Effect of food and copepod trophic level on zooplankton community structure in a subtropical stratified reservoir

Abstract

于2014年10-12月，采集厦门溪东水库浮游动物、浮游植物、浮游细菌与悬浮物样品，分析浮游动物群落与食物质量和食物浓度的关系，探讨桡足类营养级变化对浮游动物的影响.结果表明，空间上后生浮游动物群落结构在水库不同水层间的差异不显著；时间上桡足类在水华期和非水华期的差异不显著，枝角类和轮虫在水华期和非水华期的差异显著.桡足类群落组成受食物质量的影响较大，枝角类群落组成受食物浓度的影响较显著，轮虫群落组成受食物质量和食物浓度的共同影响.进一步分析表明，食物质量和食物浓度与水温显著相关，枝角类生物量受食物浓度的影响，桡足类生物量与轮虫生物量呈显著相关.为了探究桡足类与食物质量的关系，我们以优势种舌状叶镖水蚤（Phyllodiaptomus tunguidus）为对象分析化学计量特征，发现舌状叶镖水蚤体内的磷含量与水柱总磷平均浓度和水温呈显著正相关，其营养级变化范围为1.28~2.84，且营养级随着水温下降而显著增加.非水华期的食物磷含量增加可能是舌状叶镖水蚤丰度升高的原因之一，降温和种群繁殖的共同影响导致非水华期舌状叶镖水蚤体内磷含量逐渐下降，营养级增加.研究结果可为揭示浮游动物在富营养化内陆水体中的群落演变过程机制提供基础数据.;To analyze the relationship between zooplankton community structure and food quality or food concentration, and to explore the effect of copepod trophic level change on zooplankton community, the suspended matter, free-living bacteria, phytoplankton and zooplankton samples were collected in Xidong Reservoir in Xiamen from October to December of 2014. The results showed that the community structure of zooplankton did not exhibit significant difference along the water column. The community structure of copepod between the cyanobacterial bloom stage and the non-bloom stages was similar, whereas the cladocera and rotifera during cyanobacterial bloom and non-bloom stages were significantly different. Further, our results showed that the effect of food quality on copepod was significant, the effect of food concentration on cladocera was significant, while the effect of food quality and food concentration on rotifera was significant. Food quality and food concentration were significantly correlated with water temperature, copepod biomass was significantly related with rotifera biomass, cladocera biomass was significantly correlated with food concentration. In order to explore the relationship between copepod and food quality, the dominant species (Phyllodiaptomus tunguidus) was selected to analyze the stoichiometric characteristics. The results showed that the phosphorus content of P. tunguidus body was significantly and positively correlated with the average concentration of total phosphorus in water column and water temperature. The trophic level of P. tunguidus varied from 1.28 to 2.84 during the investigation period, and the trophic level increased significantly with the decrease of water temperature. Our results showed that the high quality of food in non-bloom stage was one of the reasons for the high abundance of P. tunguidus. In non-bloom stage, the joint effects of water temperature decrease and population reproduction led to decrease in the phosphorus content of P. tunguidus, and increase in the trophic level. These results provide the fundamental data for revealing the dynamic processes and mechanism of zooplankton community in eutrophic inland waters.