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Climate changes, geomorphologic modifications and the rise in water demand for human uses contribute to 'aperiodic summer drought' (ASD) events in Mediterranean-type rivers. ASD results in a reach that flows in one summer, dries in next or more summers, and then flowing again. The ecological structure and function of streams affected by ASD are understudied, especially with respect to permanent and regular intermittent streams. We tested the drying memory in a reach of Aterno River (Italy) disturbed by ASD. Leaf litter breakdown of Phragmites australis and macroinvertebrate assemblages were studied. Discharge was monitored since 2006. The experiment was performed during summer 2010 using the litterbag technique, and was replicated four times. The disturbed site was affected by drought in the three previous summers while the control was always flowing. Taxonomic diversity indices, abundance and structure of macroinvertebrate assemblages varied significantly between sites. Instead, leaf litter breakdown wasn't influenced by ASD. Therefore ASD events seem to affect the structure of macroinvertebrate assemblages, confirming the role of drying memory of the systems. The resilience of leaf litter breakdown in reach affected by ASD seems to be high, probably depending on the activity of selected microbial communities and macroinvertebrate features like metabolism and biomass. [ABSTRACT FROM AUTHOR]

Diatoms are major contributors to global carbon fixation and constitute a significant portion of biofilms found in lotic ecosystems. Despite their widespread abundance and the fact that extensive studies have been performed on morphological features of frustules, molecular tools for the identification of diatoms are not commonly available. This study focuses on the development of oligonucleotide probes for the detection of diatom species relevant to water quality assessment. The selected panel of diatoms covers all the species found in water of varying quality from the rivers of central-East Apennine (Italy). Small subunit rRNA-targeted probes were applied to a microarray platform as well as to a new technique termed Primer-Probe, with the aim of obtaining a molecular tool suitable for accurate identification of both single and mixed species diatom populations. The Primer-Probe technique together with dot-blot assays proved to be ideal for the preliminary screening of a large set of DNA oligonucleotides designed by ARB software. It was shown that microarrays, as a promising technology for rapid and simultaneous detection of a wide range of species-specific genetic markers, can be adapted to monitor changes within a diatom community. It is suggested that microarrays will provide a molecular basis for microbial identification to support standard microscopy techniques used by ecologists and environmental scientists for monitoring water quality. [ABSTRACT FROM AUTHOR]

Temporary rivers are characterized by recurrent dry phases, and global warming will stress their hydrology by amplifying extreme events. Microbial degradation and transformation of organic matter (OM) in riverbed sediment are key processes with regard to carbon and nutrient fluxes. In this study, we describe structural and functional changes of benthic microbial communities in a riverine environment subject to hydrological fluctuation. Sampling was carried out in the outlet section of the Mulargia River (Sardinia, Italy) under various water regimes, including one flood event. Overall, sediments were characterized by low bacterial cell abundance (range 0.6-1.8 × 10 cell g) as a consequence of their low nutrient and OM concentrations. No major differences were found in the community composition. Alpha- Proteobacteria dominated during the whole year (range 21-30%) followed by Beta- Proteobacteria, Gamma- Proteobacteria, and Cytophaga- Flavobacteria which always contributed <18%. Planctomycetes and Firmicutes were found in smaller amounts (<7%). In spring, when the highest total organic carbon content was also detected (0.42% w/w), both bacterial abundance and C production (BCP, 170 nmol C h g) reached relatively high values. During the flood event, an increase in BCP and the highest values of community respiration (CR, 74 nmol C h g) were observed. Moreover, most of the extracellular enzyme activities (EEA) changed significantly during the flood. The variation of the water flow itself can explain part of these changes and other factors also come into play. The presence of different patterns of functional parameters could suggest that the quality of the OM could be the major driving force in nutrient flux. [ABSTRACT FROM AUTHOR]

Phytoplankton and associated environmental factors were collected fortnightly during a 1-year cycle in the upper and lower reaches of the River Adige (northeastern Italy). The river has a typical Alpine flow, with the period of high flow and flooding occurring in the spring and summer months. Phytoplankton biomass was constrained by physical variables, mainly water discharge and associated variables directly linked to water fluxes. These factors acted negatively and synchronously by diluting phytoplankton cells and worsening the light regime. Nutrient concentrations did not appear to limit phytoplankton growth. Compared to many other central European rivers, the very low maximum algal biomasses supported by River Adige (Chl a < 7 μg l−1) are due to the Alpine flow regime, which is characterised by higher flow during the warmer months, when conditions for algal development are more favourable. Hydrology and flow regime, along with the channelisation of the river, caused development of a simplified phytoplankton community, which was almost exclusively composed of diatoms. Moreover, these factors contributed significantly to the lack of ordered and cyclic temporal patterns in phytoplankton dynamics. In fact, the gradient of species composition showed a strong association with hydrological factors. If the scenarios predicting increase of atmospheric temperatures and decrease of atmospheric precipitations and water availability in the regions south of the Alps are realistic, algal biomasses may rise and be associated with an increase of groups other than diatoms. [ABSTRACT FROM AUTHOR]

Physical constrains such as water discharge, suspended solids and turbidity act as dominant factors in driving the planktonic diatom assemblages of the River Adige (North-Eastern Italy). Two sampling stations, characterised by different hydromorphological features (Cortina all’Adige and Boara Pisani, with torrential and more potamal characteristics, respectively) were sampled fortnightly following an integrated approach encompassing physical, chemical and biological measurements and aiming at identifying the dominant factors controlling the temporal development of the community. A morpho-functional approach was used to classify the diatom assemblages where Morpho-Functional Diatom Groups (MFDG) were defined for diatom genera, according to their morphology, habitat selection and modality of adhesion to river substrate. In the two sampling points, algal growth was never limited by nutrients or zooplankton. The irregular development of MFDG was determined by the stochastic hydrological events and changes in variables related to water discharge (suspended solids and light attenuation). Tychoplanktonic, benthic and drifted taxa (such as Diatoma spp., Encyonema spp., Navicula spp. and Nitzschia spp.) were dominant in the torrential station (Cortina all’Adige), while the contribution of euplanktonic unicellular centric taxa (such as Cyclotella spp., and Stephanodiscus spp.) was higher in the potamal station (Boara Pisani). [ABSTRACT FROM AUTHOR]

The Italian goby Gobius nigricans is a running-water-dwelling species inhabiting the Tuscano-Latium district and threatened by several human activities. Many aspects of its biology are currently unknown, such as the dynamic potentialities. Since age determination and dynamic assessment are considered an important tool for a correct management strategy, we aimed to investigate some aspects of the Italian goby life history by applying the fish stock assessment principles, collecting data on fertility, population structure (age-class number), growth (i.e., curvature parameter and asymptotic length), mortality (natural and due to the fishing), and longevity of a central Italian goby population to know the status and dynamic properties of the Italian goby in Mediterranean river systems and to provide a baseline for comparison with other populations. Females are subject to a strong selective pressure to quickly reach a small size to optimize reproductive output, while acquisition of a large size favored males for a more easy access to breeder females (the asymptotic length was higher in males than in females). Moreover, appreciable between-sex differences were found in both growth pattern (the growth rate was lower in females than in males) and dynamic potentialities. In particular, the mortality rate was lower in females, whereas the longevity was slightly lower in males, although the two sexes showed similar values for the two latter properties. There is considerable scope for further work on the G. nigricans growth and other freshwater gobies because information on population and dynamic properties, and assessment of factors affecting growth are still very insufficient. [ABSTRACT FROM AUTHOR]

In this study we investigated the emergence patterns of two Systellognatha stoneflies: Perla marginata and P. grandis (Plecoptera: Perlidae) in a first order stream of the Northern Apennines (NW Italy). Exuviae of both species were collected in a selected area of the Curone creek by hand-picking, measuring the distance between river edge and substrate typology. Exuviae were found on different substrate types near the shoreline: stones in the stream bank were mainly used by both species, and gravel beach was the least-utilised substrate. No evident differences were found between the species in the typology and colour of emergence substrates. Interestingly, we found that P. grandis exuviae were significantly located at greater horizontal and vertical distances from the water edge than P. marginata ones. We discuss these findings on the basis of ecological and behavioural considerations. [ABSTRACT FROM AUTHOR]

The marble trout, a lineage of the Salmo trutta complex, is endemic to the Southern Alpine region. Although it is endangered throughout its entire distribution range, population genetic data were lacking for the central area, including the upper Etsch/Adige River system (South Tyrol, Northern Italy). A total of 672 Salmo trutta specimens, comprising phenotypic marble trout and phenotypic brown trout, from 20 sampling sites throughout South Tyrol were analysed by sequencing the complete mitochondrial DNA control region. Thirteen distinct haplotypes were identified, which clustered within three major genetic lineages: the Marmoratus (MA), the Atlantic (AT) and the Danubian (DA) lineage. 41.7% of the investigated individuals carried haplotypes of the MA lineage, 47.9% of the AT lineage and 10.4% of the DA lineage. It is noticeable that AT haplotypes were present at all sampling sites and no “pure” marble trout population with exclusively MA haplotypes was found. This points to a considerable impact of stocking with allochthonous brown trout, given that there is no evidence for natural colonisation by individuals of the AT lineage. However, our data indicate, for at least four localities, a limited gene flow between the native marble trout and hatchery-reared strains. Future conservation and rehabilitation measures will thus have to concentrate on the identification of remnant pure marble trout individuals from such mixed populations. [ABSTRACT FROM AUTHOR]

We examined vertical migration and colonisation patterns of stream macroinvertebrates within the substratum of an Apennine creek in NW Italy. Macrobenthos was sampled at three depths in the streambed (0–5, 5–10, 10–15 cm) by means of artificial baskets filled with natural substratum. We placed 42 traps (5×5×15 cm), i.e. 21 top-opened (T-traps) and 21 bottom-opened (B-traps), each composed of three overlapping baskets (high-H, medium-M and low-L), to evaluate differences in the vertical movements. We also collected Surber samples to compare interstitial assemblages with streambed communities. The multilevel traps yielded 42 taxa, compared with 60 taxa in the natural riverbed. Interstitial traps were rapidly colonised; both taxa richness and organism number increased during the 42-day study period. We found active migration in both vertical directions, but there were more invertebrates in the top-opened traps than in the bottom-opened traps. In the T-traps the most colonised baskets were those placed at the H level, while in the B-traps the L level baskets were more rapidly colonised. The interstitial assemblages differed markedly from the streambed communities in both composition and functional organisation, with more collector-gatherers and predators in the interstitial zone and more filterers and scrapers in the natural riverbed. In Apennine lotic systems, the interstitial zone is an important habitat for stream macrobenthos, although it may not be used by all species. [ABSTRACT FROM AUTHOR]

Chironomid communities from three glacial and three non-glacial high mountain streams in three Alpine river basins were analyzed (Conca, Niscli, Cornisello, NE Italy, 46°?N, 10°?E). Eighteen sampling reaches belonging to five stream types (kryal, subkryal, glacio-rhithral, kreno-rhithral, outlet) were investigated. At each reach, geomorphological, physical, chemical and biological data were collected. Field surveys were carried out during three periods per year from 1996 to 1998: immediately after spring snowmelt, in mid-summer and in early autumn. In all, 439 zoobenthos samples were collected from 5 to 10 microhabitats of 0.1?m2 in each reach and date using a standard pond net (mesh size of 250?µm). About 50% of individuals collected were chironomids (26?673 specimens, 53 taxa), with densities ranging from 4 to 2652?ind?m-2. With few exceptions, they dominated as number of taxa and individuals in all reaches. Chironomid subfamilies Diamesinae and Orthocladiinae were most abundant, especially in glacial reaches, whereDiamesaspp. constituted up to 100% of the total fauna. Chironomid distribution was analyzed in relation to 37 abiotic variables, referring to stream origin, hydrology, geomorphology, physics and chemistry.Diamesa steinboecki,D. latitarsisgr. A andPseudokiefferiella parvawere the taxa best associated with ‘glacial’ conditions (i.e. high channel instability or presence of bedrock, high suspended solids and total phosphorous content, low conductivity and silica content, highly variable diel discharge and low mean temperature), whilePseudodiamesa branickii,Corynoneuraspp.,Eukiefferiellaspp., Parorthocladius nudipennis,Tvetenia calvescens/bavarica,Thienemaniellaspp. andMicropsectra atrofasciatawere mostly associated with ‘non-glacial’ conditions. Substratum particle size, water depth, current velocity, the presence of riffles/pools and of mosses/algae (Hydrurus foetidus) were the major factors affecting microdistribution of chironomids in the investigated streams. [ABSTRACT FROM AUTHOR]

The main aim of this study, which is based on cover-abundance values of 20 species of floating-leaved and submersed macrophytes collected in 18 lakes located within the River Po catchment basin (Italy), is to investigate the relationships between lake-scale environmental features (including morphology, hydrology, trophic state and water quality variables) and the changes in species composition and species richness in macrophyte communities. The findings reveal that the main changes in community composition of the pondweed communities, identified by principal component analysis, could be effectively explained by a newly introduced morpho-hydrological parameter (the theoretical laminar water renewal rate – RL) and by the trophic state of the lakes, expressed as Carlson's trophic state index (TSI). The results of the multivariate analyses performed also show that the grouping of species is strictly related to growth-form traits. In particular, floating-leaved and submerged macrophytes appeared mutually exclusive in dominating different habitat types defined on the basis of the RL–TSI framework. An increasing trend in species richness was also observed in relation to RL. The possibility of using the bivariate RL–TSI framework for the identification of habitat utilisation patterns by single species was also investigated, and cover-abundance prediction maps based on the RL–TSI framework were produced for several macrophyte species. Observations in another system characterised by high spatial heterogeneity for hydrological and trophic conditions, support the predictions in terms of growth-form prevalence, species richness and single species cover-abundance (where available), and also suggest a more refined application of the proposed approach. [ABSTRACT FROM AUTHOR]

The purpose of this study was to test the applicability of different methods of river habitat assessment and their respective indices in a series of sample sites in Italy. These investigations were carried out within the EU AQEM project with the aim of combining the macroinvertebrate information with that achieved by investigating the hydromorphological characteristics of the river ecosystem as well as the surrounding landscape features. The River Habitat Survey (including the derived indices Habitat Modification Score and Habitat Quality Assessment) from U.K., and three Italian indices (Index of Fluvial Functioning, Buffer Strip Index and Wild State Index) were applied at 33 AQEM sites distributed in three different Italian river types. The obtained results indicate the overall ability of the applied indices to detect the degradation gradient, including river morphology and habitat, in the studied riverine ecosystems. Index of Fluvial Functioning seems useful to promptly describe the ecological quality of rivers as suggested by the good correlation with the AQEM multimetric biotic index. The Buffer Strip Index, showing a clear affinity with the Habitat Quality Assessment, seems suitable to assess richness and quality of the physical structure of a riverine site. The Habitat Modification Score recorded efficiently the morphological impact where present (e.g., North Apennine river sites), while the Italian indices appear to be not appropriate for differentiating this impact type from the general degradation of rivers. [ABSTRACT FROM AUTHOR]