The Impact of Hydromorphological Alterations on Mayfly Assemblages of a Mid-Sized Lowland River in South-Eastern Europe

Abstract

Historically, rivers have been anthropogenically modified for different purposes worldwide (e.g., flood control, drinking water abstraction, and land drainage). Although the majority of European lowland rivers are under the impact of multiple stressors (water quality, hydromorphological alterations, land-use), the consequences of these influences on aquatic macroinvertebrates, including mayflies, have not been sufficiently studied. Therefore, with the aim of providing additional data on the response of mayflies to anthropogenic disturbances in riverine habitats, we studied mayfly assemblages and their relationship to environmental factors along a mid-sized lowland river in Croatia. No significant differences in mayfly species richness and their functional traits were observed among the three habitat groups with different levels of hydromorphological alterations (near-natural, moderately altered, and severely altered habitats). This could be related to the river’s connection to the numerous tributaries, and the variety of available microhabitats along the studied system, despite the existing hydromorphological pressures. A stronger relationship was found between mayflies and the physico-chemical water characteristics and land-use. Water temperature, water velocity, oxygen content, and nutrient (e.g., nitrogen, phosphorous) concentrations related to agricultural and urban land-use were found to be the most important factors shaping mayfly assemblages in the studied lotic lowland system. These results can contribute to the planning of management and conservation activities for lowland rivers and their biota according to the requirements of the European Water Framework Directive.

The impact of the geographical environment on the hydromorphological conditions of watercourses in southern Poland

“…Changes related to modification of riverbeds and banks are observed here, as well as interference with riparian zones affecting biodiversity (Feld et al 2014, Kałuża et al 2020, Knehtl et al 2021, Kupiec et al 2021, Borek 2023, Denic et al 2023, Garbowski et al 2023). In the case of lowland rivers, a dominance of laminar flow is observed and this in turn translates into habitats for macrophytes and macroinvertebrates (Guareschi et al 2014, Kujanová et al 2018, Vilenica et al 2022). The selected river sections were therefore characterised by a relatively high diversity and abundance of hydromorphological units compared to the other sections (Akstinas et al 2022).…”