的海區(qū)通常也具有較高的浮游病毒豐度[23]。本次調(diào)查結(jié)果顯示,南海北部海域不同站位浮游病毒豐度差異較大,介于4.69×105—5.39×107個(gè)/mL之間。這一結(jié)果與以往在北冰洋[24]和中國(guó)北黃海[25]的調(diào)查結(jié)果接近,略高于西地中海[26]的調(diào)查結(jié)果。不同文獻(xiàn)報(bào)道浮游病毒數(shù)量差別較大的原因主要有以下兩個(gè)方面。其一,調(diào)查海區(qū)環(huán)境理化因子和營(yíng)養(yǎng)狀況的差異,是造成不同海區(qū)浮游病毒豐度差異較大的主要原因[27]。其二,計(jì)數(shù)方法的和染料的不同也可能造成浮游病毒計(jì)數(shù)結(jié)果的差異。研究表明,采用流式細(xì)胞儀的計(jì)數(shù)方法,獲得的病毒數(shù)量要比采用熒光顯微鏡的方法高出10%—30%[28]。同時(shí),應(yīng)用SYBR Green I染色的方法獲得的病毒數(shù)量與透射電鏡計(jì)數(shù)方法獲得的數(shù)量相近[23],也高于傳統(tǒng)的DAPI染色后熒光顯微鏡計(jì)數(shù)的方法[26]。當(dāng)運(yùn)用流式細(xì)胞儀對(duì)遠(yuǎn)洋水體[16]或浮游病毒豐度較低的水體(<108個(gè)/mL)[29]進(jìn)行計(jì)數(shù)時(shí),SYBR Green I的精度較高。不同航次采用的調(diào)查方法不可能完全一致,可能導(dǎo)致浮游病毒豐度的計(jì)數(shù)結(jié)果存在一定的差異。

有關(guān)海洋浮游細(xì)菌和病毒的垂直分布研究較多。海水水深的增加,海水理化因子的變化可能引起浮游細(xì)菌和病毒數(shù)量上的改變。本次調(diào)查發(fā)現(xiàn),浮游細(xì)菌和病毒豐度均值隨著水深的增加基本呈現(xiàn)下降的趨勢(shì)。表層浮游細(xì)菌豐度較高可能得益于光照刺激細(xì)菌生長(zhǎng),或表層浮游植物的生長(zhǎng)釋放了較多了顆粒有機(jī)物,有助于細(xì)菌的繁殖[30]。然而,在以往的研究中,底層浮游細(xì)菌豐度高于表層的現(xiàn)象也有發(fā)現(xiàn)[31]。Peierls等[32]研究發(fā)現(xiàn),底層水較高的鹽度、缺氧的環(huán)境狀況和衰亡藻類(lèi)細(xì)胞的存在,可能是造成底層細(xì)菌生產(chǎn)力高于表層的原因。這一現(xiàn)象,在本次調(diào)查部分站位中也有發(fā)現(xiàn)(圖5)。隨著這些站位取樣深度的增加,浮游細(xì)菌豐度呈現(xiàn)先升高后下降的趨勢(shì),在200 m水深處浮游細(xì)菌豐度最低,這一現(xiàn)象與之前南海[8,21]和其他海域的調(diào)查結(jié)果一致[30,33]。

水體深度對(duì)浮游病毒豐度的影響主要體現(xiàn)在深海。在深海海域,浮游病毒的豐度的最高值往往出現(xiàn)在15—150 m的水深[23],且其豐度在真光層以下快速下降。南海中西沙海域真光層水深普遍介于表層到100 m或110 m之間[34]。本研究即發(fā)現(xiàn)部分站位浮游病毒豐度隨深度變化受到真光層的影響(圖5),浮游病毒豐度在75 m層高于表層和25 m層,而之后在150 m和200 m水層則顯著下降。與此同時(shí),紫外線的照射可以導(dǎo)致海洋噬菌體衰亡速率的上升,也可能是導(dǎo)致表層水體的病毒數(shù)量低于下層水體的原因之一[28,35]。

圖5 調(diào)查區(qū)域部分站位浮游細(xì)菌和病毒豐度垂直分布Fig.5 Vertical distribution of bacterioplankton and virioplankton abundances in part of the stations

3.2 浮游細(xì)菌和病毒與環(huán)境因子相關(guān)性

在海洋環(huán)境中,浮游細(xì)菌的豐度和生物量主要受到上行控制和下行控制效應(yīng)兩種機(jī)制的影響。其中,原生動(dòng)物的攝食和病毒的裂解作用屬于下行控制,而水體中營(yíng)養(yǎng)鹽含量和浮游植物的分解則屬于上行控制[36-37]。溫度是影響海洋細(xì)菌生長(zhǎng)的重要因素。研究表明,隨著水溫升高,海洋浮游細(xì)菌生長(zhǎng)顯著增加[38-39]。在水溫低于20℃的水域,溫度是浮游細(xì)菌生長(zhǎng)的主要調(diào)節(jié)因子[31]。本次調(diào)查區(qū)域雖表層水溫均在20℃以上,但隨著取樣深度的增加,水溫逐漸下降,150 m和200 m水層各站位水溫均顯著下降,較之表層水溫普遍降低8—12℃,此時(shí)溫度通過(guò)影響浮游細(xì)菌的生長(zhǎng)速率而成為浮游細(xì)菌和病毒分布的限制因子[30],這一現(xiàn)象在以往的研究中也有發(fā)現(xiàn)[40]。He等[17]發(fā)現(xiàn)浮游細(xì)菌豐度與水溫相關(guān)性不明顯,認(rèn)為溶解有機(jī)物(DOM)和浮游植物生物量是控制加拿大海盆海域細(xì)菌生長(zhǎng)的主要因素。與此同時(shí),與溫帶水域相比,熱帶海洋全年水溫較高,日照較長(zhǎng),因此相比溫度而言,營(yíng)養(yǎng)鹽可能成為限制熱帶海洋浮游細(xì)菌生長(zhǎng)的主要因素[41]。

浮游細(xì)菌可以有效的吸收各種有機(jī)和無(wú)機(jī)營(yíng)養(yǎng)物質(zhì),它對(duì)無(wú)機(jī)鹽的吸收利用在營(yíng)養(yǎng)鹽的循環(huán)中起著非常重要的作用[42],海水中營(yíng)養(yǎng)鹽濃度的變化,會(huì)直接或間接的影響海洋浮游細(xì)菌和病毒的豐度。調(diào)查顯示,春夏季西北地中海浮游細(xì)菌生物量受到明顯的磷限制,同時(shí)受到溶解有機(jī)磷和有機(jī)碳的影響[43]。針對(duì)法國(guó)夏朗特河口區(qū)域的研究表明,浮游病毒和細(xì)菌與磷酸鹽呈現(xiàn)顯著的正相關(guān)關(guān)系[44]。較之高營(yíng)養(yǎng)海區(qū),貧營(yíng)養(yǎng)海區(qū)微食物網(wǎng)在營(yíng)養(yǎng)物質(zhì)流動(dòng)過(guò)程中發(fā)揮的作用更為明顯[45]。有研究表明,南海南部海域異養(yǎng)細(xì)菌生長(zhǎng)主要同時(shí)受到氮、磷和溶解有機(jī)碳的共同影響[46]。本研究結(jié)果顯示,南海北部浮游細(xì)菌和病毒豐度與活性磷酸鹽、硅酸鹽和硝酸鹽等營(yíng)養(yǎng)鹽含量及海水鹽度呈顯著的負(fù)相關(guān)關(guān)系,這主要是因?yàn)橐环矫?在200 m水深以?xún)?nèi),隨著深度的增加,南海海域營(yíng)養(yǎng)鹽整體呈現(xiàn)濃度增加的趨勢(shì)[47-48],而顆粒有機(jī)碳含量則呈現(xiàn)逐漸下降的趨勢(shì)[49]。另一方面,由于鹽度的升高和光照強(qiáng)度的下降等其他因素的影響抑制了海洋浮游細(xì)菌的生長(zhǎng)[50],反而導(dǎo)致細(xì)菌豐度下降,使得隨著水深和營(yíng)養(yǎng)鹽含量的增加,浮游細(xì)菌和病毒的數(shù)量并沒(méi)有升高。上述現(xiàn)象在其他海區(qū)也有發(fā)現(xiàn)[23,51],可能是由于浮游植物的生長(zhǎng)消耗營(yíng)養(yǎng)鹽的同時(shí)釋放了溶解有機(jī)碳供浮游細(xì)菌的生長(zhǎng)和繁殖,因此浮游細(xì)菌和病毒的數(shù)量可能更多受到顆粒有機(jī)碳和溶解有機(jī)碳的影響[52],但在南海中北部海域是否存在相關(guān)的影響機(jī)制需要更深入的研究。

浮游細(xì)菌和病毒的豐度與水深均呈現(xiàn)顯著的負(fù)相關(guān)關(guān)系,隨著水深度增加,鹽度梯度的變化可能造成水體溫度、營(yíng)養(yǎng)鹽、浮游植物等含量的變化,進(jìn)而影響著浮游細(xì)菌和病毒的分布。本研究發(fā)現(xiàn)南海北部海域浮游細(xì)菌和病毒與葉綠素a沒(méi)有顯著的相關(guān)性,類(lèi)似的結(jié)果在以往南海海域和其他一些海域的研究中也有發(fā)現(xiàn)[17,26]。He等[22]在分析南海北部浮游病毒豐度時(shí)發(fā)現(xiàn),病毒數(shù)量與細(xì)菌數(shù)量的相關(guān)性遠(yuǎn)遠(yuǎn)大于葉綠素a濃度,認(rèn)為在貧營(yíng)養(yǎng)的南海,細(xì)菌是海洋病毒主要的寄主。類(lèi)似結(jié)果在淡水水體的研究中也有發(fā)現(xiàn)[53],本研究的結(jié)果也進(jìn)一步證實(shí)了上述結(jié)論。

3.3 浮游細(xì)菌和病毒之間的相互關(guān)系

浮游病毒是海洋微生物組成、營(yíng)養(yǎng)動(dòng)力學(xué)的重要決定因素和細(xì)菌死亡的主要推動(dòng)者[54],病毒裂解導(dǎo)致的海洋細(xì)菌死亡可能占到細(xì)菌死亡總數(shù)的10%—20%[26],在表層水體中這一比例甚至可以達(dá)到50%[55]。本研究表明浮游細(xì)菌和浮游病毒豐度呈顯著正相關(guān)關(guān)系(r=0.755,P<0.01,n=135)(圖6),這一現(xiàn)象在包括河口[44]、半咸水環(huán)境[56]和其他海區(qū)中也有發(fā)現(xiàn)[57-58]。說(shuō)明在貧營(yíng)養(yǎng)海區(qū)中,浮游細(xì)菌是浮游病毒的主要宿主而影響著浮游病毒的豐度[26]。

VBR值通常用于指示海洋浮游細(xì)菌和病毒之間的關(guān)系,VBR值的高低可以指示不同環(huán)境中海洋噬菌體對(duì)細(xì)菌的感染幾率,高VBR值可能預(yù)示著較高的病毒感染。海洋環(huán)境中VBR值大多介于5—83之間,VBR較低則表明病毒較低的感染率、單個(gè)細(xì)菌宿主中病毒顆粒較少或病毒具有較高的衰亡速率[57]。Collins等[24]發(fā)現(xiàn)波弗特海水VBR值最高可以達(dá)到340,海冰中這一值更是高達(dá)846。Personnic等[59]認(rèn)為VBR值較高可能與流式細(xì)胞儀的計(jì)數(shù)方法有關(guān)系,以往采用的熒光顯微鏡計(jì)數(shù)方法可能低估了VBR的參數(shù)。本研究結(jié)果與上述結(jié)果基本相符,本次調(diào)查VBR值大多介于10—40之間,占到總數(shù)的57.04%,但也有較高VBR值(>100)的出現(xiàn),占到總數(shù)的4.44%。本研究不同取樣點(diǎn)之間VBR值差別較大,可以相差55倍,類(lèi)似的結(jié)果在其他的研究中也曾被報(bào)道[25,60],說(shuō)明在本調(diào)查區(qū)域中細(xì)菌和病毒的生長(zhǎng)速率差異較大。

南海中北部海域VBR與浮游細(xì)菌豐度呈現(xiàn)顯著的負(fù)相關(guān)關(guān)系(r=-0.245,P<0.01,n=135)(圖7),而與浮游病毒的相關(guān)性不明顯(r=0.153,P>0.05,n=135)。本研究發(fā)現(xiàn),200 m水層VBR值較之表層水要高,說(shuō)明相對(duì)表層水而言,底層水浮游病毒對(duì)細(xì)菌豐度的影響更大,以往的研究結(jié)果也證實(shí)了這一結(jié)論[61]。細(xì)菌病毒之間的相關(guān)性和VBR值的變化表明在中國(guó)南海北海域,病毒可能主要以噬菌體的形式存在[25]。

圖6 浮游細(xì)菌和病毒相關(guān)性Fig.6 Correlation between bacterioplankton and virioplankton

圖7 VBR值與浮游細(xì)菌豐度相關(guān)性Fig.7 Correlation between VBR and bacterioplankton

4 結(jié)論

南海中西沙海域浮游細(xì)菌和病毒豐度同時(shí)受到海水溫度、溶解氧、鹽度和營(yíng)養(yǎng)鹽的共同影響,浮游細(xì)菌作為浮游病毒主要的宿主,影響著該海區(qū)浮游病毒豐度的變化。該區(qū)域海洋浮游病毒可能主要是以噬菌體的形態(tài)存在,且細(xì)菌和病毒的生長(zhǎng)速率存在較大差異。

[1] Azam F, Fenchel T, Field J G, Gray J S, Meyer-Reil L A, Thingstad F. The ecological role of water-column microbes in the sea. Marine Ecology Progress Series, 1983, 10: 257- 263.

[2] Suttle C A. Marine viruses--major players in the global ecosystem. Nature Reviews Microbiology, 2007, 5(10): 801- 812.

[3] Fenchel T. The microbial loop- 25 years later. Journal of Experimental Marine Biology and Ecology, 2008, 366(1/2): 99- 103.

[4] Azam F, Malfatti F. Microbial structuring of marine ecosystems. Nature Reviews Microbiology, 2007, 5(10): 782- 791.

[5] 李洪波, 楊青, 周峰. 海洋微食物環(huán)研究新進(jìn)展. 海洋環(huán)境科學(xué), 2012, 31(6): 927- 932.

[6] Jiao N Z, Herndl G J, Hansell D A, Benner R, Kattner G, Wilhelm S W, Kirchman D L, Weinbauer M G, Luo T W, Chen F, Azam F. Microbial production of recalcitrant dissolved organic matter: long-term carbon storage in the global ocean. Nature Reviews Microbiology, 2010, 8(8): 593- 599.

[7] 盧龍飛, 汪岷, 梁彥韜, 王芳, 楊琳, 王健, 孫輝, 汪儉. 東海、黃海浮游病毒及異養(yǎng)細(xì)菌的分布研究. 海洋與湖沼, 2013, 44(5): 1339- 1346.

[8] Yuan X C, He L, Yin K D, Pan G, Harrison P J. Bacterial distribution and nutrient limitation in relation to different water masses in the coastal and northwestern South China Sea in late summer. Continental Shelf Research, 2011, 31(11): 1214- 1223.

[9] 李濤, 王鵬, 汪品先. 南海西沙海槽表層沉積物微生物多樣性. 生態(tài)學(xué)報(bào), 2008, 28(3): 1166- 1173.

[10] Chen B Z, Liu H B, Wang Z L. Trophic interactions within the microbial food web in the South China Sea revealed by size-fractionation method. Journal of Experimental Marine Biology and Ecology, 2009, 368(1): 59- 66.

[11] 白潔, 劉小沙, 侯瑞, 趙陽(yáng)國(guó), 高會(huì)旺. 南海南部海域浮游細(xì)菌群落特征及影響因素研究. 中國(guó)環(huán)境科學(xué), 2014, 34(11): 2950- 2957.

[12] 孫慧敏, 戴世鯤, 王廣華, 謝練武, 李翔. 南海北部巴士海峽深海沉積物中細(xì)菌多樣性分析. 熱帶海洋學(xué)報(bào), 2010, 29(3): 41- 56.

[13] 王生福, 宋星宇, 黃良民, 譚燁輝, 柯志新. 南海北部夏季浮游細(xì)菌生長(zhǎng)效率初步研究. 熱帶海洋學(xué)報(bào), 2013, 32(6): 73- 79.

[14] 劉華雪, 柯常亮, 李純厚, 廖秀麗, 黃洪輝. 南海南部懸浮顆粒物脂肪酸組成. 生態(tài)學(xué)報(bào), 2014, 34(10): 2599- 2607.

[15] Marie D, Brussaard C P D, Thyrhaug R, Bratbak G, Vaulot D. Enumeration of marine viruses in culture and natural samples by flow cytometry. Applied and Environmental Microbiology, 1999, 65(1): 45- 52.

[16] 中華人民共和國(guó)國(guó)家質(zhì)量監(jiān)督檢驗(yàn)檢疫總局, 中國(guó)國(guó)家標(biāo)準(zhǔn)化管理委員會(huì). GB/T 12763.4- 2007 海洋調(diào)查規(guī)范 第4部分: 海水化學(xué)要素調(diào)查. 北京: 中國(guó)標(biāo)準(zhǔn)出版社, 2008.

[17] He J F, Zhang F, Lin L, Ma Y X, Chen J F. Bacterioplankton and picophytoplankton abundance, biomass, and distribution in the Western Canada Basin during summer 2008. Deep Sea Research Part II: Topical Studies in Oceanography, 2012, 81- 84: 36- 55.

[18] Zhou W H, Long A M, Jiang T, Chen S Y, Huang L M, Huang H, Cai C H, Yan Y. Bacterioplankton dynamics along the gradient from highly eutrophic Pearl River Estuary to oligotrophic northern South China Sea in wet season: implication for anthropogenic inputs. Marine Pollution Bulletin, 2011, 62(4): 726- 733.

[19] Ni Z X, Huang X P, Zhang X. Picoplankton and virioplankton abundance and community structure in Pearl River Estuary and Daya Bay, South China. Journal of Environmental Sciences, 2015, 32: 146- 154.

[20] Zhou W H, Li Tao, Cai C H, Huang L M, Wang H K, Xu J R, Dong J D, Zhang S. Spatial and temporal dynamics of phytoplankton and bacterioplankton biomass in Sanya Bay, northern South China Sea. Journal of Environmental Sciences, 2009, 21(5): 595- 603.

[21] 何蕾, 殷克東, 林志芬, 田甜, 袁翔城. 黃海春季海洋病毒的空間分布特征. 海洋科學(xué), 2011, 35(2): 10- 16.

[22] He L, Yin K D, Yuan X C, Li D M, Zhang D R, Harrison P J. Spatial distribution of viruses, bacteria and chlorophyll in the northern South China Sea. Aquatic Microbial Ecology, 2009, 54(2):153- 162.

[23] Wommack K E, Colwell R R. Virioplankton: viruses in aquatic ecosystems. Microbiology and Molecular Biology Reviews, 2000, 64(1): 69- 114.

[24] Collins R E, Deming J W. Abundant dissolved genetic material in Arctic sea ice Part II: viral dynamics during autumn freeze-up. Polar Biology, 2011, 34(12): 1831- 1841.

[25] Bai X G, Wang M, Liang Y T, Zhang Z F, Wang F, Jiang X J. Distribution of microbial populations and their relationship with environmental variables in the North Yellow Sea, China. Journal of Ocean University of China, 2012, 11(1): 75- 85.

[26] Alonso M C, Jimenez-Gomez F, Rodriguez J, Borrego J J. Distribution of virus-like particles in an oligotrophic marine environment (Alboran Sea, Western Mediterranean). Microbial Ecology, 2001, 42(3): 407- 515.

[27] Boehme J, Frischer M E, Jiang S C, Kellogg C A, Pichard S, Rose J B, Steinway C, Paul J H. Viruses, bacterioplankton, and phytoplankton in the southeastern Gulf of Mexico: distribution and contribution to oceanic DNA pools. Marine Ecology Progress Series, 1993, 97: 1- 10.

[28] Magiopoulos I, Pitta P. Viruses in a deep oligotrophic sea: seasonal distribution of marine viruses in the epi-, meso-and bathypelagic waters of the Eastern Mediterranean Sea. Deep Sea Research Part I: Oceanographic Research Papers, 2012, 66: 1- 10.

[29] Bettarel Y, Sime-Ngando T, Amblard C, Laveran H. A comparison of methods for counting viruses in aquatic systems. Applied and Environmental Microbiology, 2000, 66(6): 2283- 2289.

[30] Chen B Z, Liu H B, Huang B Q. Environmental controlling mechanisms on bacterial abundance in the South China Sea inferred from generalized additive models (GAMs). Journal of Sea Research, 2012, 72: 69- 76.

[31] Shish F K, Ducklow H W. Temperature regulation of heterotrophic bacterioplankton abundance, production, and specific growth rate in Chesapeake Bay. Limnology and Oceanography, 1994, 39(6): 1243- 1258.

[32] Peierls B L, Paerl H W. Longitudinal and depth variation of bacterioplankton productivity and related factors in a temperate estuary. Estuarine, Coastal and Shelf Science, 2011, 95(1): 207- 215.

[33] Dumont I, Schoemann V, Jacquet S H M, Masson F, Becquevort S. Bacterial abundance and production in epipelagic and mesopelagic waters in the Subantarctic and Polar Front zones south of Tasmania. Deep Sea Research Part II: Topical Studies in Oceanography, 2011, 58(21- 22): 2212- 2221.

[34] Shang S L, Lee Z P, Wei G M. Characterization of MODIS-derived euphotic zone depth: results for the China Sea. Remote Sensing of Environment, 2011, 115(1): 180- 186.

[35] Weinbauer M G. Ecology of prokaryotic viruses. FEMS Microbiology Reviews, 2004, 28(2): 127- 181.

[36] Tanaka T, Rassoulzadegan F. Vertical and seasonal variations of bacterial abundance and production in the mesopelagic layer of the NW Mediterranean Sea: bottom-up and top-down controls. Deep Sea Research Part I: Oceanographic Research Papers, 2004, 51(4): 531- 544.

[37] Kobari T, Fujii T, Kobari Y, Habano A. Seasonal variations in abundance, growth and mortality of heterotrophic bacteria in Kagoshima Bay. Journal of Oceanography, 2010, 66(6): 845- 853.

[38] Mazuecos I P, Arístegui J, Vázquez-Domínguez E, Ortega-Retuerta E, Gasol J M, Reche I. Temperature control of microbial respiration and growth efficiency in the mesopelagic zone of the South Atlantic and Indian Oceans. Deep Sea Research Part I: Oceanographic Research Papers, 2015, 95: 131- 138.

[39] Kritzberg E S, Arrieta J M, Duarte C M. Temperature and phosphorus regulating carbon flux through bacteria in a coastal marine system. Aquatic Microbial Ecology, 2010, 58(2): 141- 151.

[40] 李洪波, 肖天, 丁濤, 呂瑞華. 浮游細(xì)菌在黃海冷水團(tuán)中的分布. 生態(tài)學(xué)報(bào), 2006, 26(4): 1012- 1020.

[41] Carlsson P, Granéli E, Granéli W, Rodriguez E G, Carvalho W F, Brutemark A, Lindehoff E. Bacterial and phytoplankton nutrient limitation in tropical marine waters, and a coastal lake in Brazil. Journal of Experimental Marine Biology and Ecology, 2012, 418- 519: 37- 55.

[42] 姜發(fā)軍, 胡章立, 胡超群. 大鵬灣浮游細(xì)菌時(shí)空分布與環(huán)境因子的關(guān)系. 熱帶海洋學(xué)報(bào), 2011, 30(1): 96- 100.

[43] Pinhassi J, Gómez-Consarnau L, Alonso-Sáez L, Sala M M, Vidal M, Pedrós-Alió C, Gasol M J. Seasonal changes in bacterioplankton nutrient limitation and their effects on bacterial community composition in the NW Mediterranean Sea. Aquatic Microbial Ecology, 2006, 44(3): 241- 252.

[44] Auguet J C, Montanié H, Delmas D, Hartmann H J, Huet V. Dynamic of virioplankton abundance and its environmental control in the Charente Estuary (France). Microbial Ecology, 2005, 50(3): 337- 349.

[46] 侯瑞, 白潔, 劉小沙, 高會(huì)旺, 趙陽(yáng)國(guó). 南海南部海域異養(yǎng)浮游細(xì)菌生長(zhǎng)對(duì)外源營(yíng)養(yǎng)物的響應(yīng). 中國(guó)海洋大學(xué)學(xué)報(bào), 2015, 45(10): 103- 108.

[47] Ma W T, Chai F, Xiu P, Xue H J, Tian J. Modeling the long-term variability of phytoplankton functional groups and primary productivity in the South China Sea. Journal of Oceanography, 2013, 69(5): 527- 544.

[48] Wong G T F, Pan X J, Li K Y, Shiah F, Ho T Y, Guo X H. Hydrography and nutrient dynamics in the Northern South China Sea Shelf-sea (NoSoCS). Deep Sea Research Part II: Topical Studies in Oceanography, 2015, 117: 23- 50.

[49] Ma W T, Chai F, Xiu P, Xue H J, Tian J. Simulation of export production and biological pump structure in the South China Sea. Geo-Marine Letters, 2014, 34(6): 541- 554.

[50] Zhang Y, Jiao N Z, Cottrell M T, Kirchman D L. Contribution of major bacterial groups to bacterial biomass production along a salinity gradient in the South China Sea. Aquatic Microbial Ecology, 2006, 43(3): 233- 241.

[51] Parvathi A, Jasna V, Jina S, Jayalakshmy K V, Lallu K R, Madhu N V, Muraleedharan K R, Kumar K R N, Balachandran K K. Effects of hydrography on the distribution of bacteria and virus in Cochin estuary, India. Ecological Research, 2015, 30(1): 85- 92.

[52] 高源, 何劍鋒, 陳敏, 林凌, 張芳. 北冰洋楚科奇海浮游細(xì)菌豐度和生產(chǎn)力及其分布特征. 海洋學(xué)報(bào), 2015, 37(8): 96- 104.

[53] 孫小磊, 趙以軍, 劉妮, 鄧敬軒, 程凱. 淡水濕地浮游病毒的空間分布. 生態(tài)學(xué)報(bào), 2009, 29(2): 1048- 1054.

[54] Fuhrman J A. Marine viruses and their biogeochemical and ecological effects. Nature, 1999, 399(6736): 541- 548.

[55] Zhang Y Y, Huang C X, Yang J, Jiao N Z. Interactions between marine microorganisms and their phages. Chinese Science Bulletin, 2011, 56(17): 1770- 1777.

[56] Vanucci S, Bruni V, Pulicanò G. Spatial and temporal distribution of virioplankton and bacterioplankton in a brackish environment (Lake of Ganzirri, Italy). Hydrobiologia, 2005, 539(1): 83- 92.

[57] Weinbauer M G, Fuks D, Peduzzi P. Distribution of viruses and dissolved DNA along a coastal trophic gradient in the Northern Adriatic Sea. Applied and Environmental Microbiology, 1993, 59(12): 4074- 5082.

[58] Alongi D M, Patten N L, McKinnon D, K?stner N, Bourne D G, Brinkman R. Phytoplankton, bacterioplankton and virioplankton structure and function across the southern Great Barrier Reef shelf. Journal of Marine Systems, 2015, 142: 25- 39.

[59] Personnic S, Domaizon I, Dorigo U, Berdjeb L, Jacquet S. Seasonal and spatial variability of virio-, bacterio-, and picophytoplanktonic abundances in three Peri-Alpine Lakes. Hydrobiologia, 2009, 627(1): 99- 116.

[60] Almeida M A, Cunha M A, Alcntara F. Loss of estuarine bacteria by viral infection and predation in microcosm conditions. Microbial Ecology, 2001, 42(4): 562- 571.

[61] Colombet J, Charpin M, Robin A, Portelli C, Amblard C, Cauchie H M, Sime-Ngando T. Seasonal depth-related gradients in virioplankton: standing stock and relationships with microbial communities in Lake Pavin (France). Microbial Ecology, 2009, 58(4): 728- 736.

Ecological distribution of bacterioplankton and virioplankton in the north of South China Sea in spring

ZHANG Zhe1,3,4, WANG Xiaohong2, GONG Xiuyu1,3,4, LIU Yong1,3,4, LIAO Xiuli1,3,4, CAI Wengui1,3,4, HUANG Honghui1,3,4, *

1SouthChinaSeaFisheriesResearchInstitute,ChineseAcademyofFisherySciences,Guangzhou510300,China2TeachingCenterofBiologyExperiment,SchoolofLifeSciences,SunYat-SenUniversity,Guangzhou510275,China3KeyLaboratoryforFisheryEco-Environment,GuangdongProvince,Guangzhou510300,China4KeyLaboratoryofSouthChinaSeaFisheryResourcesExploitation&Utilization,MinistryofAgriculture,P.R.China,Guangzhou510300,China

According to the concept of Microbial Loop, bacteria and virus play important role in organic matter recycling and energy flowing in marine ecosystem, and meanwhile influence many biogeochemical and ecological processes. Marine bacterial and viral ecology has become hotspot in current studies. The South China Sea (SCS) is one of the largest marginal seas in Northwest Pacific, and has already been proved to be oligotrophic. The SCS has attracted great attention due to its economic and strategic importance in recent years. Although the abundance and diversity of bacterioplankton in coastal waters and northern upwelling regions of SCS are well documented, little is known about bacterioplankton and virioplankton distribution in the central and northern area, especially the area near 18°N in SCS, and further investigations should be carried on to study the ecological functions of microbes in this region. In order to study the ecological distribution and function of bacteria and virus in this area, a cruise was conducted during Spring 2014 and water samples were collected from 27 stations. Water column at each station was divided into five layers, which were 5, 25, 75, 150 and 200 m layers respectively. Water samples were collected by Niskin bottles, fixed with glutaraldehyde and stored at liquid nitrogen immediately. Bacterioplankton and virioplankton abundances at different water layers and stations were measured by flow cytometry method. Horizontal and vertical distribution and its correlation with environmental variables, such as temperature, depth, salinity, dissolved oxygen, chlorophyll a and inorganic nutrients were also analyzed. The results showed that the bacterioplankton and virioplankton abundances in the upper 200 m of the water column were 1.28×104—9.96×105cells/mL and 4.69×105—5.39×107cells/mL, respectively. Their abundances were similar to the results in other oligotrophic oceans and lower than that of the coastal areas. With the increase in water depth, the abundances of both bacterioplankton and virioplankton decreased gradually in the vertical direction and in correlation with the euphotic layer, but no significant distribution pattern was detected in the horizontal direction. The variation in bacterioplankton and virioplankton abundance was significantly correlated with water temperature, pH, and dissolved oxygen, but negatively correlated with water depth, salinity, active phosphorus, silicate, nitrate, and total nitrogen (P<0.01). We conclude that bacterioplankton and virioplankton abundances were regulated by multiple environmental factors. Virus-to-bacteria ratio (VBR) reflects the relationship between bacteria and virus. The average VBR in this region was 32.23. The maximum value was 264.63 and it was observed at the 75 m layer of S7 station. The minimum value was 4.80 and it was detected at the 25 m layer of S11 station. A VBR value lower than 100 was detected in 95.6% of the stations. No significant correlation was found between VBR and environmental variables (P>0.05), however, a significant negative correlation was observed between bacterioplankton and VBR (P<0.01). A strong correlation between bacterioplankton and virioplankton was detected (P<0.01), indicating that bacterioplankton is probably the main host of virioplankton, and the virioplankton probably mainly existed in the form of bacteriophage. Relationships between organic carbon and bacterioplankton need to be further studied in order to illuminate growth and decline mechanism of microbes in SCS.

microbial food loop; virioplankton; bacterioplankton; South China Sea

農(nóng)業(yè)部財(cái)政重大專(zhuān)項(xiàng)項(xiàng)目(NFZX2013)；廣東省科技計(jì)劃項(xiàng)目(2013B021100014)

2015- 09- 23;

日期:2016- 07- 13

10.5846/stxb201509231958

*通訊作者Corresponding author.E-mail: huanghh@scsfri.ac.cn

張喆, 王曉紅, 鞏秀玉, 劉永, 廖秀麗, 蔡文貴, 黃洪輝.南海北部海域春季浮游細(xì)菌和病毒空間分布及其影響因素.生態(tài)學(xué)報(bào),2017,37(5):1639- 1649.

Zhang Z, Wang X H, Gong X Y, Liu Y, Liao X L, Cai W G, Huang H H.Ecological distribution of bacterioplankton and virioplankton in the north of South China Sea in spring.Acta Ecologica Sinica,2017,37(5):1639- 1649.