水生態(tài)是指環(huán)境水因子對生物的影響和生物對各種水分條件的適應(yīng)。生命起源于水中，水又是一切生物的重要組分。生物體不斷地與環(huán)境進(jìn)行水分交換，環(huán)境中水的質(zhì)(鹽度)和量是決定生物分布、種的組成和數(shù)量，以及生活方式的重要因素。

　　水生態(tài)是什么

　　水生態(tài)是指環(huán)境水因子對生物的影響和生物對各種水分條件的適應(yīng)。生命起源于水中，水又是一切生物的重要組分。生物體內(nèi)必須保持足夠的水分：在細(xì)胞水平要保證生化過程的順利進(jìn)行，在整體水平要保證體內(nèi)物質(zhì)循環(huán)的正常運轉(zhuǎn)。生物體不斷地與環(huán)境進(jìn)行水分交換，環(huán)境中水的質(zhì)(鹽度)和量是決定生物分布、種的組成和數(shù)量以及生活方式的重要因素。生物的出現(xiàn)使地球水循環(huán)發(fā)生重大變化。土壤及其中的腐殖質(zhì)大量持水，而蒸騰作用將根系所及范圍內(nèi)的水分直接送回空中，這就大大減少了返回湖海的徑流。這使大部水分局限在小范圍地區(qū)內(nèi)循環(huán)，從而改變了氣候和減少水土流失。因此，不僅農(nóng)業(yè)、林業(yè)、漁業(yè)等領(lǐng)域重視水生態(tài)的研究，由人類環(huán)境的角度出發(fā)，水生態(tài)也日益受到更普遍的重視。

　　太陽輻射能和液態(tài)水的存在是地球上出現(xiàn)生命的兩個重要條件。水之所以重要，首先因為水是生命組織的必要組分;呼吸和光合作用兩大生命過程都有水分子直接參與;蛋白質(zhì)、核糖核酸、多糖和脂肪都是由小分子脫水聚合而成的大分子，并與水分子結(jié)合形成膠體狀態(tài)的大分子，分解時也必須加入相應(yīng)的水(水解作用)。

　　其次，水具備一些對生命活動有重要意義的理化特性：

　?、? 水分子具有極性，所以能吸引其他極性分子，有時甚至能使后者離子化。因此，水是電解質(zhì)的良好溶劑，是攜帶營養(yǎng)物質(zhì)進(jìn)出機(jī)體的主要介質(zhì)，各種生化變化也大都在體液中進(jìn)行。

　?、? 因水分子具有極性，彼此互相吸引，所以要將水的溫度(水分子不規(guī)則動能的外部表現(xiàn))提高一定數(shù)值，所要加入的熱量多于其他物質(zhì)在溫度升高同樣數(shù)值時所需的熱量。這點對生物的生存是有意義的。正因水的比熱大，生物體內(nèi)化學(xué)變化放出的熱便不致使體溫驟升超過上限，而外界溫度下降時也不會使體溫驟降以至低于下限。水分蒸發(fā)所需的熱量更大，因此植物的蒸騰作用和恒溫動物的發(fā)汗或喘氣，就成為高溫環(huán)境中機(jī)體散熱的主要措施。

　　③ 水分子的內(nèi)聚力大，因此水也表現(xiàn)出很高的表面張力：地下水能借毛細(xì)管作用沿土壤顆粒間隙上升;經(jīng)根吸入的水分在蒸騰作用的帶動下能沿樹干導(dǎo)管升至頂端，可高達(dá)幾十米;一些小昆蟲甚至能在水面上行走。

　　④ 水還能傳導(dǎo)機(jī)械力：植物借膨壓變化開合氣孔或舒縮花器和葉片;水母和烏賊靠噴水前進(jìn);蠕蟲的體液實際是一種液壓骨骼，軀干肌肉施力其上而向前蠕行。

　?、?水的透明度是水中綠色植物生存的必要條件。

　　⑥ 冰的比重小于液態(tài)水，因此在水面結(jié)成冰層時水生生物仍可在下面生活。否則氣溫低于 0℃時，結(jié)成的冰沉積底部，便影響水生生物的生存。

　　降水量的多少，對固著生長的植物影響更大，地區(qū)的降水量及灌溉條件常是決定作物產(chǎn)量的關(guān)鍵因素。長期處于比較穩(wěn)定的水分條件下的植物，如湖泊中的沉水植物或荒漠中的旱生植物，表現(xiàn)出高度特化的適應(yīng)性結(jié)構(gòu)。

　　地球表面約有15億立方公里的水，其中97%為海水。海洋面積接近陸地面積的兩倍半。水在陸地上的分布很不均勻，許多地區(qū)降雨量相差懸殊，而且局部氣溫也影響水分的利用。氣溫過高則水分的蒸發(fā)和蒸騰量可能大于降雨量，造成干旱;氣溫過低則土壤水分凍結(jié)，植物不能吸收，也形成生理性干旱。如果水中所含礦質(zhì)濃度過高(高滲溶液)，植物也不能吸收，甚至?xí)⒅参矬w液反吸出來，同樣形成生理性干旱。海水中氧氣、光照和一般營養(yǎng)物質(zhì)都較陸地貧乏，這些是決定海洋生物分布的主要因子，但生物進(jìn)化到陸地上，水卻又變成影響生物分布的主要生態(tài)因子。降雨量由森林經(jīng)草原到荒漠逐漸減少，生物也越來越稀少。

　　植物水生態(tài)

　　植物的抗旱性包含兩個層次：

　?、俦芎敌裕褐参镌谡w水平上靠增加吸水、加強(qiáng)輸水或貯水以及減少失水等措施來避免原生質(zhì)受到威脅。

　?、谀秃敌裕褐参锛?xì)胞原生質(zhì)本身能耐受失水。一般說來，高等植物主要依靠避旱性，而很多低等植物卻表現(xiàn)出高度耐旱性。依據(jù)細(xì)胞水平的抗旱性，可將原核生物及植物分為兩類：一類包括細(xì)菌、藍(lán)菌、地衣、低等綠藻和真菌，它們均具有缺乏中央液泡的小型細(xì)胞。外界干燥時，細(xì)胞脫水皺縮、生命過程也遲緩下來，但細(xì)胞微結(jié)構(gòu)不被破壞，一旦吸水，細(xì)胞又可恢復(fù)其代謝活性。它們比較能耐受干旱。另一類包括其他植物，它們的細(xì)胞均有一個中央大液泡，借以保證較穩(wěn)定的原生質(zhì)含水量，不過細(xì)胞本身卻不耐干旱，因此初進(jìn)化到陸地的恒水植物只能生存在潮濕的土壤上。及至植物發(fā)展出龐大的根系、隔水的角質(zhì)層以及可開合的氣孔后，植物體內(nèi)的細(xì)胞才能借助這些整體水平的機(jī)制來保持穩(wěn)定的含水量而不受外界濕度突然變化的影響。干旱地區(qū)植物的葉面積小，角質(zhì)發(fā)達(dá)，有的植物氣孔少而深陷，因此失水大為減少，仙人掌的葉甚至變?yōu)榇?，光合作用轉(zhuǎn)而由綠色的肉質(zhì)莖來完成。另一些旱生植物根系異常發(fā)達(dá)，氣孔多，蒸騰快，高速蒸騰在烈日下有助于降低葉溫，加強(qiáng)深根吸水的力量。根據(jù)植物對水分的適應(yīng)變化，一般將植物分為水生植物、濕生植物、中生植物和旱生植物4個類型。

　　動物水生態(tài)

　　水生動物的呼吸器官經(jīng)常暴露在高滲或低滲水體中，會丟失或吸收水分;陸地動物排泄含氮廢物時也總要伴隨一定的水分丟失;而恒溫動物在高溫環(huán)境中主要靠蒸發(fā)散熱來保持恒溫，這些都要通過水代謝來調(diào)節(jié)。水生動物 大多數(shù)無脊椎動物的體液滲透勢隨環(huán)境水體而變，只是具體離子的濃度有所差異。其他水生動物特別是魚類，其體液滲透勢不隨環(huán)境變化。海生軟骨魚血液中的鹽分并無特殊，但卻保留較高濃度的尿素，因而維持著略高于海水的滲透勢。它們既要通過腎保留尿素，又要通過腎和直腸腺排出多余的鹽分。但因為滲透勢較海水略高，所以不存在失水的問題。海生硬骨魚體內(nèi)鹽分及滲透勢均低于海水。其體表特別是鰓，透水也透離子，一方面是滲透失水，一方面離子也會進(jìn)入。海生硬骨魚大量飲海水，然后借鰓膜上的氯細(xì)胞將氯及鈉離子排出。淡水軟骨魚的體液滲透勢高于環(huán)境，其體表透水性極小，但不斷有水經(jīng)鰓流入。它靠腎臟排出大量低濃度尿液，并經(jīng)鰓主動攝入鹽分，來維持體液的相對高滲。某些溯河魚和逆河魚出入于海水和淡水之間，其鰓部能隨環(huán)境的變動由主動地攝入變?yōu)橹鲃拥嘏懦鲭x子，或反之。

　　陸生動物 具有濕潤皮膚的動物(如蚯蚓、蛞蝓和蛙類)經(jīng)常生活于潮濕環(huán)境，當(dāng)暴露于干燥空氣時會經(jīng)皮膚迅速失水。在陸地上*興旺的動物應(yīng)屬節(jié)肢動物中的昆蟲、蜘蛛、多足綱和脊椎動物中的爬行類、鳥類、哺乳類。昆蟲、蜘蛛的幾丁質(zhì)外皮上覆有蠟質(zhì)，可防蒸發(fā)失水，含有尿酸的尿液排至直腸后水分又被吸回體內(nèi)，尿酸以結(jié)晶狀態(tài)排出體外。它們在干燥環(huán)境中可能無水可飲，食物內(nèi)含水及食物氧化水便是主要水源。某些陸生昆蟲甚至能直接自空氣中吸取水分。很多爬行動物棲居干旱地區(qū)，它們的外皮雖然干燥并覆有鱗片，但經(jīng)皮蒸發(fā)失水的數(shù)量仍遠(yuǎn)多于呼吸道的失水。它們主要靠行為來攝水和節(jié)水，例如棲居于潮濕地區(qū)，包括荒漠地區(qū)的地下洞穴。爬行類和鳥類均以尿酸形式排出含氮廢物，尿酸難溶，排出時需尿液極少，從而減少失水。鳥和哺乳類因恒溫調(diào)節(jié)需要更多的水分供應(yīng)。除某些哺乳動物為降溫而排汗外，鳥和哺乳類的失水主要通過呼吸道。某些動物的鼻腔長，呼氣時水分再度凝結(jié)在溫度較低的外端的鼻腔壁上。它們也主要靠行為來節(jié)水，這包括躲避炎熱環(huán)境。

　　生物體內(nèi)的水分平衡取決于攝入量和排出量之比。生物受水分收支波動的影響還與體內(nèi)水存儲量有關(guān);同樣的收支差額對存儲量不同的生物影響不同：存儲量較大的受影響較小，反之則較大。對水生生物來說，水介質(zhì)的鹽度與體液濃度之比，決定水分進(jìn)出體表的自然趨向。如果生物主動地逆濃度梯度攝入或排出水分，就要消耗能量，而且需要特殊的吸收或排泌機(jī)制。對陸地生物來說，空氣的相對濕度決定蒸發(fā)的趨勢，但液體排泌大都是主動過程。大多數(shù)生物的體表不全透水，特別是高等生物，大部分體表透水程度很差，只保留幾個特殊部分作通道。在植物，地下根吸水，葉面氣孔則是蒸騰失水的主要部位，它的開合可調(diào)節(jié)植物體內(nèi)的水量。在較高等動物，飲水是受神經(jīng)系統(tǒng)控制的意識行為，水與食物同經(jīng)消化道進(jìn)入體內(nèi)，水和廢物主要經(jīng)泌尿系統(tǒng)排出。生物體的某些水通道也是其他營養(yǎng)物質(zhì)出入的途徑，例如光合作用所需 CO2也經(jīng)葉面氣孔攝入。因此光合作用常伴有失水。相比之下，陸地動物呼吸道較長，進(jìn)出氣往復(fù)運動，這使一部分水汽重復(fù)凝集于管道內(nèi)。不過水生動物的鰓卻經(jīng)常暴露在水中，在高滲海水中傾向失水，在淡水中則攝入大量水分。

　　水生態(tài)修復(fù)技術(shù)

　　1 兩岸造樹林河岸上應(yīng)盡可能留出空間，種植樹冠較大的樹木，逐步形成林帶，地面則栽上草坪，貼岸的樹冠還可以伸向河道上空。其作用之一，可以增強(qiáng)生態(tài)功能，大樹扎在土壤時深而密的根須與草坪形成一個土壤生物體系。其作用之二，可以發(fā)揮景觀作用，岸邊的林帶草坪，與河道組合，可以有效地改善這一地區(qū)的溫度、濕度與舒適度，形成一道獨特的風(fēng)景線。

　　2 河坡植草坪(或灌木)傳統(tǒng)的做法往往忽視生態(tài)，把河坡搞成直立式，或用塊石和水泥板覆蓋河坡并勾縫，其實，在不知不覺中已經(jīng)破壞了生物的生長環(huán)境。從修復(fù)水生態(tài)系統(tǒng)出發(fā)，有條件的河坡都應(yīng)植上草坪或灌木。護(hù)坡上的草坪和灌木所起的作用很大：一是草坪和灌木與土壤形成的土壤生物體系，同樣可以像兩岸的樹林與草坪一樣，起到減少**物對河道、湖泊的沖擊和營養(yǎng)化程度的作用，有些灌木的根須還能夠直接伸到水體中吸收水中的營養(yǎng)成分;二是河坡是水域向陸域的自然過渡帶，草坪和灌木與土壤的結(jié)合，改善了溫度、濕度，提供了食物;三是在穩(wěn)定邊坡，防止水土流失的同時，改變了護(hù)坡硬、直、光的形象，給人們以綠色、柔和、多彩的享受。

　　3 墻上攀綠藤城市化地區(qū)的部分河道，由于整個地區(qū)水面積的嚴(yán)重不足，為了確保水安全，提高河道汛期的蓄水量，不得已加高加固了防汛墻。彌補的辦法是，在墻的陸域一側(cè)種植綠色的爬藤植物，從下爬到上，到了頂以后從上爬到下，一直到水面;有條件的地區(qū)，在防汛墻的兩面墻上，可依墻分層而建一些條式和點式的花壇，種上灌木或花草;硬質(zhì)結(jié)構(gòu)的直立或斜坡式護(hù)坡，宜種植一些垂枝灌木。

　　4 水邊栽植物。水邊是水生態(tài)系統(tǒng)里一個非常重要的組成部分，要盡可能構(gòu)建挺水植物多樣性的環(huán)境。在種植方法上，一般可以直接栽在河邊的灘地上、斜坡上，也可栽在盆、缸及竹木框之類的容器做成的定床上;直立式防汛墻的下面，在不影響河道斷面的基礎(chǔ)上，利用河底淤泥在墻邊構(gòu)筑一定寬度，并有斜坡的濕地帶，創(chuàng)造挺水植物生長的條件。

　　5 水流多樣化新的河道治理理念，要求在基本滿足行洪需求的基礎(chǔ)上，宜寬則寬、宜彎則彎、宜深則深、宜淺則淺，形成河道的多形態(tài)，水流的多樣性。其作用有兩條：一是水流的多樣性，能夠滿足不同生物在不同階段對水流的需要;二是河道的多形態(tài)、水流的多樣性本身是水系景觀的一個重要組成部分。

　　6 水中建濕地河流、湖泊中的濕地，是修復(fù)水生態(tài)系統(tǒng)的一項重要手段，也可以稱土壤生物工程，國內(nèi)外有些中、小城市甚至用來處理城市的生活污水。河道與湖泊的治理中，在基本不影響行洪和槽蓄功能的前提下，應(yīng)盡可能保留和建設(shè)一些濕地，一切都要因地制宜。另外，濕地也是水景觀中不可多得的重要一筆，它充滿了野趣、野味和自然氣息，是人們回歸自然的一種象征。

　　7 水面養(yǎng)萍草水面上的植物有兩種，一種是根在水里的浮水植物，它們是水葫蘆、水葫貍等;另一種是根在河、湖底泥里的浮葉植物，它們是荷花、水鱉等。

　　8 水下種水草實踐證明，水草茂盛的水體，往往水質(zhì)很好，而且與眾不同的是清澈見底。人工種植水草，也是修復(fù)河道、湖泊水生態(tài)系統(tǒng)的重要一環(huán)。

　　9 水里養(yǎng)魚蝦在放養(yǎng)魚蝦時，要注意食草性、食雜性、食肉性之間的搭配。魚蝦在的水里自由洄游，在水面泛起陣陣漣漪，使河道、湖泊顯得生機(jī)蓬勃。

　　10 水底爬螺蚌螺蚌等貝殼類動物和大量的底棲動物，在水底形成了另一個世界，它們是名副其實的水底清道夫，其作用不可小看。

　　11 曝氧放細(xì)菌人們?nèi)庋劭床坏降募?xì)菌、真菌、放線菌、土壤原生動物等生物種群的生存和繁衍，無時不刻地將水中的**物質(zhì)分解成無機(jī)物質(zhì)和水，它們需要充足的氧氣，所以，應(yīng)盡量用各種方法和手段進(jìn)行曝氧，通過增加水體中氧氣的方法來促使好氧細(xì)菌的生長繁殖，以達(dá)到增強(qiáng)和加快分解水中**污染物的目的。

　　12 管理經(jīng)常化修復(fù)水生態(tài)系統(tǒng)，就是要通過人的努力，連接河道、湖泊中產(chǎn)生者-消費者-還原者的生物鏈，并積極地、經(jīng)常不斷地進(jìn)行必要的干預(yù)，促使其達(dá)到平衡。

上海瑞柘專業(yè)承接各種河道、湖泊、魚塘等水生態(tài)修復(fù)工程！詳情請致電：400-155-8689咨詢！

附：2021年12月國家發(fā)布的《河湖生態(tài)緩沖帶保護(hù)修復(fù)技術(shù)指南》

W020211215541263714758.pdf

　　Aquatic ecology refers to the influence of environmental water factors on organisms and the adaptation of organisms to various water conditions. Life originates from water, and water is an important component of all living things. Organisms constantly exchange water with the environment. The quality (salinity) and quantity of water in the environment are important factors that determine the distribution of organisms, the composition and quantity of species, and the way of life.

　　What is aquatic ecology

　　The influence of environmental water factors on organisms and the adaptation of organisms to various water conditions. Life originates from water, and water is an important component of all living things. Sufficient water must be kept in the organism: the smooth progress of biochemical process should be ensured at the cell level, and the normal operation of material circulation in the body should be ensured at the overall level. Organisms constantly exchange water with the environment. The quality (salinity) and quantity of water in the environment are important factors that determine the distribution of organisms, the composition and quantity of species, and the way of life. The emergence of organisms has brought about great changes in the earth's water cycle. The soil and its humus hold a large amount of water, and transpiration sends the water within the range of roots directly back to the air, which greatly reduces the runoff back to the lake and sea. This makes most of the water confined to a small area, thus changing the climate and reducing soil erosion. Therefore, not only agriculture, forestry, fisheries and other fields pay attention to the study of water ecology, but also from the perspective of human environment, water ecology is increasingly receiving more and more attention.

　　Solar radiation and the existence of liquid water are two important conditions for the emergence of life on earth. Water is important, first of all, because it is a necessary component of life tissue; Water molecules are directly involved in both respiration and photosynthesis; Proteins, ribonucleic acids, polysaccharides and fats are macromolecules formed by dehydration and polymerization of small molecules, which combine with water molecules to form colloidal macromolecules. Corresponding water (hydrolysis) must also be added during decomposition.

　　Secondly, water has some physical and chemical characteristics that are important to life activities:

　?、?Water molecules have polarity, so they can attract other polar molecules, and sometimes even ionize the latter. Therefore, water is a good solvent for electrolytes and the main medium to carry nutrients into and out of the body. Various biochemical changes are mostly carried out in body fluids.

　?、?Because water molecules are polar and attract each other, it is necessary to increase the temperature of water (the external expression of the irregular kinetic energy of water molecules) by a certain value, and the heat to be added is more than that of other substances when the temperature rises by the same value. This is significant for the survival of living things. Because of the large specific heat of water, the heat released by the chemical changes in the organism will not cause the body temperature to rise above the upper limit, and the temperature will not drop below the lower limit when the external temperature drops. Water evaporation requires more heat. Therefore, transpiration of plants and sweating or panting of thermostatic animals have become the main measures of body heat dissipation in high-temperature environment.

　?、?The cohesion of water molecules is large, so water also shows high surface tension: groundwater can rise along the gap of soil particles by capillary action; Driven by transpiration, the water absorbed through the root can rise to the top along the trunk duct, which can be as high as tens of meters; Some small insects can even walk on the water.

　　④ Water can also transmit mechanical force: plants open and close stomata or stretch flower organs and leaves by changing turgor pressure; Jellyfish and squid advance by spraying water; The body fluid of the worm is actually a kind of hydraulic bone, and the trunk muscle exerts force on it and crawls forward.

　?、?The transparency of water is a necessary condition for the survival of green plants in water.

　?、?The specific gravity of ice is less than that of liquid water, so aquatic organisms can still live below when ice forms on the water surface. Otherwise, when the temperature is lower than 0 ℃, the bottom of the ice deposit will affect the survival of aquatic organisms.

　　The amount of precipitation has a greater impact on fixed plants. Regional precipitation and irrigation conditions are often the key factors to determine crop yield. Plants that have been under relatively stable water conditions for a long time, such as submerged plants in lakes or xerophytes in deserts, show a highly specialized adaptive structure.

　　There is about 1.5 billion cubic kilometers of water on the earth's surface, 97% of which is sea water. The sea area is nearly two and a half times the land area. The distribution of water on the land is very uneven, the rainfall varies widely in many areas, and the local temperature also affects the use of water. If the temperature is too high, the evaporation and transpiration of water may be greater than the rainfall, resulting in drought; If the temperature is too low, the soil moisture will freeze and the plants will not absorb it, which will also lead to physiological drought. If the mineral concentration in the water is too high (hypertonic solution), the plants can not absorb it, and even the plant body fluid will be absorbed back, which will also form physiological drought. Oxygen, light and general nutrients in seawater are poorer than those in land, which are the main factors determining the distribution of marine organisms. However, when organisms evolve to land, water has become the main ecological factor affecting the distribution of organisms. The rainfall decreases gradually from forest to grassland to desert, and the living things are becoming scarce.

　　Plant water ecology

　　The drought resistance of plants includes two levels:

　?、?Drought avoidance: at the overall level, plants can avoid the threat of protoplasm by increasing water absorption, strengthening water transmission or storage and reducing water loss.

　　② Drought tolerance: plant cell protoplasm itself can tolerate water loss. Generally speaking, higher plants mainly rely on drought avoidance, while many lower plants show high drought tolerance. According to the drought resistance at the cellular level, prokaryotes and plants can be divided into two categories: one category includes bacteria, cyanobacteria, lichens, lower green algae and fungi, all of which have small cells lacking central vacuoles. When the outside world is dry, the cell dehydrates and shrinks, and the life process slows down, but the cell microstructure is not destroyed. Once the cell absorbs water, it can restore its metabolic activity. They are more tolerant to drought. The other includes other plants. Their cells have a large central vacuole to ensure a relatively stable water content of protoplasm. However, the cells themselves are not resistant to drought. Therefore, the constant water plants that first evolved to land can only survive in moist soil. Only when the plant develops a huge root system, water-proof cuticle and openable stomata can the cells in the plant use these overall level mechanisms to maintain a stable water content without being affected by sudden changes in external humidity. In arid areas, plants have small leaf area and developed cutin. Some plants have few and deep stomata, so the water loss is greatly reduced. Cactus leaves even turn into thorns, and photosynthesis is completed by green fleshy stems. Other xerophytes have exceptionally developed roots, many stomata and fast transpiration. High-speed transpiration helps to reduce leaf temperature and strengthen the power of deep roots to absorb water in the hot sun. According to the adaptation of plants to water, plants are generally divided into four types: aquatic plants, hygrophytes, mesophytes and xerophytes.

　　Aquatic ecology of animals

　　The respiratory organs of aquatic animals are often exposed to high or low permeability water bodies, which will lose or absorb water; The excretion of nitrogen-containing wastes by terrestrial animals is always accompanied by a certain loss of water; Thermostatic animals mainly rely on evaporation and heat dissipation to maintain constant temperature in high-temperature environment, which should be regulated by water metabolism. The osmotic potential of most aquatic animals and invertebrates varies with the environmental water body, but the concentration of specific ions is different. The osmotic potential of other aquatic animals, especially fish, does not change with the environment. There is no special salt in the blood of marine cartilaginous fish, but it retains a higher concentration of urea, thus maintaining a slightly higher osmotic potential than that of seawater. They not only retain urea through the kidney, but also excrete excess salt through the kidney and rectal glands. However, since the seepage potential is slightly higher than that of seawater, there is no water loss problem. The salt content and osmotic potential of marine bony fish were lower than that of seawater. Its body surface, especially gills, is permeable to water and ions. On the one hand, it is permeable to water, and on the other hand, ions will enter. The marine bony fish drink a lot of seawater, and then use the chlorine cells on the gill membrane to discharge chlorine and sodium ions. The osmotic potential of freshwater cartilaginous fish is higher than that of the environment, and the water permeability of its body surface is very small, but water is constantly flowing through the gills. It relies on the kidney to excrete a large amount of low concentration urine, and takes in salt actively through the gill to maintain the relative hypertonic of body fluid. Some anadromous and anadromous fishes enter and leave between seawater and freshwater, and their gills can change from active intake to active discharge of ions with the change of environment, or vice versa.

　　Terrestrial animals animals with moist skin (such as earthworms, slugs and frogs) often live in humid environment. When exposed to dry air, they will quickly lose water through the skin. The most prosperous animals on land should belong to insects, spiders, polypods in arthropods and reptiles, birds and mammals in vertebrates. The chitin skin of insects and spiders is covered with wax, which can prevent evaporation and water loss. After the urine containing uric acid is discharged into the rectum, the water is absorbed back into the body, and the uric acid is discharged out of the body in a crystalline state. They may have no water to drink in a dry environment, and the water contained in food and the oxidized water of food are the main water sources. Some terrestrial insects can even draw water directly from the air. Many reptiles live in arid areas. Although their skin is dry and covered with scales, the amount of water loss through skin evaporation is still far more than that of respiratory tract. They take water and save water mainly by behavior, such as living in underground caves in humid areas, including desert areas. Reptiles and birds discharge nitrogen-containing wastes in the form of uric acid, which is difficult to dissolve and requires very little urine during discharge, so as to reduce water loss. Birds and mammals need more water supply due to thermostatic regulation. Except that some mammals sweat for cooling, the loss of water in birds and mammals is mainly through the respiratory tract. In some animals, the nasal cavity is long. When exhaling, water condenses again on the nasal wall at the outer end of the lower temperature. They also save water mainly by behavior, including avoiding the hot environment.

　　The water balance in an organism depends on the ratio of intake to output. The influence of water budget fluctuation on organism is also related to water storage in vivo; The same balance of payments has different effects on organisms with different storage capacity: those with larger storage capacity are less affected, and vice versa. For aquatic organisms, the ratio of salinity of water medium to body fluid concentration determines the natural trend of water entering and leaving the body surface. If organisms actively ingest or expel water against the concentration gradient, they will consume energy and need special absorption or excretion mechanisms. For terrestrial organisms, the relative humidity of air determines the trend of evaporation, but liquid excretion is mostly an active process. The body surface of most organisms is impervious, especially for higher organisms. Most of the body surface is poorly permeable, and only a few special parts are reserved as channels. In plants, the underground root absorbs water, and the leaf stoma is the main part of transpiration water loss. Its opening and closing can regulate the water content in plants. In higher animals, drinking water is a conscious behavior controlled by the nervous system. Water and food enter the body through the digestive tract, and water and waste are mainly discharged through the urinary system. Some water channels of organisms are also the way for other nutrients to enter and leave. For example, CO2 required for photosynthesis is also absorbed through leaf stomata. Therefore, photosynthesis is often accompanied by water loss. In contrast, the respiratory tract of terrestrial animals is long, and the air in and out moves back and forth, which makes part of the water vapor repeatedly agglutinate in the pipeline. However, the gills of aquatic animals are often exposed to water, tend to lose water in hypertonic seawater, and absorb a large amount of water in fresh water.

　　Water ecological restoration technology

　　1. Create trees on both banks. As far as possible, space should be reserved on the bank to plant trees with large crowns to gradually form a forest belt. The ground should be planted with lawns. The crowns close to the bank can also extend over the river. One of its functions is to enhance the ecological function. When the big tree is rooted in the soil, the deep and dense roots form a soil biological system with the lawn. Second, it can play the role of landscape. The Forest Lawn along the bank, combined with the river, can effectively improve the temperature, humidity and comfort of this area, forming a unique landscape.

　　2 the traditional practice of planting lawns (or shrubs) on the river slope often ignores the ecology, making the river slope vertical, or covering the river slope with stones and cement boards and pointing the joints. In fact, it has unconsciously damaged the biological growth environment. Starting from the restoration of water ecosystem, lawns or shrubs should be planted on river slopes where conditions permit. Lawns and shrubs on the slope protection play a great role: first, the soil biological system formed by lawns, shrubs and soil can also reduce the impact of organic matter on rivers and lakes and the degree of eutrophication like the trees and lawns on both banks. The roots of some shrubs can also directly extend into the water body to absorb nutrients in the water; Second, the river slope is a natural transition zone from water area to land area. The combination of lawn, shrub and soil improves the temperature, humidity and provides food; Third, while stabilizing the slope and preventing water and soil loss, it has changed the image of hard, straight and light slope protection, giving people green, soft and colorful enjoyment.

　　3. Due to the serious shortage of water area in the whole area, in order to ensure water safety and improve the water storage capacity of the river in the flood season, the flood control wall has to be raised and reinforced. The remedy is to plant green climbing rattan plants on the land side of the wall, climbing from bottom to top, and then climbing from top to bottom until reaching the water surface; In areas where conditions permit, on both sides of the flood control wall, some strip and dot flower beds can be built according to the wall layers, and shrubs or flowers and plants can be planted; For vertical or sloping slope protection with hard structure, it is appropriate to plant some vertical shrubs.

　　4. Plants planted near the water. Waterside is a very important part of the aquatic ecosystem. It is necessary to build an environment of emergent plant diversity as much as possible. In terms of planting method, it can be planted directly on the beach and slope along the river, or on the fixed bed made of containers such as pots, VATS and bamboo and wood frames; Under the vertical flood control wall, on the basis of not affecting the river section, a wet zone with a certain width and slope is constructed by using the river bottom silt at the side of the wall to create conditions for the growth of emergent plants.

　　5. The new river regulation concept of water flow diversification requires that, on the basis of basically meeting the flood discharge demand, the river should be wide, curved, deep and shallow to form a multi form of the river and the diversity of water flow. It has two functions: one is the diversity of water flow, which can meet the needs of different organisms for water flow at different stages; Second, the multi form of river channel and the diversity of water flow are an important part of water system landscape.

　　6. Building wetlands in water wetlands in rivers and lakes is an important means to repair the aquatic ecosystem, which can also be called soil bioengineering. Some medium and small cities at home and abroad are even used to treat urban domestic sewage. In the treatment of rivers and lakes, some wetlands should be preserved and constructed as far as possible, and everything should be adapted to local conditions, on the premise that the flood discharge and channel storage functions are basically not affected. In addition, wetland is also a rare and important part of the water landscape. It is full of wild interest, game and natural flavor. It is a symbol of people's return to nature.

　　There are two kinds of plants on the water surface, one is floating plants with roots in the water, they are water hyacinth, water hyacinth, etc; The other is floating leaf plants rooted in the mud at the bottom of rivers and lakes. They are lotus, water turtle, etc.

　　The practice of planting aquatic plants under water has proved that the water body with lush aquatic plants often has good water quality, and the difference is that it is crystal clear. Artificial planting of aquatic plants is also an important part of restoring the aquatic ecosystem of rivers and lakes.

　　9. When raising fish and shrimp in the water, pay attention to the combination of herbivorous, miscellaneous and carnivorous. Fish and shrimps move freely in the water, rippling on the surface of the water, making the rivers and lakes look vibrant.

　　Shellfish, such as clams, snails and mussels, and a large number of benthic animals have formed another world under the water. They are truly underwater scavengers, and their role cannot be underestimated.

　　11 oxygen exposure bacteria the survival and reproduction of bacteria, fungi, actinomycetes, soil protozoa and other biological populations invisible to the naked eye constantly decomposes organic substances in water into inorganic substances and water. They need sufficient oxygen. Therefore, various methods and means should be used for oxygen exposure to promote the growth and reproduction of aerobic bacteria by increasing oxygen in water, So as to enhance and accelerate the decomposition of organic pollutants in water.

　　The management of regular restoration of aquatic ecosystem is to connect the producer consumer restorer biological chain in rivers and lakes through human efforts, and actively and frequently carry out necessary interventions to promote its balance.