Charophytes (stoneworts and bassweeds) are a typical macrophytic component of inland water ecosystems. Well-developed submerged meadows of charophytes are expression of clear water and rather low phytoplankton concentrations. Consequently, among aquatic macroscopic primary producers, charophytes are one of the most threatened groups being very sensitive to phosphorous availability, turbidity and water level perturbations. Accordingly, charophytes have been suffering a massive diversity loss worldwide over the last century, mainly because of human-induced pressures. During summer 2011, detailed field surveys were carried out with the main purpose of filling knowledge gaps concerning aquatic flora and vegetation of the lake Garda – the largest lake in Italy and one of the deepest in Europe. Along randomly selected transects, floristic data were collected following standard procedures, as imposed by the Water Framework Directive. Overall, 12 different species of charophytes were recorded, which accounts for 36% of total Italian charophytes and 19% of European species. The most diffuse species were Chara globularis and C. intermedia; whereas, the most interesting taxa were Chara polyacantha and Nitella hyalina, two species with narrow distribution in Italy. Overall in the lake Garda, dense stands of charophytes covered almost homogeneously the littoral sectors at a water depth between 3 and 12 m. The deepest species was C. globularis, which reached a maximum depth of colonisation of about 17.5 m. Charophytes represent a major element among the primary producers in the lake Garda. The high local charophyte diversity and the rather wide most colonised areas (~1000-1200 ha) confirm that the lake Garda is an important reserve for many rare and threatened charophytes. For the first time, these results highlight the key role of the lake Garda for charophyte diversity at a national and European level

Given their documented capacity to track changes in environmental conditions and human alterations, benthic diatom communities are at present widely used in biomonitoring programs to evaluate stream water quality. However, it is becoming more and more evident that species ecological preferences are not the only drivers of diatom community composition, since dispersal-related processes also play a role. This is particularly compelling in Alpine streams, where orographic conformation and humanrelated impacts limit dispersal of organisms. In addition, several environmental variables may influence diatom community in pristine or impacted sites. We here investigate the differential role of environmental and spatial factors in driving the community assemblages of diatoms in streams of the Eastern Italian Alps, focusing on both taxonomic and functional composition. We analysed data from 110 samples collected on two different geological substrates, i.e. calcareous and siliceous, during the last eight years of biomonitoring programs, among which 64 collected in reference sites and 46 in impacted sites. We first evaluated whether diatom communities in reference and impacted sites are differentially shaped by environmental and spatial factors, highlighting the major role of spatial constraints in both of them. In particular, anthropogenic disruption of longitudinal connectivity in streams likely shaped impacted communities, as demonstrated by the increasing abundance of motile 2 taxa, which are associated with physical disturbance. Conversely, reference communities were mostly affected by spatially structured environmental variables, especially those related to streambed lithology. We then compared the taxonomic and functional composition of diatom communities between the two geological substrates in both reference and impacted sites to better highlight the differential role of this factor. Our results demonstrate that lithology strongly drives diatom community composition in reference but not in impacted sites, confirming our previous observations. The analysis of functional traits, however, highlighted how differences were due not only to the geological substrates, but also to other environmental variables, like flow velocity. Overall, the effect of the spatial component on the structure of diatom assemblages can represent a background noise in the framework of the river quality assessment, and this should be taken into account especially in those countries, like Italy, covering a broad range of mountain areas.

We investigated the influence of substrate composition and current speed on the composition of macroinvertebrate communities under controlled hydraulic conditions using a semi-artificial system. Two sizes of substrate material (20 mm and 50 mm mean diameter) in five combinations were used to present variable substrata composition. Additionally, water velocity was set at three different levels-0.4, 0.6, and 1.0 ms-1. Current speed influenced composition, diversity, and variety of macroinvertebrates; substrate composition also acted as a variability factor, both in terms of composition and heterogeneity.

Rivers serve many societal functions and are one of the most intensively human influenced ecosystems worldwide, and, due to their importance, are included under the monitoring programs of the Water Framework Directive across Europe. Macroinvertebrates play an important role when monitoring running waters for the assessment of their environmental quality due to their reliability as bioindicators and utility in long-term studies. Macroinvertebrates do not constitute a systematic unit but they are formed by a set of different taxa, grouped according to taxonomic ranks, size and habitat preferences. They represent the base of the aquatic food chain, serving as a food source for amphibians, birds, reptiles, fish and humans, and contributing in the organic matter processing. Despite the large amount of data collected on Italian river macroinvertebrates and the increased interest in the study of this group, only few data are available for research scientist and managers. In this paper, we collected and homogenized knowledge on the presence, distribution and abundances of macroinvertebrates taxa inhabiting the River Po catchment (Northern Italy) in the last decade. The data set includes 130,727 records collected between 2007 and 2018 including 143 taxa of macroinvertebrates, mostly identified at family rank level. Moreover, the data set provides information on the geographic distribution of these families and their abundance by sub-catchment, altitude, meso-and micro-habitat.Angela Boggero: contacts with data providers.

No abstract