富营养化对小型湖泊浮游甲壳动物群落结构及多样性的影响

2017年3月到2018年2月研究了临涣湖浮游甲壳动物群落结构的季节变化。临涣湖共记录浮游甲壳动物13种,其中枝角类8属8种,桡足类5属5种。短尾秀体溞(Diaphanosoma brachyurum)、广布中剑水蚤(Mesocyclops leuckarti)和象鼻溞(Bosmina sp.)等小型富营养种类是温暖季节的优势种,而近邻剑水蚤(Cyclops vicinus)是冬季的优势种。盔形溞(Daphnia galeata)等大型种类仅在少数月份中被观察到。临涣湖浮游甲壳动物的年平均密度和生物量分别为28.3个/L和0.33 mg/L。营养状态指数(TSI_M)的年平均值为62.6。浮游甲壳动物的Shannon指数、Pielou指数和Simpson指数的年平均值分别为0.86、0.74和0.49,且3种多样性指数均具有显著的季节差异。营养盐水平、营养状态指数和物种多样性指数均表明,临涣湖水体处于富营养化状态。冗余分析结果表明,水温、总磷浓度和叶绿素a浓度是影响临涣湖浮游甲壳动物群落结构变化的上行效应因子。鲢、鳙鱼的捕食压力是临涣湖浮游甲壳动物群落结构小型化的下行效应因子。

Impact of eutrophication on the community structure and species diversity of crustacean zooplankton in small lakes

The seasonal dynamics of the crustacean zooplankton community in Lake Linhuan were investigated from March 2017 to February 2018. A total of 13 species were recorded, including 8 species (8 genera) from Cladocera and 5 species (5 genera) from Copepoda. The eutrophic species Diaphanosoma brachyurum, Bosmina sp., and Mesocyclops leuckarti were the dominant species during the warm season, whereas Cyclops vicinus was the dominant species during winter. The large-sized Daphnia galeata was observed infrequently. The annual mean density and biomass of crustacean zooplankton were 28.3 ind/L and 0.33 mg/L, respectively. The annual mean trophic state index (TSI_M) was 62.6. The average yearly values of Shannon-Weiner index, Pielou index, and Simpson index of crustacean zooplankton were 0.86, 0.74, and 0.49, respectively, and there were significant seasonal differences in these indices. The nutrient levels, TSI_M, and species diversity index indicated that Lake Linhuan was affected by eutrophication. Redundancy analysis revealed that water temperature, total phosphorus concentration, and chlorophyll a concentration were the bottom-up factors affecting the community structure of crustacean zooplankton. The predation pressure from Hypophthalmichthys molitrix and Aristichthys nobilis was the top-down factor affecting the miniaturization of crustacean zooplankton community.