白洋淀不同沉水植物盖度下浮游植物群落结构及变化

为研究不同沉水植物盖度下浮游植物群落结构及变化规律,为水域生态修复提供科学依据,在白洋淀选取了4个盖度水平区域,分别为25%、50%、75%和90%(C-25、C-50、C-75、C-90),对照区域(C-0)结合水体理化参数和浮游植物群落结构特征,评价出沉水植物的最佳盖度。结果表明,沉水植物组均可有效降低水体总氮(TN)、总磷(TP)、溶解性固体总量(TDS)和电导率(SPC),而C-50组的TN和TP浓度最低。对浮游植物群落结构分析发现1)沉水植物组浮游植物种类数高于对照组,各组绿藻门比例最高且均在50%以上;2)C-50组蓝藻门优势种最少且比例显著低于其他组(P<0.05);3)浮游植物密度和生物量随沉水植物盖度的增加而降低,且占比最大的分别是蓝藻门和绿藻门;4)Margalef指数随盖度增加表现出先上升后降低的趋势;而Shannon-Weiner指数和Pielou指数随盖度的增加而增大;5)RDA表明,C-90、C-75和C-0组的浮游植物群落主要受TDS、SPC、pH、叶绿素a、高锰酸钾指数和透明度等环境因子的影响;C-50和C-25组浮游植物群落受环境因子的影响较小,说明水生态系统较稳定且受环境的影响小。鉴于盖度为50%时,TDS、SPC、TN和TP浓度最低;蓝藻门比例和优势种较低,Margalef指数最高,在水生态保护或修复时,建议沉水植物盖度以50%为宜。

Phytoplankton Community Structure in Baiyangdian Lake with Different Submerged Macrophyte Coverages

In order to study phytoplankton community structure and variation rules under different submerged macrophyte coverage, four coverages were set 25%, 50%, 75% and 90% (C-25, C-50, C-75 and C-90), respectively. No submerged plants were distributed in the control group (C-0). Firstly, the physicochemical indexes of the treatment groups and the control group were determined, and then the community structure of phytoplankton in the water was identified and analyzed to explore the relationship between submerged macrophyte with different coverage and the phytoplankton community structure in Baiyangdian lake. The results showed thatwhen the coverage is between 50% and 90%, the transparency of water body is the highest. Compared with the control group, the submerged macrophyte group could effectively reduced total nitrogen, total phosphorus, total dissolved solids and electrical conductivity, while the concentration of total nitrogen and total phosphorus in C-50 group was the lowest. Phytoplankton community structure analysis demonstrated that 1) the number of phytoplankton species in the submerged macrophyte groups with different coverage group was higher than that in the control group (except for C-75 group), and the proportion of chlorophyta in each group was the highest and over 50% (except for C-75 group).The proportion of cyanobacteria in group C-50 was significantly lower than that in other groups (P<0.05), and the proportion of chlorophyta and bacillariophyta in group C-50 was significantly higher than that in other groups (P<0.05); 2) The dominant species of cyanobacteria in the submerged macrophyte groups with different coverage group were significantly higher than those in the control group. Cyanobacteria had the least dominant species in the C-50 group. The dominant species shared by the submerged macrophyte groups with different coverage group and the control group were Limnothrix sp., Chroococcus sp. and Cyclotella sp. (except for the control group, there is no chromococcus sp.); 3) phytoplankton density and biomass decreased with the increase of submerged macrophyte coverage, and cyanophyta and chlorophyta accounted for the largest proportion of phytoplankton density in all groups; Chlorophyta had the highest proportion of biomass in each group, followed by bacillariophyta. There was no significant difference in phytoplankton biomass between the C-50 group and other groups (P>0.05). 4) With the increase of submerged macrophyte coverage, the Margalef index increased first and then decreased. Besides the control group, shannon-weiner diversity index and Pielou index increased with the increase of coverage. 5) According to the redundancy analysis, the phytoplankton community structure in baiyangdian lake under different submerged macrophyte coverage were affected by different environmental factors. The phytoplankton community structure in groups C-90, C-75 and C-0 were mainly affected by Total dissolved solids, Specific conductance, pH, Chlorophyll a, Potassium permanganate index and transparency.The phytoplankton community structure in groups C-50 and C-25 were less affected by environmental factors, indicating that the water ecosystem was relatively stable and did not change with environmental changes. Comprehensive analysis of physicochemical indexes and phytoplankton community structure, showed that when the coverage was 50%, the physical and chemical indexes of water and phytoplankton were relatively stable, that is, the water conductivity, total dissolved solids, total nitrogen and total phosphorus concentrations were the lowest and the transparency was higher. The percentage and dominant species of cyanophyta were lower, and Margalef index was the highest. This study provides scientific basis for aquatic ecology restoration.