【作者】 张贵刚；

【导师】 韩博平；

【作者基本信息】 暨南大学 ， 环境科学， 2010， 硕士

【摘要】 为认识我国南亚热带地区以杂食性鱼类为主的水库中级联反应的特点,本论文于2009年9-11月在贫-中营养水库-流溪河水库进行了大型围隔(体积约为85 m3)实验。包括控制组在内,共5个处理,每个处理有3个重复。控制组为水库原水,不添加营养盐和罗非鱼；处理组：1)在水库原水中添加营养盐(N、P)；2)水库原水中添加罗非鱼；3)在水库原水中添加营养盐和罗非鱼；4)在水库原水中添加罗非鱼和3倍营养盐。所有的N／P(质量比)都是10／1；添加罗非鱼的密度为2g／m3。水化测定与浮游生物定量样品采样每周一次,共6次采样,通过比较添加营养盐组与空白组,分析了浮游生物对营养盐的响应；比较添加罗非鱼组与空白组,或者添加营养盐的有鱼组与无鱼组作比较,分析了鱼对浮游生物的作用。在围隔实验中,在2无鱼组围隔(一个是空白组,另一个是添加营养盐组)中,浮游植物丰度和生物量都升高,添加营养盐使浮游动物的丰度和生物量显著增加。添加营养盐组中,鱼的存在使浮游植物丰度和生物量明显增加；鱼的存在对浮游动物的丰度无显著影响,但使浮游动物生物量降低。从浮游动物优势种来看,在无鱼情况下,添加营养盐使舌状叶镖水蚤、剑水蚤、网纹溞、裸腹溞、秀体溞、象鼻溞等的丰度和生物量均增加；而添加营养盐情况下,罗非鱼的存在使得枝角类的丰度和生物量降低,但是对舌状叶镖水蚤无明显影响。轮虫的优势种具有明显的更替现象,在丰度上,实验的前3周以螺形龟甲轮虫、圆筒异尾轮虫、对棘异尾轮虫、Trichocerca chattoni (T.c)等为主要优势种,此后这些种类的丰度急剧下降,方形臂尾轮虫、剪形臂尾轮虫、Brachionus dolabratus (B.d)等急剧增加,成为优势种,而这种更替现象可能是鱼类的摄食影响了这些种类在养鱼围隔中增加的幅度,以及营养盐的添加使得可食性藻类的大量繁殖导致其更替现象的发生。轮虫生物量与其丰度有相同的变化趋势。桡足类的优势种以无节幼体、桡足幼体,舌状叶镖水蚤、中剑水蚤等为主,枝角类的网纹溞、裸腹溞、象鼻溞等的丰度和生物量均明显地受到鱼类捕食的影响。但是在食物条件充足的情况下,可以缓解罗非鱼对象鼻溞和秀体溞丰度的影响。上述结果表明,在我国南亚热带水库中,当鱼类的生物量较低或不存在时,滤食性枝角类可能成为优势种群。在不同营养盐梯度对比下,杂食性鱼类的存在并没有降低级联反应的强度。更多还原

【Abstract】 In order to understand trophic cascades effects of omnivorous fish (tilapia) in warm waters, an enclosure experiment was carried out in Liuxihe Reservoir, an oligo-mesotrophic water body, from September 10 to November 14 of 2009, lasting 6 weeks.15 large enclosures in total were used, each enclosure has a water volume of 85 m3. There are 5 treatments, there are three replicates for each treatment. In the control treatment (C), the water was pumped from the reservoir after filtering small fish, other four treatments included:1) adding low nutrients (N、P) to enclosure in the filtered reservoir water (LN),2) adding tilapia with a biomass of 2g/m3 (F); 3) adding nutrients and tilapia (LNF); 4) adding tilapia and high nutrients (three times higher than in LN) (HNF).The N/P (mass ratio) of 10/1 was fixed in all the treatments. Water quality variables and quantitative plankton samplings were measured or taken every week (7 days). The response of plankton to nutrient addition was analyzed through the nutrients enrichment treatments and controls. Top-down effects of tilapia on plankton were analyzed between the fish treatments and only nutrient enrichment treatments.In two no fish treatments (C and LN treatments), the abundance and biomass of phytoplankton increased, but significantly in the LN. In the treatments without fish, the abundance and biomass of zooplankton increased markedly in nutrients enrichment treatments (LN). However, fish treatments only had slight effects on the abundance of zooplankton but decreased their biomass significantly.In all the encousres, zooplankton were dominated by copepods, such as Phyllodiaptomus tunguidus, Mesocyclops thermocyclopoides. The cladocerans were mainly composed of Bosmina longirostris, Moina micrura, Diaphanosoma orghidani and Ceriodaphnia cornuta. In the treatments with fish (F and LNF), the abundance and biomass of cladocerans were reduced, but little influence to Phyllodiaptomus tunguidus was detected.The dominant species of rotifer showed an evident temporal succession in the adding nutrients treatments. In the first 3 weeks, Keratella cochlearis, Trichocerca cylindrica, Trichocerca stylata and Trichocerca chattoni were primary dominant species in abundance, and their abundance sharply decreased from the third week. On the other hand, Brachionus quadridentatus, Brachionus forficula and Brachionus dolabratus increased quickly. Even if they were suppressed by fish predation in the fish treatments, nutrient enrichments improved edible phytoplankton. The rotifer biomass showed a variation pattern similar to the abundance. The copepods were dominated naupli, copepodites, Phyllodiaptomus tunguidus, Mesocyclops thermocyclopoides. The abundance and biomass of Bosmina longirostris, Moina micrura and Ceriodaphnia cornuta was evidently influenced by fish predation. When edible phytoplankton was abundant, the predation pressure seems to be buffered in Bosmina longirostris and Diaphanosoma orghidani.These results indicate that cladocerans could become the dominant population only in water bodies without fish or with low fish biomass in the warm water. By comparing nutrient enrichments, the omnivorous tilapia does not decrease trophic cascade effects when large calanoids replace Cladocera in dominance.更多还原