乌梁素海冰封期营养盐及浮游植物的分布特征

摘要

乌梁素海地处我国内蒙古自治区乌拉特前旗境内，位于我国北方干旱半干旱地区，属温带大陆性气候，每年的11月至翌年3月为冰封期，湖泊面积现为273 km2，其主要补给水源是河套灌区的农田退水。目前，整个湖区呈Ⅴ类水质，且呈现富营养化状态。以往对营养物质与浮游植物群落结构特征的研究都是在常温水体条件下进行的，而在冰封条件下，水体和冰体中的营养盐与浮游植物群落特征的研究尚不多见。因此，本研究以冰封期的乌梁素海为研究对象，于2012年11月至2013年2月在湖区的10个采样点分别采集冰样和水样，并将水样分成冰水界面水、中层水、水底泥界面水，冰样分成表层冰、中层冰、冰水界面冰，从冰体和水体两个不同的角度出发，探究该期间冰、水营养盐浓度和藻类密度分布及其结构的变化情况，以期为该方向的研究提供理论基础。研究结果显示：冰封期乌梁素海的冰厚介于0.22~0.74 m之间，水深在0.28~2.45 m之间，且水深和冰厚存在较好的负相关性；由于冰体的排斥作用，在冰体的形成和生长过程中，营养盐和浮游植物逐渐从冰层迁移至水体中，监测结果显示，冰封期乌梁素海水体中的 TN、TP、COD 含量和藻类密度均值分别是冰体中的1.65、2.42、3.07、1.92倍，大量的营养物质迁移至水体中，从而加剧了水体的富营养化程度，因此，冰封期的湖泊更需要治理；另外，针对湖冰对污染物的排斥效应这一特点，可将其利用于降低有机物含量的相关研究中。研究还对监测点位进行了藻类监测，共采集到浮游植物共计7门67属105种（含变种），统计结果显示绿藻和硅藻的种类数分别占总种数的33.3%和26.7%，冰封期乌梁素海浮游植物种类组成呈绿藻-硅藻型。%Wuliangsuhai Lake is located in Wulate Front Banner, Bayannaoer city, Inner Mongolia Autonomous Region, North China. It is in arid and semi-arid area,temperate continental climate,from November to March of the following year called icebound season. The area is 273 square kilometers, mainly supplied by farmland drainage in HETAO Irrigation Area. At present, the water quality is grade V, and the state of eutrophication. Study on nutrient and phytoplankton community structure under icebound season is rarer than former ones on that under normal temperature. So this research is aimed at ice samples and water samples of icebound period in Wuliangsuhai Lake. We collected them from 10 sampling points from November 2012 to February 2013. Water samples include water on the ice water interface, intermediate water and water on bottom sediment interface;ice samples include ice on the surface, intermediate ice and ice on the ice water interface. We research both distribution and structure of nutrients concentration and algae density, respectively from ice samples and water samples, expecting to offer theory basis to this study. Result indicated that in the icebound period ice thickness was between 0.22 to 0.74 meter, while depth of water between 0.28 to 2.45 meter, which had a negative correlation with each other;Because of exclusion among ices,nutrient and phytoplankton removed from being-formed ices to water, which aggravated the eutrophication in water. Statistics showed the contents of TN, TP and COD and algae density in water were respectively1.65, 2.42, 3.07, 1.92 times of those in ice. Therefore, we have to strength management of lakes in icebound period;In addition, we can apply the exclusion of pollution from ice to decrease contents of organic material in the related research. We also tested algae, collected 105 species (including varieties) of phytoplankton belonging to 7 phylum and 67 genera., and concluded the percentage of Chlorophyta and Bacillariophyta respectively being 33.3% and 26.7%. The statistics showed that the community structure of phytoplankton was Chlorophyta-Bacillariophyta type in Wuliangsuhai Lake during the icebound season.