Silverio Abati

Response of macrophyte communities to flow regulation in mountain streams

River macrophytes are widely used in freshwater ecosystem assessment because of their sensitivity to anthropogenic pressures, even if there are only a few studies that investigated how macrophytes respond to water regime alterations. In this study, we analyzed the effects of dams on river macrophyte communities through a comparison between upstream and downstream sides from 18 dams located in Alps and Apennines. A co-inertia analysis and a Mantel test were applied to assess if the analysis of environmental parameters could be effective in predicting macrophyte community structure. We analyzed morphological and physicochemical inter-site differences and tested the influence of dams on various aspects of community structure (composition, richness, diversity, dominance, coverage) using multivariate randomized block permutation procedure. Plant similarity between sites was evaluated at the level of phylum, and indicator species analysis was performed to identify the taxa most sensitive or tolerant to water regulation. We found that the overall environmental setting overwhelms the dam impact and that the influence of hydrological alteration became apparent when comparing upstream and downstream assemblages at the same dam. In particular, we found that most of taxa had a higher affinity with the downstream side and that in general, stream regulation increases plant richness and coverage, but reduces community evenness. Analyses based on higher taxonomic groups (phyla) demonstrated that this community can be effectively used in bioassessment even at phylum level analysis. In particular, we found that bryophytes, strictly linked with changes in substrate stability, show particular sensitivity to water regulation in mountain streams.

Bryophytes of Alpine and Apennine mountain streams: floristic features and ecological notes

Abstract Floristic and ecological features of aquatic bryophytes, and main abiotic factors, were studied in 23 mountain streams located in the Western Alps and Central Apennines (Italy). At 46 stations, a total of 36 taxa were collected. Most species showed both low occurrence (≤ 2 records) and low cover respect to sampled area (< 4%). However, in over 50% of stations, bryophyte communities with at least three species and cover over 10% were recorded. Platyhypnidium riparioides, Fontinalis antipyretica subsp. antipyretica and Hygrohypnum luridum were the most common and abundant species. Other species, more rarely recorded, have limited distribution in the Mediterranean region (Blindia caespiticia) and Italy (Hygrohypnum duriusculum). Some species show specific ecological preferences. In particular, Hygrohypnum luridum and Palustriella falcata are mostly linked to turbulent and cold waters (11.0–16.0°C), neutro-alkaline (7.3–8.4), with low conductivity (< 160 µS) and phosphates (< 0.01 mg/l) values. Brachythecium rivulare, Platyhypnidium riparioides and Fontinalis antipyretica subsp. antipyretica occur abundantly in less turbulent and less cold (15.3–18.2°C) waters, shaded, alkaline (8.3–8.6), with moderate conductivity (330–440 µS), and higher values of phosphates (0.06–0.09 mg/l). This study provides new floristic and ecological data on bryophyte communities occurring in mountain streams. It can also represent a useful contribution for biomonitoring activities of these habitats, often understudied floristically, where bryophytes are a significant part of the aquatic macroflora.

Ecological comparison between duckweeds in central Italy: The invasive Lemna minuta vs the native L. minor

Abstract The American duckweed Lemna minuta shows an invasive behaviour in Europe, causing weed problems in aquatic habitats there. Few studies addressed this species’ ecological requirements for a suitable establishment in a site. In this paper, L. minuta populations were analysed through field surveys so as (1) to define the autoecology of this duckweed as regards the main environmental factors characterizing invaded habitats, and (2) to identify possible overlaps/differences in ecological requirements between the alien L. minuta and the common native L. minor, with which it is often associated and in direct competition. The occurrence/abundance of the two species and environmental data were collected from 41 wetlands in central Italy. Currently, L. minuta is more common and abundant than L. minor in the study-area, despite its recent arrival there (2007). The two species have a partially overlapped autoecology. However, L. minuta differs from L. minor since it occurs in waters which are less alkaline, slightly less warm, and richer in nitrates. It shows tolerance for environmental conditions which are limiting for most of macrophytes, including L. minor, such as high shading and low water oxygenation. This enables L. minuta to increase its invasion potentiality and thus to enlarge its distribution area.