Unilever Centre for Environmental Water Quality, Institute for Water Research, Rhodes University, P.O Box 94, Grahamstown, 6140, South Africa.
Zoology and Entomology, Rhodes University, P O Box 94, Grahamstown, 6140, South Africa.
Environ Monit Assess. 2020 Mar 5;192(4):214. doi: 10.1007/s10661-020-8187-4.
Sedimentation arising from agricultural run-offs, riparian habitat fragmentation and channel bank erosion has long been known to impair the structure and ecological functioning of stream and river ecosystems. This study examined the effects of fine sediment grain sizes on the functional feeding group structure of Ephemeroptera, Plecoptera and Trichoptera (EPT) in the Tsitsa River catchment in the Eastern Cape Province of South Africa. Fine sediments and EPT were sampled between August 2016 and April 2017 from eight selected sampling sites. The eight sites were classified into four groups in terms of fine sediments and turbidity to represent a gradient of sediment stress, with site groups 4 and 3 being less influenced and groups 2 and 1 as the highly influenced groups. EPT genera/species were assigned to five functional feeding groups (FFGs) and their responses to sediment stress assessed. The results of the study showed that of the five FFGs, four (i.e. collector-filterer, collector-gatherer, scraper/grazer and shredder) were significantly different between the four groups, separating the impacted groups from the less impacted groups. Redundancy analysis (RDA) showed that FFGs such as scraper/grazer, collector-gatherer and shredder were tolerant to fine sediment, especially during the dry season. Collector-filterers and predators were the most sensitive FFGs observed in the studied river systems. The RDA results showed that the coarser grain size fractions (very coarse and coarse silt, very fine sand and turbidity) displayed more severe negative effects on EPT FFGs when compared with the finer grain size fractions such as very fine and fine silt. The results obtained in this study provided more insights into the response patterns and functional dynamics of EPTs in the Tsitsa River systems, a knowledge that can contribute to trait-based biomonitoring in South Africa.
农业径流、河岸带生境破碎化和河道岸坡侵蚀导致的泥沙淤积，长期以来一直被认为会破坏溪流和河流生态系统的结构和生态功能。本研究调查了细颗粒泥沙粒径对南非东开普省 Tsitsa 河流域蜉蝣目、襀翅目和毛翅目（EPT）功能摄食类群结构的影响。2016 年 8 月至 2017 年 4 月，从 8 个选定的采样点采集了细颗粒泥沙和 EPT。这 8 个采样点根据细颗粒泥沙和浊度分为 4 组，以代表泥沙胁迫的梯度，其中组 4 和组 3 受影响较小，组 2 和组 1 受影响较大。将 EPT 属/种分为 5 个功能摄食类群（FFG），评估它们对泥沙胁迫的响应。研究结果表明，在这 5 个 FFG 中，有 4 个（即集食滤食者、集食搜集者、刮食者/食草者和碎食者）在 4 个组之间存在显著差异，将受影响的组与受影响较小的组区分开来。冗余分析（RDA）表明，刮食者/食草者、集食搜集者和碎食者等 FFG 对细颗粒泥沙具有较强的耐受性，尤其是在旱季。集食滤食者和捕食者是在研究河流系统中观察到的最敏感的 FFG。RDA 结果表明，与较细的颗粒粒径（极细和细粉砂、极细砂和浊度）相比，较粗的颗粒粒径（粗砂和极粗砂、粗粉砂）对 EPT FFG 产生更严重的负面影响。本研究的结果提供了对 Tsitsa 河流系统中 EPT 响应模式和功能动态的更深入了解，这一知识有助于南非基于特征的生物监测。
