Developing environmental flow targets for benthic macroinvertebrates in large rivers using hydraulic habitat associations and taxa thresholds

Longitudinal recovery gradient of macroinvertebrates during different hydrological scenarios in a downstream river reach

“…In spite of the fact that Dusabe et al, (2022) reported only weak dam-induced effect on low-diversity downstream river reaches, all aspects of NFR are still changed (Krajenbrink et al, 2019). The consequence from this influence is a significant reduction of macroinvertebrate richness (Trottier et al, 2022) which is better detected from the metrics reflecting the state of compositional changes than the diversity indices (Wegscheider et al, 2023). Those organisms are important for the overall vitality of a riverine ecosystem because they impact the biotic component through their trophic function into the instream food web and impact the abiotic component through biogeochemistry processes (Wang et al, 2020;Wang et al, 2021).…”

“…Most studies connected to regulated rivers are planned and executed short term (Krajenbrink et al, 2019) although they should be designed in a manner that must allow observations during diverse flow and water level scenarios. This is needed to obtain samples from extreme high and low flow events, which are crucial in structuring the biodiversity in rivers (Wegscheider et al, 2023). Although this is an assumption made by Wegscheider et al (2023) about large rivers, it seems that the same principles are valid for lotic water bodies of smaller size, too (White et al, 2017).…”

“…This is needed to obtain samples from extreme high and low flow events, which are crucial in structuring the biodiversity in rivers (Wegscheider et al, 2023). Although this is an assumption made by Wegscheider et al (2023) about large rivers, it seems that the same principles are valid for lotic water bodies of smaller size, too (White et al, 2017). This is consistent with our study, because in 2018 the overall richness of macroinvertebrates was improved for half of the studied longitudinal distance (800 m), followed by a decline.…”

“…Modifications of the hydrological regime also led to changes in the physical habitats, which in turn strongly determines community composition and supports the production and sustainability of aquatic ecosystems (European Commission, 2015;Wegscheider et al, 2023). The effect of these hydrological alterations and rate of recovery can be detected by one of the most sensitive river communities, whose composition and structure reflect the overall degradation in rivers -macrozoobenthic organisms (Doichev et al, 2020;Wang et al, 2020;Dusable et al, 2022).…”

“…Following that, insufficient regulation of discharge into downstream river reaches from dams is a significant impediment to the presence of diverse freshwater biota (Voelz and Ward, 1991), because the organisms have evolved developing life strategies coupled with natural flow regimes (Bunn and Arthington, 2002;Rivas and Koleva-Lizama, 2017;Carlisle et al, 2019). Therefore, the natural variability of stream flows, the so-called "natural flow regimes" (NFR), is crucial to sustain populations of different freshwater organisms, along with ecosystem health, function, and services (Poff et al, 2007;Poff et al, 2010;European Commission, 2015;Wegscheider et al, 2023).…”