浙江饮用水源地浮游动物群落特征及环境响应

2010年1月至2011年10月,对浙江省16个饮用水源地(H1—H8为河网型,K1—K8为水库型)的浮游动物群落进行季节调查。共记录浮游动物优势种(属)21种(轮虫8种、枝角类5种、剑水蚤5种和哲水蚤3种),各类群第一优势种分别为针簇多肢轮虫(Polyarthra trigla)、长额象鼻溞(Bosmina longirostris)、粗壮温剑水蚤(Thermocyclops dybowskii)和汤匙华哲水蚤(Sinocalanus dorrii)。2年间,河网和水库浮游动物平均密度分别为345.2 L-1和199.4 L-1,生物量分别为0.667 mg/L和0.421mg/L。各类群密度百分比例均以轮虫和桡足类无节幼体为主,甲壳动物以剑水蚤为主。经逐步回归分析表明,浮游动物群落密度(生物量)与河网水质因子(P0.01)之间相关性比水库(P0.05)更密切,总磷和氨氮分别入选了河网和水库所有有效的回归方程中。通径分析和决策系统分析表明,河网的总磷和叶绿素a含量对浮游动物群落变动具有正效应,溶解氧具有负效应;总磷含量是影响河网群落变动的最重要因子,叶绿素a含量则是影响群落增长最主要的限制因子。河网剑水蚤、无节幼体和轮虫群落的密度(生物量)与水体综合营养指数TLIc密度(TLIc生物量)之间有显著的线性回归关系(P0.001),无节幼体密度构成了TLIc密度变动的限制因子,轮虫生物量成为TLIc生物量变动的限制因子,而剑水蚤是一类最重要、稳定的水质指示群落,这对于筛选浮游动物群落的一些拓展性监测指标具有重要的参考作用。

Characteristics of the zooplankton community and their association with environmental factors in drinking water sources, Zhejiang Province, China

This study aimed to understand the characteristics of zooplankton community structure and their association with environmental factors in different sources of drinking water. A seasonal investigation was conducted on zooplankton from two drinking water sources (8 rivers and 8 reservoirs) in Zhejiang Province, China, from January 2010 to October 2011. A total of 21 dominant species (genus) of zooplankton (8 Rotifera, 5 Cladocera, 5 Cyclopoida, and 3 Calanoida) were recorded. The primary dominant species in each group of zooplankton were Polyarthra trigla, Bosmina longirostris, Thermocyclops dybowskii, and Sinocalanus dorrii, respectively. Nine of the dominant species (genera) were at the same time indicator species of water trophic state. The more frequently that indicator species of trophic state occurred, the more comprehensive the trophic level index (TLIc) (P < 0.01) of the rivers was. Over the 2-year study period, the average density of zooplankton in the rivers and reservoirs was 345.2 L^-1 and 199.4 L^-1, respectively, while the biomass was 0.667 mg/L and 0.421 mg/L, respectively. Rotifer and copepod nauplii dominated both the rivers and reservoirs, representing 87.9% and 88.3% density, respectively. Crustaceans were mainly Cyclopoida, which had 2 times the biomass of Calanoida in the rivers, whereas Calanoida had 2 times the biomass of Cyclopoida in the reservoirs. The river community density (biomass) coefficient of variation ranged between 158.2% and 325.5%, while that of reservoirs ranged between 107.8% and 345.2%. The results of the stepwise regression analysis showed that the correlative coefficient between the density (biomass) of the zooplankton community and the water quality factors was much higher in the rivers (P < 0.01) than in the reservoirs (P < 0.05). Total phosphorus (TP) and ammonia nitrogen primarily occurred in the rivers and the reservoirs in all effective regression equations, respectively. Path and decision coefficient analysis showed that TP and chlorophyll a (Chl.a) content in the rivers had a positive effect on the population dynamics of the zooplankton community (rotifers, copepod nauplii, and Cyclops), whereas dissolved oxygen content had a negative effect. TP was the most important factor affecting population dynamics of rotifers, copepod nauplii, and Cyclops in the rivers, whereas Chl.a was the most important factor limiting the communities growth. The reservoir fishery resources aquaculture might cause zooplankton abundance to decline, the Calanoida community to gradually disappear, and the water trophic state to transform from nitrogen limitation conditions to phosphorus limitation conditions. The river community (rotifers, copepod nauplii, and Cyclops) density (biomass) had a significant linear regression relationship with the water trophic index TLIc_Density (TLIc_Biomass) (P < 0.001). Copepod nauplii density constituted a limiting factor for TLIc_Density, due to its maximum average coefficient of variation (261.8%). Rotifer biomass constituted a limiting factor for TLIc_Biomass, due to its maximum average coefficient of variation (257.9%). The average variation coefficient of Cyclops density (biomass) was moderate, with small fluctuations; thus, this group represented the most important and stable water quality indicator. The study results provide an important reference for selecting specific expansion indicators of the zooplankton community in water quality monitoring. None of the zooplankton community density (biomass) groups in the reservoirs had any significant linear regression relationships with the water TLIc (P > 0.05).