李超然,苗令占,侯 俊

間歇性河流中生物膜對(duì)干濕脅迫的動(dòng)態(tài)響應(yīng)

李超然,苗令占*,侯 俊

(河海大學(xué),環(huán)境學(xué)院淺水湖泊綜合治理與資源開(kāi)發(fā)教育部重點(diǎn)實(shí)驗(yàn)室,江蘇 南京 210098)

針對(duì)近年來(lái)關(guān)于河流生態(tài)系統(tǒng)中生物膜在干濕脅迫下的響應(yīng)研究進(jìn)展,綜述了生物膜結(jié)構(gòu)和功能的適應(yīng)性變化,主要分析了生物膜中不同功能類群(自養(yǎng)和異養(yǎng))以及群落結(jié)構(gòu)(多樣性以及多樣性)的動(dòng)態(tài)變化;結(jié)構(gòu)性變化主要表現(xiàn)為隨著干旱進(jìn)行多樣性的降低以及多樣性的升高, 另外系統(tǒng)總結(jié)了干濕脅迫下生物膜生產(chǎn)力和代謝功能的動(dòng)態(tài)響應(yīng);重點(diǎn)分析了生物膜微生物群體對(duì)干濕脅迫的抗性機(jī)制,并展望了分子生態(tài)網(wǎng)絡(luò)分析在生物膜動(dòng)態(tài)響應(yīng)研究中的應(yīng)用前景.

間歇性河流；生物膜；群落結(jié)構(gòu)；功能特性；網(wǎng)絡(luò)分析

世界范圍內(nèi)大部分的河流網(wǎng)絡(luò)由間歇性河流構(gòu)成,間歇性河流不同于恒定河流,其流動(dòng)具有間歇性且非流期的持續(xù)時(shí)間與頻率受環(huán)境影響較大[1].特別是面臨全球變暖、季節(jié)更替等自然影響以及河流上游庫(kù)壩建設(shè)等人為影響,間歇性河流出現(xiàn)減脫水現(xiàn)象、斷流干旱的頻率更高,嚴(yán)重影響河流生態(tài)系統(tǒng).近年來(lái),國(guó)內(nèi)外研究學(xué)者針對(duì)河流減脫水與流域生態(tài)響應(yīng)的相關(guān)關(guān)系進(jìn)行了大量研究,發(fā)現(xiàn)在河流水文變化與河流生態(tài)狀況之間存在著三種不同的關(guān)系,表明河流水文變化強(qiáng)度(如減脫水過(guò)程和強(qiáng)度)對(duì)河流生態(tài)系統(tǒng)結(jié)構(gòu)與功能等方面的不同影響路徑[2].

因此明確間歇性河流減脫水與河流生態(tài)狀況變化之間的關(guān)系,定性與定量探究干濕脅迫對(duì)河流生態(tài)系統(tǒng)結(jié)構(gòu)與功能的影響,是減脫水河流進(jìn)行生態(tài)評(píng)估和生態(tài)修復(fù)的必要前提.

河流底棲生物膜是由微生物及其分泌的胞外聚合物(EPS)構(gòu)成的一個(gè)復(fù)雜、具有一定功能的微生物集合體,由10%的微生物和90%的EPS,構(gòu)成[3-5].生物膜作為河流環(huán)境中最重要的初級(jí)生產(chǎn)者,廣泛存在于河流、湖泊、濕地等水環(huán)境中的固相物質(zhì)(沙石、沉積物等)表面().同時(shí)作為河流生態(tài)系統(tǒng)的基礎(chǔ),對(duì)河流系統(tǒng)的初級(jí)生產(chǎn)、物質(zhì)循環(huán)和能量流動(dòng)起著關(guān)鍵的驅(qū)動(dòng)作用[6-15].在不同的水文階段,河流底棲生物膜相應(yīng)地改變它的結(jié)構(gòu)功能和群落組成[16].因此河流生物膜作為生態(tài)系統(tǒng)結(jié)構(gòu)和功能耦合的指標(biāo)[17-18],在減脫水河段的研究中逐漸受到關(guān)注.

基于微生物豐度的數(shù)據(jù)分析,通過(guò)合理閾值選擇和相關(guān)性采用網(wǎng)絡(luò)分析手段[20-25],理解群落中不同物種之間的相互作用以及它們對(duì)環(huán)境變化的響應(yīng)并揭示其構(gòu)建機(jī)制,而不是只關(guān)注單一物種在不同環(huán)境條件下的變化,是理解生物多樣性、群落穩(wěn)定性和生態(tài)系統(tǒng)功能模式的基礎(chǔ).

1 間歇性河流中的生物膜

生物膜作為河流生態(tài)系統(tǒng)中主要的生物界面,是間歇性河流中最重要的生物組分[1].如圖1,生物膜作為自養(yǎng)生物和異養(yǎng)生物的聯(lián)合體,共存于(EPS)基質(zhì)中,主要由細(xì)菌、藻類、真菌及古菌組成[15,26-29],另外微生物和小型底棲動(dòng)物也棲息在生物膜中,捕食生物體和有機(jī)顆粒,并促進(jìn)其進(jìn)化和擴(kuò)散[19].因此,生物膜形成了一個(gè)高度活躍的生物聯(lián)合體,可以利用水中的有機(jī)和無(wú)機(jī)物質(zhì)[30-34],也可以利用光能或化學(xué)能.其中EPS能夠保留細(xì)胞外酶,利用環(huán)境中的物質(zhì),并將這些物質(zhì)轉(zhuǎn)化為可溶性的營(yíng)養(yǎng)物質(zhì)[35-38],供藻類和細(xì)菌使用.

圖1 自然界中的生物膜

在間歇性河流中的生物膜微生物群落能夠適應(yīng)環(huán)境并具有在復(fù)水后恢復(fù)和擴(kuò)散能力的關(guān)鍵可能在于:任何能暫時(shí)提供潮濕環(huán)境的地方都能成為生物膜的生存場(chǎng)所[39-43].但微生物的存活程度依舊取決于干旱的嚴(yán)重程度,:在干燥時(shí)間很長(zhǎng)、條件很惡劣的系統(tǒng)中,大部分微生物依然無(wú)法存活[39,44].因此研究生物膜在干濕脅迫下的結(jié)構(gòu)功能響應(yīng),探究微生物在間歇性河流中的抗性機(jī)制,在間歇性河道修復(fù)中具有重要的理論意義.

2 生物膜結(jié)構(gòu)對(duì)干濕脅迫的適應(yīng)性變化

2.1 干濕脅迫對(duì)生物膜群落結(jié)構(gòu)組成的影響

在河流的減脫水過(guò)程中,河流較深的部分形成了水池,其中的原生群落逐漸被其他水生、半水生或陸生群落生物所取代.由于干燥不均勻,在河流沿岸可能會(huì)出現(xiàn)斑塊[46-48],有礁巖的陸地分隔區(qū)則提供了更多的生態(tài)位,形成了高于預(yù)期的Beta多樣性(β多樣性).

自養(yǎng)生物群落面對(duì)干旱擾動(dòng)表現(xiàn)出多種生存策略,包括產(chǎn)生不動(dòng)因子、囊泡或保護(hù)卵等[48-50].其中硅藻屬的彎藻屬和異極藻屬能夠在細(xì)胞寄主處形成莖或管,但硅藻相比于其他藻類如紅藻門(mén)和褐藻門(mén)等細(xì)胞壁較厚的藻類,不耐干燥.紅藻能夠在完全干燥的環(huán)境中存活很長(zhǎng)一段時(shí)間,并在水流恢復(fù)后立即恢復(fù)其光合活性[51-52].同時(shí)研究發(fā)現(xiàn),在低至無(wú)地表水時(shí)期,OTU數(shù)較高的群落向較低群落轉(zhuǎn)移,其中厚壁菌門(mén)(一種細(xì)菌門(mén),包含許多內(nèi)孢形成屬)在間歇性河流的非流期臨時(shí)取代了生物膜中的藍(lán)藻.因此在間歇性河流的減脫水階段,河流流域內(nèi)藻類的Alpha多樣性(α多樣性)出現(xiàn)大幅度的下降.

非流動(dòng)階段除了降低了細(xì)菌群落結(jié)構(gòu)組成的豐度和多樣性,還為某些細(xì)菌類群提供了新的生境機(jī)會(huì)[36-37,44].有研究指出,由于物理上的接近性,陸地來(lái)源的細(xì)菌在間歇性河流非流期中的貢獻(xiàn)最大,并且隨著河流規(guī)模的增大而減少[53].Timoner等[37,53]觀察到粗砂、鵝卵石和潛流沉積物上的生物膜對(duì)復(fù)濕的響應(yīng)不同.當(dāng)前對(duì)于干濕交替條件下生物膜的響應(yīng)實(shí)驗(yàn)結(jié)果表明,不同生物膜的響應(yīng)結(jié)果都是特殊的,這取決于它們所處的特定環(huán)境和它們的恢復(fù)力,并突出了每個(gè)生物膜群落的環(huán)境因素.

但是目前的研究大多針對(duì)生物膜中藻類和細(xì)菌的群落結(jié)構(gòu)豐度、多樣性等方面,而對(duì)生物膜中的真菌和古菌對(duì)干旱的響應(yīng)研究較少[54].以往認(rèn)為古菌只是生物膜微生物群落中的一個(gè)次要組成部分,但是目前的研究表明了產(chǎn)甲烷基團(tuán)或氨氧化古菌在C和N循環(huán)中的重要作用.比如稀有微生物能夠通過(guò)還原硫酸鹽,進(jìn)而抑制甲烷的排放.Yang等[55]以mcrA 基因?yàn)榘悬c(diǎn)對(duì)稀有產(chǎn)甲烷古菌進(jìn)行研究發(fā)現(xiàn),在考慮稀有類群的情況下,a多樣性與甲烷的產(chǎn)生呈正相關(guān),稀有產(chǎn)甲烷類群在很大程度上解釋了稀有微生物圈的整體群落動(dòng)態(tài),并可能在有利的環(huán)境條件下轉(zhuǎn)化為優(yōu)勢(shì)群落河床生境提供了大量低氧化還原條件下的缺氧微生態(tài)位,供給產(chǎn)甲烷古菌的生長(zhǎng)和活動(dòng)[56],一些產(chǎn)甲烷物種能夠在干燥脅迫下生存,這表明它們?cè)诟珊禃r(shí)期也可能存在于間歇流中.事實(shí)上,在湖泊沉積物中進(jìn)行的人工實(shí)驗(yàn)已經(jīng)提供了證據(jù),表明盡管古菌群落的數(shù)量和多樣性發(fā)生了變化,但在干燥過(guò)程中古菌的活性和甲烷的產(chǎn)生仍然持續(xù)存在.

以此來(lái)看,近期的研究結(jié)果突出了河道生態(tài)系統(tǒng)中真菌和古菌的研究?jī)r(jià)值,應(yīng)當(dāng)加強(qiáng)對(duì)于真菌和古菌群落的生長(zhǎng)機(jī)制研究,進(jìn)一步分析其在C、N循環(huán)等方面的作用貢獻(xiàn).同時(shí)還需要深度探究在間歇性河流的整個(gè)水文循環(huán)中(如圖2a),微生物群落結(jié)構(gòu)和多樣性的響應(yīng)和恢復(fù)機(jī)制.

2.2 干濕脅迫對(duì)生物膜中不同功能類群(自養(yǎng)和異樣)的影響

在間歇性河流的干濕交替過(guò)程中,生物膜中細(xì)菌和藻類的細(xì)胞密度和生物量受影響較大,但兩者的模式不同.河床干燥時(shí),藻類生物量下降了80%,而細(xì)菌僅下降了20%[57],表明了異養(yǎng)生物對(duì)于干濕脅迫的抵抗力高于自養(yǎng)生物[53],原因在于有些細(xì)菌在低濕度條件下仍能保持活性,但在光照有限的條件下,水分的缺乏直接影響藻類的光合作用,導(dǎo)致生物量的迅速下降[37,53,58].而研究發(fā)現(xiàn),復(fù)水后自養(yǎng)生物的恢復(fù)力要高于異養(yǎng)生物,這可能與殘留在介質(zhì)表面的干藻等藻類的生理恢復(fù)機(jī)制有關(guān)[45].另外研究發(fā)現(xiàn)干旱脫水的速度和強(qiáng)度決定了生物膜的結(jié)構(gòu)響應(yīng)[49],干旱是導(dǎo)致生物膜結(jié)構(gòu)向新的穩(wěn)定狀態(tài)過(guò)渡的干擾.過(guò)快或未預(yù)料到的干旱,對(duì)生物膜抗性結(jié)構(gòu)的形成有一定的阻礙,相反,漸進(jìn)式干燥有利于形成抗性結(jié)構(gòu)的藻類或細(xì)菌種類[59].

當(dāng)前研究揭示了自養(yǎng)生物和異養(yǎng)生物對(duì)干濕脅迫的不同響應(yīng)模式[6],然而對(duì)于自養(yǎng)和異養(yǎng)生物在間歇性河流中的抗性機(jī)制需要進(jìn)一步的研究,明確間歇性河流中生物膜微生物各生物組成在干濕脅迫下的演化路徑,并在自然斷流(除干燥外其他環(huán)境壓力同時(shí)作用)情況下進(jìn)行實(shí)驗(yàn)驗(yàn)證.

3 生物膜功能對(duì)干濕脅迫的適應(yīng)性變化

3.1 干濕脅迫對(duì)生物膜生產(chǎn)力和呼吸功能的影響

Acu?a等[60]通過(guò)一組干燥強(qiáng)度不同的河道模擬實(shí)驗(yàn)證明(如圖2a),干旱時(shí)間對(duì)生物膜自養(yǎng)和異養(yǎng)過(guò)程產(chǎn)生了不同的影響,導(dǎo)致生物膜的異養(yǎng)性相對(duì)增加;而在間歇性河流的復(fù)水階段,自養(yǎng)過(guò)程則顯現(xiàn)出更高的恢復(fù)力.這項(xiàng)研究表明,自養(yǎng)過(guò)程(如初級(jí)生產(chǎn)力GPP).在干旱一開(kāi)始就受到損害,而異養(yǎng)呼吸在一定濕度下仍能夠持續(xù)存在,導(dǎo)致非線性呼吸響應(yīng)[61-62].總的來(lái)說(shuō),初級(jí)生產(chǎn)作用對(duì)干旱的抵抗力比生態(tài)系統(tǒng)呼吸低(ER)(;生態(tài)呼吸是指生態(tài)系統(tǒng)中植物和異養(yǎng)生物呼吸的總和),但恢復(fù)力更高.這是因?yàn)槌跫?jí)生產(chǎn)作用在面臨干旱擾動(dòng),需要較少的能量來(lái)移動(dòng)到其穩(wěn)定流域之外,而生態(tài)系統(tǒng)呼吸需要更高的能量,因此生態(tài)系統(tǒng)呼吸具有更強(qiáng)的抵抗力. Sabater等[44]定義了一個(gè)等同于恢復(fù)力的坡度(如圖2b),相同的擾動(dòng)能量對(duì)生物膜微生物群落呼吸作用和初級(jí)生產(chǎn)作用產(chǎn)生不同的影響,這兩個(gè)過(guò)程的坡度也是不同的.而當(dāng)流量恢復(fù)時(shí),生態(tài)系統(tǒng)初級(jí)生產(chǎn)作用的恢復(fù)力則更高.

圖2 間歇性河流系統(tǒng)中的概念示意

Timoner等[54]研究發(fā)現(xiàn)生物膜的光合效率或自養(yǎng)生物利用光合的能力與水分含量成正比關(guān)系,水分脅迫、高溫或光的直接作用是影響葉綠素降解的主要因素[34,43,60,62-64].因此,間歇性河流在減脫水時(shí)期,生物膜的光合能力急劇下降,這些低值一直保持到復(fù)濕為止,多達(dá)60%～90%的活性葉綠素(Chl-a)在河床干燥過(guò)程中消失[65].在間歇性河流干旱過(guò)程中, Chl-a的減少和光合效率的降低,直接導(dǎo)致了GPP值的降低.

Zlatanovi?等研究發(fā)現(xiàn)當(dāng)水流恢復(fù)量高于流動(dòng)期后,生物膜的酶活性和光合過(guò)程可以立即得到增強(qiáng)(如圖3)[65],這種增強(qiáng)的活動(dòng)類似于脈沖效應(yīng)(干燥土壤再濕時(shí)的呼吸脈沖),這可能會(huì)顯著影響生態(tài)系統(tǒng)的碳平衡.另外當(dāng)水流恢復(fù)時(shí),生物膜的硝化和反硝化速率也會(huì)提高[68].McClain等[68]研究發(fā)現(xiàn)在干旱時(shí)期,河床中積累的有機(jī)物(一直是緩慢礦化的對(duì)象)被循環(huán)水突然移動(dòng).循環(huán)水回到原先干旱的河床,這是一個(gè)典型的生物地球化學(xué)時(shí)刻——當(dāng)經(jīng)過(guò)長(zhǎng)時(shí)間的靜止期后,生物地球化學(xué)反應(yīng)重新開(kāi)始或加速,河流中生物的呼吸作用和初級(jí)生產(chǎn)力都得到增強(qiáng).因此有機(jī)物在流動(dòng)期河床上的積累以及在非流期的生物膜內(nèi)積累,促進(jìn)了生物膜復(fù)濕后初級(jí)生產(chǎn)力的快速響應(yīng)(如圖3).

圖3 干濕脅迫對(duì)群落呼吸和凈初級(jí)生產(chǎn)作用的影響曲線[65]

當(dāng)前研究給出了生物膜生產(chǎn)力和呼吸功能在干濕脅迫下出現(xiàn)適應(yīng)性變化的多種影響因素,例如有機(jī)物累積、光照可用性以及沉積物結(jié)構(gòu)等.但是現(xiàn)有研究以室內(nèi)模擬實(shí)驗(yàn)為主,在復(fù)雜的自然生態(tài)系統(tǒng)網(wǎng)絡(luò)下,間歇性河流生物膜生產(chǎn)力和呼吸功能的運(yùn)行機(jī)制不夠明確,無(wú)法在大尺度上對(duì)微生物進(jìn)行功能預(yù)測(cè),因此需要進(jìn)一步掌握更多生物關(guān)聯(lián)信息以及整體上的生態(tài)模式,進(jìn)而全面指示當(dāng)前環(huán)境變化是否有利于生態(tài)系統(tǒng)健康.

3.2 干濕脅迫對(duì)生物膜代謝功能的影響

間歇性河流的干濕交替不僅影響淡水生態(tài)系統(tǒng)可利用有機(jī)質(zhì)總量,而且影響可利用有機(jī)質(zhì)的組成.有研究發(fā)現(xiàn)在河流干旱過(guò)程中,底棲有機(jī)物中的總多糖、氨基酸和脂類含量高于流量恢復(fù)期,而肽含量則低于流量恢復(fù)期[53].

Timoner等[53]測(cè)定了間歇性河流干旱-復(fù)水過(guò)程中3種不同外源酶的活性,用來(lái)評(píng)估異養(yǎng)生物和自養(yǎng)生物轉(zhuǎn)化有機(jī)物的能力.研究結(jié)果表明間歇性河流在陸生階段,胞外酶活性普遍下降,但細(xì)菌群落降解碳(β-葡萄糖苷酶,BG)和磷(堿性磷酸酶活性,AP)化合物的潛在能力仍然存在[53],而這一階段氮降解相關(guān)酶(亮氨酸氨基肽酶活性,LAP)的活性降低,表明生物膜降解肽的能力受到了極大的限制.這些模式表明,細(xì)菌在干旱階段優(yōu)先使用碳和磷,很可能是為了獲得能量而不是為了生長(zhǎng)[69-72].

而自然水體的自凈能力包括稀釋擴(kuò)散、氧化還原以及水中微生物對(duì)有機(jī)物的分解等,且直接關(guān)系到流域環(huán)境系統(tǒng)的穩(wěn)定性[73],因此將干濕交替對(duì)有機(jī)物降解的影響與水體自凈能力聯(lián)系起來(lái),有助于后續(xù)的生態(tài)修復(fù)研究.在陸生階段結(jié)束時(shí),由于循環(huán)水將河床上積累的有機(jī)物調(diào)動(dòng)起來(lái)[74],加上生物膜對(duì)氮化合物降解能力的限制以及對(duì)碳和磷在陸生階段仍然存在的降解能力,所以在流量重新連接時(shí),水體的自凈能力有一定程度的損傷,但又由于生物膜對(duì)碳和磷降解能力的迅速恢復(fù),保證了水體一定程度的自凈能力[75].后續(xù)應(yīng)該以實(shí)驗(yàn)為依據(jù),探究干濕脅迫對(duì)于水體自凈能力的損傷程度以及影響自凈能力的多種因素.

但是當(dāng)前的研究,對(duì)于生物膜在干濕脅迫下代謝功能發(fā)生改變的適應(yīng)機(jī)制尚不明確.過(guò)去對(duì)于微生物的代謝能力主要是基于功能基因研究微生物類群的豐度和多樣性,及其隨實(shí)驗(yàn)條件不同的變化規(guī)律[56,76],這些研究更多的是集中于某些特定的微生物類群或者把微生物組成的交互網(wǎng)絡(luò)作為黑箱處理,容易忽略微生物群落中豐度不占優(yōu)勢(shì)但起關(guān)鍵作用的稀有種[77-79],難以全面揭示驅(qū)動(dòng)生物地球化學(xué)循環(huán)的微生物及其功能基因之間的相互作用.因此對(duì)于后面的研究,需要綜合考慮間歇性河流生態(tài)系統(tǒng)中微生物內(nèi)部物質(zhì)循環(huán)與能量流動(dòng)的網(wǎng)絡(luò)結(jié)構(gòu),將微生物功能與其他環(huán)境因子相耦合闡明微生物類群間的相互作用關(guān)系.

3.3 生物膜微生物群落對(duì)干濕脅迫的抗性機(jī)制

目前很多研究探究了生物膜群落結(jié)構(gòu)功能對(duì)外界擾動(dòng)的不同響應(yīng),但是過(guò)去衡量群落組成變化的方法只量化或列出了某幾個(gè)物種(節(jié)點(diǎn))的改變,而忽略了它們之間的相互作用[80-81].近期Sun等[82]發(fā)現(xiàn),生物膜的生態(tài)功能穩(wěn)定性是通過(guò)限制生態(tài)網(wǎng)絡(luò)中的正反饋和改變物種間相互作用來(lái)增強(qiáng)的.生態(tài)穩(wěn)定是生態(tài)學(xué)和全球變化生物學(xué)中最具影響力的概念之一,但它很少被應(yīng)用于恢復(fù)生態(tài)學(xué).為了更好的了解河流生物膜群落對(duì)于干濕脅迫的抗性機(jī)制及河流生態(tài)系統(tǒng)穩(wěn)定性的維持機(jī)制,需要綜合考慮生物膜微生物的群落結(jié)構(gòu)與物種間相互作用關(guān)系及其他環(huán)境因素.

圖4 擾亂發(fā)生后的生態(tài)系統(tǒng)恢復(fù)機(jī)制時(shí)間軸[81]

河流微生物在復(fù)雜的生態(tài)網(wǎng)絡(luò)中共存,物種間存在著不同類型的共生、競(jìng)爭(zhēng)或捕食等關(guān)系,大多數(shù)生態(tài)功能以及封閉的營(yíng)養(yǎng)循環(huán)等都不是單一物種的作用結(jié)果,而是微生物物種間密切協(xié)作或相互競(jìng)爭(zhēng)的產(chǎn)物[20,22,80-81,83].分子生態(tài)網(wǎng)絡(luò)就是將河流生態(tài)系統(tǒng)構(gòu)建為一個(gè)網(wǎng)絡(luò),是由節(jié)點(diǎn)和邊兩個(gè)部分組成的生態(tài)系統(tǒng)的時(shí)間或空間快照[84],其中各物種(節(jié)點(diǎn))通過(guò)成對(duì)相互作用連接.展現(xiàn)了微生物生態(tài)網(wǎng)絡(luò)的整體結(jié)構(gòu)和節(jié)點(diǎn)的特性,因此常被用來(lái)了解大規(guī)模樣本的生物關(guān)聯(lián)網(wǎng)絡(luò)和復(fù)雜性.這種分析可以幫助鑒定可以替代的群落狀態(tài)和生態(tài)位[84]

基于微生物豐度的數(shù)據(jù)分析,通過(guò)合理閾值選擇和相關(guān)性分析,可有效識(shí)別網(wǎng)絡(luò)中具有生態(tài)意義的關(guān)鍵物種及其物種聚類,有助于進(jìn)一步了解微生物種間交互多樣性及其生態(tài)系統(tǒng)穩(wěn)定性[80-81,85].如圖6所示,系統(tǒng)度量復(fù)雜度較高的群落結(jié)構(gòu)在經(jīng)歷外界擾動(dòng)后恢復(fù)周期較長(zhǎng)[80].其次,分子生態(tài)網(wǎng)絡(luò)可以發(fā)掘不同環(huán)境中維持群落完整性、保障網(wǎng)絡(luò)穩(wěn)定性的關(guān)鍵物種,它們的存在與消失會(huì)直接影響整個(gè)微生物群落.例如,分子生態(tài)網(wǎng)絡(luò)可以將生態(tài)位表示為微生物相互作用的中介,有助于我們理解生態(tài)平衡和生態(tài)失調(diào)的機(jī)制[84].因此,考慮到生態(tài)學(xué)、宏組學(xué)和代謝組學(xué)的信息,分子生態(tài)網(wǎng)絡(luò)為深入了解微生物群落多樣性的形成與維持提供了更多信息[79-81,83,85-88],具有同時(shí)處理微生物規(guī)模和多樣性的優(yōu)點(diǎn),分子生態(tài)網(wǎng)絡(luò)是微生物組數(shù)據(jù)的直觀可視化[84].

4 結(jié)語(yǔ)

4.1 本文綜述了減脫水河段作為一類生態(tài)系統(tǒng)嚴(yán)重退化的河流中主要生物組分(生物膜)在面臨干濕交替時(shí)的只有結(jié)構(gòu)和功能變化.結(jié)構(gòu)變化主要表現(xiàn)為β多樣性的增加和α多樣性的減小,以及不同功能之間的不同響應(yīng),但問(wèn)題是,流量修復(fù)后,生物膜的初級(jí)生產(chǎn)力、代謝功能是否是可逆恢復(fù)？生物膜微生物群落結(jié)構(gòu)和功能指標(biāo)與流量恢復(fù)率之間呈現(xiàn)什么樣的相關(guān)關(guān)系？等一系列問(wèn)題仍需進(jìn)一步研究分析.

4.2 近期的研究結(jié)果突出了河道生態(tài)系統(tǒng)中真菌和古菌的研究?jī)r(jià)值,應(yīng)當(dāng)加強(qiáng)對(duì)于真菌和古菌群落的生長(zhǎng)機(jī)制研究,進(jìn)一步分析其在C、N循環(huán)等方面的作用貢獻(xiàn).

4.3 明確了干濕脅迫中生物膜對(duì)河流中有機(jī)物的轉(zhuǎn)化能力的變化,后續(xù)應(yīng)以實(shí)驗(yàn)為基礎(chǔ),探究水體自凈能力的受損程度,為后續(xù)的生態(tài)修復(fù)提供理論依據(jù).

4.4 未來(lái)研究需同時(shí)綜合考慮間歇性河流生態(tài)系統(tǒng)中微生物內(nèi)部物質(zhì)循環(huán)與能量流動(dòng)的網(wǎng)絡(luò)結(jié)構(gòu),將微生物功能與其他環(huán)境因子相耦合闡明微生物類群間的相互作用關(guān)系.深度探究在間歇性河流的整個(gè)水文循環(huán)中微生物群落結(jié)構(gòu)和多樣性的響應(yīng)和恢復(fù)機(jī)制.

4.5 目前以統(tǒng)計(jì)學(xué)為基礎(chǔ)的生態(tài)網(wǎng)絡(luò)推理方法有一定的局限性,因此建議構(gòu)建微宇宙試驗(yàn)?zāi)M可控條件下物種多樣性-生態(tài)系統(tǒng)功能關(guān)系,揭示與驗(yàn)證多重外界干擾對(duì)微生物群落間互作和功能變化更有依據(jù).

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Dynamic response of biofilm to dry and wet stress in intermittent rivers.

LI Chao-ran, MIAO Ling-zhan*, HOU Jun

(Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China)., 2021,41(11)：5245～5253

This paper reviews the adaptive changes of biofilm structure and function under dry and wet stress in river ecosystem, and analyses the dynamic changes of different functional groups (autotrophic and heterotrophic) and community structure (biodiversity andbiodiversity) in biofilm. The dynamic responses of biofilm productivity and metabolic function under dry and wet stress were systematically summarized. The resistance mechanism of biofilm microbial community to dry and wet stress was analyzed, and the application prospect of molecular ecological network analysis in biofilm dynamic response was prospected.

intermittent river；biofilm；community structure；functional characteristics；network analysis

X17

A

1000-6923(2021)11-5245-09

李超然(1997-),女,山東臨沂人,河海大學(xué)碩士研究生,研究方向?yàn)楹恿魑⑸锷鷳B(tài)學(xué).

2021-04-09

國(guó)家自然科學(xué)基金資助項(xiàng)目(51979075)

* 責(zé)任作者, 教授, lzmiao@hhu.edu.cn