太湖滨岸带芦苇区沉积物磷的特征

Characteristics of Phosphorus of Sediments with Reed Community in the Littoral Zone of Lake Taihu

为了进一步揭示大型水生植物对湖泊滨岸带沉积物磷的生物地球化学影响,探讨芦苇(Phragmites austra-lis)群落对沉积物磷的生态效应,于2003年9月18日、10月17日和12月3日,用柱状采样器分别在太湖梅梁湾滨岸带芦苇区和无草对照区采样。用HClO4-H2SO4消化法和H2SO4-H2O2消煮法测定芦苇区和对照区沉积物及芦苇根、茎组织中的总磷含量。结果表明,在芦苇生长旺盛期(9月),芦苇区和对照区沉积物的总磷含量最高,在芦苇生长的衰弱期(10月),其总磷含量次之,在芦苇生长的枯萎期(12月),其总磷含量最低;对照区沉积物距地表0～2cm的表层是磷的富集峰值层,而芦苇生长区距地表4～7cm的沉积物层为磷的富集峰值层;芦苇须根对磷的富集效应大于其根状茎,而芦苇根状茎对磷的富集效应又大于其茎,但它们的总磷含量都小于距根0～2cm范围芦苇根际沉积物的总磷含量。

Littoral zone has important influence on the eco - environment of lakes, in which most of the physical phenomena and ecological process changes take place because plants are in close contact with the environmental conditions of a lake, through the root - system of plant which has the function of purifying the nutrition. At the same time, eutrophication is one of the most widespread environmental problems of inland waters, and is their unnatural enrichment with one of plant nutrients, phosphorus. Aquatic macrophyte plays an important role in biogeochemical process of phosphorus nutrients of sediments in the lake. On the one hand, the roots of aquatic macrophyte can take up nutrients from the sediments; on the other hand, they can release oxygen to the sediments and thus affect the biogeochemical circling of phyte and its effects on the eco -environment phosphorus. It is significant to study the littoral zone with macrofor better understand the lake of eutrophication with eco - restoration or the regional eco -environment evolvement. In order to examine aquatic macrophyte effects ecological effects of phosphate in the sediment with on sediment biogeochemistry of the littoral zone as well as the Phragmites australis community, the indicators, including total phosphorus of sediment samples with and without macrophyte, tissuses of reed, were collected from littoral zone of Meiliang Bay, Lake Taihu. In this study area, 2 representative types of littoral zone in hyper - eutrophic Meiliang Bay, Taihu Lake, were selected. One is a macrophyte- covered littoral zone, and the other is eroded by wave and is a bare littoral zone. 8 sampling sites were established along the gradient from the open water to the land. The sediment cores for analyses were sampled with Hand - held corer （ 8 cm） and into a polyethylene bag from the Littoral Zone of Meiliang Bay, Lake Taihu of the site with and without reed on September 18, October 17 and December 3, 2003. Each treatment was with 3 replicates in every sample site. Sediments were gotten out for various depth intervals according to hardness of the sediments, such as （0 -2 cm, 2 -4 cm, 4 -7cm, 7 -10 cm, 10 -15 cm, 15 -20 cm） and then stored at 4℃ in a refrigerator. Samples of sediment and plant tissues were brought back to the laboratory and dried in the air at room temperature until they became dry. Total phosphorus （TP） of sediments and plant tissues were examined using standard methods based on molybdenum blue formation. At first, sediments and plant tissues of reed were brought back to the laboratory and remained there overnight until they became dry and then grinded with agate mortar, at last through a 0. 149 mm mesh sieve to remove any gravel or other large particle. Characteristics of phosphorus distribution in the sediments with reed community in the Littoral Zone of Lake Taihu were analyzed to further study the impacts of aquatic macrophyte on phosphorus biogeochemical process in the sediments of lake in the paper. The results indicated that the TP retention capacity of the surface sediment （0 -2 cm） without reed community was significantly higher than those of the sediments with reed community （p 〈0.05）. The order of TP retention capacity in the sediment was prosperous period of reed more than period of turnover, and then more than period of withered. TP retention was the highest in 2 - 4 cm of bare sediment, while in d - 7 cm of reed community. The order of TP contents in the tissues was TP content of fine roots more than that of rhizome, and then more than that of stem, but all of them were lower than that of rhizosphere （0 - 2 cm）