鄱阳湖丰水期水位波动对浮游动物群落演替的影响

为了解鄱阳湖夏季丰水期水位剧烈波动过程中浮游动物的群落演替特征,2012年夏季鄱阳湖水位剧烈波动期间,于6月24日、7月7日和8月27日当水位下降且接近17.6 m时,在江西鄱阳湖国家级自然保护区内的1个浅水碟形湖泊设置4个采样点进行采样调查。共发现浮游动物65种,其中轮虫52种,枝角类7种,桡足类6种,多为营浮游生活的广温性和嗜温性种类。单因子方差分析(one-way ANOVA)显示3个月之间浮游动物的密度和生物量均具有显著差异(P0.05),7月份浮游动物密度(1030.17±68.18个/L)显著高于6月份(325.16±41.60个/L)和8月份(203.79±24.91个/L);6月份浮游动物的生物量(0.56±0.04 mg/L)显著低于7月份(1.22±0.11 mg/L)和8月份(0.99±0.11 mg/L)。基于浮游动物多度的聚类分析和自组织映射神经网络图均揭示夏季3个月份的浮游动物可区分为明显的3个群落:6月群落、7月群落和8月群落。蒙特卡罗检验发现水温、电导率、浊度和溶氧与浮游动物群落结构变化显著相关(P0.05)。典型相关分析显示,6月份浮游动物群落与叶绿素a含量呈显著正相关关系,7月份浮游动物群落与水体温度呈显著正相关关系,8月份浮游动物群落与水深和电导率、浊度和溶氧呈显著正相关关系(P0.05)。在3个月均为优势物种的盖氏精囊轮虫与叶绿素a含量呈正相关关系(P0.05),与水温、pH、溶氧呈负相关(P0.05)。夏季水位波动过程中浮游动物的群落结构在时间上(月份之间)发生明显演替,呈现轮虫密度逐渐降低,枝角类和桡足类密度逐渐增加的变化规律。水位波动引起环境因子的改变,从而对浮游动物的群落演替产生了重要影响。

Impact of water level fluctuations on the succession of zooplankton in Poyang lake

This study aims to understand the succession characteristics of zooplankton communities during dramatic water level fluctuations in Poyang Lake. During the drastic fluctuations in water levels of Poyang Lake in the summer, and on June 24, July 7 and August 27, 2012 when the water level dropped and approached 17.6 meters, four sampling points were established in a shallow dished sub-lake in Poyang Lake National Nature Reserve for the survey of zooplankton. A total of 65 species of zooplankton, including 52 species of rotifers, seven species of cladocerans and six species of copepods, were found during the study period. The zooplanktons were mostly the wide-temperature and mesophilic species of the planktonic type. The one-way analysis of variance revealed significant differences in zooplankton density and biomass within the three-month period (P<0.05). The density of zooplankton in July (1030.17 ±68.18 ind./L) was significantly higher, when compared to that in June (325.16 ±41.60 ind./L) and August (203.79 ±24.91 ind./L). Furthermore, the biomass of zooplankton in June (0.56 ±0.04 mg/L) was significantly lower than that in July (1.22 ±0.11 mg/L) and August (0.99 ±0.11 mg/L). The clustering of zooplankton communities by Bray-Curtis similarity measure and self-organizing maps revealed that the zooplankton was clearly divided into three communities:June community, July community, and August community. The Monte Carlo test revealed that water temperature, conductivity, turbidity and dissolved oxygen were significantly correlated with zooplankton community structure changes (P<0.05). The typical correlation analysis revealed that there was significantly positive correlation between zooplankton community and chlorophyll-a content in June. The water temperature and zooplankton community had a significant positive correlation in July. Furthermore, there were significant positive correlations between the zooplankton community and water depth, conductivity, turbidity and dissolved oxygen in August (P<0.05). Asplanchna girodi, which was the dominant species in the three-month period, was positively correlated with the chlorophyll-a content (P<0.05), but was negatively correlated with water temperature, pH and dissolved oxygen (P<0.05). The present study revealed that the zooplankton community structure exhibited a significant succession between months. Furthermore, the density of rotifers gradually decreased, and the density of cladocerans and copepods gradually increased. Moreover, the water level fluctuations caused changes in environmental factors, which had an important impact on the community succession of zooplankton.