The use of reference conditions is essential to the monitoring and management of aquatic ecosystems. We examined existing and potential reference sites through historical data, maps, and field data collected from river sites in KwaZulu-Natal (KZN), South Africa. In our study, we applied nine criteria that best reflect the characteristics of South African rivers on 24 a priori selected reference sites. These nine criteria comprised of catchment conditions (flow modification and natural landscape) and site-specific attributes (water quality, human disturbance, river channel, water abstraction, riparian vegetation, riparian zone modification, and instream habitat quality). The a priori selected reference sites were subjected to validation using multivariate methods, such as analysis of similarities (ANOSIM), similarity percentages (SIMPER), and non-parametric multidimensional scaling (MDS) based on the macroinvertebrate fauna by applying a SASS5 threshold considered to be an indicator of undisturbed sites in South African rivers. We identified differences in the macroinvertebrate assemblages of the reference conditions for each river group based on their ecoregions, geomorphology and seasonal variations. Ecoregions and river geomorphology were better in the grouping of sites with similar reference conditions than the seasons. Our findings indicated that all of the selected sites could be considered as valid reference sites; however, caution should be taken in applying this method to lowland rivers because of their noticeable seasonal variability and habitat instability which tend to alter their reference states. We recommend that a type-specific reference condition be developed for lowland rivers. Also, statistical validation of reference conditions should be a continuous process in river biomonitoring.

中文翻译：

---

南非夸祖鲁-纳塔尔河参考条件选择和验证的多变量方法

参考条件的使用对于水生生态系统的监测和管理至关重要。我们通过从南非夸祖鲁-纳塔尔 (KZN) 的河流站点收集的历史数据、地图和现场数据检查了现有和潜在的参考站点。在我们的研究中，我们在 24 个先验选择的参考地点上应用了九个最能反映南非河流特征的标准。这九个标准包括集水条件（流量改变和自然景观）和特定地点的属性（水质、人为干扰、河道、取水、河岸植被、河岸带改变和河内栖息地质量）。使用多变量方法对先验选择的参考位点进行验证，例如相似性分析 (ANOSIM)、相似性百分比 (SIMPER)、和基于大型无脊椎动物群的非参数多维尺度 (MDS)，通过应用 SASS5 阈值被认为是南非河流中未受干扰地点的指标。我们根据每个河流群的生态区、地貌和季节变化，确定了参考条件下大型无脊椎动物群落的差异。生态区和河流地貌在具有相似参考条件的站点分组中优于季节。我们的研究结果表明，所有选定的站点都可以被视为有效的参考站点；然而，在将这种方法应用于低地河流时应谨慎，因为它们明显的季节性变化和栖息地不稳定性往往会改变它们的参考状态。我们建议为低地河流制定特定类型的参考条件。此外，参考条件的统计验证应该是河流生物监测中的一个连续过程。