Search

In this study, we analysed the diet of two populations of Perlodes intricatus (Pictet, 1841) inhabiting river sections characterised by different environmental quality. Macrobenthic communities and...

Calanoids of the family Diaptomidae are the most widespread copepods in the lentic inland waters of the Palearctic region. In Italy, studies on the family date back to the end of 19th century. Since then, several papers contributed to increasing the knowledge on their presence, distribution, and ecological preferences. Nevertheless, new records for the area and the discovery of putative new species stress that the current knowledge on these inland water crustaceans is still far from being exhaustive. This paper presents an updated and annotated checklist and bibliography of the Diaptomidae of the Italian peninsula and surrounding islands, including Corsica and the Maltese islands, compiled through a critical review of the existing literature and carrying out further field research. The doubtful records reported in the literature are discussed and clarified. The updated checklist includes 30 diaptomid species and subspecies; among them, an alien species and three putative new species pending formal description are reported. About 20% of the observed species are endemic or subendemic to the study area. The faunal provinces ascribed to the Mediterranean limnofaunistic region host the highest species richness and contribute to the checklist with rare species and unique occurrences. The high species richness observed in the Mediterranean area supports the hypothesis of a long-lasting persistence of an ancient and peculiar copepod fauna.

One of the main challenges in river management is the setting of nutrient thresholds that support good ecological status, which is the main objective to achieve for the European member states. This is a complex process, which needs an accurate analysis of the data collected so far for the ecological classification of rivers belonging to different typologies. We analysed the data of the multiannual monitoring concerning diatoms and nutrients in the upper Po River (NW Italy) with the aim of exploring the response of diatom community in terms of species composition, ecological guilds and indices. We considered data of 390 samples, of which 2/3 belonging to the “Central macrotype” (i.e. lowland stretches) and 1/3 to “Alpine siliceous”. We performed a Principal Coordinate Analysis to detect community patterns with respect to water chemical classification and macrotypes highlighting species and ecological guilds characteristic of samples along a water quality gradient. We then performed a partial RDA to focus on the role of environmental and spatial factors in shaping the diatom community in each of the two macrotypes. Finally, we investigated the concordance between the Italian normative indices ICMi (for diatoms) and LIMECO (a chemical index of water quality). We found significant differences in the diatom communities of the two macrotypes and in their response to water quality and to spatial factors. Communities resulted as much more uniform in sites with a low water quality, with characteristic species such as Navicula gregaria, Nitzschia palea and Sellaphora nigri. On the other hands, moderately disturbed sites (in terms of trophic level) were characterised by the highest guild diversity. The RDA confirmed the importance of spatial factors in shaping the diatom assemblages, especially in Alpine streams where the physical barriers may condition species dispersion. The comparison between the two normative indices highlights that the correspondence in the classification is achieved in the 57% (Alpine macrotype) and 43% (Central macrotype) of samples. According to our findings, we suggest the revision of the ICMi, both class boundaries and reference value. In addition, we recommend to lower LIMECO threshold for total phosphorus: indeed, several studies have shown significant changes in the diatom community composition starting from very low values (below the current LIMECO threshold, i.e. 50 µgL-1). Moreover, the extension of our study to the whole Po River basin will complete our knowledge of species not yet included in the diatom indices and of the community response to nutrient levels also in other macrotypes.

The order Odonata comprises many predaceous species that inhabit aquatic systems, and a few that are restricted to flowing waters. Cordulegaster boltoni is a widespread Odonata in Europe, which usually inhabits small lotic systems. In this study we analysed the gut contents of C. boltoni immature stages, collected in the Rocchetta Tanaro Natural Park (Italy, Piemonte). Two hundred and eleven individuals were collected, and their diet analyzed by dissection or clearing. Larvae appeared to be opportunistic predators, feeding on a variety of prey. Aquatic insects dominated their diet, while crustaceans, annelids, molluscs and terrestrial invertebrates were sporadically observed in the gut contents. An ontogenetic shift in the diet was detected, as small larvae consumed different prey than large ones. Our study suggests that C. boltoni is one of the dominant predators in the benthic communities of lowland small order streams of Piemonte, which, because of their environmental characteristics, are devoid of fish and stoneflies.

Several Alpine streams are currently changing from perennial to intermittent systems with expected detrimental consequences on benthic invertebrates, through the alteration of hydrological conditions, substrate composition, and trophic resources. We examined the ecological niche of three phylogenetically-related scraper macroinvertebrates, namely Ecdyonurus, Epeorus, and Rhithrogena (Ephemeroptera, Heptageniidae) experiencing recurrent summer dewatering events in perennial and intermittent stretches in 13 Alpine streams. We evaluated the overlap among the ecological niches of the three examined taxa in terms of hydraulic stress, substrate coarseness, and total primary production and we investigated their ecological preferences in perennial and intermittent sites. Our results showed a broad overlap of their ecological niches, suggesting exploitative competition among the examined taxa. Their ecological niches were smaller in intermittent than perennial sites, pointing out a reduction of available microhabitats. All groups were favored by substrate coarseness and total primary production in reach types, while the hydraulic stress showed an opposite effect in perennial (negative) and intermittent (positive) sites. Overall, our results emphasize how stream physical parameters play a key role in determining the ecological niche of Heptageniidae and underline how benthic communities in intermittent sections of previously perennial Alpine streams are currently under pressure.

Assessing the water quality by using biological indicators is a reliable and economically feasible way to promote environmental conservation in developing tropical countries. Here, we report one of the few examples of river biomonitoring in Honduras. In June 2005, benthic macroinvertebrates were collected from six sites in the Río Cangrejal basin. An adapted version of the Biological Monitoring Working Party index (BMWP) was used to assess the water quality because it is simple, consolidated, relatively easy to use, and needs a family-level identification. Moreover, two other community metrics were calculated, namely the total taxon richness and local contribution to beta diversity (LCBD). Differences in the biomonitoring and diversity metrics among sites and their correlations were statistically tested. Thirty-nine macroinvertebrate taxa were collected and, despite significant differences in the BMWP score, all sampling sites were classified in the high environmental quality class. A very strong and positive correlation between the BMPW and taxon richness was found, while LCBD did not vary significantly and did not correlate with the other metrics. Our results suggest that taxon richness could be used as a surrogate indicator to assess the water quality when consolidate biomonitoring methods are not available.

Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1mmolm(-2) h(-1) at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams. Diel patterns can greatly impact total stream carbon dioxide emissions, with 39% greater carbon dioxide flux during the night-time relative to the day-time, according to a study of 34 streams across Europe.

The MesoHABitat SImulation Model (MesoHABSIM) is the preferred method to calculate spatio-temporal variation in the fish habitat availability in Italian rivers. With the aim of improving the applicability of the MesoHABSIM approach in the Italian territory, we carried out a systematic review of physical habitat preferences for 31 freshwater fish species and three freshwater lampreys, representing 75% of the total indigenous freshwater fish community of Italy. Information related to suitable ranges of depth, flow velocity, biotic/abiotic substrates, covers/shelters was collected and summarized for two critical life stages (adult and juvenile) and two bioperiods (rearing/growth and spawning). Overall, 250 publications were reviewed, classified as 206 peer-reviewed papers, 20 books, 7 PhD thesis, and 17 grey literature sources. Our analysis revealed substantial deficits of information about habitat requirements for more than 30% of Italian freshwater fish species. This information is particularly scarce for the most threatened endemic species, especially for their most critical bioperiod (i.e., spawning). With the aim of preserving freshwater fish biodiversity as required in the EU Biodiversity Strategy for 2030 (European Commission, 2020), accurate information on physical habitat requirements for spawning is crucial. As an example application of MesoHABSIM, the collected habitat preference information was used to define and apply mesohabitat suitability criteria for one fish species (Telestes muticellus) in a regulated river reach of Argentina Creek (Province of Imperia, Italy). This analysis demonstrates the potential for applying information from the current review to other fish species.

Background: Globally, streams emit significant amounts of methane, a highly potent greenhouse gas. However, little is known about the stream sediment microbial communities that control the net methane balance in these systems, and in particular about their distribution and composition at large spatial scales. This study investigated the diversity and abundance of methanogenic archaea and methane-oxidizing microorganisms across 16 European streams (from northern Spain to northern Sweden and from western Ireland to western Bulgaria) via 16S rRNA gene sequencing and qPCR. Furthermore, it examined environmental factors influencing both abundance and community composition and explored the link to measured potential methane production and oxidation rates of the respective sediments. Results: Our results demonstrated that the methanogenic and methanotrophic microbiomes of the studied European streams were linked to both the temperature and degree of anthropogenic alteration. The microbiomes could be separated into two to three groups according to environmental factors at both stream and catchment scales. Main methanogenic taxa found within more anthropogenically-altered, warm, and oxygen-poor environments were either Methanospirillum spp. or members of the families Methanosarcinaceae and Methanobacteriaceae . Within such environments, methane oxidizing communities were strongly characterized by members of the family Methylobacteriaceae ( Meganema spp. and Microvirga spp.). Contrastingly, communities in colder environments rich in oxygen and with relatively little anthropogenic impact at the catchment scale were characterized by the methanogenic Methanosaetaceae , Methanocellaceae and Methanoregulaceae and the methanotrophic Methyloglobulus spp ., members of the CABC2E06 group (all Methylococcaceae ) and by various Candidatus Methanoperedens. Overall, diversity of methanogenic archaea increased with increasing water temperature. Methane oxidizing communities showed higher diversities in southern sampling sites and in streams with larger stream areas and widths. Potential methane production rates significantly increased with increasing abundance of methanogenic archaea, while potential methane oxidation rates did not show significant correlations with abundances of methane oxidizing bacteria, presumably due to the more diverse physiological capabilities of this group. Conclusions: We present the first large scale overview of the large-scale microbial biogeography of two microbial groups driving the methane cycle dynamics within stream sediments and deduce the impact that future anthropogenic alterations may cause.

The most important environmental characteristic in streams is flow. Due to the force of water current, most ecological processes and taxonomic richness in streams mainly occur in the riverbed. Benthic algae (mainly diatoms) and benthic macroinvertebrates (mainly aquatic insects) are among the most important groups in running water biodiversity, but relatively few studies have investigated their complex relationships. Here, we review the multifaceted interactions between these two important groups of lotic organisms. As the consumption of benthic algae, especially diatoms, was one of the earliest and most common trophic habits among aquatic insects, they then had to adapt to the particular habitat occupied by the algae. The environmental needs of diatoms have morphologically and behaviorally shaped their scrapers, leading to impressive evolutionary convergences between even very distant groups. Other less evident interactions are represented by the importance of insects, both in preimaginal and adult stages, in diatom dispersion. In addition, the top-down control of diatoms by their grazers contributes to their spatial organization and functional composition within the periphyton. Indeed, relationships between aquatic insects and diatoms are an important topic of study, scarcely investigated, the onset of which, hundreds of millions of years ago, has profoundly influenced the evolution of stream biological communities., FESR, Interreg Alcotra 2014-2020, EcO Project of the Piter Terres Monviso

Over the last decades, the ongoing global climate change, combined with consequent increasing water demand for human needs, is causing recurrent droughts in previously perennial streams. These phenomena have been dramatically increasing their extent, with significant repercussions on the entire food web. Consequences of water scarcity are particularly remarkable in mountain streams, where the frequency of droughts is increasing at a rate that does not allow species to adapt. In the present research, we monitored benthic diatom communities within an intermittent Alpine river (Pellice River; North-Western Italy) during the three key phases of its hydrological cycle: i) stable flow ii) lentification iii) rewetting of the riverbed after a supraseasonal drought lasting five months. We tested the response of diatom communities in terms of compositional, structural and functional metrics (primary production, species composition, ecological guilds, life forms and eco-morphological groups) hypothesising both taxonomic and functional changes during the different steps of this hydrological cycle. Significant changes in benthic chlorophyll a occurred in the three hydrological phases. In particular, the relative proportion of the chlorophyll a of the three main autotrophic groups inhabiting the periphyton (namely diatoms, cyanobacteria and green algae) resulted as a reliable metric for the evaluation of the hydrological disturbance. Diatom chlorophyll a significantly decreased during both lentification and drought. The three phases were significantly characterized by different species and functional groups. During the stable flow the low profile (i.e., species of short stature, adapted to high current velocities and low nutrients concentrations) was the most representative guild and Achnanthidium pyrenaicum was the most abundant species; this phase was also characterized by the presence of stalked taxa. We observed a significant decrease of high profile species (i.e., species of tall stature, adapted to high nutrients concentrations and low current velocities) during the lentification phase, which was characterized by taxa belonging to the genera Navicula, Nizschia and Ulnaria. During the rewetting, small and medium sized high profile diatoms as well as motile ones (i.e., fast moving species) characterized the assemblages. Our results showed that the complete recovery of diatom communities took at least 70 days after water return. The rapid and widespread extension of droughts in the Alpine area will have severe consequences on the river biota, also favouring the spread of invasive taxa. For this reason, outlining patterns of diatom response to droughts and detecting reliable metrics for the evaluation of this specific impact is very urgent and important.

We investigated the impact of intermittence in previously-perennial Alpine stream reaches, targeting the role of the hyporheic zone in increasing the resilience of these aquatic systems. We selected a perennial and an intermittent site in a reach of the Po River (North-Western Italy). We installed piezometers reaching &minus, 1 m (permanent and intermittent site), and &minus, 3 m (intermittent site) and monitored three supraseasonal droughts over a period of three years. We classified the hyporheic fauna into three categories of increasing affinity to life in the hyporheic (stygoxene, stygophile, stygobite), and used communities composition, abundance, beta-diversity and functional groups: (1) to compare assemblages at the same depth but with different hydrological characteristics, as well as assemblages from two depths at the intermittent site, and (2) to assess how the connection with surface water and the direction of the vertical aquifer flow determined the faunistic assemblages. Different taxonomic groups responded differently to intermittence, the hyporheic zone acted as a refuge increasing the resilience of the system, but resilience decreased with increasing degree of affinity to hyporheic life. Disentangling the effects of intermittence on the different faunistic component in the hyporheic zone can help guiding effective protection and restoration measures of river systems with temporary reaches.

The roles of macroinvertebrate and microbial communities in stream ecosystems are recognized to be important to energy flow and nutrient cycling. While the linkages of these major groups of aquatic organisms have not been thoroughly investigated, determining how they interact is particularly important for understanding the mechanisms and potential evolutionary relationships that contribute to ecosystem processes, such as organic matter decomposition. We evaluated the microbiomes of several aquatic insect species differing in trophic ecology and belonging to different functional feeding groups at two sites along an Italian Alpine river with different elevation and environmental characteristics, one located above the tree line and the other in a forested environment. We found that the internal microbial communities of the different species significantly varied in taxonomic and functional composition and could be used to classify samples to both species and environment. We demonstrated that functional differences existed between the microbiota of different insect species with variable feeding behaviors, and that species differences were more important, in this context, than environmental or habitat conditions. These results provide new information on how the microbiomes of aquatic insects may potentially be influenced by their hosts and habitat conditions in Alpine streams.

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.

Several Alpine streams are currently facing recurrent summer drying events with detrimental consequences on stream detritivores, i.e., shredders, due to negative effects via changes the organic matter (CPOM) availability. We examined the ecological requirements of three phylogenetically related shredder genera belonging to the family of Nemouridae (Plecoptera), namely Nemoura, Protonemura and Amphinemura, in 14 Alpine streams recently facing recurrent summer flow intermittency events. We evaluated the overlap among their ecological niches measured in terms of hydraulic stress, substrate composition, changes in CPOM availability and competition with other shredder taxa (i.e., presence of individuals of other shredders) and we examined potential changes in their ecological niches between permanent and intermittent sites. The ecological niches of Protonemura and Amphinemura overlap broadly, but not with Nemoura, suggesting only partial potential competition. The reduced CPOM availability decreased the individual abundance of the three genera in intermittent sites, where they consistently preferred microhabitats with high CPOM availability and low competition with other shredder taxa, possibly due to food limitation. Overall, our results emphasize how the negative effect of flow intermittency on shredders in Alpine streams is mainly due to the decrease in CPOM availability, with consequent potential bottom up effects on stream ecosystem functionality.

Clogging, the streambed colmation by fine sediments, is an important widespread source of impact affecting freshwaters. Alterations in stream morphology and hydrology, added to the effects of global climate change, are responsible for this phenomenon, that is particularly pernicious in mountainous lotic systems naturally characterized by coarse substrates. Among the studies investigating this issue some were descriptive, while others used artificial substrates to compare ongoing fine sediment accumulation and macroinvertebrate assemblage recruitment. Other studies used from the outset artificial substrates arranged with different levels of clogging. Our study fits into this line, but adding an innovative element simulating different availability of coarse particulate organic matter, i.e. the main trophic input in low-order, mountainous stream. To investigate how clogging and CPOM can influence macroinvertebrate communities, we placed 135 artificial substrates in the upper Po river (NW Italy). We set up a three way factorial design with three different levels of sedimentation and terrestrial leaf material. Artificial substrates were removed on three different dates. Benthic invertebrates were identified and classified according to their bio-ecological traits. We also measured macroinvertebrate dry mass and CPOM degradation in the different trap types. Our findings show that clogging acts as a selective filter influencing taxa richness, density, functional composition and biomass of benthic assemblage. Moreover, fine sediments affect the energetic dynamics in the river ecosystem, decreasing the mass loss rate of terrestrial leaves. Interestingly, our results clearly demonstrate that high availability of CPOM can buffer the negative effect of clogging, suggesting that an adequate input of allochthonous organic matter may lessen the impact of fine sediment deposition. Because land use transformation and removal of wooded riparian areas increase clogging and simultaneously reduces the input of CPOM, our findings stress the importance to include the management of river basins in the conservation strategies of mountainous streams.

Several mountain streams are currently changing from perennial to temporary regimes due to increasing water abstraction and global climate change with expected detrimental effects on stream biodiversity and functionality. We here examined whether macroinvertebrates and diatoms, experiencing recurring non-flow periods, showed alterations even after complete flow resumption in 13 mountain streams in SW Italian Alps. Benthic communities were sampled after complete flow resumption in April 2017 in a control section, with permanent flow, and in an intermittent section, which experiences recurrent non-flow periods during summer, in each stream. We tested for differences in terms of taxonomic composition, diversity and functional groups between permanent and temporary sections. Our results showed a significant alteration of benthic invertebrate, but not diatom communities in temporary sections. Different species composition and low diversity values in temporary sections were due to the replacement of monovoltine taxa, with aquatic respiration, preferring medium to fast flowing, oligotrophic waters by plurivoltine taxa, with aerial respiration preferring lentic habitats. Such results provide some insights into the mechanisms by which non-flow periods impact Alpine streams, and further investigations in mountain areas are required in the future to better unravel the repercussions on stream ecosystem processes.

The number of dams is predicted to increase worldwide under the current global change scenario. A major environmental problem associated with dams is the release of large quantities of fine sediment downstream. Therefore, future studies in river conservation will largely be focused on the management of sediments trapped by reservoirs. The aim of this study was to investigate the downstream ecological impacts of sediment flushing from a dam and the effectiveness of artificial flash floods as a recovery strategy. Artificial flash floods have often been employed to remove large amounts of sediment from riverbeds, but their importance in improving the biological quality of lotic environments is almost unknown. We carried out a series of quantitative macroinvertebrate samplings over a 2-year period that started before sediment release and included the artificial flushing events. We characterized the macroinvertebrate community in its structural and functional aspects and tested the performance of two biomonitoring indexes, comparing their diagnostic ability. Our results demonstrated that sediment flushing significantly altered the structure and composition of benthic communities for more than 1 year. Flash floods exacerbated the overall biological quality, but we believe that this treatment was useful because, by removing large amounts of sediment, the biological recovery process was accelerated. Finally, regarding the water quality assessment, we found that the biomonitoring index for siltation, composed of a selection of taxonomical and functional metrics, was more reliable than the generic one.

Aim of this study was to investigate the presence and distribution of Hydraenidae in relation to selected abiotic parameters in a single, uniform riffle of the Caramagna Stream (northwestern Italy). Six species belonging to the genus of Hydraena Kugelann, 1794 were found (H. andreinii D'Orchymont, 1934, H. subimpressa Rey, 1885, H. assimilis Rey, 1885, H. heterogyna Bedel, 1898, H. truncata Rey, 1884 and H. devillei Ganglbauer, 1901), with evident niche preferences. Our study provided interesting information about ecological requirements of minute moss beetles at small-scale and evidenced that maintaining elevate habitat diversity is essential to preserve high species abundance at local scale.

Hydrological alterations in Alpine rivers have been largely increasing due to the combined effects of global climate change and local impacts. Water flow intermittency starts with a process called lentification, which leads to the transformation of the aquatic ecosystem with severe consequences on biotic communities. These consequences have a greater impact in Alpine headwater streams, which are considered important and fragile hotspots of biodiversity and a source of threatened species; the new regime creates conditions to which native biota are poorly adapted. The main aim of our work was to evaluate taxonomical, functional and structural changes of diatom communities in Alpine rivers during the lentification process that precedes a supra-seasonal drought. Contrary to what was expected, communities exposed to river shrinking showed a level of homogeneity comparable to those collected in permanent sections. We therefore hypothesized that lentification created an intermediate disturbance that favoured heterogeneity of assemblages. Conversely, ecological guilds, growth forms and eco-morphological groups varied along temporal and spatial gradients driven by the lentification process. Small, motile and medium-sized low profile species were more abundant during summer, as well as adnate and stalked ones. Lentification limited the presence of high profile guilds and mucous-forming colonies. Droughts in Alpine streams are fairly recent processes, and the dynamics of aquatic communities facing water scarcity are largely unknown. The results we obtained provide important insights towards a more refined functional classification of diatoms for evaluating hydrological alterations.

Despite their wide distribution and ecological importance, almost no information is available about the role of freshwater crayfish as basibiont for epizoic algae. Moreover, studies on epizoic freshwater diatoms have been largely neglected. In this study, we examined the occurrence of diatoms on two sympatric species, the native white-clawed crayfish Austropotamobius pallipes and the non-indigenous signal crayfish Pacifastacus leniusculus, coexisting in the same stream in NW Italy. We detected that signal crayfish showed a far more productive epizoic algal community than white-clawed crayfish. Microscopical analysis confirmed that non-indigenous crayfish hosted rich and diversified diatom communities while virtually no diatom was found on the native. After analyzing different hypotheses, we suggested that this significant difference can be the result of diverse crayfish behavioral habits. Because of the lack of studies investigating epibiontic diatoms on freshwater crayfish, we performed a detailed characterization on the epizoic flora, including comparisons with natural epilithic communities. The exponential diffusion of non-indigenous freshwater crayfish is a subject of greatest interest. Increasing our knowledge on their role as basibionts is definitely necessary to better understand their ecological role, also considering their influence on primary producer community and their role as vectors of algal species of concern, such as Didymosphenia geminata.

Excessive fine sediment accumulation (i.e., siltation) in streams and rivers originates from several human activities and globally results in heavy alterations of aquatic habitats and biological communities. In this study the correlation between fine sediment and several benthic invertebrate community metrics was tested through a manipulative approach in alpine streams, where siltation mainly results as a physical alteration (i.e., the clogging of substrate interstices) without the influence of co-occurring confounding factors. We selected 12 candidate metrics, belonging to three different categories: compositional, structural and functional. We first carried out a manipulative experiment where artificial substrates were used to provide standardized conditions of siltation. All candidate metrics were calculated for each artificial substrate and the selection of the best combination of metrics was statistically performed with an information-theoretic approach. All candidate metrics were calculated both at family level and also at a mixed level (family and genus) in order to account for the systematic resolution. Then, data from a field study on alpine streams affected by mining activities were used as independent dataset for testing the performance of the selected metrics. We found that the total taxa richness, the EPT (Ephemeroptera, Plecoptera and Trichoptera) richness and the abundance of benthic invertebrates associated to rheophilous conditions and coarse mineral substrates were the most sensitive metrics. When these metrics were aggregated into a multimetric index in the validation dataset, we observed high and significant correlations between index values and the quantity of fine sediment for both taxonomic levels, especially for the mixed level. The findings of this study provide useful tools for biomonitoring the effects of fine sediment in low order, mountainous streams and contribute to improve our diagnostic ability on stressor-specific alterations.

The ecological impact of fine sediments is one of the major causes of ecological degradation affecting lotic systems. Interestingly, many studies have investigated the impact of increased sediment loads on specific compartments of the lotic system, but little or no information is available about the overall impact of sedimentation. Aim of this paper was to analyse the influence of fine sedimentation on allochthonous and autochthonous energy inputs and on the structural and functional characteristics of diatom and macroinvertebrate communities. Data were collected in two Alpine streams in NW Italy, one interested by the presence of an intense mining area and the other pristine, used as a control. The two rivers greatly differed in terms of suspended solids and bed load characteristics. From 10 stations, we analysed main physico-chemical characteristics, fine sediment indicators (using 60 sediment traps), coarse particulate organic matter (CPOM) and photosynthetic pigments amounts, taxonomic and functional characteristics of macroinvertebrate communities. We tested several causal models via path analysis. Functional traits seem to better reflect the integrated impact originating from quarries in the river basin than traditional community metrics like total abundance and specific richness. This outcome was enforced through the co-inertia analysis, which took in consideration also metrics based on diatom communities. Our study yielded quantitative relations between sediment loads induced by quarrying activities and the degree of biological impairment and suggests which metrics are more suitable to assess this specific impact. Copyright © 2015 John Wiley & Sons, Ltd.

Biological invasions are commonly recognised among the most significant elements of global change (Genovesi et al. 2015; Fenoglio et al. 2016) and represent one of the leading causes of local biodi...

The extent of drought in Mediterranean streams has been intensifying recently, and the mean annual discharge is expected to experience a decreasing trend in coming years, with significant effects on aquatic ecosystems. The aim of this study was to analyse colonisation patterns of diatom communities that differed in terms of taxonomic composition and percentage of endangered taxa exploring the possible development of resistance mechanisms. To this end, we selected three Mediterranean streams comparable in terms of water quality, but different in terms of surrounding land use, and we performed two experimental treatments. The first treatment consisted in artificially drying and cleaning of substrates (cobbles) to analyse the post-drought recolonisation process that is only driven by drift and immigration. In the second treatment cobbles coming from a site experiencing a seasonal drought were transplanted upstream in a perennial stretch to explore the possible development of resistance mechanisms within diatom communities periodically exposed to droughts. We observed that stream identity played an important role in determining diatom assemblage composition. Highly natural stretches had a high abundance of endangered species, which were less resilient to drought than assemblages composed of general and widespread taxa. Moreover, according to our results, resistance mechanisms did not play a significant role in recovery patterns. Improving our knowledge of diatom resilience mechanisms is very important in a global climate change scenario, especially in Mediterranean streams.

Over fifty years of research on freshwater macroinvertebrates has been driven largely by the state of the taxonomy of these organisms. Significant advances have been and continue to be made in developing ever more refined keys to macroinvertebrate groups. When advances in macroinvertebrate ecological research are restricted by the level of detail in identifications, then analysis by function is a viable alternative. The focus on function, namely adaptations of macroinvertebrates to habitats and the utilization of food resources, has facilitated ecological evaluation of freshwater ecosystems. This classification is based not on what insects eat, but how they obtain their food. These categories are called 'functional feeding groups', as the name implies, denoting their functional role when describing how and where they feed. This is the basis for the functional feeding group (FFG) method that was initially developed in the early 1960s. Taxonomy is applied only to the level of detail that allows assignment to one of five functional feeding group categories: detrital shredders, scrapers, filtering collectors, gatherers, and predators. The aim of this short communication, originating from the presentation of R.W. Merritt at the Biomonitoring Symposium in Rome, 2015, is to promote the use of a functional approach in biomonitoring, especially in Italian and European lotic systems. Here, we present two case studies and we discuss the advantages of the method, especially considering the great availability of quantitative data on macroinvertebrates after the implementation of the WFD 2000/60. We are confident that the increase of functional assessment of ecosystem attributes could have important and direct repercussions in the understanding and management of running waters.

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.

Sampling in springs has several technical problems due to their reduced dimensions and habitat heterogeneity. A standardized quantitative method for sampling crenic macroinvertebrates has never been proposed. The aim of this study was to compare different sampling methods and consider their environmental impacts. First, we present a review of sampling methods found in the literature and discuss their advantages and disadvantages with respect to selective collection of the target community and habitat disturbance. Altogether, 10 different methods have been reported, the use of nets being the most common protocol. Second, we report the results of macroinvertebrate samplings performed in three springs, each surveyed twice, using three different methods (multi-habitat proportional hand net, baited traps, and vegetation washing), in order to compare their effectiveness in collecting macroinvertebrates. Overall, 32 macroinvertebrate taxa, mostly identified at family level, were collected in the sampled springs....

Biological invasions have increased significantly in response to global change and constitute one of the major causes of biodiversity loss. Insects make up a large fraction of invasive species, in general, and freshwaters are among the most invaded ecosystems on our planet. However, even though aquatic insects dominate most inland waters, have unparalleled taxonomic diversity and occupy nearly all trophic niches, there are almost no invasive insects in freshwaters. We present some hypotheses regarding why aquatic insects are not common among aquatic invasive organisms, suggesting that it may be the result of a suite of biological, ecological and anthropogenic factors. Such specific knowledge introduces a paradox in the current scientific discussion on invasive species; therefore, a more in-depth understanding could be an invaluable aid to disentangling how and why biological invasions occur.

The influence of day/night conditions on individual animal/plant species has been widely studied, but diel cycle studies of the entire stream macroinvertebrate community are extremely rare. This study explored potential dissimilarities between daytime and nighttime macroinvertebrate assemblages by extensive fieldwork conducted in the Lemme stream, a natural water course of NW Italy. Here numerous structural and functional metrics (richness, abundance, biomass, indicator taxa, composition, biomonitoring values and feeding groups) were evaluated at the family level. Small-scale environmental variables were investigated to understand possible differences between macroinvertebrate assemblages in the daytime/nighttime. After collecting and identifying 21 459 organisms of 50 taxa, Chironomidae (Diptera) was the most abundant under both day and night conditions. Our findings stressed that similar results and biological information on daytime/nighttime data were obtained. No marked differences could be related to various factors: heterotrophic condition of small-order streams, presence of aquatic predators under night and day conditions, absence of taxa with a specific phototaxis. Of all the environmental variables, velocity was always the most important in both situations, with some differences detected in the importance of the second variable (riverbed substrate diameter). This research, and future studies on different conditions and geographic areas, will contribute knowledge on stream macroinvertebrate diel activity, and provide useful information about efficient sampling strategies.

Neotropical Plecoptera represent an interesting subject of study, for their phylogenetic, biogeographical and ecological importance. The Plecopterofauna of a large portion of the Neotropics is represented by only one genus of Perlidae, Anacroneuria Klapalek. This work provides information about the stonefly fauna of Nicaragua, a country for which few previous investigations have been undertaken for this insect group. Eight species of Anacroneuria are currently recorded, including A. curiosa Stark, A. holzenthali Stark, A. planicollis Klapalek, A. starki Fenoglio & Morisi, A. talamanca Stark, A. litura (Pictet), and the two new records: A. divisa (Navas), and A. lineata (Navas). In addition, a key for adult males is provided and the putative nymph of A. talamanca is described.