珠江干流初级生产力时空变化特征及影响因素

水体初级生产力是保证水生生物种群再生产速率的一种体现,可为河流生态系统的运转提供能量来源。为探究珠江干流初级生产力(Primary Productivity,PP)状况及水环境影响因子,于2016年3月(平水期)、6月(丰水期)、9月(枯水前期)进行采样调查分析,采用Pearson相关性分析对初级生产力及其与水环境因子的关系进行了分析。结果显示,初级生产力介于6.0~866.5 mg/m²/d,均值为111.1 mg/m²/d。初级生产力水情期变化明显,表现为枯水前期>平水期>丰水期;各站位初级生产力除鲁布革站位异常高外,其他站位差异不明显。初级生产力与总氮、亚硝酸盐、硅酸盐、叶绿素a(Chlorophyll a,Chl-a)、透明度等指标显著相关(P<0.05,n=42);该水域2016年呈现以中营养和贫营养为主,而在上游建坝库区存在局部“富营养”的水体状况。研究结果表明面源污染和珠江干流修建水坝所导致的河流水文情势的改变是引起初级生产力时空差异的主要影响因素。

Temporal and Spatial Variation Characteristics and Influencing Factors of Primary Productivity in the Main Stream of the Pearl River

The primary productivity of a water body is a reflection for ensuring the reproduction rate of aquatic organism population,which can provide energy source for the operation of river ecosystems.To explore the primary productivity(PP)and water environment impact factors in the main stream of the Pearl River,investigations were carried out in March(normal period),June(wet season),and September(early dry season)of 2016,and the primary productivity and its relationship with water environmental factors were analyzed by Pearson correlation analysis.The results showed that the primary productivity ranged from 6.0 to 866.5 mg·m^-2·d^-1,with a mean value of 111.1 mg·m^-2·d^-1.The primary productivity in different periods varied obviously,and the early dry season possessed highest primary productivity,followed by normal period and wet season.The primary productivity of each station presented not obvious difference except for Lubuge station with the abnormally high primary productivity.Moreover,primary productivity was significantly correlated with total nitrogen,nitrite,silicate,chlorophyll a,transparency,etc.(P<0.05,n=42).Through comprehensive evaluation,this water area in 2016 was mainly mesotrophic and oligotrophic,while there were partial“eutrophied”water conditions in the upstream dam reservoir area.The results demonstrated that changes in the hydrological regime of river caused by non-point source pollution and the damming on the main stream of the Pearl River were the main influencing factors leading to the temporal and spatial differences in primary productivity.