Spatio-temporal dynamics of aquatic organism community and their relationships to environment in Niyang River,Tibet: 2. periphytic algae

Abstract

本文于2008-2009年按照季节调查了西藏地区尼洋河着生藻类群落的组成、丰度和多样性,并运用多元统计方法定量分析了着生藻类的空间和季节变化特征及其与主要环境因子之间的关系.结果显示,尼洋河着生藻类共计6门30科49属,其中硅藻为优势着生藻类.着生藻类的Shannon-Wiener多样性指数在尼洋河中游最高,在中上游河段和中下游河段呈下降趋势,符合中间高度膨胀(mid-altitude bulge)假说.着生藻类的总丰度、物种丰富度以及Shannon-Wiener多样性指数在尼洋河沿程不存在显著差异,总丰度在各个季节之间不存在显著差异,但物种丰富度在秋季和冬季存在显著差异,夏、秋季着生藻类的Shannon-Wiener多样性指数显著高于冬、春季.主成分分析(PCA)表明,随着海拔的升高,着生藻类的物种丰富度和总丰度呈递减趋势;典范对应分析(CCA)表明,尼洋河部分硅藻与理化因子相关联,如:双壁藻(Diploneis)的丰度与总磷相关联,窗纹藻(Epithemia)的丰度与铵态氮相关联,双菱藻属(Surirella)的丰度与pH值相关联;部分绿藻与理化因子相关联,如:小球藻属(Chlorella)、栅藻属(Scenedesmus)、溪菜属(Prasiola)的丰度与水温相关联,小椿藻(Characium)的丰度与硬度相关联,转板藻(Mougeotia)的丰度与表层溶氧、矿化度相关联,新月藻属(Closterium)的丰度与碱度相关联;分类回归树(CART)模型预测了尼洋河着生藻类时空分布与主要环境因子之间的定量关系,即低海拔水域的着生藻类总丰度较高海拔高,高矿化度水域的着生藻类总丰度较低矿化度的高,不能用影响尼洋河着生藻类种类和数量的环境因子来解释着生藻类的Shannon-Wiener多样性指数.这些关键环境因子对尼洋河水域着生藻类的时空变化有着重要的指示作用,建议加强对着生藻类及这些环境因子的关注,保障尼洋河水域生态环境的可持续发展.;We have seasonally investigated the constitution,abundance and diversity of periphytic algae (PA) in Niyang River,the branch of the Yarlung Zangbo River,Tibet from year of 2008 to 2009,and taken quantitative analysis on the spatio-temporal PA characteristics and their relationships with environment factors using multivariate statistics method.The results are listed as follows.Firstly,PA in Niyang River belongs to 6 phyla 30 families 49 genus,among which bacillariophyta is dominant.Secondly,Shannon-Wiener diversity pattern for Niyang River justified the theory of mid-altitude bulge,with higher Shannon-Wiener diversity index in the middle of the river.Thirdly,using Duncan comparison method to judge the difference among sampling sites and seasons for species richness,total abundance and Shannon-Wiener diversity index,there are no significant differences among four sampling sites for three indices mentioned above.In terms of sampling season,there is no significant difference for total abundance.There is significant difference between autumn and winter for species richness,and also significant difference exists between summer,autumn and winter,spring for Shannon-Wiener diversity index.Fourthly,based on the PCA method,total abundance and species richness of periphytic algae descended with the elevation ascending.Even more,based on the CCA method,portion of bacillariophyta and chlorophyta are related with environment factors.Last but not least,we predict the relationship between total PA abundance and environment factors,and the relationship between PA Shannon-Wiener diversity and environment factors based on CART method.The results reveal that PA total abundance from lower elevation of Niyang River is higher than that of higher elevation,and total abundance from higher degree of mineralization of Niyang River is lower than that in lower degree of mineralization.The environment factors that influence the PA quantity should not be applied to PA Shannon-Wiener diversity index.This paper also suggests paying close attention to PA and the environment factors mentioned above owing to their important indication function,in order to warrantee the sustainable development of Niyang River aquatorium ecology.