Macroinvertebrates from a small forest stream in central-south Chile were sampled monthly from September 2017 to August 2018 to assess temporal variability in the assemblage and the effects of that variability on ecological indicators. Higher precipitation and flows occurred in winter months, and water quality varied among months. We collected 59 macroinvertebrate taxa, finding higher taxa richness and abundances in summer months than in winter months. Four taxa demonstrated marked seasonality, being abundant in some months and then decreasing in following months (Limnoperla jaffueli (Navás), Nousia maculata (Demoulin), Smicridea sp. (McLachlan), Chironomidae spp.). The scores of the family Hilsenhoff Biotic Index (HBI), Hilsenhoff Species-level Biotic Index (HSBI), Multimetric Macroinvertebrate Index (MMI), and Chilean Biological Monitoring Working Party (ChBMWP) index varied throughout the year reflecting natural variability. However, only HBI and HSBI scores were significantly different among seasons, ranging across three water quality classes (excellent, very good, and good), showing the lowest water classes in spring, coinciding with higher abundances of tolerant species. The MMI and ChBMWP indicated good and very good site conditions throughout the year, respectively. Shannon-Weaver diversity ranged between 2.59 (April) and 1.78 (February); however, Pielou evenness had high values throughout the year (> 0.62), except in February. Changes in macroinvertebrates composition throughout the year were explained primarily by discharge, water temperature, and conductivity. Our findings indicate that natural monthly variability in macroinvertebrate assemblages influences the scores of biological indices throughout the year. Therefore, we recommend that natural stream variability be accounted for in biomonitoring programs. We also emphasize the need to use caution when interpreting biological index scores to avoid misinterpretations in stream quality classification.

2017 年 9 月至 2018 年 8 月，对来自智利中南部一条小型森林溪流的大型无脊椎动物进行了每月采样，以评估组合的时间变异性以及这种变异性对生态指标的影响。冬季月份降水量和流量较高，水质因月份而异。我们收集了 59 个大型无脊椎动物类群，发现夏季月份的类群丰富度和丰度高于冬季月份。四个分类群表现出明显的季节性，在某些月份丰富，然后在接下来的几个月中减少（Limnoperla jaffueli (Navás)、Nousia maculata (Demoulin)、Smicrideasp. (McLachlan), Chironomidae spp.)。家族 Hilsenhoff 生物指数 (HBI)、Hilsenhoff 物种级生物指数 (HSBI)、多度量大型无脊椎动物指数 (MMI) 和智利生物监测工作组 (ChBMWP) 指数的分数全年变化，反映了自然变异性。然而，只有 HBI 和 HSBI 分数在不同季节之间存在显着差异，涵盖三个水质等级（优秀、非常好和良好），显示春季最低水等级，与较高丰度的耐受物种一致。MMI 和 ChBMWP 分别显示全年良好和非常好的场地条件。Shannon-Weaver 多样性介于 2.59（四月）和 1.78（二月）之间；然而，除二月外，皮楼均匀度全年都很高（> 0.62）。全年大型无脊椎动物组成的变化主要通过排放、水温和电导率来解释。我们的研究结果表明，大型无脊椎动物组合的自然月变化影响全年生物指数的得分。因此，我们建议在生物监测程序中考虑自然流变率。我们还强调在解释生物指数分数时需要谨慎，以避免在流质量分类中出现误解。我们建议在生物监测计划中考虑自然流变率。我们还强调在解释生物指数分数时需要谨慎，以避免在流质量分类中出现误解。我们建议在生物监测计划中考虑自然流变率。我们还强调在解释生物指数分数时需要谨慎，以避免在流质量分类中出现误解。