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题名: 长江中下游浅水湖泊的浮游动物群落结构研究
作者: 王松波
答辩日期: 2008-06-12
导师: 谢平
授予单位: 中国科学院水生生物研究所
授予地点: 水生生物研究所
学位: 博士
关键词: 总磷 ; 叶绿素 a ; 种类组成 ; 典型对应分析 ; 捕食 ; 温度 ; 平均体长 ; 浮游动物牧食 ; 冗余分析 ; 变异分解 ; 形态特征 ; 平均怀卵量 ; 内禀增长力
其他题名: Zooplankton structure in shallow lakes along the middle and lower reaches of the Yangtze River
摘要: 本文选取长江中下游地区的30个浅水湖泊作为研究对象。我们首先探讨了浮游甲壳动物的群落结构特征以及它们的分布与环境因子之间的关系,检验了两个假设:(1)在不同营养条件的湖群中,浮游甲壳动物的生物量与营养状态指标之间的关系具有一致性;(2)养殖湖泊中大的浮游甲壳动物结构也意味着大的牧食压力。然后评价了在亚热带的浅水湖泊中,营养盐和浮游动物对浮游植物生物量控制的相对重要性,以及理化因子和浮游甲壳动物在决定轮虫密度和种类分布上的相对重要性。最后,通过生活史的实验,探讨了养殖湖泊中的优势枝角类微型裸腹溞(Moina micrura)对高浓度鱼类化学信息素的响应,对它们在鱼类捕食下依然是优势种的可能机制进行了讨论。 研究湖泊的营养水平波动很大,总磷(TP)和叶绿素a(Chl a)的变化范围分别为0.008~1.448 mg L-1和0.7~146.1 µg L-1。一共鉴定到了38个种属;其中枝角类20属25种,桡足类11属13种。最常见的和占优势的种类为简弧象鼻溞(Bosmina coregoni)、微型裸腹溞(Moina micrura)、短尾秀体溞(Diaphanosoma brachyurum)、近邻剑水蚤(Cyclops vicinus)、台湾温剑水蚤(Thermocyclops taihokuensis)、南方中剑水蚤(Mesocyclops notius)和汤匙华哲水蚤(Sinocalanus dorrii)。大型的溞属(Daphnia)密度一般很小。从中营养到超富营养的湖泊中,浮游甲壳动物群落结构总的变化趋势是:大型植食性枝角类(Daphnia)的优势地位逐渐降低,与之相伴随的是剑水蚤(Cyclops,Thermocyclops,Mesocyclops)和小型枝角类(Moina,Diaphanosoma)的优势地位不断增加。典型对应分析显示除了4个特别的种外(D. hyalina、S. dorrii、C. vicinus、M. micrura),其余的优势种类对环境因子具有相同的喜好。温度、肉食性的剑水蚤和浮游生物食性鱼类似乎是决定种类分布的关键因子。 枝角类和桡足类的生物量在各个湖泊中的变异也很大。在大部分的湖泊中,枝角类的生物量占主体。TP对浮游动物生物量的预测能力要强于Chl a。然而在三类湖群中,浮游甲壳动物的生物量与营养状态指标之间并没有一致的关系出现,可能的原因是下行效应和上行效应对浮游动物的控制是随着湖泊的营养水平而变化的。浮游甲壳动物与浮游植物生物量之间显著负相关关系的缺失表明:在这些浅水的亚热带湖泊中大型浮游动物对浮游植物的控制作用有限。 浮游甲壳动物的平均体长与Chl a(r2 = 0.40, P = 0.000)和TP显著正相关(r2 = 0.38, P = 0.000),与经验性的研究相反。然而,浮游动植物生物量的比值却与TP(r2 = 0.27, P = 0.005)和平均体长(r2 = 0.46, P = 0.000)显著负相关。同时大小结构在解释Chl a-TP残差的分布变异时并没有显著的贡献(P = 0.231)。这些结果显示大的浮游甲壳动物大小结构并不总是意味着大的牧食压力。在养殖湖泊中浮游甲壳动物的大小结构似乎对浮游植物生物量的控制并不重要,并且主要受鱼类捕食强度的影响。我们的研究和经验性的研究所显示的结果可能是对湖泊处于不同富营养化和鱼类捕食强度的两个阶段的反映。 因子分析和多元回归分析显示浮游植物的生物量与TN、 NH4+、NO3- 和 TP显著正相关。但浮游植物与浮游动物生物量之间不存在任何的负相关关系。同时,在春季和夏季,浮游植物的生物量与TN/TP比的关系相反,意味着在高营养水平的湖泊中优势浮游植物对TN/TP比有着不同的喜好。下行效应对浮游植物生物量的不显著控制可能与蓝藻占优势和鱼类的捕食以及其它的因子导致的小型浮游甲壳动物占优势和它们小的生物量有关。因此,在亚热带的湖泊中,营养盐对浮游植物生物量变异的解释要比浮游动物重要的多。 多元回归分析显示理化因子(包括Chl a、TN、温度、水深、pH、透明度)和浮游甲壳动物(包括S. dorrii、Daphnia、D. brachyurum、C. vicinus、Bosmina、S. forbesi、Diaptomidae)分别解释了轮虫密度变异的38.5%和34.1%,表明这两组解释变量对轮虫密度可能有着相同的影响。冗余分析显示浮游甲壳动物和理化因子分别解释了轮虫种类分布变异的26.9%和28.9%。进一步的分析显示纯粹的浮游甲壳动物和纯粹的理化因子分别解释了轮虫种类分布变异的10.9% 和13.6%,而且这两个百分比之间不存在显著的差异(P = 0.261),意味着浮游甲壳动物和理化因子对轮虫种类的分布有着同等重要的贡献。轮虫的种类分布与湖泊的营养水平密切相关,它们与浮游甲壳动物的共存似乎与它们对水体营养状态的喜好以及某些轮虫特殊的外部形态特征有关。 通过对微型裸腹溞生活史的研究,发现高浓度的鱼类化学信息素对微型裸腹溞的生长、初次繁殖时的体长和第一窝幼体的大小没有显著的影响。总的后代数、平均怀卵量、寿命和窝数在各处理组间也没有显著的差异(Post-Hoc, Tukey-test, P > 0.05)。世代时间和内禀增长力在各处理间的变化范围也很小。这些结果表明微型裸腹溞有可能通过与该鱼类的长期共存而适应了这类物质。但是我们的结果与前人的相比还是存在着很大的差异,尤其是明显提高的总后代数、平均怀卵量和内禀增长力,意味着微型裸腹溞有可能通过生活史的的改变来进化对浮游生物食性鱼类捕食的抵抗力。另外短的世代时间、小的初次繁殖时的体长和年龄有可能也是微型裸腹溞在高密度鱼类捕食压力下占优势的良好证据。
英文摘要: A total of 30 shallow lakes, located along the middle and lower reaches of the Yangtze River, were selected for this study. We aimed at presenting a snapshot of crustacean zooplankton communities and their relations to environmental factors, and then tested two hypotheses: (1) that there is a consistent relationship between crustacean biomass and trophic indicators among lake groups with different trophic conditions;(2) that larger size structure in aquaculture lakes is associated with higher grazing pressure. Assessment was made for the relative importance of nutrients and zooplankton biomass in determining the phytoplankton biomass in subtropical shallow lakes, and for the relative importance of physicochemical factors and crustacean zooplankton as determinants of rotifer density and species distribution. Finally, a life-table demographic study was performed to reveal the responses of Moina micrura in aquaculture lakes to high concentrations of chemical cues from planktivorous fish, and the underlying mechanism accounting for the dominance of M. micrura under planktivorous fish predation was also discussed. The study lakes showed a wide range of trophic status, with total phosphorus (TP) ranging from 0.008 to 1.448 mg L-1, and chlorophyll a (Chl a) from 0.7 to 146.1 µg L-1, respectively. 38 species of Crustacea were found, of which Cladocera were represented by 25 taxa (20 genera), and Copepoda by 13 taxa (11 genera). The most common and dominant species were Bosmina coregoni, M. micrura, Diaphanosoma brachyurum, Cyclops vicinus, Thermocyclops taihokuensis, Mesocyclops notius and Sinocalanus dorrii. Daphnia was rare in abundance. There was a general trend from mesotrophic to hypertrophic lakes: the diminishing significance of large herbivorous cladocerans (Daphnia) was accompanied by the increasing predominance of cyclopoids (Cyclops, Thermocyclops and Mesocyclops) and small cladocerans (Moina, Diaphanosoma). Canonical correspondence analysis showed that except for four species (D. hyalina, S. dorrii, C. vicinus and M. micrura), almost all the dominant species had the same preference for environmental factors. Temperature, predatory cyclopoids and planktivorous fishes seem to be the key factors determining species distribution. Biomass of cladocerans and copepods also varied greatly, with cladocerans being dominant in most lakes. TP was a better trophic indicator than Chl a to predict crustacean biomass. Within the three groups of lakes, however, there was no consistent relationship between crustacean biomass and trophic indicators. The possible reason might be that top-down and bottom-up control on crustaceans vary with lake trophic status. The lack of significant negative correlation between crustacean biomass and Chl a suggests that there was little control of phytoplankton biomass by macrozooplankton in these shallow subtropical lakes. Mean body length (a proxy of size structure) of crustaceans, was positively correlated with increasing Chl a (r2 = 0.40, P = 0.000) and TP (r2 = 0.38, P = 0.000), contrary to the empirical studies. However, the ratio of zooplankton to phytoplankton biomass decreased significantly with increasing TP (r2 = 0.27, P = 0.005) and mean body length (r2 = 0.46, P = 0.000). Meanwhile, size structure showed no significant contributions in explaining residual variations of chlorophyll-phosphorus relationship (P = 0.231). These results indicate that larger size structure of crustaceans was not always associated with higher grazing pressure. It is likely that in aquaculture lakes, size structure of crustacean zooplankton was of minor importance in the control of phytoplankton biomass, and it was mainly regulated by fish predation. Our results and previous empirical studies might be a reflection of two different stages of lake eutrophication and fish predation intensity. Factor analysis and multiple linear regressions showed that phytoplankton biomass was positively correlated with TN, NH4+, NO3- and TP, but did not show any negative relationship to zooplankton biomass. Meanwhile, contrary relationships were observed between phytoplankton biomass and the mass ratio of TN/TP in spring and summer, indicating that in nutrient-richer lakes the dominant phytoplankton species have different preferences for TN/TP ratio. The insignificant top-down control of phytoplankton biomass might be attributed to the dominance of small-sized crustaceans and low crustacean biomass resulting from cyanobacterial dominance and planktivorous fish predation as well as other factors. Thus, it is likely that nutrients were more important than zooplankton biomass in explaining the total variance of phytoplankton biomass in the subtropical lakes. Multiple linear regressions showed that 38.5% and 34.1% of the variance in rotifer density were respectively explained by physicochemical factors (including Chl a, TN, temperature, depth, pH, transparency) and crustaceans (including S. dorrii, Daphnia, D. brachyurum, C. vicinus, Bosmina, Schmackeria forbesi, Diaptomidae), suggesting that these two sets of explanatory variables might have similar impacts on rotifer density. Redundancy analysis showed that the variance of rotifer species distribution explained by crustaceans and physicochemical factors was 26.9% and 28.9%, respectively. Further analysis demonstrated that the adjusted variance explained by pure crustaceans and pure physicochemical factors was 10.9% and 13.6%, respectively. Moreover, these two percentages were not statistically different (P = 0.261), indicating that crustaceans and physicochemical factors had equal contributions in determining rotifer species distribution. The distribution of rotifers was strongly associated with the gradient of trophic status, and their coexistence with crustaceans seemed to be determined by their preferences for trophic status and the morphological characteristics of particular rotifers. During the life table demographic study, increasing concentration of planktivorous fish cues had no significant effect on M. micrura growth and size at first production as well as size of neonates in first brood. Total offspring, mean clutch size, life span and clutch number also did not show any significant difference between treatments (Post-Hoc, Tukey-test, P > 0.05). The generation time and intrinsic rate of population increase showed a narrow range between treatments. These results indicate that M. micrura might have accustomed themselves to the cues from their long-term coexistence with planktivorous fish. However, total offspring, mean clutch size and intrinsic rate of population increase were much larger than values reported from previous studies, suggesting that M. micrura might have already evolved a strong resistance to predation of planktivorous fish through changes of life history. In addition, decreased generation time, age and size at first reproduction might be also responsible for their resistance to predation of planktivorous fish.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ihb.ac.cn/handle/342005/12256
Appears in Collections:中科院水生所知识产出(2009年前)_学位论文

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Recommended Citation:
长江中下游浅水湖泊的浮游动物群落结构研究.王松波[d].中国科学院水生生物研究所,2008.20-25
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