呂笑天,呂永龍,*,宋 帥,王鐵宇

1 中國科學(xué)院生態(tài)環(huán)境研究中心城市與區(qū)域生態(tài)國家重點(diǎn)實(shí)驗(yàn)室,北京 100085 2 中國科學(xué)院大學(xué),北京 100049

氣候變化與人類活動雙重驅(qū)動的冷水湖泊富營養(yǎng)化

呂笑天1,2,呂永龍1,2,*,宋 帥1,王鐵宇1

1 中國科學(xué)院生態(tài)環(huán)境研究中心城市與區(qū)域生態(tài)國家重點(diǎn)實(shí)驗(yàn)室,北京 100085 2 中國科學(xué)院大學(xué),北京 100049

富營養(yǎng)化對水生生態(tài)系統(tǒng)造成的負(fù)面影響已在世界范圍內(nèi)廣泛發(fā)生,尤其對淡水水源地湖泊的水環(huán)境質(zhì)量影響深遠(yuǎn),進(jìn)而引起當(dāng)?shù)鼐用竦娘嬘盟踩c健康隱患。在人類活動和氣候變化的雙重驅(qū)動下,富營養(yǎng)化輻射的范圍不斷擴(kuò)大,從過去主要集中于溫帶大型淺水湖泊已經(jīng)擴(kuò)展到寒冷地區(qū)的冷水湖泊。分析了近年來世界范圍內(nèi)高寒地區(qū)冷水湖泊富營養(yǎng)化的趨勢特征與研究進(jìn)展,探討了氣候變化、人類干擾(農(nóng)業(yè)活動、畜牧業(yè)生產(chǎn)、管理措施不當(dāng)?shù)?在不同地區(qū)冷水湖泊富營養(yǎng)化進(jìn)程中的作用。在未來的研究中,應(yīng)進(jìn)一步加強(qiáng)對冷水湖泊富營養(yǎng)化機(jī)制的探討,并對已有富營養(yǎng)化癥狀的湖泊進(jìn)行生態(tài)修復(fù),以確保冷水湖泊生態(tài)系統(tǒng)健康并改善飲用水源地的環(huán)境質(zhì)量。

冷水湖泊；富營養(yǎng)化；氣候變化；營養(yǎng)鹽

富營養(yǎng)化已經(jīng)成為影響世界各地水資源環(huán)境的重大問題,對水體質(zhì)量安全和水生生態(tài)系統(tǒng)健康有深刻影響[1-2]。湖泊富營養(yǎng)化問題是湖泊水體在自然環(huán)境因子和人類活動的雙重影響下,大量營養(yǎng)鹽輸入湖泊使水體逐步由生產(chǎn)力水平較低的貧營養(yǎng)狀態(tài)向生產(chǎn)力水平較高的富營養(yǎng)狀態(tài)變化的一種現(xiàn)象。隨著自然環(huán)境的變遷,湖泊經(jīng)歷發(fā)生、發(fā)展、衰老直至消亡的必然過程,由湖泊形成初始階段的貧營養(yǎng)逐漸向富營養(yǎng)過渡,直至最后消亡。在自然條件下,湖泊的這種演變過程是極為緩慢的,但在人類活動的影響下,這種演化過程大大加快,人為的富營養(yǎng)化(Cultural Eutrophication)引起的環(huán)境問題日益嚴(yán)重[3-4]。近幾十年來,工業(yè)化、城市化的快速推進(jìn)伴隨著污水排放量日益增大,湖泊水環(huán)境富營養(yǎng)化趨勢明顯,引起了世界范圍的關(guān)注。已有大量研究報(bào)道富營養(yǎng)化污染來源、發(fā)生機(jī)制、浮游藻類與營養(yǎng)鹽負(fù)荷相互作用與關(guān)系等,但研究多集中于低緯度、人口密集的溫暖流域,而隨著氣候變化作用的逐漸凸顯[5-8],富營養(yǎng)化影響區(qū)域不斷擴(kuò)大,較高緯度地區(qū)或人類活動影響相對較少的高山冷水湖泊也開始逐步表現(xiàn)出富營養(yǎng)化的癥狀。本文將圍繞氣候變化和人類活動對冷水湖泊富營養(yǎng)化的驅(qū)動作用,對近年來寒冷地區(qū)冷水湖泊富營養(yǎng)化的特征與研究進(jìn)展進(jìn)行綜述。

1 冷水湖泊生態(tài)系統(tǒng)的脆弱性

冷水湖泊一般屬于高海拔的高山湖泊,或位于高緯度地區(qū),由于氣候原因,導(dǎo)致全年水溫偏低[9]。這些湖泊大部分發(fā)育時(shí)間較長,地處偏遠(yuǎn),以前極少受到人類活動干擾,在世界很多地區(qū)是飲用水的發(fā)源地。通常這些地區(qū)的大氣層更為稀薄,溶解性有機(jī)碳濃度也較低,使得冷水湖泊常處于高紫外線暴露水平[10]。同時(shí)年均氣溫一般低于0℃,水溫大部分時(shí)間低于4℃,一年中有5—9個月的冰期[11]。紫外線和低溫條件的聯(lián)合作用使得這類湖泊生態(tài)系統(tǒng)的垂直結(jié)構(gòu)與平原湖泊截然不同,嚴(yán)酷的自然條件對生物體的生存較為不利。

因?yàn)闅夂蜉^為寒冷,冷水湖泊的解凍期和適宜浮游植物生長期較短,營養(yǎng)鹽含量偏低,周圍陸生植物覆蓋較少,冷水湖泊生境更易因周邊環(huán)境的改變和污染而遭到破壞,成為環(huán)境變化的敏感區(qū)和指示器[10, 12-13]。有證據(jù)表明,高海拔地區(qū)氣候變暖的幅度有明顯的海拔依賴性,氣候變化在高山區(qū)域存在放大效應(yīng),氣候變暖在冰雪反照率反饋效應(yīng)、水汽-云-輻射反饋效應(yīng)、水汽與輻射通量反饋和氣溶膠等作用下,速率正在加快。而高海拔地區(qū)快速變暖會加劇山區(qū)生態(tài)環(huán)境、冰凍圈、水文循環(huán)和生物多樣性的變化,由此可能帶來一系列環(huán)境問題,造成冷水湖泊的萎縮退化,深刻改變冷水湖泊的生態(tài)系統(tǒng)結(jié)構(gòu)特征與功能服務(wù)[14-16]。

冷水湖泊一般為靜水生態(tài)系統(tǒng),水量的補(bǔ)給主要來自流域的冰川和積雪融水,以及降雨帶來的徑流,而水量的減少則是由于蒸發(fā)和滲流效應(yīng)[17-18]。在冷水湖泊生態(tài)系統(tǒng)中,硅藻占據(jù)浮游藻類的優(yōu)勢地位,湖泊細(xì)菌類群則以放線菌為主。經(jīng)過全球變化背景下多環(huán)境過程的相互作用,藻類群落結(jié)構(gòu)與冷水湖泊環(huán)境顯示出同步變化的特征,原有的優(yōu)勢種群大多被星桿藻和巴豆葉脆桿藻等取代[19-22]。由于冷水湖泊會從大氣中吸收大量的營養(yǎng)鹽成分,因此對大氣沉降量及化學(xué)組成變化都非常敏感[23]。而人為活動已經(jīng)顯著改變了大氣化學(xué)組成和關(guān)鍵營養(yǎng)元素的全球流動性[24]。同時(shí),冷水湖泊對外界干擾尤其外來魚種引入的抵抗性較差[25]。有研究發(fā)現(xiàn),亞洲高山湖泊生態(tài)系統(tǒng)在人類活動和全球氣候持續(xù)變暖的影響下,生態(tài)系統(tǒng)將進(jìn)一步退化,可能會產(chǎn)生嚴(yán)重的富營養(yǎng)化問題,該區(qū)域淡水供應(yīng)形勢將更為嚴(yán)峻[26]。但是目前全球針對冷水湖泊研究仍主要集中于有毒化學(xué)品在高海拔地區(qū)的“蒸餾效應(yīng)”[12],對其富營養(yǎng)化進(jìn)程的關(guān)注嚴(yán)重不足。水體富營養(yǎng)化問題在氣候變化和人類活動的雙重驅(qū)動下,向冷水湖泊地區(qū)的快速蔓延,已成為冷水湖泊生態(tài)系統(tǒng)研究的新熱點(diǎn)和新挑戰(zhàn)。

2 氣候變化對冷水湖泊富營養(yǎng)化的驅(qū)動作用

從統(tǒng)計(jì)學(xué)意義上看,氣候變化是指氣候平均狀態(tài)在較長的時(shí)間尺度上(以年或若干年為尺度)產(chǎn)生重要改變的氣候變動,而人類活動被認(rèn)為是近百年來全球氣候變化的主要原因。工業(yè)革命以來,化石燃料大量燃燒、土地利用變化等人類活動加劇,大氣溫室氣體濃度大幅增加,擾動了全球的能量平衡從而引起全球氣候變暖[27-29]。目前研究已觀察到的氣候變化癥狀主要表現(xiàn)在3個方面：全球地表溫度升高、海平面上升及北半球積雪面積的下降[30]。

2.1 湖泊生態(tài)系統(tǒng)對全球氣候變化的響應(yīng)

湖泊生態(tài)系統(tǒng)作為水生態(tài)系統(tǒng)的重要組成,為居民供水和經(jīng)濟(jì)發(fā)展提供飲用水源,擔(dān)負(fù)和提供了多重生態(tài)系統(tǒng)服務(wù)功能。大量研究表明,湖泊生態(tài)系統(tǒng)對氣候變化敏感,湖泊與流域環(huán)境的變化密切相關(guān),整個流域?qū)夂蜃兓捻憫?yīng)都可由湖泊生態(tài)系統(tǒng)綜合反映,因而湖泊被看作氣候變化的信號指示器和累積調(diào)節(jié)器[31-38]。

氣候變化對湖泊生態(tài)系統(tǒng)的影響及湖泊對氣候變化響應(yīng)的關(guān)鍵參數(shù)主要包括3個方面：湖泊的物理、化學(xué)及生物特性,這些響應(yīng)參數(shù)能夠通過氣候變化對流域的作用而直接或間接地反映出氣候?qū)吹挠绊?表1)。

表1 湖泊生態(tài)系統(tǒng)參數(shù)對氣候變化的響應(yīng)

(1) 物理特性參數(shù)包括表層及上層水溫的升高[48-49],水位的波動[50-52],冰期與間冰期的變化[53-54]：在很多湖泊已經(jīng)觀察到溫水層的變暖趨勢,湖泊的表水層溫度被認(rèn)為是大氣層變暖的良好指標(biāo),全球湖泊夏季表層水溫的年均增溫率為0.034℃[55],而下層滯水帶溫度的響應(yīng)行為更為復(fù)雜,與湖泊的形態(tài)和季節(jié)因素等相關(guān)[56-57]。通過影響水柱的密度梯度、水溫垂直的非均勻變化會導(dǎo)致湖泊的垂直分層、熱穩(wěn)定性和溫躍層深度的長期變化,而這種長期變化又將改變湖泊的混合和循環(huán)模式[58]；

(2)化學(xué)特性參數(shù)包括營養(yǎng)鹽濃度與比例、溶解性有機(jī)碳和溶解氧濃度[59-62]：湖泊的許多化學(xué)特性可以反映地表變化過程。氣候因素會影響到風(fēng)化速率、降水、徑流、火災(zāi)頻率、陸生植物初級生產(chǎn)力等,進(jìn)而影響到陸源營養(yǎng)鹽的負(fù)荷,改變湖泊的營養(yǎng)鹽濃度和比例[63-66]。溶解性有機(jī)碳(DOC)濃度是湖泊多維響應(yīng)的綜合結(jié)果,包括水體透明度、熱吸收、湖泊自身代謝、流域徑流的增加、永久凍土的消融、植被覆蓋和濕地的變化等,從而可以很好地反映陸地環(huán)境的變遷[59, 62, 67-68]。由于氧氣水平與氣溫和熱力學(xué)結(jié)構(gòu)密切相關(guān),湖泊的溶解氧濃度也能指示氣候的變遷[69]；

(3) 生物參數(shù)包括浮游動植物生長發(fā)育模式的改變與種類組成[70-73]、外來入侵種的優(yōu)勢擴(kuò)張等[74]：浮游生物已廣泛應(yīng)用于生態(tài)系統(tǒng)變化的指示,由于它們能對微小的熱力學(xué)改變進(jìn)行快速響應(yīng),可以通過物候?qū)W的改變反映氣候變化。對于魚類和橈足類等壽命較長的有機(jī)體來說,氣候變暖可以加速其發(fā)育過程[75-76]。增溫通常會加快個體生物的生長和發(fā)育速度[77],物種組成的變化也可在較長的地質(zhì)時(shí)間尺度上指示氣候的改變,比如在較高溫度下,水華藻類——藍(lán)藻細(xì)菌較其他浮游植物種類更具競爭優(yōu)勢[78]。

2.2 氣候變化與湖泊富營養(yǎng)化

對淡水湖泊系統(tǒng)來說,氣候變化正通過改變降雨模式、土壤升溫、冰川融化等增加營養(yǎng)鹽負(fù)荷的面源,從而驅(qū)動富營養(yǎng)化加速發(fā)展[79-80]。氣候變化作用的機(jī)理如圖1所示：

圖1 氣候變化對湖泊富營養(yǎng)化的驅(qū)動作用 (在[5]基礎(chǔ)上改進(jìn))Fig.1 Lake eutrophication driven by climate change (modified from Ref.[5])

(1)氣候變暖的直接作用：增暖效應(yīng)會促進(jìn)藍(lán)藻細(xì)菌更適應(yīng)較高溫度環(huán)境的有害藻類生長,增加浮游植物的初級生產(chǎn)力,加快藻型湖泊形成；(2)氣候變暖的間接作用：由于雜食性魚類更偏愛溫暖水體,它們的快速繁殖會取代浮游動物成為優(yōu)勢種群,從而減少了湖泊生態(tài)系統(tǒng)自身對藻類的控制能力,間接促進(jìn)藻類的過度增殖；(3)降水模式轉(zhuǎn)變：改變湖泊營養(yǎng)物質(zhì)的入湖通量及水體的水力停留時(shí)間,最終導(dǎo)致水體富養(yǎng)化的發(fā)生[5]。

為了評估湖泊生態(tài)系統(tǒng)對氣候變化和流域內(nèi)環(huán)境因子變化所產(chǎn)生的響應(yīng),可以進(jìn)行水質(zhì)采樣測定、浮游植物群落現(xiàn)場調(diào)查和氣候數(shù)據(jù)分析,而由于湖泊長期監(jiān)測數(shù)據(jù)的缺乏,時(shí)間序列的演化過程分析往往非常困難,古湖沼學(xué)發(fā)展了多種利用湖泊沉積物的多代用記錄來重現(xiàn)湖泊生態(tài)系統(tǒng)變化情況的方法[81]。同時(shí),很多考慮氣候因子變化的研究湖泊富營養(yǎng)化的模型方法也在不斷探索和發(fā)展。如對氣候因子和湖泊環(huán)境因子進(jìn)行相關(guān)分析的數(shù)理統(tǒng)計(jì)與分析模型、將氣候因子作為變量加入或進(jìn)行耦合的生態(tài)動力學(xué)模型、模擬不同氣候情景下湖泊富營養(yǎng)化影響的系統(tǒng)生態(tài)學(xué)模型、浮游植物生態(tài)機(jī)理性模型、智能算法等[82]。

2.3 氣候變化對冷水湖泊富營養(yǎng)化的觸發(fā)作用

以往研究的富營養(yǎng)化水體多分布于溫帶地區(qū),野外觀測結(jié)果也發(fā)現(xiàn)“水華”多在夏季溫度最高時(shí)發(fā)生。從生態(tài)位的角度看,不同的浮游藻類最適生長的溫度范圍不同,硅藻適應(yīng)的溫度較廣,在 15—35℃之間均可生長良好,但以20—30℃時(shí)為最佳,綠藻為20—25℃,藍(lán)藻為20—30℃,夏季藍(lán)藻數(shù)量的增加可能是水溫升高的直接結(jié)果[8]。一般認(rèn)為水溫在17℃以下時(shí),不會大量發(fā)生水華,而當(dāng)溫度上升到28℃左右時(shí),由于其它藻類的生長受到抑制,藍(lán)藻很容易形成優(yōu)勢種群而大量暴發(fā)[83]。如典型平原淡水淺水湖泊——太湖(30°55′—31°33′N,119°52′—120°36′E)微囊藻水華頻繁發(fā)生,水華爆發(fā)時(shí)水溫波動范圍25—30℃,室內(nèi)實(shí)驗(yàn)表明太湖微囊藻的最適生長溫度為30—35℃[84]。對于冷水湖泊來說,在營養(yǎng)鹽加富作用誘導(dǎo)下,也可能引起水體富營養(yǎng)化。冷水湖泊年均氣溫較低,夏季最高水溫約15—20℃,但是由于上文所述的氣候變暖在高海拔地區(qū)的放大效應(yīng),在過去20年間,冷水湖泊年均水溫已經(jīng)上升了2℃,預(yù)計(jì)至2100年會上升7℃[85]。而溫度會直接影響植物的光合作用和呼吸作用,增溫會提高光能自養(yǎng)的生產(chǎn)者的光飽和效率,從而增加植物生長速率和生物量的累積[86]。因此,全球氣候變化,尤其是夏季水溫的上升將大大促進(jìn)藻類的生長,從而觸發(fā)有害藻華和富營養(yǎng)化的發(fā)生發(fā)展進(jìn)程。

內(nèi)蒙古呼倫湖(48°31′—49°20′N,116°58′—117°48′E)是我國地理位置最北的大湖,由于水體中營養(yǎng)鹽濃度上升,自1980s以來呼倫湖開始出現(xiàn)富營養(yǎng)化的趨勢,2009年起夏季有藍(lán)藻水華爆發(fā),水體中總氮TN和總磷TP濃度達(dá)3.346mg/L和0.435mg/L[87]。有研究認(rèn)為呼倫湖位于呼倫貝爾草原,其營養(yǎng)物質(zhì)主要來源于草場,近些年來氣候的暖干使入湖流量大大減少[87-88],入湖河流中TN和TP濃度也比1980s大幅增加,而水量的減少又使水體中氮磷濃度因濃縮效應(yīng)急劇上升,最終引起銅綠微囊藻的過度增殖。此外,冰蓋效應(yīng)、低出水量以及沉積物對營養(yǎng)鹽的釋放作用會進(jìn)一步惡化水質(zhì)狀況[89]。將呼倫湖藍(lán)藻爆發(fā)情況與太湖進(jìn)行比較后發(fā)現(xiàn),盡管呼倫湖營養(yǎng)鹽濃度高于太湖,其藍(lán)藻爆發(fā)強(qiáng)度和時(shí)長均低于太湖,可能與呼倫湖夏季氣溫較低有關(guān)。由于該流域人類活動的干擾較小,呼倫湖的富營養(yǎng)化狀況更多的受自然的氣候因素影響和控制[89-90]。新疆的博斯騰湖(41°46′—42°08′N,86°19′—87°28′E)位于天山山脈中段南麓,是中國最大的內(nèi)陸淡水湖泊,也是干旱地區(qū)代表性湖泊。李紅等對博斯騰湖的浮游植物群落結(jié)構(gòu)特征進(jìn)行調(diào)查后發(fā)現(xiàn),該湖泊全年浮游植物硅藻為主,在夏-秋季形成硅藻-綠藻型以富營養(yǎng)型的浮游藻類為優(yōu)勢類群,年平均水溫16.14℃,最高水溫不超過26.5℃,適合喜低溫的硅藻生長繁殖,基于Canoco的多變量分析也表明環(huán)境變量共解釋了浮游植物群落總變異的 54.5%,水溫是影響浮游植物分布最重要的環(huán)境因子[91]。烏倫古湖(46°52′—47°28′N,87°00′—87°30′E)在新疆準(zhǔn)格爾盆地北部,該湖區(qū)氣候寒冷干燥,降水稀少。劉宇等于2006年11月—2008年7月按季度對烏倫古湖浮游植物的群落結(jié)構(gòu)組成及時(shí)空分布規(guī)律進(jìn)行為期兩年的調(diào)查,得到的結(jié)果為湖泊種類組成以綠藻門和硅藻門為主,群落結(jié)構(gòu)組成時(shí)空變化明顯,水溫、總磷、高錳酸鹽指數(shù)、透明度是影響浮游植物現(xiàn)存量時(shí)空變化的主要環(huán)境因子。其中,水溫對現(xiàn)存量的季節(jié)分布影響極為顯著,總磷對現(xiàn)存量的水平分布和垂直分布有極為顯著的影響,水質(zhì)評價(jià)為中營養(yǎng)-富營養(yǎng)水平,處于輕度污染狀態(tài)。該研究認(rèn)為烏倫古湖是內(nèi)陸封閉型湖泊,水體換水周期長,本地年蒸發(fā)量是降水量的近16倍,而全球氣候變暖、降雨減少,烏倫古河及額爾齊斯河由于人為徑流調(diào)節(jié),致使入湖淡水補(bǔ)給減少,因此導(dǎo)致烏倫古湖水位下降,鹽堿化進(jìn)程加速。周圍農(nóng)業(yè)開發(fā),面源污染加劇,則加速了該湖向富營養(yǎng)化發(fā)展[92]。

在對氣候和外界干擾的響應(yīng)中,湖泊的區(qū)域性自然地理等特征會影響水體狀況。Jeppesen等人認(rèn)為,在北歐的溫帶地區(qū)(如丹麥),流域內(nèi)極端氣候事件以及地表徑流的增加使得更多的營養(yǎng)負(fù)荷進(jìn)入湖泊,然而這并不意味著水體中更高的年均營養(yǎng)鹽濃度,與此相反,進(jìn)水中的營養(yǎng)鹽濃度可能由于水量增加的稀釋作用而降低。而在溫暖的南歐地區(qū),降水稀發(fā)蒸發(fā)強(qiáng)烈,在未來會更加明顯,地中海地區(qū)的地表徑流預(yù)估會減少高達(dá)30%—40%,西班牙和土耳其可能是受害最深的地區(qū)。磷負(fù)荷會隨著徑流的減少而減少,但是濃度可能會由于水量的減少反而上升[29]。Sickman等人以Emerald湖(36°35′49″N,118°40′29″W,海拔2800m)作為美國加州內(nèi)達(dá)華山脈地區(qū)高海拔小型湖泊的代表,對該區(qū)域的高山湖泊在1980—20世紀(jì)末營養(yǎng)狀態(tài)的變遷進(jìn)行了評價(jià)。他們監(jiān)測到整個區(qū)域湖泊水體中P含量都有明顯上升趨勢,因而排除了地域性P污染源(如城市和農(nóng)村的地表徑流)的作用。Emerald湖的總磷濃度在1983—1999年中增長了1倍,有富營養(yǎng)化趨勢出現(xiàn)。在分析Emerald湖的磷來源時(shí),用一級近似法對流域的磷源和磷匯通量做了評估,結(jié)果表明湖泊沉積物(3000 kg)和流域的土壤(2100 kg)是Emerald湖最大的磷儲存庫,大氣沉降作用和氣候變化作用引起的P在水體中的循環(huán)過程被認(rèn)為是內(nèi)達(dá)華山區(qū)高山湖泊磷負(fù)荷增加的主要來源[93]。Saros等人對洛基山脈中段位于美國黃石國家公園東北部的熊牙山脈高山湖泊(大部分海拔超過2500m)進(jìn)行了調(diào)研,主要研究了Beartooth湖沉積物記錄的硅藻群落結(jié)構(gòu),發(fā)現(xiàn)截至1995年左右,該湖泊的硅藻群落表現(xiàn)出典型的高山湖泊特征—以小型脆桿藻屬為主,此后巴豆葉脆桿藻和廣源小環(huán)藻在總硅藻群落結(jié)構(gòu)中的比例快速上升,對該區(qū)域其他3個湖泊進(jìn)行對比研究后也有類似結(jié)果。在分析這種湖泊浮游植物群落結(jié)構(gòu)變更的驅(qū)動力時(shí),他們認(rèn)為該區(qū)域在過去一個世紀(jì)中大型降水(主要以降雪的形式)發(fā)生率的增加,提高了該區(qū)域大氣氮沉降的速率,抬升了湖泊水體營養(yǎng)水平并改變了水體中營養(yǎng)元素的動態(tài)變化,而氣候變化導(dǎo)致的湖泊熱力分層特性改變也對群落結(jié)構(gòu)產(chǎn)生了影響[94-95]。

全球氣候變化對冷水湖泊富營養(yǎng)化的驅(qū)動表現(xiàn)出區(qū)域性特征,在干旱半干旱地區(qū),氣候的暖干效應(yīng)大大減少了冷水湖泊的徑流補(bǔ)給,湖泊水量減少、水位下降,營養(yǎng)鹽富集和濃縮,在水溫上升的協(xié)同作用下觸發(fā)了富營養(yǎng)化的進(jìn)程；而在相對濕潤地區(qū),氣候條件的改變使降水頻率和強(qiáng)度大大增加,大氣沉降作用導(dǎo)致更多的氮磷營養(yǎng)鹽進(jìn)入湖泊,水體營養(yǎng)負(fù)荷顯著增加,改變了湖泊的營養(yǎng)水平和浮游植物群落結(jié)構(gòu)。

3 人類活動加速冷水湖泊的富營養(yǎng)化

冷水湖泊由于地理位置偏僻、地形地貌復(fù)雜、氣候寒冷等自身?xiàng)l件的特殊性,生物多樣性小,流域生態(tài)系統(tǒng)偏于單一、脆弱,環(huán)境承載力低,對人類干擾的緩沖和自凈能力較差,它們會更容易在流域人類活動的壓力下產(chǎn)生富營養(yǎng)化,而目前對冷水湖泊富營養(yǎng)化進(jìn)程的研究與關(guān)注相對較少。

烏梁素海(40°36°—41°03′ N,108°43′—108°57′ E)是黃河改道形成的河跡淺水湖泊,它是全球范圍內(nèi)干旱草原及荒漠地區(qū)極為少見的大型多功能湖泊,也是地球同一緯度最大的濕地。由于接收了大量農(nóng)業(yè)灌溉排水及生活和工業(yè)污水烏梁素海自1990s起水體富營養(yǎng)化不斷加重,成為蘆葦和沉水植物大量生長的草型富營養(yǎng)化湖泊,水體流動性不斷下降,水體處于嚴(yán)重缺氧狀態(tài)。而植物腐敗后又構(gòu)成二次污染,湖泊水質(zhì)進(jìn)一步惡化[96]。Yang等人分別運(yùn)用水質(zhì)參數(shù)法、修正卡森指數(shù)法和營養(yǎng)狀態(tài)綜合指數(shù)法對烏梁素海的富營養(yǎng)化狀況進(jìn)行評價(jià),分別得到的結(jié)果為中度富營養(yǎng)化、富營養(yǎng)化和輕度富營養(yǎng)狀態(tài)[97]。Bernd等人在博斯騰湖入湖開都河三角洲邊緣及湖體中分別采集了沉積物深鉆和淺鉆樣品,并用放射性碳定年法進(jìn)行年代鑒定。研究發(fā)現(xiàn),在所有的淺鉆短芯沉積物樣品的表層,磷酸鹽含量呈現(xiàn)急速增加的趨勢,可能主要與富含營養(yǎng)鹽的農(nóng)業(yè)灌溉用水大量排入有關(guān),而最頂層約13cm的沉積物由營養(yǎng)豐富的淤泥以及大量的綠藻和硅藻的殘骸。在過去的150年里博斯騰湖水質(zhì)不斷趨于富營養(yǎng)化,這很可能是由化肥的大量使用引起[98]。Liu等人分別調(diào)查了新疆博斯騰湖和瑪納斯湖表層沉積物中8種甾醇類化合物含量與分布,研究表明,在所有的樣品中,糞甾醇的含量都顯著低于植物甾醇,β-谷甾醇是最主要的植物甾醇。高濃度的植物甾醇表明這兩個湖泊都有明顯富營養(yǎng)化趨勢。絕大部分人類排泄物的污染源來自鄰近居民聚集地和進(jìn)水口的樣點(diǎn),而只有少數(shù)沉積物沒有受到污染,說明了流域內(nèi)人口密度和人類活動壓力的增加[99]。Liu等人運(yùn)用沉積學(xué)、地球化學(xué)以及孢粉學(xué)數(shù)據(jù),重建了烏倫古湖全新世以來的環(huán)境與氣候變遷歷程,以綠藻門盤星藻屬的豐度為指標(biāo),指示由于水土流失以及施用牛糞肥料和化學(xué)肥料的人類干擾所引起水體的營養(yǎng)水平升高。重建的古湖沼學(xué)結(jié)果表明,距今約560年左右開始,盤星藻豐度急劇上升,體現(xiàn)了該流域人類活動的強(qiáng)度大大增加引起營養(yǎng)鹽水平的增長[100]。

位于北阿坎德邦的庫蒙-喜馬拉雅山脈湖泊群,由于其自身獨(dú)特的自然條件,成為印度北部最主要的旅游勝地。近年來的水土流失、違章建筑施工、每年旅游旺季的汽車尾氣排放以及游輪的大量使用等,使得湖區(qū)水體發(fā)生富營養(yǎng)化和水質(zhì)惡化[101-102]。湖區(qū)中Nainital湖海拔最高(1938m),并擁有較高人口密度,居民約50000人[103-104],湖泊四周為地勢不穩(wěn)的陡坡所圍繞,易于發(fā)生塌方和滑坡,湖體富營養(yǎng)化情況較為嚴(yán)重。Nainital湖的富營養(yǎng)化問題自1980年開始就有研究報(bào)道,Pant等人于1977年9月—1978年8月對該湖進(jìn)行野外調(diào)查,結(jié)果發(fā)現(xiàn),該湖泊熱力分層特性屬于暖-單循環(huán)湖,表層水中可溶性磷酸鹽濃度范圍為0.0065—0.07mg/L,全年大部分時(shí)間都遠(yuǎn)高于富營養(yǎng)化閾值(0.01mg/L),浮游植物群落中的優(yōu)勢種也出現(xiàn)了如微囊藻、魚腥藻、衣藻等富營養(yǎng)化的指示種類。研究認(rèn)為由于流域內(nèi)旅游輸入和定居人口的不斷增加,生活污水大量排放使該湖富營養(yǎng)化進(jìn)程大大加快[105]。Ali等人于1997年對Nainital湖進(jìn)行季度性采樣后發(fā)現(xiàn),湖水富含硝酸鹽(0.55—1.59mg/L)和氨氮(0.025—0.329mg/L),直接造成了浮游植物與大型水生植物的過度生長,水華的發(fā)生以銅綠微囊藻為主。相對自然輸入,生活和市政污水的排放可能是該湖泊的主要污染源,附近森林枯枝落葉層以及沉積物的輸入作用也不可忽視[103]。Gupta等人于2006年按月對Nainital湖進(jìn)行水樣分層采集,得到水體月均水溫為9.7—18.96℃,表層水溫最高可達(dá)17.4℃；可溶性磷酸鹽含量為0.094—0.193mg/L,全年整個湖泊平均值為(0.130±0.0557)mg/L；水體年均透明度僅1.23m,顯示水體已經(jīng)處于超富營養(yǎng)狀態(tài),較低的透明度會阻礙水體對太陽光照的吸收,從而對區(qū)域小氣候產(chǎn)生負(fù)面影響。同時(shí)該研究認(rèn)為Nainital湖水體的高pH、低N/P值會對藍(lán)藻水華的發(fā)生起到促進(jìn)作用[106]。Choudhary等人于2004年12月在湖水最深處采集了兩個40—45cm長度的沉積柱,以沉積物中色素含量作為生物標(biāo)志物分析,結(jié)果表明近年來浮游植物群落結(jié)構(gòu)逐漸轉(zhuǎn)為以藍(lán)藻為優(yōu)勢種類,而沉積物C/N為10—15,認(rèn)為沉積物有機(jī)質(zhì)主要來源為藻源性,流域的地表徑流并沒有增加水體的陸源性有機(jī)質(zhì)[107]。然而,Purushothaman等人認(rèn)為湖泊沉積物中Al2O3/K2O的高值水平表明流域有較為嚴(yán)重的水土流失發(fā)生,部分磷的來源是以地表徑流的方式從流域的磷灰石礦物進(jìn)入了湖體中,最終使得湖水中總磷含量達(dá)到了中等-重度富營養(yǎng)化水平[101]。

溫尼伯湖(52°7′N,97°15′W),是加拿大重要冰川淡水湖泊。自20世紀(jì)90年代中期以來,異形藍(lán)藻水華爆發(fā)的規(guī)模增長了近一倍,研究認(rèn)為藍(lán)藻水華是磷負(fù)荷和濃度增長的結(jié)果。影響P增加的因素主要包括兩方面：牧業(yè)生產(chǎn)和化肥的使用,以及溫尼伯市及附近流域人類活動的作用；另一方面為氣候變化的影響,近年來流域內(nèi)春季洪水頻率和強(qiáng)度的增加,大大加強(qiáng)了磷從地表進(jìn)入水體的遷移過程。從營養(yǎng)鹽來源看,流域畜牧業(yè)不斷發(fā)展,為了滿足作物生長對N的需求,大量動物糞肥被施用于作物,使得P過量,湖水P負(fù)荷大大增加,湖水N/P比低,浮游植物群落結(jié)構(gòu)以固氮類的藍(lán)藻細(xì)菌為主。從氣候變化看,1995年以來流域降水增加,春季融雪降水季徑流大大增加,使水文學(xué)的負(fù)荷增加,從而導(dǎo)致營養(yǎng)鹽可獲得性增加的放大效應(yīng),成為溫尼伯湖的“雙重災(zāi)難”[108]。Zhang等人于2002—2007年運(yùn)用WASP模型對溫尼伯湖水質(zhì)富營養(yǎng)化狀況進(jìn)行評估,該模型包括氮磷的營養(yǎng)鹽循環(huán)過程和3個浮游植物功能組(非藍(lán)藻細(xì)菌,固氮類藍(lán)藻,非固氮類藍(lán)藻),模型對浮游植物群落結(jié)構(gòu)的時(shí)空特征有很好的重現(xiàn)性。藍(lán)藻主要在夏季季末出現(xiàn)于北部流域,其中非固氮類藍(lán)藻比例有增加趨勢,而非藍(lán)藻細(xì)菌會在春季出現(xiàn)在南部流域。通過對多種營養(yǎng)鹽削減的情景分析,研究認(rèn)為增加氮磷的負(fù)荷比(P削減>12%,N削減<7%)對提高溫尼伯湖水質(zhì)較為有效[109]。

Bennion等人運(yùn)用古湖沼學(xué)技術(shù),對英國的106個湖泊(50°—58°N)沉積物記錄進(jìn)行分析后發(fā)現(xiàn),富營養(yǎng)化已經(jīng)影響了區(qū)域內(nèi)所有不同類型湖泊,>50%的湖泊的群落結(jié)構(gòu)發(fā)生了明顯改變[112]。外來物種的入侵會改變湖泊生態(tài)系統(tǒng)結(jié)構(gòu),可能會引起有害藻類的過度增殖,而Winfield對英國主要的4大淡水湖泊(羅蒙湖56°7′ N；內(nèi)伊湖54°37′N；巴拉湖52°53′N；溫德米爾湖54°21′N)外來魚種生物入侵情況進(jìn)行了研究,認(rèn)為入侵的鯉魚科適于更富營養(yǎng)化、更溫暖的環(huán)境生活,而研究流域內(nèi)營養(yǎng)鹽的不斷加富以及氣候變暖使得水溫上升,反過來又大大加速了入侵種不斷增殖,最終成為優(yōu)勢種群的進(jìn)程[113]。

綜上所述,人類活動的驅(qū)動作用主要包括：(1) 冷水湖泊流域人口壓力增大帶來了大量生活和市政污水的排放；(2) 在人口日趨密集的背景下,流域農(nóng)業(yè)和畜牧業(yè)活動強(qiáng)度大大增加,肥料的使用和水土流失成為冷水湖泊營養(yǎng)鹽負(fù)荷的主要外源；(3) 社會經(jīng)濟(jì)效益驅(qū)動下的水利工程建設(shè)、旅游開發(fā)、經(jīng)濟(jì)魚類的引入等使流域水生態(tài)環(huán)境不斷惡化,加速了湖泊富營養(yǎng)化。

4 結(jié)論和展望

湖泊是淡水生態(tài)系統(tǒng)的重要單元,作為飲用水源地的載體,湖泊富營養(yǎng)化在全球范圍內(nèi)的發(fā)生發(fā)展,正深刻影響流域的人口資源配置、生態(tài)安全格局與社會經(jīng)濟(jì)發(fā)展。冷水湖泊有其自身獨(dú)特的自然條件和營養(yǎng)發(fā)育特征,在氣候變化和人類干擾不斷加劇的大背景下,目前世界各地已有許多冷水湖泊相繼表現(xiàn)出富營養(yǎng)化癥狀和趨勢。由于冷水湖泊生態(tài)系統(tǒng)的敏感性和脆弱性,在氣候變化和人類活動的雙重驅(qū)動下,其富營養(yǎng)化進(jìn)程正不斷加速。溫度上升促進(jìn)了有害藻類的過度增殖,降水模式的改變影響了營養(yǎng)鹽的外源性負(fù)荷,與此同時(shí),人口壓力增加、人類活動干擾強(qiáng)度觸發(fā)了冷水湖泊富營養(yǎng)化發(fā)生發(fā)展的級聯(lián)效應(yīng),冷水湖泊流域也因此進(jìn)入水質(zhì)惡化的惡性循環(huán)。

氣候變化因素和外源性營養(yǎng)負(fù)荷的增加,對湖泊水動力學(xué)、熱力學(xué)分層、生態(tài)系統(tǒng)結(jié)構(gòu)等影響深遠(yuǎn)。未來的研究方向應(yīng)加強(qiáng)對在氣候變化和人類活動雙重驅(qū)動力作用下冷水湖泊富營養(yǎng)化機(jī)制的研究；關(guān)注冷水湖泊富營養(yǎng)化的演化規(guī)律及浮游植物的生態(tài)響應(yīng),預(yù)測和調(diào)控冷水湖泊營養(yǎng)狀態(tài)的變遷過程,控制冷水湖泊富營養(yǎng)化惡化的態(tài)勢,保護(hù)高山和寒冷地區(qū)生態(tài)系統(tǒng)的完整性和棲息地的生物多樣性；研究富營養(yǎng)化湖泊的生態(tài)修復(fù)對策與措施,為冷水湖泊流域管理政策的制定實(shí)施提供科學(xué)支持。

[1] Ansari A A, Gill S S. Eutrophication: Causes, Consequences and Control. Vol. 2. Netherlands: Springer, 2014.

[2] Lu Y L, Wang R S, Zhang Y Q, Su H Q, Wang P, Jenkins A, Ferrier R C, Bailey M, Squire G. Ecosystem health towards sustainability. Ecosystem Health and Sustainability, 2015,. 1(1): 1-15.

[3] Bennett E M, Carpenter S R, Caraco N F. Human impact on erodable phosphorus and eutrophication: a global perspective: increasing accumulation of phosphorus in soil threatens rivers, lakes, and coastal oceans with eutrophication. BioScience, 2001, 51(3): 227-234.

[4] Paerl H W. Assessing and managing nutrient-enhanced eutrophication in estuarine and coastal waters: interactive effects of human and climatic perturbations. Ecological Engineering, 2006, 26(1): 40-54.

[5] Moss B, Kosten S, Meerhoff M, Battarbee R W, Jeppesen E, Mazzeo N, Havens K, Lacerot G, Liu Z W, De Meester L, Paerl H, Scheffer M. Allied attack: climate change and eutrophication. Inland Waters, 2011, 1(2): 101-105.

[6] Mooij W M, Hülsmann S, De Senerpont Domis L N, Nolet B A, Bodelier P L E, Boers P C M, Pires L M D, Gons H J, Ibelings B W, Noordhuis R, Portielje R, Wolfstein K, Lammens E H R R. The impact of climate change on lakes in the Netherlands: a review. Aquatic Ecology, 2005, 39(4): 381-400.

[7] Jones J, Brett M T. Lake nutrients, eutrophication, and climate change // Freedman B, ed. Global Environmental Change. Netherlands: Springer, 2014: 273-279.

[8] Paerl H W, Paul V J. Climate change: links to global expansion of harmful cyanobacteria. Water Research, 2012, 46(5): 1349-1363.

[9] Swanson E D, Bergersen E P. Grass carp stocking model for coldwater lakes. North American Journal of Fisheries Management, 1988, 8(3): 284-291.

[10] Rose K C, Williamson C E, Saros J E, Sommaruga R, Fischer J M. Differences in UV transparency and thermal structure between alpine and subalpine lakes: implications for organisms. Photochemical & Photobiological Sciences, 2009, 8(9): 1244-1256.

[12] Williamson C E, Dodds W, Kratz T K, Palmer M A. Lakes and streams as sentinels of environmental change in terrestrial and atmospheric processes. Frontiers in Ecology and the Environment, 2008, 6(5): 247-254.

[13] 李均力, 方暉, 包安明, 楊遼. 近期亞洲中部高山地區(qū)湖泊變化的時(shí)空分析. 資源科學(xué), 2011, 33(10): 1839-1846.

[14] 張淵萌, 程志剛. 青藏高原增暖海拔依賴性研究進(jìn)展. 高原山地氣象研究, 2014, 34(2): 91-96.

[15] Rangwala I, Sinsky E, Miller J R. Amplified warming projections for high altitude regions of the northern hemisphere mid-latitudes from CMIP5 models. Environmental Research Letters, 2013, 8(2): 024040.

[16] Mountain Research Initiative EDW Working Group. Elevation-dependent warming in mountain regions of the world. Nature Climate Change, 2015, 5(5): 424-430.

[17] Song C Q, Huang B, Ke L H, Richards K S. Remote sensing of alpine lake water environment changes on the Tibetan Plateau and surroundings: a review. ISPRS Journal of Photogrammetry and Remote Sensing, 2014, 92: 26-37.

[18] Sommaruga R. The role of solar UV radiation in the ecology of alpine lakes. Journal of Photochemistry and Photobiology B: Biology, 2001, 62(1/2): 35-42.

[19] Saros J E, Michel T J, Interlandi S J, Wolfe A P. Resource requirements of Asterionella formosa and Fragilaria crotonensis in oligotrophic alpine lakes: implications for recent phytoplankton community reorganizations. Canadian Journal of Fisheries and Aquatic Sciences, 2005, 62(7): 1681-1689.

[20] Anneville O, Souissi S, Gammeter S, Straile D. Seasonal and inter-annual scales of variability in phytoplankton assemblages: comparison of phytoplankton dynamics in three peri-alpine lakes over a period of 28 years. Freshwater Biology, 2004, 49(1): 98-115.

[21] Kissman C E H, Williamson C E, Rose K C, Saros J E. Response of phytoplankton in an alpine lake to inputs of dissolved organic matter through nutrient enrichment and trophic forcing. Limnology and Oceanography, 2013, 58(3): 867-880.

[22] Anneville O, Gammeter S, Straile D. Phosphorus decrease and climate variability: mediators of synchrony in phytoplankton changes among European peri-alpine lakes. Freshwater Biology, 2005, 50(10): 1731-1746.

[23] Brahney J, Ballantyne A P, Kociolek P, Spaulding S, Otu M, Porwoll T, Neff J C. Dust mediated transfer of phosphorus to alpine lake ecosystems of the Wind River Range, Wyoming, USA. Biogeochemistry, 2014, 120(1/3): 259-278.

[24] Brahney J, Mahowald N, Ward D S, Ballantyne A P, Neff J C. Is atmospheric phosphorus pollution altering global alpine Lake stoichiometry? Global Biogeochemical Cycles, 2015, 29(9): 1369-1383.

[25] Knapp R A, Matthews K R, Sarnelle O. Resistance and resilience of alpine lake fauna to fish introductions. Ecological Monographs, 2001, 71(3): 401-421.

[26] Liu J B, Rühland K M, Chen J H, Xu Y Y, Chen S Q, Chen Q M, Huang W, Xu Q H, Chen F H, Smol J P. Aerosol-weakened summer monsoons decrease lake fertilization on the Chinese Loess Plateau. Nature Climate Change, 2017, 7(3): 190-194.

[27] Hoegh-Guldberg O, Bruno J F. The impact of climate change on the world′s marine ecosystems. Science, 2010, 328(5985): 1523-1528.

[28] Hansen J, Sato M, Ruedy R, Lo K, Lea D W, Medina-Elizade M. Global temperature change. Proceedings of the National Academy of Sciences of the United States of America, 2006, 103(39): 14288-14293.

[29] Jeppesen E, Kronvang B, Meerhoff M, S?ndergaard M, Hansen K M, Andersen H E, Lauridsen T L, Liboriussen L, Beklioglu M, ?zen A, Olesen J E. Climate change effects on runoff, catchment phosphorus loading and lake ecological state, and potential adaptations. Journal of Environmental Quality, 2009, 38(5): 1930-1941.

[30] Solomon S. Climate Change 2007-The Physical Science Basis: Working Group I Contribution to the Fourth Assessment Report of the IPCC. Cambridge: Cambridge University Press, 2007.

[31] Arctic Climate Impact Assessment. Impacts of A Warming Arctic-Arctic Climate Impact Assessment. Cambridge, UK: Cambridge University Press, 2004: 1-1.

[32] Rosenzweig C, Casassa G, Karoly D J, Imeson A, Liu C, Menzel A, Rawlins S, Root T L, Seguin B, Tryjanowski P. Assessment of observed changes and responses in natural and managed systems//Parry M L, Canziani O F, Palutikof J P, van der Linden P J, Hanson C E, eds. Climate Change, 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge University Press, 2007: 79-131.

[33] Adrian R, O′Reilly C M, Zagarese H, Baines S B, Hessen D O, Keller W, Livingstone D M, Sommaruga R, Straile D, Van Donk E, Weyhenmeyer G A, Winder M. Lakes as sentinels of climate change. Limnology and Oceanography, 2009, 54(6): 2283-2297.

[34] Schindler D W, Bayley S E, Parker B R, Beaty K G, Cruikshank D R, Fee E J, Schindler E U, Stainton M P. The effects of climatic warming on the properties of boreal lakes and streams at the Experimental Lakes Area, northwestern Ontario. Limnology and Oceanography, 1996, 41(5): 1004-1017.

[35] Magnuson J J, Robertson D M, Benson B J, Wynne R H, Livingstone D M, Arai T, Assel R A, Barry R G, Card V, Kuusisto E, Granin N G, Prowse T D, Stewart K M, Vuglinski V S. Historical trends in lake and river ice cover in the Northern Hemisphere. Science, 2000, 289(5485): 1743-1746.

[36] Verburg P, Hecky R E, Kling H. Ecological consequences of a century of warming in Lake Tanganyika. Science, 2003, 301(5632): 505-507.

[37] O′Reilly C M, Alin S R, Plisnier P D, Cohen A S, McKee B A. Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa. Nature, 2003, 424(6950): 766-768.

[38] Williamson C E, Saros J E, Vincent W F, Smol J P. Lakes and reservoirs as sentinels, integrators, and regulators of climate change. Limnology and Oceanography, 2009, 54(6part2): 2273-2282.

[39] Arhonditsis G B, Brett M T, DeGasperi C L, Schindler D E. Effects of climatic variability on the thermal properties of Lake Washington. Limnology and Oceanography, 2004, 49(1): 256-270.

[40] Gillet C, QuéTin P. Effect of temperature changes on the reproductive cycle of roach in Lake Geneva from 1983 to 2001. Journal of Fish Biology, 2006, 69(2): 518-534.

[41] Hampton S E, Izmest′eva L R, Moore M V, Katz S L, Dennis B, Silow E A. Sixty years of environmental change in the world′s largest freshwater lake-Lake Baikal, Siberia. Global Change Biology, 2008, 14(8): 1947-1958.

[42] Austin J A, Colman S M. Lake Superior summer water temperatures are increasing more rapidly than regional air temperatures: a positive ice-albedo feedback. Geophysical Research Letters, 2007, 34(6), doi: 10.1029/2006GL029021.

[43] Livingstone D M. Impact of secular climate change on the thermal structure of a large temperate central European lake. Climatic Change, 2003, 57(1/2): 205-225.

[44] Winder M, Schindler D E. Climate change uncouples trophic interactions in an aquatic ecosystem. Ecology, 2004, 85(8): 2100-2106.

[45] Todd M C, Mackay A W. Large-scale climatic controls on Lake Baikal ice cover. Journal of Climate, 2003, 16(19): 3186-3199.

[46] Assel R A. Classification of annual Great Lakes ice cycles: winters of 1973-2002. Journal of Climate, 2005, 18(22): 4895-4905.

[47] Shimoda Y, Azim M E, Perhar G, Ramin M, Kenney M A, Sadraddini S, Gudimov A, Arhonditsis G B. Our current understanding of lake ecosystem response to climate change: what have we really learned from the north temperate deep lakes? Journal of Great Lakes Research, 2011, 37(1): 173-193.

[48] Coats R, Perez-Losada J, Schladow G, Richards R, Goldman C. The warming of lake Tahoe. Climatic Change, 2006, 76(1/2): 121-148.

[49] Moore M V, Hampton S E, Izmest′eva L R, Silow E A, Peshkova E V, Pavlov B K. Climate change and the world′s “sacred sea”—Lake Baikal, Siberia. BioScience, 2009, 59(5): 405-417.

[50] van der Kamp G, Keir D, Evans M S. Long-term water level changes in closed-basin lakes of the Canadian prairies. Canadian Water Resources Journal, 2008, 33(1): 23-38.

[51] Rodionov S N. Global and Regional Climate Interaction: The Caspian Sea Experience. Netherlands: Springer 1994.

[52] Ghanbari R N, Bravo H R. Coherence between atmospheric teleconnections, Great Lakes water levels, and regional climate. Advances in Water Resources, 2008, 31(10): 1284-1298.

[54] Livingstone D M, Adrianb R. Modeling the duration of intermittent ice cover on a lake for climate-change studies. Limnology and Oceanography, 2009, 54(5): 1709-1722.

[55] O′Reilly C M, Sharma S, Gray D K, Hampton S E, Read J S, Rowley R J, Schneider P, Lenters J D, McIntyre P B, Kraemer B M, Weyhenmeyer G A, Straile D, Dong B, Adrian R, Allan M G, Anneville O, Arvola L, Austin J, Bailey J L, Baron J S, Brookes J D, de Eyto E, Dokulil M T, Hamilton D P, Havens K, Hetherington A L, Higgins S N, Hook S, Izmest′eva L R, Joehnk K D, Kangur K, Kasprzak P, Kumagai M, Kuusisto E, Leshkevich G, Livingstone D, MacIntyre S, May L, Melack J M, Mueller-Navarra D C, Naumenko M, Noges P, Noges T, North R P, Plisnier P D, Rigosi A, Rimmer A, Rogora M, Rudstam L G, Rusak J A, Salmaso N, Samal N R, Schindler D E, Schladow S G, Schmid M, Schmidt S R, Silow E, Soylu M E, Teubner K, Verburg P, Voutilainen A, Watkinson A, Williamson C E, Zhang G Q. Rapid and highly variable warming of lake surface waters around the globe. Geophysical Research Letters, 2015, 42(24): 10773-10781.

[56] Gerten D, Adrian R. Differences in the persistency of the North Atlantic Oscillation signal among lakes. Limnology and Oceanography, 2001, 46(2): 448-455.

[57] Straile D, J?hnk K, Henno R. Complex effects of winter warming on the physicochemical characteristics of a deep lake. Limnology and Oceanography, 2003, 48(4): 1432-1438.

[58] Livingstone D M. A change of climate provokes a change of paradigm: taking leave of two tacit assumptions about physical lake forcing. International Review of Hydrobiology, 2008, 93(4/5): 404-414.

[59] Tranvik L J, Downing J A, Cotner J B, Loiselle S A, Striegl R G, Ballatore T J, Dillon P, Finlay K, Fortino K, Knoll L B, Kortelainen P L, Kutser T, Larsen S, Laurion I, Leech D M, McCallister S L, McKnight D M, Melack J M, Overholt E, Porter J A, Prairie Y, Renwick W H, Roland F, Sherman B S, Schindler D W, Sobek S, Tremblay A, Vanni M J, Verschoor A M, von Wachenfeldt E, Weyhenmeyer G A. Lakes and reservoirs as regulators of carbon cycling and climate. Limnology and Oceanography, 2009, 54(6part2): 2298-2314.

[60] Parker B R, Vinebrooke R D, Schindler D W. Recent climate extremes alter alpine lake ecosystems. Proceedings of the National Academy of Sciences of the United States of America, 2008, 105(35): 12927-12931.

[61] Jankowski T, Livingstone D M, Bührer H, Forster R, Niederhauser P. Consequences of the 2003 European heat wave for lake temperature profiles, thermal stability, and hypolimnetic oxygen depletion: implications for a warmer world. Limnology and Oceanography, 2006, 51(2): 815-819.

[62] Keller W, Paterson A M, Somers K M, Dillon P J, Heneberry J, Ford A. Relationships between dissolved organic carbon concentrations, weather, and acidification in small Boreal Shield lakes. Canadian Journal of Fisheries and Aquatic Sciences, 2008, 65(5): 786-795.

[63] Bergstr?m A K, Jansson M. Atmospheric nitrogen deposition has caused nitrogen enrichment and eutrophication of lakes in the northern hemisphere. Global Change Biology, 2006, 12(4): 635-643.

[64] Kelly E N, Schindler D W, Louis V L S, Donald D B, Vladicka K E. Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs. Proceedings of the National Academy of Sciences of the United States of America, 2006, 103(51): 19380-19385.

[65] Boisvenue C, Running S W. Impacts of climate change on natural forest productivity-evidence since the middle of the 20th century. Global Change Biology, 2006, 12(5): 862-882.

[66] Westerling A L, Hidalgo H G, Cayan D R, Swetnam T W. Warming and earlier spring increase western U.S. forest wildfire activity. Science, 2006, 313(5789): 940-943.

[67] Evans C D, Chapman P J, Clark J M, Monteith D T, Cresser M S. Alternative explanations for rising dissolved organic carbon export from organic soils. Global Change Biology, 2006, 12(11): 2044-2053.

[68] Benoy G, Cash K, McCauley E, Wrona F. Carbon dynamics in lakes of the boreal forest under a changing climate. Environmental Reviews, 2007, 15(NA): 175-189.

[69] Hanson P C, Carpenter S R, Armstrong D E, Stanley E H, Kratz T K. Lake dissolved inorganic carbon and dissolved oxygen: changing drivers from days to decades. Ecological Monographs, 2006, 76(3): 343-363.

[70] Winder M, Hunter D A. Temporal organization of phytoplankton communities linked to physical forcing. Oecologia, 2008, 156(1): 179-192.

[71] Blenckner T, Adrian R, Livingstone D M, Jennings E, Weyhenmeyer G A, George D G, Jankowski T, J?rvinen M, Aonghusa C N, Noges T, Straile D, Teubner K. Large-scale climatic signatures in lakes across Europe: a meta-analysis. Global Change Biology, 2007, 13(7): 1314-1326.

[72] Winder M, Reuter J E, Schladow S G. Lake warming favours small-sized planktonic diatom species. Proceedings of the Royal Society B: Biological Sciences, 2009, 276(1656): 427-435.

[73] Seebens H, Straile D, Hoegg R, Stich H B, Einsle U. Population dynamics of a freshwater calanoid copepod: complex responses to changes in trophic status and climate variability. Limnology and Oceanography, 2007, 52(6): 2364-2372.

[74] RahelF J, Olden J D. Assessing the effects of climate change on aquatic invasive species. Conservation Biology, 2008, 22(3): 521-533.

[75] Winder M, Schindler D E, Essington T E, Litt A H. Disrupted seasonal clockwork in the population dynamics of a freshwater copepod by climate warming. Limnology and Oceanography, 2009, 54(6part2): 2493-2505.

[76] Adrian R, Wilhelm S, Gerten D. Life-history traits of lake plankton species may govern their phenological response to climate warming. Global Change Biology, 2006, 12(4): 652-661.

[77] Blenckner T. A conceptual model of climate-related effects on lake ecosystems. Hydrobiologia, 2005, 533(1): 1-14.

[78] Wagner C, Adrian R. Cyanobacteria dominance: quantifying the effects of climate change. Limnology and Oceanography, 2009, 54(6part2): 2460-2468.

[79] Jeppesen E, Moss B, Bennion H, Carvalho L, DeMeester L, Feuchtmayr H, Friberg N, Gessner M O, Hefting M, Lauridsen T L, Liboriussen L, Malmquist H J, May L, Meerhoff M, Olafsson J S, Soons M B, Verhoeven J T A. Interaction of climate change and eutrophication//Kernan M, Battarbee R W, Moss B, eds. Climate Change Impacts on Freshwater Ecosystems. Oxford: Blackwell, 2010: 119-151.

[80] Jeppesen E, Kronvang B, Olesen J E, Audet J, S?ndergaard M, Hoffmann C C, Andersen H E, Lauridsen T L, Liboriussen L, Larsen S E, Beklioglu M, Meerhoff M, ?zen A, ?zkan K. Climate change effects on nitrogen loading from cultivated catchments in Europe: implications for nitrogen retention, ecological state of lakes and adaptation. Hydrobiologia, 2011, 663(1): 1-21.

[81] Smol J P. The power of the past: using sediments to track the effects of multiple stressors on lake ecosystems. Freshwater Biology, 2010, 55(S1): 43-59.

[82] 蘇潔瓊, 王烜, 楊志峰. 考慮氣候因子變化的湖泊富營養(yǎng)化模型研究進(jìn)展. 應(yīng)用生態(tài)學(xué)報(bào), 2012, 23(11): 3197-3206.

[83] O′Neil J M, Davis T W, Burford M A, Gobler C J. The rise of harmful cyanobacteria blooms: the potential roles of eutrophication and climate change. Harmful Algae, 2012, 14: 313-334.

[84] Ke Z X, Xie P, Guo L G. Controlling factors of spring-summer phytoplankton succession in Lake Taihu (Meiliang Bay, China). Hydrobiologia, 2008, 607(1): 41-49.

[85] Holzapfel A M, Vinebrooke R D. Environmental warming increases invasion potential of alpine lake communities by imported species. Global Change Biology, 2005, 11(11): 2009-2015.

[86] Winder M, Sommer U. Phytoplankton response to a changing climate. Hydrobiologia, 2012, 698(1): 5-16.

[87] Li Z, Zhang Z B, Jiang F Y, Wang S W, Wang F J. Lake Hulun Chi (continuous Chi two). Nimenggu: Neimenggu Culture Press, 2008.

[88] Xue B, Qu W C, Wang S M, Ma Y, Dickman M D. Lake level changes documented by sediment properties and diatom of Hulun Lake, China since the late Glacial. Hydrobiologia, 2003, 498(1/3): 133-141.

[89] Chuai X, Chen X, Yang L, Zeng J, Miao A, Zhao H. Effects of climatic changes and anthropogenic activities on lake eutrophication in different ecoregions. International Journal of Environmental Science and Technology, 2012, 9(3): 503-514.

[90] Chen X F, Chuai X M, Yang L Y, Zhao H Y. Climatic warming and overgrazing induced the high concentration of organic matter in Lake Hulun, a large shallow eutrophic steppe lake in northern China. Science of the Total Environment, 2012, 431: 332-338.

[91] 李紅, 馬燕武, 祁峰, 謝春剛, 陳朋. 博斯騰湖浮游植物群落結(jié)構(gòu)特征及其影響因子分析. 水生生物學(xué)報(bào), 2014, 38(5): 921-928.

[92] 劉宇. 新疆烏倫古湖浮游植物群落結(jié)構(gòu)的時(shí)空變化規(guī)律[D]. 武漢: 華中農(nóng)業(yè)大學(xué), 2009.

[93] Sickman J O, Melack J M, Clow D W. Evidence for nutrient enrichment of high-elevation lakes in the Sierra Nevada, California. Limnology and Oceanography, 2003, 48(5): 1885-1892.

[94] Saros J E, Interlandi S J, Wolfe A P, Engstrom D R. Recent changes in the diatom community structure of lakes in the Beartooth Mountain Range, U.S.A. Arctic, Antarctic, and Alpine Research, 2003, 35(1): 18-23.

[95] Saros J E, Anderson N J. The ecology of the planktonic diatom Cyclotella and its implications for global environmental change studies. Biological Reviews, 2015, 90(2): 522-541.

[96] 郭嘉, 韋瑋, 于一雷, 宋香靜, 張曼胤, 李勝男. 烏梁素海濕地富營養(yǎng)化研究進(jìn)展. 生態(tài)學(xué)雜志, 2015, 34(11): 3244-3252.

[97] Yang H, Yu R H, Guo R H, Hao Y, Zhang Y J. Assessment of Eutrophication in Wuliangsuhai Lake. Advanced Materials Research, 2014, 955-959: 1098-1102.

[98] Wünnemann B, Mischke S, Chen F H. A holocene sedimentary record from Bosten Lake, China. Palaeogeography, Palaeoclimatology, Palaeoecology, 2006, 234(2/4): 223-238.

[99] Liu J, Yao X R, Lu J J, Qiao X W, Liu Z L, Li S M. Distribution and factors affecting adsorption of sterols in the surface sediments of Bosten Lake and Manas Lake, Xinjiang. Environmental Science and Pollution Research, 2016, 23(6): 5892-5901.

[100] Liu X Q, Herzschuh U, Shen J, Jiang Q F, Xiao X Y. Holocene environmental and climatic changes inferred from Wulungu Lake in northern Xinjiang, China. Quaternary Research, 2008, 70(3): 412-425.

[101] Purushothaman P, Mishra S, Das A, Chakrapani G J. Sediment and hydro biogeochemistry of Lake Nainital, Kumaun Himalaya, India. Environmental Earth Sciences, 2012, 65(3): 775-788.

[102] Purushothaman P, Chakrapani G J. Phosphorus biogeochemistry in sediments of high altitude lakes, Kumaun Himalayas, India. Arabian Journal of Geosciences, 2015 8(2): 701-709.

[103] Ali M B, Tripathi R D, Rai U N, Pal A, Singh S P. Physico-chemical characteristics and pollution level of lake Nainital (U.P., India): role of macrophytes and phytoplankton in biomonitoring and phytoremediation of toxic metal ions. Chemosphere, 1999, 39(12): 2171-2182.

[104] Dash R R, Mehrotra I, Kumar P, Grischek T. Lake bank filtration at Nainital, India: water-quality evaluation. Hydrogeology Journal, 2008, 16(6): 1089-1099.

[105] Pant M C, Sharma A P, Sharma P C. Evidence for the increased eutrophication of lake nainital as a result of human interference. Environmental Pollution Series B, Chemical and Physical, 1980, 1(2): 149-161.

[106] Gupta P, Nagdali S S, Tewari P, Singh N, Gupta R. Water chemistry of a national lake of India: lake nainital, uttarakhand // Proceedings of Taal2007: The 12th World Lake Conference. India: International Lake Environment Committee, 2007.

[107] Choudhary P, Routh J, Chakrapani G J, Kumar B. Biogeochemical records of paleoenvironmental changes in Nainital Lake, Kumaun Himalayas, India. Journal of Paleolimnology, 2009, 42(4): 571-586.

[108] Schindler D W, Hecky R E, McCullough G K. The rapid eutrophication of Lake Winnipeg: greening under global change. Journal of Great Lakes Research, 2012, 38 Suppl 3: 6-13.

[109] Zhang W T, Rao Y R. Application of a eutrophication model for assessing water quality in Lake Winnipeg. Journal of Great Lakes Research, 2012, 38 Suppl 3: 158-173.

[110] Popovskaya G I. Ecological monitoring of phytoplankton in Lake Baikal. Aquatic Ecosystem Health and Management, 2000, 3(2): 215-225.

[111] Kravtsova L S, Izhboldina L A, Khanaev I V, Pomazkina G V, Rodionova E V, Domysheva V M, Sakirko M V, Tomberg I V, Kostornova T Y, Kravchenko O S, Kupchinsky A B. Nearshore benthic blooms of filamentous green algae in Lake Baikal. Journal of Great Lakes Research, 2014, 40(2): 441-448.

[112] Bennion H, Simpson G L. The use of diatom records to establish reference conditions for UK lakes subject to eutrophication. Journal of Paleolimnology, 2011, 45(4): 469-488.

[113] Winfield I J, Fletcher J M, James J B. Invasive fish species in the largest lakes of Scotland, Northern Ireland, Wales and England: the collective UK experience. Hydrobiologia, 2011, 660(1): 93-103.

Eutrophicationincold-waterlakesdrivenbycombinedeffectsofclimatechangeandhumanactivities

Lü Xiaotian1,2, Lü Yonglong1,2,*, SONG Shuai1, WANG Tieyu1

1StateKeyLaboratoryofUrbanandRegionalEcology,ResearchCenterforEco-EnvironmentalSciences,ChineseAcademyofSciences,Beijing100085,China2UniversityofChineseAcademyofSciences,Beijing100049,China

Eutrophication has become one of the most serious threats to aquatic ecosystems in the world, especially to water quality of lakes as drinking water sources, and further posed negative effects on the health of local residents. With the combined drivers of climate change and human activities, eutrophication has expanded from shallow lakes in temperature zone to water lakes in cold areas (named as cold-water lakes). Trends, characteristics and research advances in eutrophication of cold-water lakes throughout the world were summarized. Besides, influences of climate change and human activities, including agricultural activities, livestock farming and misguided policies, on eutrophication processes of cold-water were also analyzed. In the future research, eutrophication mechanism of cold-water lakes should be further explored and ecological restoration is desiderated to ensure the ecosystem health of the cold-water lakes and improve the quality of drinking water.

cold-water lakes; eutrophication; climate change; nutrients

國家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2017YFC0505704)；國家自然科學(xué)基金重點(diǎn)國際合作項(xiàng)目(41420104004)

2017- 04- 11;

2017- 08- 31

*通訊作者Corresponding author.E-mail: yllu@rcees.ac.cn

10.5846/stxb201704110632

呂笑天,呂永龍,宋帥,王鐵宇.氣候變化與人類活動雙重驅(qū)動的冷水湖泊富營養(yǎng)化.生態(tài)學(xué)報(bào),2017,37(22):7375- 7386.

Lü X T, Lü Y L, Song S, Wang T Y.Eutrophication in cold-water lakes driven by combined effects of climate change and human activities.Acta Ecologica Sinica,2017,37(22):7375- 7386.