黄河上游龙羊峡至积石峡段春秋季浮游植物群落结构及多样性评价

Phytoplankton Community Structure and Diversity Assessment in the Upper Reach of the Yellow River during Spring and Autumn

于2013年春季(3月)和秋季(8月)对黄河上游龙羊峡至积石峡段的浮游植物进行初步研究。结果显示:浮游植物共7门64种(属),以硅藻门最多,25种(属),占39.1%;其次是绿藻门19种(属),占29.7%;蓝藻门12种(属),占18.8%;金藻门和甲藻门各3种属,分别占4.6%;裸藻门和隐藻门各1种属,分别占1.6%。浮游植物优势种为小环藻(Cyclotella sp)、普通等片藻(Diatoma vulgare)、星杆藻(Asterionella sp)、脆杆藻(Fragilaria sp)、针杆藻(Synedra sp)、尖针杆藻(Synedra acus)、曲壳藻(Achnanthes sp)、席藻(Phormidium sp)、平裂藻(Merismopedia sp)、锥囊藻(Dinobryon sp)、衣藻(Chlamydomona sp)、小球藻(Chlorella sp)和实球藻(Pandorina sp)13种,其中硅藻门7种,占优势种类的53.8%。浮游植物种类组成的季节变化较明显,秋季(8月)高于春季(3月),2季均以硅藻为优势种群。浮游植物平均密度25.33×104个/L,平均生物量0.0732 mg/L,硅藻密度和生物量分别占70.7%和77.9%,为优势种群。浮游植物现存量表现为秋季(8月)高于春季(3月)。Shannon-Wiener指数平均值2.21,Pielou指数平均值0.73,Marggalef指数平均值0.66,多样性指数存在一定的季节变化,Shannon-Wiener指数、Marggalef指数秋季(8月)略高于春季(3月),Pielou指数春季(3月)高于秋季(8月)。黄河上游龙羊峡至积石峡段浮游植物群落结构比较稳定,种类分布较为均匀,水体属贫营养型,水域生态环境良好。

The 300 km Longyangxia to Jishixia section of the upper Yellow River,provides habitat for a variety of rare and peculiar fish and is important for spawning,feeding and over-wintering. A preliminary study of species composition,biomass and spatial-temporal variation of phytoplankton in this section was conducted at ten sample sites in March（ spring） and August（ autumn） of 2013. Results shed light on the phytoplankton community structure in the upper Yellow River and provide data to evaluate the aquatic environment and support efforts to use Yellow River water resources sustainably in Qinghai Province. Phytoplankton and water samples for qualitative and quantitative analysis were collected from the water surface（ 〈50 cm）. The geographical coordinates,height above sea level,water temperature and pH of each sample site were measured at the same time. Dissolved oxygen（ DO）was determined by the iodine method（ GB 7489-87） within 24 h. A total of 7 phyla,including 64 species of phytoplankton,were observed. Bacillariophyta was the dominant phylum,including 25 species（ genera） and accounting for 39. 1% of the total phytoplankton species,followed by Chlorophyta [19 species（ genera）,29. 7% ],Cyanophyta [12 species（ genera）,18. 8% ],Chrysophyta and Pyrrophyta[3 species（ genera）,4. 6% ],Euglenophyta and Cryptophyta [1 species（ genera）,1. 6%]. The most commonly encountered species were Cyclotella sp.,Diatoma vulgare,Asterionella sp.,Fragilaria sp.,Synedra sp.,Synedra acus,Achnanthes sp.,Phormidium sp.,Merismopedia sp.,Dinobryon sp.,Chlamydomona sp.,Chlorella sp.,and Pandorina sp. The seven most common species of Bacillariophyta accounted for 53. 8% of the 13 dominant species. Seasonal variation of phytoplankton composition was obvious,with higher species richness in autumn,but Bacillariophyta was dominant in both seasons. The phytoplankton density ranged from 1. 27 × 104 cell /L to 180. 48 × 104 cell /L,with an average of 25. 33× 104 cell /L,and the phytoplankton biomass ranged from 0. 0049 mg /L to 0. 4293 mg /L,with an average of0. 0732 mg /L. The density and biomass of Bacillariophyta accounted for 70. 7% and 77. 9% of the total phytoplankton community. The phytoplankton biomass was larger in autumn than in spring. The mean Shannon-Wiener diversity index,Pielou evenness index and Margalef richness index were 2. 21,0. 73,and 0. 66,respectively,with the Shannon-Wiener diversity index and Margalef richness index higher in autumn,while the Pielou evenness index higher in spring. In conclusion,the phytoplankton community at Longyangxia to Jishixia section in the upper reach of the Yellow River was relatively stable and the species distribution was even. The characteristics of the phytoplankton community structure combined with the phytoplankton as water quality indicators indicated that the water quality of this section was oligotrophic and aquatic environment was good.