三峡库区古夫河着生藻类叶绿素a的时空分布特征及其影响因素

古夫河系长江三峡水库湖北省境内香溪河的一条支流，发源于神农架林区并最终汇入三峡水库香溪河库湾，是流域生态学研究的热点水体。本文对古夫河2010年9月至2011年8月干流及主要支流21个样点的着生藻类叶绿素a和14项环境因子进行了调查，采用多元统计方法对调查数据进行了方差分析、聚类分析、偏相关分析和逐步回归分析，研究了着生藻类叶绿素a的时空分布特征及其主要环境影响因子。结果表明：叶绿素a含量范围为0.07—145.96 mg/m2，平均值为11.63 mg/m2。不同样点的叶绿素a含量差异显著，其中古夫河干流上游低于下游，支流竹园河上游高于下游，表现为人为影响大的区域高于人为影响小的区域；不同季节着生藻类叶绿素a含量差异显著，表现出冬春季高、夏秋季低的趋势。古夫河着生藻类叶绿素a与总磷和硬度呈极显著正相关，与电导率、氨氮和总氮呈显著正相关，而与流速呈极显著负相关；水体总磷是古夫河流域着生藻类生长的第一限制因子，流速对着生藻类的生长具有显著抑制作用；古夫河着生藻类生物量空间格局可能由其生境尺度（营养盐）和流域尺度（硬度和电导率）的特征决定，而古夫河着生藻类生物量时间变化主要受水动力（流速）的影响。

Spatio-temporal distribution of epilithic algal chlorophyll a in relation to the physico-chemical factors of Gufu River in Three Gorges Reservoir

Originating from the Shennongjia Forest District, Gufu River is a tributary of Xiangxi River which is the largest tributary of Three Gorges Reservoir Area in Hubei Province, central China. With the development of mining, urbanization and intensification of water source exploitation, the impacts of anthropogenic activities have gradually increased in the Gufu River Basin. Gufu River is diverse with regard to the hydrological and biological characteristics which influence the biomass of epilithic algae. However, there are no previous studies investigating the spatio-temporal variation of epilithic algal biomass and the interactions between epilithic algae and the environmental factors from the headstream of the Gufu River Basin to the Xiangxi Bay. To obtain basic biotic data of the biomass of epilithic aglae and explore the relationship between algal biomass and the environmental conditions in the stream ecosystems with substantially different human impacts, we measured the chlorophyll a of epilithic algae and the main environmental factors at 21 sites in the Gufu River and its major tributaries (Zhuyuan River) once a month from September 2010 to August 2011. From the monitored data, we analyzed the spatial and temporal distribution of chlorophyll a and the main environmental factors influencing the distribution pattern with methods of one-way ANOVA, cluster analysis, partial correlation analysis and stepwise regression analysis. The chlorophyll a concentration ranged between 0.07 mg/m2 and 145.96 mg/m2 with a mean of 11.63 mg/m2. According to the similarity of chlorophyll a concentration in different sampling sites, all samples were divided into five groups by cluster analysis: Group 1, Group 2, Group 3, Group 4 and Group 5. The mean chlorophyll a of epilithic algae in the five groups were 5.90 mg/m2, 24.51 mg/m2, 23.83 mg/m2, 45.59 mg/m2, 50.03 mg/m2 respectively. This result showed that the concentration of epilithic algal chlorophyll a had obvious spatial heterogeneity: the biomass in the upstream was lower than the downstream in Gufu River while it is contrary in Zhuyuan River tributary. This indicated that higher biomass might caused by the increased anthropogenic interference. There were significant differences in chlorophyll a concentration among various seasons: the concentration tended to be higher in winter and spring than in summer and autumn. The analysis of the relationship between the physico-chemical characteristics and the chlorophyll a concentration of the benthic algae demonstrated that chlorophyll a concentration were significantly positively correlated with total phosphorous and hardness of the water and significantly negatively correlated with water velocity. This indicated that total phosphorus in the water could be the first restriction factor of the algal growth, and water velocity has significant inhibitory effect on the algal growth. The results of the stepwise regression between chlorophyll a concentration and the environmental factors showed that water velocity, total nitrogen and dissolved oxygen were related to chlorophyll a concentration in winter and spring, while total phosphorus, water velocity, hardness, dissolved silicate and ammonia were related to chlorophyll a concentration in summer and autumn. We concluded that the spatial pattern of the algal biomass in Gufu River were determined by its habitat scale (nutrients) and watershed-scale characteristics (hardness and conductivity), while the temporal pattern of the algal biomass was mainly affected by its hydrodynamic characteristics (water velocity).