李巧玉，劉 瑞，向 蓉，喻 燚，董聰聰，張紅波，施軍瓊，吳忠興

(1:西南大學(xué)三峽庫(kù)區(qū)生態(tài)環(huán)境教育部重點(diǎn)實(shí)驗(yàn)室，重慶市三峽庫(kù)區(qū)植物生態(tài)與資源重點(diǎn)實(shí)驗(yàn)室，重慶 400715)(2:武漢市環(huán)境監(jiān)測(cè)中心，武漢430015)

三峽庫(kù)區(qū)支流底棲硅藻功能群特征及其驅(qū)動(dòng)因子分析
——以汝溪河為例*

李巧玉1，劉 瑞2，向 蓉1，喻 燚1，董聰聰1，張紅波1，施軍瓊1，吳忠興1**

(1:西南大學(xué)三峽庫(kù)區(qū)生態(tài)環(huán)境教育部重點(diǎn)實(shí)驗(yàn)室，重慶市三峽庫(kù)區(qū)植物生態(tài)與資源重點(diǎn)實(shí)驗(yàn)室，重慶 400715)(2:武漢市環(huán)境監(jiān)測(cè)中心，武漢430015)

以三峽庫(kù)區(qū)重要支流汝溪河為研究區(qū)域，分析汝溪河中底棲硅藻功能群季節(jié)演替特征，并探討影響其季節(jié)演替的驅(qū)動(dòng)因子. 結(jié)果表明，3個(gè)水情期(平水期、枯水期及豐水期)共鑒定出底棲硅藻168種，隸屬8科27屬，共劃分為B、C、D、LO、MP、P、X3和TB8個(gè)功能群，其中MP在3個(gè)水情期中均占主導(dǎo)地位. 通過冗余分析(RDA)發(fā)現(xiàn)，汝溪河中底棲硅藻功能群季節(jié)演替的主要驅(qū)動(dòng)環(huán)境因子為亞硝酸鹽濃度、電導(dǎo)率、溶解性磷酸鹽濃度、高錳酸鉀指數(shù)和溫度.

底棲硅藻；功能群；季節(jié)演替；驅(qū)動(dòng)因子；汝溪河;三峽庫(kù)區(qū)

在河流生態(tài)系統(tǒng)中，藻類能進(jìn)行光合作用，對(duì)污染物反應(yīng)靈敏，且群落結(jié)構(gòu)組成變化隨著水體生態(tài)環(huán)境變化而變化，常被用于水質(zhì)監(jiān)測(cè)和評(píng)價(jià)[1]. 傳統(tǒng)研究常根據(jù)形態(tài)學(xué)水平劃分不同的類群，不同生境下浮游植物群落往往高度多樣化且大多數(shù)物種的發(fā)生難以預(yù)測(cè)，因此，不能很好體現(xiàn)出河流生態(tài)環(huán)境特征. 為了彌補(bǔ)傳統(tǒng)分類方法在應(yīng)用方面的不足，Reynolds依據(jù)浮游植物生理、生態(tài)、形態(tài)特點(diǎn)等綜合特征提出了相對(duì)完整的浮游藻類功能群理論[2]，并依據(jù)浮游植物對(duì)不同環(huán)境因子的耐受性及個(gè)體形態(tài)差異將浮游植物劃分出31個(gè)功能群[3]. Padisák在Reynolds的基礎(chǔ)上，依據(jù)在功能上適應(yīng)性較強(qiáng)的物種，更能耐受因子缺失的限制條件和在受光照、P、C、N或其他因子限制的生境更有可能生存等特征，進(jìn)一步將功能群歸納整理為包括A、B、D、MP、TB等39個(gè)功能群[4-6]. 近些年來，該理論被廣泛應(yīng)用于國(guó)內(nèi)外浮游植物的研究[7]，如Becker等[3]對(duì)巴西亞熱帶深水水庫(kù)、Crossetti等[8]對(duì)Mangueira湖、Devercelli等[9]對(duì)Salado河、Xiao等[10]對(duì)流溪河水庫(kù)及李磊等[11]對(duì)阿哈水庫(kù)等開展了相應(yīng)的研究. 然而，對(duì)硅藻功能群的研究相對(duì)較少. 硅藻是食物鏈中的主要初級(jí)生產(chǎn)者，具有繁殖快、生長(zhǎng)周期短且對(duì)水體理化環(huán)境的變化反應(yīng)迅速、敏銳的特點(diǎn)，被廣泛關(guān)注[12-13]. 特別是底棲硅藻具有分布廣泛，便于采集和對(duì)水體生態(tài)變化的敏感性強(qiáng)的優(yōu)點(diǎn)，常被用于水體監(jiān)測(cè)[14].

自三峽大壩建成蓄水后，水位升高，水流減緩，水體擴(kuò)散能力減弱，支流水體富營(yíng)養(yǎng)化問題嚴(yán)重，局部地區(qū)水華頻繁發(fā)生，對(duì)水質(zhì)健康狀況產(chǎn)生嚴(yán)重威脅[15]. 汝溪河是三峽庫(kù)區(qū)重要支流之一，發(fā)源于萬(wàn)州，流經(jīng)忠縣汝溪鎮(zhèn)，最后經(jīng)涂井鄉(xiāng)匯入長(zhǎng)江. 全流域面積720 km2，主河道長(zhǎng)54.5 km，在忠縣的流域面積為272.9 km2，主河道長(zhǎng)25.4 km. 庫(kù)區(qū)蓄水后，在忠縣區(qū)域形成長(zhǎng)15 km的回水區(qū)[16]. 目前，關(guān)于汝溪河底棲硅藻的研究較少，而對(duì)汝溪河底棲硅藻功能群的特征以及其與環(huán)境之間的關(guān)系未見相關(guān)報(bào)道，為了揭示人為活動(dòng)影響下汝溪河底棲硅藻群落結(jié)構(gòu)及功能群變化，本研究主要對(duì)汝溪河上游區(qū)域開展底棲硅藻功能群季節(jié)演替特征以及季節(jié)演替的驅(qū)動(dòng)因子的研究，為汝溪河及相應(yīng)流域的水生生態(tài)系統(tǒng)保護(hù)和管理提供一定依據(jù).

1 材料與方法

1.1 樣點(diǎn)設(shè)置

本實(shí)驗(yàn)對(duì)汝溪河忠縣段(30°27′～30°31′N，108°1′～108°6′E)的汝溪鎮(zhèn)至涂井鄉(xiāng)設(shè)置了9個(gè)樣點(diǎn)(圖1). 在汝溪鎮(zhèn)至涂井鄉(xiāng)自上而下分布有桐油灘、長(zhǎng)溪、高洞梁和鑫家源等4個(gè)水電站. S1為控制樣點(diǎn)，距最上游的桐油灘水電站1000 m左右，基本不受梯級(jí)電站的影響，樣點(diǎn)S2、S4、S6、S8分別為桐油灘水電站、長(zhǎng)溪水電站、高洞梁水電站以及鑫家源水電站上游樣點(diǎn)，而樣點(diǎn)S3、S5、S7、S9為4個(gè)電站下游的樣點(diǎn). 根據(jù)對(duì)汝溪河長(zhǎng)期的監(jiān)測(cè)(2011-2013年)，于2013年4月(豐水期)、8月(平水期)和12月(枯水期)進(jìn)行樣品采集與理化指標(biāo)的測(cè)定和分析.

圖1 汝溪河樣點(diǎn)分布Fig.1 Distribution of sampling sites in Ruxi River

1.2 樣品采集與理化指標(biāo)

1.3 數(shù)據(jù)處理及分析

功能群分類參照Reynolds和Padisák[4-5,19]等分類體系進(jìn)行劃分. 用Excel整理數(shù)據(jù)，SPSS 22.0軟件進(jìn)行多元逐步回歸分析，其中以環(huán)境因子為自變量，不同功能類群藻密度為因變量，根據(jù)P值和F值逐步篩選出主要影響環(huán)境因子，得到回歸方程和相關(guān)系數(shù). 采用Canoco 5.0軟件進(jìn)行排序分析[20]. 排序分析前，先將物種數(shù)據(jù)進(jìn)行除趨勢(shì)對(duì)應(yīng)分析(DCA)，4個(gè)軸最大梯度大于4.0，選用典范對(duì)應(yīng)分析(CCA)，如果小于3.0，選用冗余分析(RDA). 本文4個(gè)軸最大梯度均小于3.0，故選用RDA分析，除pH外其余數(shù)據(jù)均進(jìn)行l(wèi)g(x+1)轉(zhuǎn)換，進(jìn)行RDA分析前，用SPSS軟件對(duì)環(huán)境因子進(jìn)行Pearson相關(guān)分析.

2 結(jié)果

2.1 汝溪河底棲硅藻的群落結(jié)構(gòu)及功能群

在豐水期、平水期、枯水期3個(gè)時(shí)期，對(duì)汝溪河9個(gè)樣點(diǎn)底棲硅藻進(jìn)行采樣，結(jié)果表明9個(gè)樣點(diǎn)中共鑒定出硅藻門8科27屬168種，其中中心綱和羽紋綱所占比例分別為6.55%和93.45%，舟形藻屬(28種)、菱形藻屬(23種)和異極藻屬(21種)為主要優(yōu)勢(shì)屬，分別占總種數(shù)的16.7%、13.7%和12.5%. 依據(jù)生境的不同，對(duì)168種硅藻進(jìn)行功能群劃分，結(jié)果發(fā)現(xiàn)168種硅藻可劃分為8個(gè)功能類群(表1)，分別為B、C、D、LO、MP、P、TB、X3. 從種類組成(圖2)來看，所占種數(shù)比例最大的是MP類群(62種)，其次為D(29種)，最少的為C(2種)和TB(3種). 豐水期底棲硅藻功能類群的種類比例分布為MP(53.45%)最大，其次為D(19.83%)，C(0.86%)最??；平水期的種類比例分布為MP(45.95%)最大，其次為D(20.30%)，C(1.35%)最??；枯水期的功能群種類比例為MP(48.60%)最大，其次為D(27.10%)，而B、LO、C(各占1.87%)最小. 從藻密度來看，豐水期MP類群占絕對(duì)優(yōu)勢(shì)(7703.5 cells/cm2)，其次為C(2994.7 cells/cm2)；平水期MP類群占絕對(duì)優(yōu)勢(shì)(2891.8 cells/cm2)，其次為P(776.1 cells/cm2);枯水期MP類群占絕對(duì)優(yōu)勢(shì)(12226.3 cells/cm2)，其次為D(3107.5 cells/cm2).

表1 汝溪河底棲硅藻功能群組成

圖2 汝溪河不同水情期底棲硅藻功能類群的組成 Fig.2 The functional groups composition of benthic diatoms in Ruxi River during different hydrological periods

2.2 不同時(shí)期功能類群與環(huán)境因子的逐步回歸分析

方差分析結(jié)果(表3)顯示，在豐水期，B、C、MP、P、TB、X3類群的F值范圍為5.892～37.122，6個(gè)類群受環(huán)境因素的影響較大；在平水期，B、C、D、MP、P、X3類群的F值范圍為8.229～795.697，受環(huán)境因素的影響較大；在枯水期，D、MP、TB、X3類群的F值范圍為7.926～15589.766，4個(gè)類群受環(huán)境因素的影響較大.

2.3 不同時(shí)期功能類群藻密度與環(huán)境因子的相關(guān)性分析

表2 不同水情期汝溪河底棲硅藻功能類群藻密度與環(huán)境因子的逐步回歸分析

表3 不同時(shí)期汝溪河底棲硅藻功能群藻密度受環(huán)境因子影響的單因素方差分析統(tǒng)計(jì)結(jié)果

表4 不同時(shí)期汝溪河底棲硅藻功能類群藻密度與主要環(huán)境因子間的RDA分析

圖3 不同時(shí)期功能群藻密度與環(huán)境因子RDA排序圖：(a)豐水期；(b)平水期；(c)枯水期Fig.3 The RDA diagrams between environmental factors and densities of benthic diatoms functional classifications in Ruxi River during different water periods: (a) high water period; (b) level water period; (c) low water period

3 討論

由于許多物種往往代表著一定的生境類型，因此基于傳統(tǒng)藻類分類單元進(jìn)行水體生態(tài)學(xué)的研究已經(jīng)被廣泛應(yīng)用[21]. 然而，藻類對(duì)環(huán)境的反應(yīng)往往依賴于地理環(huán)境或棲息地特征，Kelly認(rèn)為由于地理環(huán)境或棲息地的變化可能導(dǎo)致相同的物種出現(xiàn)不一樣的結(jié)果[22]，甚至同一物種生態(tài)型出現(xiàn)不同的生態(tài)特征[23]. 因此，基于傳統(tǒng)的藻類分類單元研究水生生態(tài)系統(tǒng)一直受到質(zhì)疑[22]. 而功能性狀特征能夠反映真實(shí)的生態(tài)環(huán)境條件，近年來在國(guó)外水體生態(tài)系統(tǒng)評(píng)價(jià)中經(jīng)常被報(bào)道，如：Passy提出的“guild”功能群[24]，Reynolds提出的“function group”[2]. “guild”和“function group”是同義詞，本質(zhì)上都是基于功能性狀提出的分類單元，兩者區(qū)別在于前者強(qiáng)調(diào)資源共用，而后者強(qiáng)調(diào)生態(tài)功能相似. 由于Blondel認(rèn)為“guild”更多應(yīng)用在動(dòng)物方面[25]，因此，功能群“function group”常被用于藻類學(xué). Becker利用浮游植物功能群對(duì)地中海水庫(kù)的浮游植物驅(qū)動(dòng)特征進(jìn)行研究，證實(shí)了浮游植物功能群具有潛在用途，能夠?yàn)榱私庠孱惿L(zhǎng)的策略、適應(yīng)和耐受等特性以及水庫(kù)浮游植物動(dòng)力學(xué)提供信息[3]. 先前功能群的研究主要基于浮游植物提出的浮游植物功能群的概念，卻很少用于底棲藻類，特別是底棲硅藻的研究. 然而，底棲硅藻分布廣泛、便于采集,繁殖快、生長(zhǎng)周期短且對(duì)水體中理化環(huán)境的變化反應(yīng)迅速、能快速敏銳地做出反應(yīng)的特點(diǎn)[12-13]，如果能更好地確定功能特性與環(huán)境因子相關(guān)性，用其作為水生生態(tài)系統(tǒng)研究將具有很好的應(yīng)用價(jià)值[21]. 本文利用功能群對(duì)汝溪河開展了研究，發(fā)現(xiàn)汝溪河中有近緣橋彎藻(Cymbellaaffinis)、披針形舟形藻(Naviculalanceolata)等為優(yōu)勢(shì)種，均屬于功能群中的MP類群；通過汝溪河3個(gè)水情期環(huán)境因子分析得到，透明度均值為0.59 m、流速均值為0.11 m/s，這與MP類群的生境特征相符. Reynolds[2]研究表明，由于物種的選擇性，比表面積大且能耐受低光照的硅藻(如MP類群為典型代表)利于生活在水體渾濁環(huán)境中. 受三峽庫(kù)區(qū)周期性蓄水變動(dòng)的影響，庫(kù)區(qū)支流水體懸浮顆粒物攪拌頻繁，因此，汝溪河3個(gè)水情期底棲硅藻功能群中均以MP占主(表1). 這一結(jié)果也支持了閔文武等[26]對(duì)渭河流域不同時(shí)期浮游植物功能群的研究結(jié)論.

4 結(jié)論

1)汝溪河流域中共鑒定出硅藻168種，劃分出8個(gè)功能群，在種類水平上，3個(gè)時(shí)期均以MP類群占主導(dǎo)地位，其次為D類群；在藻密度水平上，豐水期中MP類群占絕對(duì)優(yōu)勢(shì)，其次為C類群，平水期中MP類群占絕對(duì)優(yōu)勢(shì)，其次為P類群，枯水期中MP類群占絕對(duì)優(yōu)勢(shì)，其次為D類群，總體來看3個(gè)時(shí)期均以MP類群占主導(dǎo)優(yōu)勢(shì)地位.

致謝：感謝許金鑄師兄、楊燕君師姐和徐沙師姐對(duì)本次野外實(shí)驗(yàn)和室內(nèi)藻類鑒定的辛苦付出.

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FunctionalgroupcharacteristicsofbenthicdiatomsanditsdrivingfactorsinthebranchofThreeGorgesReservoir:AcasestudyofRuxiRiver

LI Qiaoyu1, LIU Rui2, XIANG Rong1, YU Yi1, DONG Congcong1, ZHANG Hongbo1, SHI Junqiong1& WU Zhongxing1**

(1:KeyLaboratoryofEco-environmentsinThreeGorgesReservoirRegion,MinistryofEducation,KeyLaboratoryofPlantEcologyandResourcesResearchinThreeGorgesReservoirRegion,SouthwestUniversity,Chongqing400715,P.R.China)(2:WuhanEnvironmentalMonitoringCenter,Wuhan430015,P.R.China)

The seasonal succession of function groups in benthic diatom and its relationship with environmental factors were investigated in Ruxi River, an important branch of Three Gorges Reservoir. Results showed that 168 species of benthic diatoms belonging to 27 genus, 8 families were found in this river, and these species were categorized to 8 functional groups including B, C, D, LO, MP, P, X3 and TBduring three different water periods for low, level and high water period, and MP was absolutely dominant. Redundancy analysis suggested that seasonal succession of functional groups in the benthic diatom was mainly determined by nitrite, conductivity, phosphate, permanganate index and water temperature.

Benthic diatoms; functional groups; seasonal dynamics; driving factors; Ruxi River; Three Gorges Reservoir

*中央高?；緲I(yè)務(wù)費(fèi)專項(xiàng)(XDJK2016C111)和西南大學(xué)博士基金項(xiàng)目(SWU110065)聯(lián)合資助. 2016-11-14收稿；2017-02-24收修改稿. 李巧玉(1993～)，女，碩士研究生；E-mail： 1255805492@qq.com.

**通信作者；E-mail： wuzhx@swu.edu.cn.