Exploring Macroinvertebrates Ecological Preferences and Trait-Based Indicators of Suspended Fine Sediment Effects in the Tsitsa River and Its Tributaries, Eastern Cape, South Africa

Abstract

The taxonomy-based response pattern of macroinvertebrates to sediment stress is well established, with tolerant taxa increasing in impacted conditions, while sensitive taxa decrease along a deteriorating water quality gradient. However, the distribution patterns of traits in response to environmental stress gradient, including suspended sediments, remain unclear, particularly in Africa, where trait-based studies are under-explored. We examined the distribution patterns of macroinvertebrate traits along a suspended sediment stress gradient and identified tolerant and sensitive traits for suspended sediment stress. We sampled macroinvertebrates and environmental variables seasonally in winter, spring, summer and autumn of 2016 to 2018 in eight selected sites in the Tsitsa River and its tributaries. We selected 12 traits and ecological preferences, resolved them into 47 trait attributes, and analysed them using the RLQ and fourth-corner analyses. Our results revealed that macroinvertebrate traits and ecological preferences were differentially influenced by fine suspended sediments in the Tsitsa River and its tributaries. Traits such as a preference for CPOM, collector-filtering, and a high sensitivity to oxygen depletion, were deemed sensitive to suspended sediments stress, exhibiting positive associations with the control sites, and negatively associated with any of the environmental parameters (sediment grain sizes, turbidity, TSS and EC). Tolerant indicator traits included a high tolerance of oxygen depletion, skating and a preference for FPOM. The fourth-corner analysis results indicated that suspended fine sediment grain sizes, (including coarse sand, fine silt and clay) were the most important variables influencing macroinvertebrate trait distribution patterns during the dry season, while gravel, mud and medium sand were more important during the wet season. Overall, our study provided critical insights towards trait-based responses of macroinvertebrates communities to suspended sediment stress, key information that could stimulate the development of macroinvertebrate trait-based biomonitoring tools for the assessment of suspended sediment stress in the Afrotropical region.

Determining Tipping Points and Responses of Macroinvertebrate Traits to Abiotic Factors in Support of River Management

“…The transport of fine particles can result in a build-up on the organs, which disrupts the normal functioning of the organisms. Fine sediments also impair habitats by clogging the interstices and reducing oxygen levels in the hyporheic zone, decrease food availability by attenuating light needed for optimal algal growth and covering algal food for grazers, and reduce the quality and palatability as well as access to food for shredders [ 72 , 73 , 74 , 75 ]. Sedentary invertebrates and cemented eggs or clutches are also affected by fine sediment deposition by being buried, leading to a lack of access to food and a reduced oxygen supply [ 71 ].…”

Diversity and variability of macroinvertebrates in ponds within the limestone post-exploitation area in Górażdże (Poland) over a 10-year period

“…Many interrelated environmental factors, such as the water body size, the diversity of habitats or water chemistry affects the abundance of macroinvertebrates (in general and of individual groups), thus making it difficult to determine precisely which of them is the leading one. However, it can be assumed that a pivotal factor in the surveyed ponds was the specificity of the bottom substrate (Ntloko et al, 2021). The weathering of limestone rock led to the accumulation of a thick layer of unconsolidated clay sediments.…”

Effects of river regulation on aquatic invertebrate community composition: A comparative analysis in two southern African rivers

“…Furthermore, studies have also found alterations and declines in aquatic invertebrate diversity, community composition and functional traits within regulated and anthropogenically influenced streams and riverine systems (Gallardo et al, 2008(Gallardo et al, , 2014Kuiper et al, 2014). However, there is a scarcity of research in Africa, despite being one of the most affected continents in terms of anthropogenic use of freshwater systems (Akamagwuna et al, 2022;Ntloko et al, 2021;Odume, 2020). de de Necker, Manfrin, et al, 2020;de Necker, Neswiswi, et al, 2020;Dube et al, 2015Dube et al, , 2019.…”

“…These organisms encompass a diverse group of species with a widespread distribution and range of traits and adaptations to ensure survival in various aquatic environments (de Necker et al., 2021 ; de Necker, Brendonck, et al., 2022 ; Dube et al., 2022 ; Jeffries et al., 2016 ; Lake, 2011 ; Wantzen et al., 2016 ). Furthermore, aquatic invertebrates are known to undergo shifts in community composition in response to anthropogenic stressors (Akamagwuna et al., 2022 ; Cai et al., 2017 ; Foster et al., 2015 ; Helson & Williams, 2013 ; Magbanua et al., 2010 ; Mangadze et al., 2019 ; Ntloko et al., 2021 ; Villastrigo & García‐Criado, 2017 ). As a result, aquatic invertebrate traits and sensitivities have successfully been used as a biomonitoring method to assess ecosystem health (Akamagwuna et al., 2022 ; de Necker et al., 2023 ; Magbanua et al., 2010 ; Mangadze et al., 2019 ; Ntloko et al., 2021 ; Odume, 2020 ).…”

“…Furthermore, aquatic invertebrates are known to undergo shifts in community composition in response to anthropogenic stressors (Akamagwuna et al., 2022 ; Cai et al., 2017 ; Foster et al., 2015 ; Helson & Williams, 2013 ; Magbanua et al., 2010 ; Mangadze et al., 2019 ; Ntloko et al., 2021 ; Villastrigo & García‐Criado, 2017 ). As a result, aquatic invertebrate traits and sensitivities have successfully been used as a biomonitoring method to assess ecosystem health (Akamagwuna et al., 2022 ; de Necker et al., 2023 ; Magbanua et al., 2010 ; Mangadze et al., 2019 ; Ntloko et al., 2021 ; Odume, 2020 ). It is therefore crucial to consider aquatic invertebrate traits and ecological preferences in freshwater studies to help understand community structure and disturbance effects and ensure maintenance of ecological processes (Akamagwuna et al., 2022 ; Vinagre et al., 2017 ).…”