洪泽湖淮河入湖河口区群落间营养元素分布特征

The allocation of nutrient elements among plant communities in estuary of Huaihe River in Hongze Lake

【目的】洪泽湖是淮河中游的河道型大型水库,是淮河上游污染的"汇"。笔者研究营养元素在洪泽湖淮河入湖河口区不同群落间的分布差异,探讨营养元素在群落间的转移机制,为湖泊水体富营养化的防治提供依据。【方法】采集并分析了洪泽湖淮河入湖河口区的芦苇(Phragmites australis)、莲(Nelumbo nucifera)、菹草(Potamoge-ton crispus)、篦齿眼子菜(Potamogeton pectinatus)等群落及毗邻航道的表层沉积物和上覆水中氮(N)、磷(P)等元素含量及分布特征,利用冗余分析(RDA)比较了样地水深、pH、沉积物营养元素含量以及粒级结构特征与上覆水营养元素含量的相关性。【结果】①研究地表层沉积物中,总氮(TN)含量与总有机碳(TOC)含量、平均粒径显著正相关;总磷(TP)含量与平均粒径极显著负相关,与TOC含量弱正相关;表层沉积物中碳氮比(C/N)值为6~20,碳磷比(C/P)值为11~79,群落间差异显著;②研究地上覆水TN质量浓度与表层沉积物TN、TOC含量、平均粒径均显著负相关,与沉积物TP含量弱正相关,上覆水TP质量浓度与沉积物TN、TOC含量、平均粒径等弱正相关,与沉积物TP含量弱负相关;③研究地不同群落上覆水体与沉积物中N、P等营养元素含量的"平衡比例"不同。不同群落类型中,沉积物中TN、TP含量相对较高,群落上覆水体TN、TP质量浓度较低。【结论】入湖河口区沉积物平均粒径对上覆水水质的解释率相对较高,显示沉积作用显著影响沉积物中元素分布特征,对TP含量影响最大;不同群落上覆水体与沉积物中N、P等营养元素的平衡比例存在较大差异,可能原因是河口区不同植物群落间水体主要水质指标存在浓度梯度,影响营养元素在不同群落间转移,进而实现群落间表层沉积物中营养元素再分配的一种重要机制。

【Objective】Hongze Lake is a large-scale river reservoir in the middle reaches and a sink of pollution in the upper reaches of Huaihe River.The authors studied the distribution characteristics of nutrients in the estuary of Huaihe River and discussed the transfer mechanism of nutrients between communities,which can provide a theoretical basis for the prevention and control of lake eutrophication.【Method】We compared the contents and distribution characteristics of N and P in communities of Phragmites australis,Potamogeton pectinatus,Potamogeton crispus and Nelumbo nucifera,respectively,in the water channel in Huaihe River estuary of Hongze Lake.Redundancy analysis(RDA)was used to compare the correlation between water depth,pH,nutrient content in sediment,grain size structure in sediment,and nutrient content in overlying water.【Result】①In surface sediments,total nitrogen(TN)content was significantly positively correlated with total organic carbon(TOC)content and the average grain diameter of sediments;total phosphorus(TP)content was negatively correlated with the average grain diameter and weakly positively correlated with TOC content.The ratio of carbon to nitrogen content(C/N)in surface sediments was 6-20 and the ratio of carbon to phosphorus content(C/P)was 11-79.There were significant differences among communities.②The TN concentration in overlying water was significantly negatively correlated with TN,TOC content,and average grain diameter in sediments,and was weakly positively correlated with TP content.The TP concentration in overlying water was weakly positively correlated with TN,TOC content,and average grain diameter in sediments,and was weakly negatively correlated with TP content.③Among various microhabitats of the estuary,the ratio of TN and TP contents between water and sediment in adjacent plant communities was different,and the higher the content of TN and TP in the sediments was,the lower the concentrations of TN and TP in the overlying water would be.【Conclusion】In the estuary area,the average grain diameter has a relatively high explanatory rate on who affects the quality of overlying water.Sediment deposition significantly affects the distribution characteristics of elements in sediments,and has the greatest effect on the content of TP.The balance ratios of N and P in the overlying water and sediments of different communities are quite different.These ratios could be an important mechanism for concentration gradients existing in main water quality indexes of different plant communities in estuary areas,for affecting the transfer of nutrient elements between different communities,and for realizing the redistribution of nutrient elements in surface sediments between communities.