ABSTRACT

Density and biomass are commonly used in ecological studies of zooplankton. However, these metrics are not functionally equivalent and provide different information regarding community structure. Differences in the response of zooplankton, as estimated through both density and biomass in relation to environmental variability, were investigated in a large subtropical lake. Results based on 2 years of seasonal sampling at 9 points in Lake Mangueira (southern Brazil) showed a large difference in the pattern of dominance of zooplankton between the density and biomass metrics. Ciliates composed >58% of zooplankton density (rotifers 29.4%) but only 16.1% of zooplankton biomass. Analyzing the composition of zooplankton based only on biomass might therefore underestimate the importance of microzooplankton components, which are an important trophic link in pelagic food webs of subtropical systems. The differences between the 2 metrics in relation to abiotic variables were assessed through redundancy analysis. Seasonality was the main factor driving the variability of zooplankton, and density proved to be the best metric to show the seasonal variation of zooplankton taxa and taxonomic groups in relation to environmental conditions. Density was also the most appropriate metric for analyzing annual cycles and the seasonal succession of species. However, the biomass metric was significantly related to production-related parameters (pH and chlorophyll a) and was essential to better understand zooplankton grazing relationships and the trophic structure of the system.

抽象的

密度和生物量通常用于浮游动物的生态研究。但是，这些指标在功能上并不等效，并提供有关社区结构的不同信息。在一个大型的亚热带湖泊中，通过密度和生物量估算的浮游动物响应差异与环境变化有关。根据曼圭拉湖（巴西南部）9个点的2年季节性采样得出的结果表明，密度和生物量指标在浮游动物主导模式上有很大差异。纤毛虫占浮游动物密度的> 58％（轮虫占29.4％），但仅占浮游生物量的16.1％。因此，仅根据生物量来分析浮游动物的组成可能会低估微浮游动物成分的重要性，这是亚热带系统中上层食物网中重要的营养纽带。通过冗余分析评估了与非生物变量有关的两个指标之间的差异。季节性是驱动浮游动物变异性的主要因素，密度被证明是显示浮游动物分类群和生物分类群与环境条件相关的季节性变化的最佳指标。密度也是分析物种的年度周期和季节演替的最合适指标。但是，生物量指标与生产相关参数（pH和叶绿素）显着相关。季节性是驱动浮游动物变异性的主要因素，密度被证明是显示浮游动物分类群和生物分类群与环境条件相关的季节性变化的最佳指标。密度也是分析物种的年度周期和季节演替的最合适指标。但是，生物量指标与生产相关参数（pH和叶绿素）显着相关。季节性是驱动浮游动物变异性的主要因素，密度被证明是显示浮游动物分类群和生物分类群与环境条件相关的季节性变化的最佳指标。密度也是分析物种的年度周期和季节演替的最合适指标。但是，生物量指标与生产相关参数（pH和叶绿素）显着相关。a），对于更好地了解浮游动物的放牧关系和系统的营养结构至关重要。