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Damming and impoundment are among the main flow-related alterations in rivers worldwide. However, compared to the highland river sections where the impacts associated with dams have been largely studied, still scarce evidence is available in scientific literature for large, lowland rivers. In this study, the ecological effects of a hydropower dam in the Po River (Italy) on the taxonomic and functional responses of benthic macroinvertebrates were examined by comparing one station upstream of the dam with one downstream station over a six-year period. Weak and not significant differences were observed for taxon richness, abundance and community composition. By contrast, community-level proportion of macroinvertebrates associated with water velocity increased during medium and high flow condition and decreased during low flow condition in downstream stations. Such differences were also mirrored by the Flow-T index, that is a biomonitoring index recently developed to assess hydraulic conditions in rivers. Results of this study support the adoption of stressor-specific metrics in river biomonitoring.

Benthic macroinvertebrates respond to several factors characterizing the physical habitats, as water depth, current and streambed substrate. Thus, anthropogenic disturbances altering these factors may have different effects on benthos, also depending on mesohabitats. These disturbances include sediment flushing operations, commonly carried out to recover reservoir capacity, and investigating their effects at mesohabitat scale could be relevant for an adequate ecological impact assessment of these operations. Here, we compared benthic macroinvertebrate communities sampled before and after a controlled sediment flushing operation in three different mesohabitats (a pool, a riffle and a step-pool) of an Alpine stream. Contrary from expectations, the composition of macroinvertebrate assemblages was not significantly different among mesohabitats. Moreover, the impact of sediment flushing was more significant in terms of density rather than in richness. Two stressor-specific indices were tested, but only one (the Siltation Index for LoTic EcoSystems − SILTES) clearly detected the impact of sediment flushing on the macroinvertebrate community structure. Finally, some differences in the temporal trajectories and recovery times to pre-flushing conditions were observed among mesohabitats, both if the three mesohabitats were considered separately and if all their possible combinations were accounted for. Particularly, riffle was the most sensitive mesohabitat, not fully recovering one year after the sediment disturbance.

In biomonitoring great attention has been paid on the selection of the best indices and metrics, often neglecting a simple but fundamental aspect: how reliable are the sampling methodologies? We tested the efficiency of the Surber net in collecting stream macroinvertebrates by comparing two samples collected consecutively on the same plot. We found that substrate particle size and water depth and velocity significantly affected sampling efficiency, especially regarding the total taxa richness, EPT (Ephemeroptera, Plecoptera and Trichoptera) richness and density. This study therefore provides useful insights to collect stream macroinvertebrates using the Surber net under different near-bed conditions.

Ditches are widespread and common elements of the agricultural landscape. Although they can provide habitats for aquatic biodiversity, their ecosystem integrity and processes are generally limited or even unknown due to anthropogenic pressures and the paucity of studies on this type of aquatic ecosystem. This study aimed to enhance the knowledge on the biodiversity, ecosystem attributes and ecological status of agricultural ditches by analyzing the macroinvertebrate communities of six different ditches and those of the main river in the same area. While negligible differences in taxonomic richness were observed, macroinvertebrate community composition significantly varied among sites as a function of the heterogeneous habitat conditions. These compositional differences strongly affected the relative abundance of functional feeding groups among sites and their derived ecosystem attributes. Moreover, the ecological status assessment depicted different scenarios depending on the biomonitoring indices applied. By means of a multifaceted, but still poorly adopted, analysis of the macroinvertebrate community, ranging from the taxonomic and functional diversity to ecosystem attributes and biomonitoring indices, the results obtained in this study offer useful information on the ecology of agricultural ditches with potential insights to improving their management. [ABSTRACT FROM AUTHOR]

The River Continuum Concept (RCC) is a milestone in stream ecology because of its comprehensive evaluation of the structure and function of lotic ecosystems. Linking stream physical and geomorphological attributes with patterns in biodiversity, functional traits, and metabolism dynamics, this theory describes downstream gradients in community composition and ecosystem processes. The aim of this review is to evaluate how the RCC, 40 years from its publication in the Canadian Journal of Fisheries and Aquatic Sciences, has influenced basic and applied research in stream ecology, focusing on the most important contributions and recent developments. This work puts into perspective the historical importance of the RCC in the scientific process and integrates past and recent theories, including metacommunity and metaecosystem theories and the river network perspective, to predict taxonomic and functional diversity of benthic communities. Thus, this review provides a unifying overview of the historical context of the field for exploring basic and applied ecological questions to the next generation of stream ecologists. Le concept de continuum fluvial (CCF) est un important jalon en ecologie fluviale en raison de l'evaluation exhaustive de la structure et de la fonction des ecosystemes lotiques qu'il permet. Cette theorie, qui relie les attributs physiques et geomorphologiques du cours d'eau aux motifs de biodiversite, a des caracteres fonctionnels et a la dynamique du metabolisme, decrit les gradients vers l'aval de la composition des communautes et des processus ecosystemiques. La presente synthese a pour objectif d'evaluer, 40 ans apres sa publication dans le Journal canadien des sciences halieutiques et aquatiques, l'influence du CCF sur la recherche fondamentale et appliquee en ecologie fluviale, en mettant l'accent sur les contributions les plus importantes et les avancees recentes. Ces travaux mettent en perspective la signification historique du CCF dans le processus scientifique et integrent des theories passees et recentes, dont les theories des metacommunautes et des metaecosystemes et la perspective du reseau hydrographique, pour predire la diversite taxonomique et fonctionnelle des communautes benthiques. La synthese fournit donc a la prochaine generation de specialistes de l'ecologie fluviale un survol unificateur du contexte historique du domaine pour l'exploration de questions ecologiques fondamentales et appliquees. [Traduit par la Redaction], Introduction The scientific process tends to be slow and steady, punctuated by times of rapid growth and change in the field, as Thomas Kuhn once described as a 'scientific revolution' [...]

Benthic macroinvertebrates are important for stream ecosystem function and are considerable food resources for vertebrate consumers such as fish. The diversity, composition, and distribution of stream macroinvertebrate taxa are affected by factors that act at different spatial scales, from microhabitat to watershed‐level effects. While comparative studies of watershed‐level and between stream influences on benthic diversity are common, the effects of scale are less investigated within individual river segments. Benthic macroinvertebrates were systematically sampled across nested spatial scales along a 2.2‐km near‐pristine stretch of the Upper Black River (MI, USA), and analyzed in relation to near‐bed flow and substrate features. Responses of community diversity metrics to near‐bed conditions were quantified, and diversity was modeled to determine the contribution of each spatial scale to total diversity. Near‐bed conditions, especially Froude number and substrate size, were positively associated with macroinvertebrate diversity and abundance. Larger (e.g., 100 m stream reach) and finer scales (e.g., individual samples) accounted for a greater proportion of variation in taxon richness and abundance, respectively. Longitudinal variation in environmental conditions was an important driver of macroinvertebrate diversity, with replacement between sites (i.e., turnover) contributing a considerably greater proportion of variation in total diversity than nestedness. Results demonstrate that macroinvertebrate communities were shaped by both local flow and substrate conditions as well as taxa replacement over larger spatial scales. This emphasizes the importance of maintaining the hydro‐morphological integrity along stream courses as a requisite condition to further watershed and fisheries conservation and management. [ABSTRACT FROM AUTHOR]

Droughts are affecting an increasing number of lotic ecosystems worldwide due to the combined effects of climatic and anthropogenic pressures. Unlike naturally intermittent rivers, where the drying phase is a part of the annual flow regime, water scarcity in Alpine rivers represents a relatively recent phenomenon and, therefore, a major threat for the biodiversity of these lotic ecosystems. However, Alpine stream community response to drought is still poorly investigated. Here, we assess the recovery of macroinvertebrates in two Alpine streams after a supraseasonal drought. As water returned, a total of 10 sampling sessions were carried out, and temporal patterns in diversity, density, and taxonomic composition of benthic communities, as well as in the percentage of functional feeding groups, were investigated. We found that the resistance of invertebrate communities in Alpine streams is generally low: drought markedly reduced the diversity and density of macroinvertebrates. Conversely, our results suggest that the passive dispersal by drift from the upstream river sections seems the most probable mechanism promoting the post‐drought recovery. Nevertheless, this resilience ability appears to be stream specific and influenced by intrinsic stream characteristics, including the flow permanence and distance from the nearest upstream perennial reach. This work sheds light on the ecological consequences of droughts on macroinvertebrate communities. As flow intermittency in Alpine areas is expected to intensify under current global change scenarios, results of this study provide important information to predict changes in the taxonomic composition and diversity of macroinvertebrate communities. [ABSTRACT FROM AUTHOR]

Fine sedimentation was quantified in the upper stretch of the Pellice river basin (Italian Alps), in an area partially disturbed by mining activities. Sediment traps were placed in 52 sites and benthic samples were collected to assess the amount of coarse particulate organic matter and the structure of macroinvertebrate community. The results indicated that the increase of fine sediment in the river reduced the amount of coarse particulate organic matter, affecting the abundance of invertebrate shredders. In small alpine streams, where allochthonous organic matter is the main energy source, fine sedimentation reduces the availability of trophic resources, affecting the abundance of benthic communities. [ABSTRACT FROM AUTHOR]