【作者】 谢贻发；

【导师】 刘正文；

【作者基本信息】 暨南大学 ， 水生生物学， 2008， 博士

【摘要】 沉水植物是湖泊生态系统的重要组成部分,具有十分重要的生态功能,沉水植物的消失将使湖泊生态系统发生一系列变化。因此,沉水植物的恢复与维持在湖泊生态系统保护与恢复中占有重要的地位。造成沉水植物消失的重要原因之一是由于水体富营养化,而水体富营养化的限制因子主要是氮、磷,因而研究沉水植物与氮、磷营养盐的相互作用具有重要的意义。本文选择常见的沉水植物——苦草(Vallisneria natans)和黑藻(Hydrillaverticilla)为实验材料,通过室内模拟试验,首先,研究了沉水植物对水体氮、磷和悬浮物含量的影响,探讨了沉水植物对沉积物中不同赋存形态磷的影响,其后研究了沉水植物对外源性P在生态系统中分配的影响,最后研究了水体营养盐和沉积物营养对沉水植物生长的影响,探讨沉水植物生长所需要的水质条件和沉积物条件。主要结果如下:(1)沉水植物对水质有一定的改善作用,能有效降低水体中氮、磷、叶绿素含量以及悬浮物浓度。水质改善的效果与外源负荷的强度以及沉水植物的种类有关。与对照组相比,在低营养盐负荷条件下,苦草组的水体总氮、总磷、叶绿素和悬浮物含量分别下降56.9%、39.1%、17.2%和20.5%;黑藻组的水体总氮、总磷、叶绿素和悬浮物含量分别下降82.4%、93.4%、94.2%和93.5%。在中营养盐负荷条件下,苦草处理的水体总氮、总磷、叶绿素和悬浮物含量分别下降37.1%、28.6%、38.0%和8.6%;黑藻处理的水体总氮、总磷、叶绿素和悬浮物含量分别下降73.2%、93.5%、96.6%和90.2%。在高营养负荷盐条件下的效果最差,苦草处理的水体总氮和叶绿素分别降低了9.7%和14.0%,总磷和悬浮物含量则分别上升了37.1%和1.4%。黑藻处理的水体总氮和叶绿素分别降低了24.8%和75.9%,总磷和悬浮物含量则分别上升了64.5%和5.1%。(2)存在外源营养负荷时,沉水植物的生长显著地降低了沉积物中TN、TP的含量,原因可能主要是通过根直接吸收沉积物中的磷作为营养。此外,沉水植物通过改变根区微环境影响磷在沉积物中的赋存形态,与对照相比,沉水植物使沉积物中不同赋存形态的磷均有不同程度的降低。(3)沉水植物对外源性P在水生态系统中的分配具有重要作用。在沉水植物生长旺盛的系统中,沉水植物可以很好地吸收外源性P,是系统中重要的营养库。而在没有沉水植物的或沉水植物生长差的系统中,系统中的浮游植物占优势,外源性P主要沉降于沉积物中,同时有很大部分滞留在水体并以颗粒态的形式存在。沉水植物对外源性P在系统中的分配的影响受到营养负荷强度的影响:在低营养负荷强度下,沉水植物生长良好,外源性P主要分配于沉水植物中。当营养负荷增强至一定程度时,沉水植物生长受到抑制,外源性P分配于植物中的比例下降,而分配于沉积物和水体浮游植物中的比例则相应上升。(4)水中营养盐含量的增加对沉水植物的生长具有抑制作用,这种抑制作用与外源营养负荷的强度及沉水植物的种类有关。苦草在低营养负荷条件下可以正常生长,在中营养条件下生长开始受到限制,其生物量只有低营养负荷的72.3%,在高营养负荷条件下则完全受到抑制。黑藻在各种营养负荷条件下,开始阶段皆能正常生长,适当的营养负荷还能促进其生长,但随着营养负荷的不断增强,生长逐步受到抑制。(5)沉积物营养盐对苦草形态特征、生物量积累及分配格局的具有影响明显。在营养盐较丰富的湖泥中,苦草的生物量、分株数量和匍匐茎总长度等指标显著大于粘土和沙土,也显著大于营养盐和有机质更高的河泥;沙土中生长的苦草根系纤细,根系直径显著小于其他三种基质类型上的苦草;河泥和沙土上生长的苦草叶绿素含量显著地低于湖泥和粘土上的苦草。由此可见,基质条件对苦草的生长和形态有较大的影响,苦草在一定程度上能够适应肥沃的基质条件,但当氮、磷、有机质含量过高时,苦草的生长受到抑制。更多还原

【Abstract】 Submerged macrophytes are an important components in lake ecosystems,and have an important ecological function.The disappearance of submerged macrophytes would lead to deterioration of lake ecosystems.The restoration and maintaining of submerged vegetation play important roles in lake procection and restoration.The major factor causing disappearance of submerged macrophytes is eutrophication of water,especially the increase of nitrogen（N） and phosphorus（P） in water.It is important to study the interaction of submersed macrophytes and N、P of water environment in lakes.In this thesis,based on the experimental approach,effects of growth of submersed macrophytes Hydrilla verticilla and Vallisneria natans on dynamic change of the TN、TP and suspended solids in water body was studied firstly.And then the variation of chemical forms of phosphorous in sediments brought by the submersed macrophytes was analyzed.Thirdly,effect of submerged macrophytes on the allocation of external phosphorus in simulative aquatic ecosystems was studied. Lastly,the responses of submersed macrophytes to external nutrient source and of sediment type were investigated.The main results are summarized as following:（1） The results showed that the existing of submerged aquatic plant can improve the water quality obviously when receiving three different nutrient loadings(4 mg·N L^-1 and 200μg·P L^-1,1 mg·N L^-1 and 50μg·P L^-1,or 0.2 mg·N L^-1,10μg·P L^-1 every tow weeks).Effects on water quality differed depending on nutrient loadings and the submerged macrophytes species.Under the low nutrient loading,compared with CK, the concentration of TN,TP,Chl-a and SS in Vallisneria natans tanks were reduced by 56.9%,39.1%,17.2%and 20.5%at the end of the experiments.The concentration of TN,TP,Chl-a and SS in Hydrilla verticilla tanks were reduced by 82.4%,93.4%, 94.2%and 93.5%.Under the medium nutrient loading,compared with CK,the concentration of TN,TP,Chl-a and SS in Vallisneria natans tanks were reduced by 37.1%,28.6%,38.0%and 8.6%at the end of the experiments.The concentration of TN,TP,Chl-a and SS in Hydrilla verticilla tanks were reduced by 73.2%,93.5%, 96.6%and 90.2%.Under the high nutrient loading,compared with CK,the concentration of TN and Chl-a in Vallisneria natans tanks were reduced by 9.7%and 14.0%.The concentration of TN and Chl-a in the waterof Hydrilla verticilla tanks were reduced by 24.8%and 75.9%.（2） Submersed macrophytes could effectively decrease the content of total nitrogen（TN）,total phosphorus（TP） and different chemical forms of phosphorus in the sediment,especially Vallisneria natans.The two submersed macrophytes can change the phosphorus in the sediment through shoot oxygenation and nutrition allocation or some other mechanisms.Though the mechanism is complicated,the submersed macrophytes really reduce the content of phosphorus to the different extend during their growing period.（3） Submerged macrophytes have an important role on the allocation of external phosphorus.In the aquatic ecosystems where submerged macrophytes grew well, submerged macrophytes took up lots of phosphorus.In such ecosystems,submerged macrophytes are a nutrient sink.In the other ecosystems where phytoplankton dominated,sediment were the main sink of external phosphorus,and lots of external phosphorus remained in the water as PP.Effects of submerged macrophytes on the allocation of phosphorus was influenced by the degree of phosphorus loading.When the nutrient loading was low,the phosphorus sunk on the submerged macrophytes mainly.Submerged macrophytes were limited with the increase of nutrient loading. And the exogenous phosphorus sunk on the sediment mostly.（4） The results suggested that nutrient loading could have a nagetive effect on the growth of submersed macrophytes,and such effect differs among different species. Vallisneria natans grew well when the nutrient loading was low.The growth of Vallisneria natans got limited under medium nutrient loading,the biomass of Vallisneria natans in medium nutrient loading is 72.3%of which in low nutrient loading.In the high nutrient loading,the growth of Vallisneria natans got most limited.In definite limit concentration,Hydrilla verticilla grew better with the increase of nutrient loading.However,when the nutrient loading was too high,which a nagetive effect on the growth of Hydrilla verticilla was also detected.When the experiment ended,the biomass of Hydrilla verticilla was 11.3 g,18.1 g and 8.9 g under low,medium and high nutrient loading.（5） To determine the effect of different sediments on the morphology,biomass accumulation and allocation of Vallisneria natans,plants were planted in four different sediments:lake sediment,bank sediment,sandy loam and river sediment. After growth of 7 weeks,plants were dried,separated into above and below ground parts and weighed.The results showed that among the test sediments,the biomass, ramet number and total stolon length of V.natans grown in the lake sediment was significantly higher than the plants grown in the sandy loam,bank sediment or river sediment.Compared with the plants grown in the other sediments,V.natans grown in sandy loam allocated more biomass to roots and had the highest r:s,0.48.But root diameter of V.natans grown in sandy loam was lowest.Chlorophyll content of V. natans grown in sandy loam and river sediment were significantly lower than the plants grown in the lake sediment and bank sediment.The results suggest that sediment type plays an important role in growth of this submerged macrophyte:to some extent,V.natans is able to grow normally under conditions of the fertile sediments,but the heavily eutrophic sediment as well as sterile sediment poses a negative effect on the growth of V.natans.更多还原