王世歡,張 生,武 蓉,史小紅,趙勝男,孫 標(biāo)

寒旱區(qū)湖泊浮游植物特征及其對(duì)營(yíng)養(yǎng)狀態(tài)的指示作用

王世歡,張 生*,武 蓉,史小紅,趙勝男,孫 標(biāo)

(內(nèi)蒙古農(nóng)業(yè)大學(xué)水資源保護(hù)與利用自治區(qū)重點(diǎn)實(shí)驗(yàn)室,內(nèi)蒙古 呼和浩特 010018)

為揭示內(nèi)蒙古典型湖泊浮游植物群落特征及其對(duì)營(yíng)養(yǎng)狀態(tài)的響應(yīng),于2019年和2020年7月對(duì)呼倫湖,岱海,烏梁素海和居延海浮游植物和水質(zhì)理化指標(biāo)進(jìn)行取樣調(diào)查.結(jié)果顯示,呼倫湖,岱海,烏梁素海和居延海分別鑒定出浮游植物101種,44種,125種和42種,綠藻門,硅藻門和藍(lán)藻門是其優(yōu)勢(shì)門類.調(diào)查期間4個(gè)湖泊浮游植物的總豐度分別為5.71×105,0.18×105,3.45×105和6.96×105cells/L;根據(jù)優(yōu)勢(shì)度分析,居延海優(yōu)勢(shì)種最少為6種,其他湖泊優(yōu)勢(shì)種都在10種以上;CCA分析表明,綜合營(yíng)養(yǎng)指數(shù)(TLI),水溫(),總?cè)芙庑怨腆w(TDS),氨氮(NH4+-N),鹽度(SAL),pH值(<0.01)是浮游植物優(yōu)勢(shì)種的主要影響因子.4個(gè)湖泊的浮游植物Shannon-Wiener多樣性指數(shù)(′),豐富度(),均勻度()指數(shù)均值分別為1.4,0.38和2.79 (呼倫湖),2.28,0.87和1.42(岱海),2.99,0.74和4.46(烏梁素海),2.39,0.75和0.75(居延海),其對(duì)應(yīng)評(píng)價(jià)結(jié)果分別為中富/中/中營(yíng)養(yǎng),中/中富/貧營(yíng)養(yǎng),中/貧中/貧營(yíng)養(yǎng),中/中/貧營(yíng)養(yǎng);綜合營(yíng)養(yǎng)指數(shù)(TLI)評(píng)價(jià)結(jié)果依次為重度富營(yíng)養(yǎng)、中度富營(yíng)養(yǎng)、輕度富營(yíng)養(yǎng)和中度富營(yíng)養(yǎng).3種多樣性指數(shù)的評(píng)價(jià)結(jié)果存在不同,整體上浮游植物指數(shù)評(píng)價(jià)結(jié)果顯著低于理化指標(biāo)的評(píng)價(jià)結(jié)果,這是由于3種多樣性指數(shù)不僅僅受TLI相關(guān)指標(biāo)TP,TN,SD和Chl.a的影響,,pH值,SAL和TDS都與其顯著相關(guān),其中與上述指標(biāo)都顯著相關(guān),而′與TLI相關(guān)指標(biāo)關(guān)系顯著,與,pH值,SAL和TDS關(guān)系顯著.因此,單獨(dú)的采用多樣性等生物評(píng)價(jià)可能并不適用于內(nèi)蒙古高原湖泊,建議結(jié)合理化指標(biāo)使用多種評(píng)價(jià)方式進(jìn)行綜合評(píng)價(jià).

寒旱地區(qū)；浮游植物；群落結(jié)構(gòu)；湖泊；營(yíng)養(yǎng)狀態(tài)

浮游植物是湖泊水體的主要初級(jí)生產(chǎn)者,對(duì)水生態(tài)系統(tǒng)的物質(zhì)循環(huán)與能量流動(dòng)至關(guān)重要[1-2].浮游植物群落對(duì)水質(zhì)變化響應(yīng)靈敏[3-4],群落結(jié)構(gòu)和多樣性常作為評(píng)價(jià)水質(zhì)和營(yíng)養(yǎng)狀況的生物指標(biāo)[5].但在實(shí)際應(yīng)用中,受地理環(huán)境和氣候因素(如水溫,降雨,水動(dòng)力等)影響,浮游植物群落多樣性對(duì)營(yíng)養(yǎng)狀態(tài)和水質(zhì)變化的響應(yīng)具有明顯的時(shí)空特征[6],這些時(shí)空特征限制基于浮游植物群落多樣性的評(píng)價(jià)方法的推廣和應(yīng)用[7-8].在特定區(qū)域內(nèi),應(yīng)用浮游植物群落生物指標(biāo)評(píng)價(jià)方法[7],需要研究積累,明確研究區(qū)的特征和應(yīng)用評(píng)價(jià)方法的條件.

特定時(shí)期浮游植物群落反映的是所處環(huán)境狀態(tài)[7],浮游植物與營(yíng)養(yǎng)鹽的響應(yīng)關(guān)系受其他因素的影響[8].例如,由于水溫,流速等環(huán)境因素的影響,太湖流域96條河流以浮游植物為指標(biāo)的水質(zhì)評(píng)價(jià)結(jié)果低于物理化學(xué)參數(shù)的評(píng)價(jià)結(jié)果[9],在撫仙湖[10]也有類似的研究結(jié)果,喀爾巴阡盆地(匈牙利)湖泊和河流的相關(guān)研究表明,由于氣候和其它因素的影響,使用浮游植物多樣性作為生態(tài)指標(biāo)的有效性與水體類型有關(guān)[11].

內(nèi)蒙古高原大部分地區(qū)屬于溫帶大陸性季風(fēng)氣候區(qū),區(qū)域內(nèi)湖泊多屬內(nèi)陸型湖泊,地表徑流補(bǔ)給貧乏,區(qū)域特征明顯.與環(huán)境梯度相關(guān)的地理,氣候以及水文條件是浮游植物生長(zhǎng)與分布的重要影響因素[12],此外,獨(dú)特的湖泊形態(tài)和光熱條件(如湖泊面積,光熱狀況和晝夜季節(jié)變化)[13-15]對(duì)浮游植物多樣性也有重要作用.但目前尚缺乏系統(tǒng)的研究闡述應(yīng)用浮游植物多樣性作為內(nèi)蒙古高原湖泊水質(zhì),營(yíng)養(yǎng)水平評(píng)價(jià)指標(biāo)的有效性.

本研究旨在揭示內(nèi)蒙古典型湖泊浮游植物特征,分析浮游植物多樣性與湖泊營(yíng)養(yǎng)狀態(tài)和水質(zhì)的關(guān)系,闡述應(yīng)用浮游植物多樣性作為內(nèi)蒙古高原湖泊水質(zhì),營(yíng)養(yǎng)水平評(píng)價(jià)指標(biāo)的有效性.選取內(nèi)蒙古典型湖泊呼倫湖,岱海,烏梁素海和居延海4個(gè)湖泊為研究對(duì)象,分析了各湖泊的浮游植物群落特征和營(yíng)養(yǎng)狀態(tài)水平,確定了各湖泊浮游植物多樣性的主要影響因子,闡明了浮游植物多樣性作為內(nèi)蒙古高原湖區(qū)水質(zhì)指標(biāo)的適用性以及其對(duì)營(yíng)養(yǎng)狀態(tài)的指示作用.

1 材料與方法

1.1 研究區(qū)域概況

表1 內(nèi)蒙古典型湖泊基本特征

圖1 內(nèi)蒙古典型高原湖泊位置圖

●為采樣點(diǎn)

呼倫湖(達(dá)賚湖)位于內(nèi)蒙古自治區(qū)呼倫貝爾草原西部的新巴爾虎右旗境內(nèi),是我國(guó)第四大淡水湖,也是我國(guó)內(nèi)陸高緯度半干旱地區(qū)的第一大草原型湖泊[16].湖泊主要的補(bǔ)給來(lái)源4條入湖河流分別為烏爾遜河,克魯倫河,海拉爾河和新開河,以及降水和周圍的地下水[17].岱海位于內(nèi)蒙古自治區(qū)烏蘭察布市涼城縣境內(nèi),屬于典型內(nèi)陸咸水湖泊.湖水補(bǔ)給主要來(lái)源于地表徑流,地下水補(bǔ)給和湖面降水.近年來(lái)湖面萎縮和礦化度升高速率加劇,2019年年均礦化度達(dá)13878mg/L,是2004年4658.6mg/L[18]的2.98倍,生物多樣性銳減,魚類滅絕.烏梁素海位于內(nèi)蒙古巴彥淖爾市烏拉特前旗境內(nèi),是黃河改道形成的河跡湖.主要承接河套灌區(qū)農(nóng)田退水,也是當(dāng)?shù)厣钗鬯?工業(yè)廢水的唯一承納水體[19],出水排至黃河.居延海位于內(nèi)蒙古自治區(qū)阿拉善盟額濟(jì)納旗,是黑河流域的尾閭湖,主要受上游人工生態(tài)下泄水量調(diào)控.湖泊所在區(qū)域受極端干旱區(qū)氣候影響,常年降雨稀少,年均降水量為34.5mm[20],年平均水面蒸發(fā)量高達(dá)1526.6mm[21].受極端干旱氣候影響在20世紀(jì)多次干涸,自2002年黑河上游生態(tài)下泄水量增加以來(lái)至今未見干涸,是典型的人工控制性湖泊.

1.2 采樣點(diǎn)布設(shè)與樣品采集

于2019年和2020年7月分別對(duì)選定的4個(gè)典型湖泊進(jìn)行水質(zhì)和浮游植物進(jìn)行調(diào)查(圖1).浮游植物定性與定量采集方法參考《湖泊生態(tài)調(diào)查觀測(cè)與分析》[22].定性樣品采集使用25#浮游生物網(wǎng)在表層水體中呈用于浮游植物的定量計(jì)數(shù).

1.3 樣品分析與方法

現(xiàn)場(chǎng)測(cè)定水深(),并且使用便攜式多參數(shù)水質(zhì)分析儀(YSI)測(cè)定pH值,溶解氧(DO),電導(dǎo)率(EC),總?cè)芙庑怨腆w(TDS),鹽度(SAL),水溫(),使用塞斯盤測(cè)定透明度(SD),總磷(TP),總氮(TN),葉綠素(Chl.a),氨氮(NH4+-N)的測(cè)定按照《水和廢水監(jiān)測(cè)分析方法》[23].

浮游植物定量計(jì)數(shù)使用光學(xué)顯微鏡(Zeiss Axioskop microscope),種類鑒定參照《中國(guó)淡水藻類-系統(tǒng),分類及生態(tài)》,細(xì)胞計(jì)數(shù)參照《淡水生物資源調(diào)查技術(shù)規(guī)范》(DB43/T 432-2009)[24].通過(guò)Jaccard相似性指數(shù)()反映各湖泊之間群落的相似程度(表2)[4],用Shannon-Wiener多樣性指數(shù)(H′), Margalef物種豐富度指數(shù)(D),Pielou均勻度指數(shù)(J)及優(yōu)勢(shì)度(Y)指數(shù)分析浮游植物多樣性[4].計(jì)算公式如下:

式中:為相似性指數(shù);為群落共有種數(shù);為每個(gè)群落的種數(shù).

表2 相似性評(píng)價(jià)標(biāo)準(zhǔn)

式中:￠為多樣性指數(shù);P為第種個(gè)體數(shù)量占總個(gè)體數(shù)量的比例;為物種豐富度指數(shù);為藻種數(shù)目;為群落中藻類的總個(gè)體數(shù);均勻度指數(shù);為藻類優(yōu)勢(shì)度,30.02即為優(yōu)勢(shì)種[5];f為第個(gè)物種在采樣點(diǎn)的出現(xiàn)頻率;n為第個(gè)種的個(gè)體數(shù)目.

用綜合營(yíng)養(yǎng)狀態(tài)指數(shù)(TLI)和浮游植物,￠和指數(shù)分別評(píng)價(jià)湖泊營(yíng)養(yǎng)狀態(tài)(表3)[25-26].

表3 水體營(yíng)養(yǎng)狀態(tài)評(píng)價(jià)的指標(biāo)及標(biāo)準(zhǔn)

2 結(jié)果與分析

2.1 浮游植物群落特征

2.1.1 種類組成 4個(gè)湖泊鑒定出的浮游植物種類數(shù)為:呼倫湖8門101種,岱海8門44種,烏梁素海8門125種,居延海7門42種(表4).烏梁素海與呼倫湖種類數(shù)是岱海和居延海的2～3倍.4個(gè)湖泊的浮游植物均以綠藻門和硅藻門種類最多,藍(lán)藻門次之,除居延海其他湖泊均檢到黃藻門種類.

表4 各湖泊浮游植物種類

從浮游植物細(xì)胞豐度看,呼倫湖均值為5.71× 105cells/L,其中藍(lán)藻細(xì)胞豐度最高,其次是綠藻,二者占總豐度的90%;岱海均值為0.18×105cells/L,其中藍(lán)藻占總豐度的36%～72%;烏梁素海均值為3.45× 105cells/L,硅藻與綠藻為主,占總豐度的64%～89%;居延海均值為6.96×105cells/L,藍(lán)藻為主,占總豐度的32%～90%,其次是綠藻與金藻(圖2).

2.1.2 浮游植物優(yōu)勢(shì)種 呼倫湖優(yōu)勢(shì)種主要為藍(lán)藻和綠藻,岱海優(yōu)勢(shì)種7門兼有,烏梁素海優(yōu)勢(shì)種主要為硅藻,藍(lán)藻和綠藻,居延海優(yōu)勢(shì)種主要為藍(lán)藻.4個(gè)湖泊浮游植物優(yōu)勢(shì)種差異明顯,居延海優(yōu)勢(shì)種與其它3個(gè)湖泊完全不同,其它3個(gè)湖泊有多個(gè)相同優(yōu)勢(shì)種(表5).

圖2 各湖泊浮游植物豐度及各門相對(duì)豐度

表5 內(nèi)蒙古各湖泊浮游植物優(yōu)勢(shì)種及優(yōu)勢(shì)度

續(xù)表5

注:優(yōu)勢(shì)度30.02為優(yōu)勢(shì)種,優(yōu)勢(shì)度>0.1為絕對(duì)優(yōu)勢(shì)種.

2.1.3 浮游植物多樣性 4個(gè)湖泊浮游植物多樣性有明顯的差異:呼倫湖的Shannnon-Wiener(￠)與均勻度()均顯著低于其它湖泊,而岱?！槊黠@高于烏梁素海與居延海,無(wú)明顯差異;但呼倫湖豐富度指數(shù)()明顯高于岱海與居延海,且4個(gè)湖泊間的豐富度指數(shù)差異顯著(圖3).基于￠,和的湖泊營(yíng)養(yǎng)狀態(tài)評(píng)價(jià)結(jié)果表明:￠表明呼倫湖的營(yíng)養(yǎng)狀態(tài)為中富營(yíng)養(yǎng),岱海,烏梁素海和居延海的營(yíng)養(yǎng)狀態(tài)為中營(yíng)養(yǎng);表明除呼倫湖的營(yíng)養(yǎng)狀態(tài)為中營(yíng)養(yǎng)外,其余湖泊營(yíng)養(yǎng)狀態(tài)都為極貧營(yíng)養(yǎng);表明呼倫湖和居延海的營(yíng)養(yǎng)狀態(tài)為中營(yíng)養(yǎng),岱海為中富營(yíng)養(yǎng),烏梁素海為貧中營(yíng)養(yǎng).相同湖泊,三種多樣性指標(biāo)的評(píng)價(jià)結(jié)果不一致.

圖3 內(nèi)蒙古各湖泊浮游植物多樣性指數(shù)與差異性分析

2.1.4 湖泊間浮游植物群落相似性 結(jié)果表明湖泊間浮游植物群落差異明顯(表6),其中烏梁素海與呼倫湖為中度相似,岱海與烏梁素海,呼倫湖呈輕度相似,而居延海與其他湖泊差異較大,為極不相似.

表6 內(nèi)蒙古典型湖泊浮游植物群落相似度指數(shù)

2.2 浮游植物群落與環(huán)境因子的關(guān)系

2.2.1 多樣性指數(shù)與環(huán)境因子的關(guān)系 結(jié)果顯示營(yíng)養(yǎng)鹽是浮游植物多樣性指數(shù)￠,,的主要影響因素,富營(yíng)養(yǎng)狀態(tài)會(huì)在一定程度上對(duì)￠,產(chǎn)生負(fù)影響., SD,水深,pH值,TDS和SAL等都是多樣性指數(shù)的重要影響因子,值得注意的是,除外的其他環(huán)境因子都對(duì)D和H￠呈負(fù)相關(guān)(表7).

2.2.2 浮游植物豐度與環(huán)境因子的關(guān)系 將各湖泊不同門類浮游植物豐度與環(huán)境因子進(jìn)行相關(guān)性分析,結(jié)果顯示,浮游植物豐度與環(huán)境因子之間的相關(guān)性在湖泊之間差異明顯.呼倫湖藍(lán)藻豐度與水深和TLI顯著相關(guān),居延海藍(lán)藻豐度與顯著相關(guān),但岱海各門浮游植物豐度均與環(huán)境因子沒(méi)有顯著相關(guān)關(guān)系.從環(huán)境因子上看,NH4+-N,TLI,H與呼倫湖和居延海浮游植物豐度有顯著相關(guān)關(guān)系;EC和SAL與3個(gè)湖泊的浮游植物豐度都呈顯著關(guān)系.

表7 浮游植物多樣性指數(shù)與環(huán)境因子的相關(guān)性

注:*<0.05;**<0.01.

圖4 各湖泊各門類浮游植物豐度與環(huán)境因子相關(guān)性分析

*<0.05; **<0.01

2.2.3 浮游植物優(yōu)勢(shì)種與環(huán)境因子的CCA分析 4個(gè)湖泊共篩選出優(yōu)勢(shì)種33種,將各湖泊浮游植物優(yōu)勢(shì)種屬(優(yōu)勢(shì)度30.02)與TN,TP,DO等12項(xiàng)環(huán)境因子進(jìn)行典范對(duì)應(yīng)分析(CCA,梯度長(zhǎng)度6.9).結(jié)果顯示,共篩選出6個(gè)對(duì)浮游植物優(yōu)勢(shì)種起重要作用的影響因子,即TLI,,TDS,NH4+-N,SAL,pH值,其對(duì)浮游植物優(yōu)勢(shì)種的共同解釋率達(dá)72.1%,TLI解釋率為23.3% (=0.002,=10.3),為18.1% (=0.002,=10.2), TDS為21.8 (=0.002,=18.9),NH4+-N為3.7% (=0.006,=3.4),SAL為3.1%(=0.008,=3.0)和pH值為2.1% (=0.01,=2.2),且第一排序軸和第二排序軸累計(jì)解釋了53.64%的浮游植物信息,這說(shuō)明排序圖較好地反映了浮游植物與環(huán)境因子之間的關(guān)系(圖5).

4個(gè)湖泊浮游植物樣本明顯分開,表明湖泊間浮游植物群落差異明顯.呼倫湖浮游植物優(yōu)勢(shì)種主要位于第三象限,其中n1(針形纖維藻),n2(纖維藻), n8(四尾柵藻)和n13(魚腥藻)離排序軸中心較近,說(shuō)明其受多個(gè)環(huán)境因子的影響,而其他優(yōu)勢(shì)種與pH值,TLI呈正相關(guān),與SAL,TDS呈負(fù)相關(guān).烏梁素海優(yōu)勢(shì)種位于第二象限,岱海優(yōu)勢(shì)種位于第二三象限中間,二者與,SAL,TDS呈正相關(guān),與pH值和TLI呈反比.居延海優(yōu)勢(shì)種位于第四象限,與呈明顯的正相關(guān)關(guān)系,與其他環(huán)境因子相關(guān)關(guān)系相對(duì)較弱.

圖5 浮游植物優(yōu)勢(shì)種與環(huán)境因子CCA排序

2.3 湖泊營(yíng)養(yǎng)鹽狀態(tài)

4個(gè)湖泊的營(yíng)養(yǎng)狀態(tài)差異顯著.呼倫湖,岱海,烏梁素海和居延海TN濃度均值分別為7.03,3.53,1.08和1.6mg/L(圖6a).呼倫湖TN濃度最高,約是岱海TN的2倍,是烏梁素海與居延海的5～6倍,且呼倫湖和岱海TN濃度呈現(xiàn)較大的空間差異.4個(gè)湖泊TP濃度均值分別為0.16,0.19,0.03和0.1mg/L(圖6b),TP濃度水平較為相近,其中岱海和呼倫湖TP濃度較高,烏梁素海最低.

綜合富營(yíng)養(yǎng)化指數(shù)評(píng)價(jià),結(jié)果顯示,呼倫湖TLI(S)均值為82.13,總體呈重度富營(yíng)養(yǎng)狀態(tài),岱海TLI(S)均值為67.02,總體呈中度富營(yíng)養(yǎng)狀態(tài),烏梁素海,居延海TLI(S)均值分別為54.72,66.08,分別呈輕度富營(yíng)養(yǎng)狀態(tài)和中度富營(yíng)養(yǎng)狀態(tài)(圖6c).整體來(lái)看,呼倫湖富營(yíng)養(yǎng)化狀況最嚴(yán)重,為重度富營(yíng)養(yǎng)化;岱海,居延海和烏梁素海均呈中度富營(yíng)養(yǎng)狀態(tài).

圖6 內(nèi)蒙古典型湖泊TN,TP和TLI分布

3 討論

3.1 內(nèi)蒙古典型湖泊浮游植物群落結(jié)構(gòu)特征

結(jié)果顯示,呼倫湖,岱海和烏梁素海浮游植物種類主要由硅藻,綠藻和藍(lán)藻組成,三類群占總種數(shù)的80%以上,而居延海則是以藍(lán)藻,綠藻和金藻為主.豐度上,呼倫湖和居延海浮游植物主要由藍(lán)藻和綠藻組成,這與查干湖(2015年)[27],洱海(2016年)[5],達(dá)里諾爾湖(2015年)[13]研究結(jié)果一致;烏梁素海以硅藻,綠藻為主;岱海藍(lán)藻,綠藻,硅藻和裸藻數(shù)量相當(dāng),且總豐度較其他湖泊小一個(gè)數(shù)量級(jí).除岱海外,呼倫湖,烏梁素海和居延海的調(diào)查結(jié)果與楊朝霞[28](呼倫湖2019年),Chen[29]、孫鑫[30](烏梁素海2016年,2019年)和郝媛媛[15](居延海2014年)等人的研究結(jié)果相近,說(shuō)明其浮游植物群落結(jié)構(gòu)及水體環(huán)境處于相對(duì)穩(wěn)定的狀態(tài).岱海浮游植物相較于吳東昊[31]、徐兆安[32]的研究結(jié)果種類增多了35種而豐度下降了3個(gè)數(shù)量級(jí).

從湖泊面積來(lái)看,呼倫湖與烏梁素海面積更大,能為浮游植物提供更豐富的生境,本研究結(jié)果也表明兩湖的物種多樣性更高.相對(duì)其他類群,藍(lán)藻喜高溫,受氣候影響,內(nèi)蒙古夏季氣溫較高(藍(lán)藻適宜的生長(zhǎng)溫度:25～35℃)[33],居延海夏季水體平均溫度更是達(dá)27℃以上,這可能是藍(lán)藻在居延海占絕對(duì)優(yōu)勢(shì)的主要原因.相比于硅藻,藍(lán)藻和綠藻更偏好靜止或弱紊動(dòng)的水體[34],烏梁素海自2015年以來(lái)加大生態(tài)補(bǔ)水量[35],每年自湖冰消融(3月下旬)開始補(bǔ)水,并于7月雨季來(lái)臨前加大排水預(yù)防山洪,大排大補(bǔ)下對(duì)湖水的擾動(dòng)較強(qiáng),可能是硅藻門浮游植物在烏梁素海形成生長(zhǎng)優(yōu)勢(shì)的重要原因.岱海浮游植物結(jié)構(gòu)與其他湖泊有較大的差異,鹽度和礦化度的急劇增長(zhǎng)可能在一定程度上抑制了適宜淡水生境的浮游植物生長(zhǎng).

3.2 浮游植物與環(huán)境因子的關(guān)系

環(huán)境選擇是浮游植物群落結(jié)構(gòu)形成的主導(dǎo)作用[4].浮游植物多樣性是浮游植物群落的主要特征.本研究結(jié)果表明,3個(gè)多樣性指數(shù)與TN,TP,TLI,H以及pH值都呈負(fù)相關(guān),表明營(yíng)養(yǎng)鹽升高可能導(dǎo)致浮游植物群落多樣性下降.

由CCA分析的結(jié)果表明, TLI,,TDS,NH4+-N, SAL,pH 值(<0.01)是浮游植物群落結(jié)構(gòu)的主要影響因子,其對(duì)浮游植物優(yōu)勢(shì)種共同解釋率達(dá)72.1%,但優(yōu)勢(shì)種對(duì)環(huán)境因子的響應(yīng)表現(xiàn)出顯著的湖泊間差異.水體營(yíng)養(yǎng)狀態(tài)是浮游植物種群和組成的重要影響因子[36],高溫條件下,中營(yíng)養(yǎng)或富營(yíng)養(yǎng)化的水體中易暴發(fā)藍(lán)藻水華,而重富營(yíng)養(yǎng)化水體由于綠藻的競(jìng)爭(zhēng)抑制作用反而不易形成藍(lán)藻水華[37],這可能是藍(lán)藻在呼倫湖中僅在豐度上占據(jù)主導(dǎo)地位,而居延海中在豐度和種類上都占據(jù)主導(dǎo)地位的原因.此外,CCA分析表明,TN,TP濃度對(duì)浮游植物優(yōu)勢(shì)種無(wú)顯著影響,而NH4+-N對(duì)其有顯著影響.這是由于4個(gè)湖泊氮,磷濃度都滿足藻類生長(zhǎng)需要的臨界值(0.2和0.02mg/L)[38],而浮游植物新陳代謝更偏好于銨態(tài)氮[39].

pH值是水體重要的理化因子,對(duì)浮游植物的生長(zhǎng)繁殖有重要作用[40].4個(gè)湖泊pH值常年>8,高pH值環(huán)境有利于藍(lán)藻[41]發(fā)揮競(jìng)爭(zhēng)優(yōu)勢(shì),可能是藍(lán)藻成為浮游植物主要組成的重要原因.

3.3 營(yíng)養(yǎng)狀態(tài)評(píng)價(jià)對(duì)比

基于浮游生物多樣性指數(shù)(￠,,)對(duì)水體營(yíng)養(yǎng)狀態(tài)評(píng)價(jià)的結(jié)果與基于綜合營(yíng)養(yǎng)狀態(tài)指數(shù)的評(píng)價(jià)結(jié)果不一致,前者評(píng)價(jià)的營(yíng)養(yǎng)狀態(tài)低于后者.類似情況在其他水體[10,42]也有出現(xiàn).印度邁索爾的10個(gè)湖泊(2010年)[43],太湖(2019年)[44]和白洋淀(2014年)[45]等湖泊兩種評(píng)價(jià)結(jié)果相近,主要是因?yàn)槠浜瓷鷳B(tài)系統(tǒng)中浮游植物多樣性與豐度較高,并且多樣性指數(shù)與環(huán)境因子有較好的相關(guān)性.而本研究中,四個(gè)湖泊的多樣性指數(shù)H￠,,與TN,TP以及TLI的相關(guān)性差異明顯,表明多樣性指數(shù)與營(yíng)養(yǎng)鹽的響應(yīng)關(guān)系不同,這可能是以H￠,,指數(shù)評(píng)價(jià)結(jié)果不一致的原因.同時(shí),SAL,TDS和pH值也與多樣性指數(shù)有顯著相關(guān)關(guān)系,表明這些因子可能影響浮游植物與營(yíng)養(yǎng)鹽的響應(yīng)關(guān)系.有研究表明,在地理跨度大,地形復(fù)雜的河流生態(tài)系統(tǒng),浮游植物并不是合適的水質(zhì)評(píng)價(jià)指標(biāo)[46],同樣湖泊浮游植物多樣性在經(jīng)度,緯度以及海拔等方面也顯現(xiàn)出很強(qiáng)的梯度變化[47],并且其顯著區(qū)域特征可能會(huì)在一定程度上削弱浮游植物與環(huán)境因子之間的關(guān)系.因此,目前形成的基于浮游植物多樣性的水質(zhì)評(píng)價(jià)標(biāo)準(zhǔn)并不適合在內(nèi)蒙古高原地區(qū)湖泊.對(duì)湖泊富營(yíng)養(yǎng)化評(píng)價(jià),應(yīng)當(dāng)充分考慮多樣性指標(biāo)及其主要的受控因子,并結(jié)合理化因子進(jìn)行多種方式綜合評(píng)價(jià).

表8 各湖泊營(yíng)養(yǎng)狀態(tài)評(píng)價(jià)結(jié)果

4 結(jié)論

4.1 呼倫湖,岱海,烏梁素海和居延海浮游植物種類數(shù)分別101種,44種,125種和42種.其中岱海浮游植物豐度最低藍(lán)藻最少,居延海浮游植物種類數(shù)最少藍(lán)藻優(yōu)勢(shì)度最大.

4.2 4個(gè)湖泊浮游植物共有33個(gè)優(yōu)勢(shì)種,各湖優(yōu)勢(shì)種組成存在明顯差異,TLI,,TDS,NH4+-N,SAL,pH值是影響優(yōu)勢(shì)種組成的主要因子.

4.3 基于浮游植物多樣性指數(shù)的富營(yíng)養(yǎng)評(píng)價(jià)結(jié)果顯著低于基于綜合營(yíng)養(yǎng)狀態(tài)指數(shù)的評(píng)價(jià)結(jié)果,目前的多樣性評(píng)價(jià)標(biāo)準(zhǔn)不適用于該區(qū)域水體評(píng)價(jià),建議使用生物評(píng)價(jià)和理化指標(biāo)評(píng)價(jià)等多種方法進(jìn)行綜合評(píng)價(jià).

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Characteristics of phytoplankton in cold and arid areas and their indicator of trophic status.

WANG Shi-huan, ZHANG Sheng*, WU Rong, SHI Xiao-hong, ZHAO Sheng-nan, SUN Biao

(IMAR Key Laboratory of Water Resources Protection and Utilization, Inner Mongolia Agricultural University, Hohhot 010018, China)., 2023,43(1)：311～320

To reveal the characteristics of phytoplankton community structure and their response to nutrient, phytoplankton and physicochemical indexes of water quality in Lake Hulun, Daihai, Ulansuhai and Juyanhai were sampled and investigated in July 2019 and July 2020. 101, 44, 125 and 42 phytoplankton species were identified in Lake Hulun, Daihai, Ulansuhai and Juyanhai with a total phytoplankton abundance of 5.71×105, 0.18×105, 3.45×105and 6.96×105cells/L, respectively.,andwere the dominant phyla. However, only 6dominant species were identified in Juyanhai, which was the least compared with more than 10 dominant species in the three other lakes. The dominant species of phytoplankton were mainly impacted by TLI,, TDS, NH4+-N, SAL and pH (<0.01). The mean values ??of phytoplankton Shannon-Wiener diversity (′), richness () and evenness () were 1.4, 0.38 and 2.79 in Hulun Lake, 2.28, 0.87 and 1.42 in Daihai, 2.99, 0.74 and 4.46 in Ulansuhai, 2.39, 0.75 and 0.75 in Juyanhai, which indicated the corresponding evaluation results were medium rich/medium/medium nutrition, medium/medium rich/poor nutrition, medium/poor medium/poor nutrition, medium /moderate/poor nutrition, respectively. However the evaluation results of the comprehensive nutrition index (TLI) were severe eutrophication, moderate eutrophication, mild eutrophication and moderate eutrophication, respectively. Obviously, the evaluation results of the three approaches were different. On the whole, the evaluation result of phytoplankton index was significantly lower than that of physical and chemical indicators. This might be because the three diversity indexes were not only affected by the comprehensive nutrition indexes like TP, TN, SD and Chl.a, but also significantly correlated with, pH, SAL and TDS. The analyzed results showed thatwas significantly correlated with all the indexes, while′ was significantly correlated with the indexes that were related to the comprehensive nutritional indexes andwas significantly correlated with T, pH, SAL and TDS. Therefore, the use of biological evaluation such as biodiversity alone may not be applicable to the lakes in the Inner Mongolia Plateau and it is suggested to use multiple evaluation methods in combination with physical and chemical indicators for a comprehensive evaluation.

cold and arid regions；phytoplankton；community structure；lake；nutritional status

X171.1

A

1000-6923(2023)01-0311-10

王世歡(1997-),男,內(nèi)蒙古巴彥淖爾人,碩士研究生,主要從事湖泊水環(huán)境污染物控制與修復(fù)研究.

2022-05-24

國(guó)家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2017YFE0114800,2019YFC0409204);國(guó)家自然科學(xué)基金資助項(xiàng)目(51869020,52060022,51909123)

* 責(zé)任作者, 教授, shengzhang@imau.edu.cn