The Zhalong wetland is located in the western portion of the Heilongjiang Province,downstream of the Wuyuer River,which is the most complete wetland in north China at similar latitudes.It is an important habitat for cherish cranes and waterfowl.Recently,water in the Zhalong wetland became more saline.In 2012,algae samples were collected from six sites in spring,summer,and autumn.In total,140 diatom taxa were observed,including 121 species,19 varieties belonging to 2 classes,6 orders,9 families,and 30 genera.Pennatae diatoms were rich in species and accounted for 95％ of the total number.Diatom community showed seasonal succession,with the richness and relative abundance of diatom species in autumn higher than during spring and summer.Most of the dominant species were freshwater,brackish,or weakly alkaline water species.Dominant species occurred in response to salinity and pH of water;an obvious correlation with environmental conditions.Navicula cryptocephala was the dominant species of the Zhalong wetland in spring,summer,and autumn.Meanwhile,Amphipleura pellucida,Gomphonema micropus,and Nitzschia palea were abundant in alkaline water.This indicated that the Zhalong wetland was affected by soil salinization.Environmental parameters,including pH,water temperature (WT),conductivity (SpCond.),chemical oxygen demand (CODCr),permanganate index (CODMn),biochemical oxygen demand (BOD5),dissolved oxygen (DO),total phosphorus (TP),and total nitrogen (TN) were measured.The relationships between environmental factors and the variation in diatom community structure were analyzed by canonical correspondence analysis(CCA).CCA showed that water temperature,conductivity,pH,and DO were the most important factors influencing the structure of diatom communities.TN and TP were also important driving factors of the seasonal succession of diatom communities.Combining the diversity index and diatom quotient,the Shannon Wiener diversity index ranged from 2.70 to 5.65;Simpson dominance index ranged from 0.67 to 0.97;Pielou evenness index was between 0.43 and 0.91,and Diatom Quotient ranged from 0.007 to 0.11.The water in the Zhalong wetland was mesosaprobic-oligosaprobic;Some parts of the water were clear,but a few parts were slightly polluted by humans.%扎龙湿地位于黑龙江省西部、松嫩平原乌裕尔河下游,是我国北方同纬度地区最完整的湿地.于2012年春、夏、秋3季,对扎龙湿地6个代表性区域进行硅藻标本采集,经观察鉴定,发现硅藻植物140个分类单位,包括121种19变种,隶属于2纲6目9科30属.羽纹纲物种较丰富,占总种类数的95％.硅藻植物群落呈现明显的季节演替,秋季硅藻种类丰富度及相对丰度明显高于春、夏两季,优势种多以淡水、半咸水、喜弱碱的种类为主,优势种与水体的盐度和酸碱度存在一定的响应关系.应用典范对应分析(Canonical Correspondence Analysis,CCA)探讨硅藻植物群落变化与环境因子之间的关系.CCA结果显示在扎龙湿地中,水温、电导率、pH、溶解氧是影响硅藻群落结构变化的主要因素,此外总氮、总磷也是硅藻群落季节演替的重要驱动因子.结合硅藻植物多样性指数和硅藻商对扎龙湿地水质进行综合评价,结果显示扎龙湿地整体为中-寡污带水体,部分水域水质较清洁,少数样点受人为因素影响,呈轻污染.
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