【作者】 杨明生；

【导师】 熊邦喜；

【作者基本信息】 华中农业大学 ， 水产养殖， 2009， 博士

【摘要】 大型底栖动物(Macrozoobenthos)是湖泊生态系统中的重要组成部分,具有重要的生态功能。它可以加速水底有机碎屑的分解和利用,调节泥--水界面的物质交换,促进水体自净；同时本身也是湖泊生态系统中食物链的重要环节,而且部分大型底栖动物(螺、蚌)具有直接利用的经济价值。水生昆虫中的摇蚊幼虫在富营养湖泊中的密度大,能摄食消化大量的沉积有机碎屑,成虫羽化后离开水体飞往陆地。可作为湖泊沉积物中N、P的有效利用者和清除者,可为湖底沉积的大量营养物的清除开辟一条新途径；另一方面,通过食物链,大型底栖动物为鱼所摄食后转化为鱼产品,通过捕获从水体中取出,是清除湖泊中N、P的又一途径。进入20世纪80年代以来,随着工业化和城市化的不断发展,人口的剧增,加上不合理的渔业行为,湖泊的富营养化程度越来越高,湖泊环境发生了显著改变。湖泊环境的变化,特别是富营养化后对大型底栖动物带来什么样的影响,大型底栖动物又会采取哪些生态响应,缺乏系统研究。为此,以武汉市南湖为例,对浅水富营养湖泊中的大型底栖动物的群落结构、时空分布、主要优势类群的N和P的含量及对N、P的释放和清除效率、繁殖和与鱼类的关系等问题进行了研究,主要结果如下：1、在南湖共采集到大型底栖动物34种,其中寡毛类7种,软体动物4科12种,水生昆虫12种,其它动物3种。湖心区定量采样中只发现寡毛类和水生昆虫幼虫,没有采到活体的软体动物。寡毛类目前主要由耐污种类组成,其年平均密度为3802ind/m2,最高达16576 ind./m2。水生昆虫中摇蚊幼虫的优势种为刺铗长足摇蚊Tanypus punctipennis (Fabricius),年均密度为730 ind./m2,其次为红裸须摇蚊Propsilocerus akamusi (Tokunaga),年均密度为50 ind./m2。从季节分布看,霍甫水丝蚓Limnodrilus hoffmeisteri Claperede以春季的5月份密度最大,夏季的8月份密度最低；刺铗长足摇蚊T.punctipennis和红裸须摇蚊P. akamusi的幼虫密度均以秋季的11月份最大。2、南湖大型底栖动物在湖底沉积物中的最大分布深度为25 cm,主要集中在0-15cm深度范围内。0-20 cm深度范围内,寡毛类占到了30 cm柱样中同类总量的99.28%,摇蚊幼虫占同类总量的99.31%,20 cm深度的样品,大型底栖动物的采集量可达到99%以上；实验室模拟,也证实其垂直迁移幅度不会超过20 cm深度。梨形环棱螺Bellamya aeruginosa和铜锈环棱螺Bellamya purificata 24 h运动的水平距离是不一样的,梨形环棱螺B. purificata最远达7m,平均为3.4 m；而铜锈环棱螺B.aeruginosa的最远距离为3.6 m,平均为2.4 m。3、南湖中大型底栖动物的生物多样性较低,优势种主要为寡毛类和摇蚊幼虫,其总生物量分别为176759.35 kg和46810.30 kg,其次为螺类,生物量为899.34kg,它们能够转移或清除的TN、TP量分别为3463.61kg和350.92 kg,大型底栖动物对南湖中N和P的清除是一条重要途径。但大型底栖动物的TN量只占到水体TN量的2.49%,因此,南湖在完全实现截污前,大型底栖动物从湖泊中清除N和P的量是有限的。颤蚓和摇蚊幼虫可以促进湖泊底泥中氮和磷的释放,其密度与释放量紧密相关；颤蚓在湖泊沉积物中氮和磷的循环与转化方面扮演了重要的角色。4、铜锈环棱螺B. aeruginosa的绝对繁殖力平均为63.97个,其中最大怀胚数为169个,最小怀胚数为4个,相对繁殖力为26.85个/克。而梨形环棱螺B. purificata的绝对繁殖力平均为38.57个,其中最大怀胚数为115个,最小怀胚数为3个,相对繁殖力为23.28个/克。铜锈环棱螺B. aeruginosa 3月开始产仔螺,而梨形环棱螺B.purificata要到4月才开始产仔螺。耳萝卜螺Radix auricularia 3月上旬开始产卵(水温8-12℃),繁殖高峰期在3、4月份,5月份以后产卵量和产卵次数均下降。产卵最适水温为16～24℃,在繁殖高峰期,可多次产卵。两次产卵的间隔期在1-10d之间,一般为1-3d。性成熟的个体一生可产4-5个卵囊,而每个卵囊中的怀卵量可达几十个到几百个。耳萝卜螺R. auricularia卵的受精率一般为95%-100%。平均孵化率为95.28%,最高可达100%,最低为85.7%。孵化时间与水温密切相关,水温越高,孵化时间越短。5、摇蚊幼虫集中羽化的时间有两次,主要为春末夏初的4-5月和秋末冬初的11-12月。两种摇蚊的个体繁殖力和卵囊结构均有所不同,刺铗长足摇蚊T. punctipennis的个体绝对繁殖力平均为665.7粒,红裸须摇蚊P. akamusil的个体绝对繁殖力超过1000粒。6、南湖0～10 cm深度范围内,水生植物残体量与水栖寡毛类和摇蚊幼虫的分布密度之间紧密相关,随着水生植物残体量的减少,水栖寡毛类和摇蚊幼虫的分布密度也会降低。TN与沉积深度相关不显著。在垂直分布上,水生植物残体的TP与沉积深度呈紧密负相关,即沉积年代越早,TP含量越低,沉积年代越晚,TP含量越高,较好地反映了南湖中营养盐类的变化情况。研究认为,水生植物残体可作为一种研究湖泊沉积学新的证据材料。7、鱼类对饵料生物(包括底栖动物)会产生下行效应(top-down)。在南湖中由于水草完全消失,发现鲤和鲫的繁殖行为被迫进行改变,由草上产卵变为在岸边的岩石上产卵。湖边及水中的岩石既是软体动物中螺类的栖息地和产仔地,也是摇蚊和鲤、鲫的产卵场所,同时也是摇蚊幼虫和鲤、鲫鱼苗的孵化场所,于是在栖息生境上出现了重叠,在同一岩石上共同构成一个复杂的群落。环棱螺成为了群落中的顶级消费者,由于捕食作用,会严重影响到鱼卵和摇蚊幼虫的孵化率,进而影响到产粘性卵的底层鱼类和水生昆虫新个体的产生和种群数量的增加。因此,螺类对产粘性卵的鱼类的繁殖和资源增殖所带来的影响不容忽视。更多还原

【Abstract】 Macrozoobenthos is an important part of the lake ecosystem which has many ecology functions, such as accelerating the decomposition of the organics detritus, adjusting the substantial exchange of mud-water microcosms and promoting the self-cleaning of the water bodies. Meanwhile, macrozoobenthos itself is a significant link in the food chain in the lake ecosystem. The density of Chironomid larvae in the eutrophic lake is high. They can consume a large amout of organics detritus before the adult emergence and fly away to land. As the cleaner of nitrogen and phosphorus contained in sediments, macrozoobenthos broke a new path to clean nurition accumulated at the bottom of the lake. On the other hand, macrozoobenthos can be ingested by fish through food chain and then fished out of the water bodies, which makes another way to clean nitrogen and phosphorus in lakes.Since 1980s, as the development of industry and urbanization and the booming popultion of human being as well as the inappropriate fishing, the eutrophic degree of lakes has become higher and higher. Consequently, the envrionment changed dramatically. What is the effect on macrozoobenthos brought by the changed envrionment and what will macrozoobenthos do as a response? Research on these problems is lacking. In order to find the answers to these questions, we have studied the community structure, temporal and spatial distribution of macrozoobenthos in Nanhu Lake, a shallow eutrophic lake. We have also studied the relation between the release, as well as reproducing of nitrogen and phosphorus and fish. The results of our study are as follow:1. We have collected 34 kinds of macrobenthos from the Nanhu Lake in total, which includes 7 kinds of Oligochaeta,12 kinds of Mollusca,12 kinds of aquatic insects and 3 kinds of other animals. Only Oligochaeta and aquatic insects larval have been found in the epilimnion while no living mollusk has been found. Oligochaeta was mainly composed by tolerant species, with an annually average density of 3802 ind/m2 and the maximum reached 16576 ind/m2. The preponderant Chironomid larva of aquatic insects was Tanypus punctipennis with an annually average density of 730 ind/m2. Next to T. punctipennis was Propsilocerus akamusi, with an annually average density of 50 ind/m2. From the aspect of seasonal distribution, the largest density of Limnodrilus hoffmeisteri was in May while the least in August and the largest density of both T. punctipennis and P. akamusi were in November.2. The largest depth of macrozoobenthos was 25 cm and the depth range of major distribution was 0～15cm. In 30cm sediment core, the content of Oligochaeta within the depth of 0-20cm took up 99.28% of the total and the percentage of Chironomid larvae was 99.31%. in 20cm sediment core, the amount of macrozoobenthos was above 99% of the total. The horizontal motion distance in 24h of B. purificata and B. aeruginosa are different from each other. The maximum distance of the former is 7 m and the average distance is 3.4 m, while the figures of the latter are 3.6 m and 2.4 m.3. The biodiversity of macrozoobenthos in the Nanhu Lake is comparatively low. The dominant species are Oligochaeta and Chironomid larvae and the biomass of the two are 176759.35kg and 46810.30kg, respectively. Next to Oligochaeta and Chironomid larvae are freshwater snails, the biomass of which is 899.34 kg. The total nitrogen and total phosphorus transferred or removed by Oligochaeta as well as Chironomid larvae and freshwater snails are 3463.61kg and 350.92 kg respectively. As a result, macrozoobenthos is an important approach to remove nitrogen and phosphorus in the Nanhu Lake. However, the total nitrogen of macrozoobenthos takes up only 2.49% of the whole water body, so the nitrogen and phosphorous removed by macrozoobenthos is very limit before sewage interception is completely realized in the Nanhu Lake.4. The average absolute fecundity, the maximum and the minimum number of embryo and the relative fecundity of B. aeruginosa are 63.97 eggs,169 eggs,4 eggs and 26.85 eggs/g. While the figures of B. purificata are 38.57 eggs,115 eggs,3 eggs and 23.28 eggs/g. B. aeruginosa begins to spawn from March while B. purificata begins from April. Radix auricularia begins to spawn from the beginning of March (water temperature 8～12℃), and the peak appears in March or April. After May, both the fecundity and the frequency of spawning decline. The most suitable water temperature for spawning is 16～24℃. R. auricularia can spawn several times at the peak of fecundity and the interval between two spawning is 1～10 days, but normally 1-3 days. Mature individuals may spawn 4-5 oocysts during the whole life and the amount of eggs of each oocyst vary from dozens to hundreds. The fertilization rate of R. auricularia normally is 95% to 100%. The average hatching rate is 95.28%, while the maximum is 100% and the minimum is 85.7%. Incubation time is highly related to water temperature. The higher the water temperature is, the shorter the incubation time will be. 5. The centralized adult emergence of Chironomid larvae appears twice a year and normally appears in April to May and November to December. There are some differences between both the individual fecundity and the structure of oocyst. The average individual absolute fecundity of T. punctipennis is 665.7 while the figure of P. akamusil is more than 1000.6. In the Nanhu Lake, within the depth range between 0cm and 10cm, the density of Oligochaeta and Chironomid larvae is highly related to the amount of aquatic plant residues. As the amount of aquatic plant residues declines, the density of Oligochaeta and Chironomid larvae declines, too. The relation between total nitrogen and sediment depth is not obvious. In terms of vertical distribution, there is a highly negative relation between total phosphorous of aquatic plant residues and sediment depth. That is to say, the earlier the sedimentary age is, the lower the total phosphorous will be. This relationship can illustrate the change of nutritional salts in the Nanhu Lake very well. Aquatic plant residues can serve as an evidence for sedimentology of lake.7. Fish can cause a top-down effect on food organisms (including benthic animal). Cyprinus carpio haematopterus and Carassius auratus auratus are compelled to change their reproductive behavior, changing their spawning place from the grass to the rocks along the shore of the lake. The rocks along the shore are not only the habitat and spawn place of snails, but also the spawn place of Chironomid and C. carpio haematopterus and C. auratus auratus. Meanwhile, they are also the hatching place of Chironomid larvae, fry of C. carpio haematopterus and C. auratus auratus. So there is overlap in terms of geographical distribution. Complicated assemblage is formed on the same rocks. Bellamy a occupies the top of the food chain, so it can affect the hatching rate of fishes’s adhesive eggs and Chironomid larvae through predation, so as to affect the increase of both demersal fishes’s and aquatic insects’population. Therefore, the effect on the breeding and resource enhancement of demersal fishes brought by freshwater snail cannot be ignored.更多还原