Classificazione dello stato ecologico e variabilità locale dell'idromorfologia/habitat: potenziali effetti sull'efficacia delle misure di recupero e criteri per ridurre l'incertezza. Parte B: Laghi

This deliverable presents a first analysis linking some selected hydromorphological information and quality elements. In particular, we investigated the relationships between biological quality elements (macroinvertebrates, fishes and macrophytes) and some hydromorphological parameters, collected with the Lake Habitat Survey (LHS) method, as the characteristics of the substratum of the littoral and sub-littoral zone, the characteristics of the bank with or without artificial elements, level variations, and human activities in the lake and in the riparian zone, as camping, nautical activities. In this deliverable we also analyzed some meteorological parameters (precipitations and temperatures pluriannual average) of the two studied Regions, in order to identify peculiarities and to establish if anomalies were registered during the sampling period and to identify possible natural biologic variability connected to particular climatic events. For each biologic element, numerical analyses were performed to evaluate its response to hydromorphological parameters. In particular for the macroinvertebrates, we only used data collected in Lake Viverone, as samples collected in both winter and autumn samplings were analyzed. Beside Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA), the BQIES index was also calculated, to evaluate if the anthropogenic pressures on the coast can influence the benthic community. The analysis was performed using as response variable the relative abundance of each taxa, selecting taxa with maximum relative abundance above 1%. Independent variables included the chemical data (TP, TN, alkalinity and percent oxygen saturation), and hydromorphological parameters. The statistical significance of the analyses was checked using a Monte Carlo permutation test. According to the described numerical analysis, fauna composition in and the sampling stations can be classified in three principal groups, according seasonality and anthropogenic modifications on the littoral zone. Correlations between BQIES indexes and the hydromorphological variables do exist, but did not result statistically significant. From our analysis, it appears that to better understand the quality of the waterbody, it is necessary to sample the littoral zone in several points around the shore, avoiding points close to inflows. Concerning fish fauna, data were available 8 lakes or reservoirs, 3 in Piedmont (Candia, Mergozzo, Morasco) and 5 in Sardinia (Serrù, Posada, Liscia, Bidighinzu and Sos Canales). We investigated the relationship between hydromorphological parameters and (1) the number of the species caught with nets, (2) the number of species caught with electrofishing, (3) species abundances, (4) fish weight and (5) fish length. The matrixes for the analysis were built choosing electrofishing points or nets located close to the hab-plots, where hydromorphological characteristics of the riparian zone were evaluated. Numerical analysis used again CCA with Monte Carlo permutation tests. In particular, two CCAs were performed relating hydromorphological parameters and fish fauna synthetic parameters, such as the number of fish for net/point, the total weight for net/point, the medium length and the medium weight. Monte Carlo permutation test did not detect any significant variable relating habitat features and the species distribution, while the number of collected fishes was more representative of hydromorphological condition. In general, with this limited dataset the relationships between fish fauna and chemical and physical variables seems stronger than the relationships with hydromorphological features; however it will be possible repeat the analysis with a larger dataset when other InHabit lakes (Viverone, Sirio and Avigliana piccolo) will be sampled. Concerning macrophytes, numerical analysis were based on data collected on 5 natural lakes in Piedmont: Avigliana Piccolo, Candia, Mergozzo, Sirio and Viverone. We first selected macrophytes sampling transects close to LHS habplots, using a geographical information system, and considering the extension of the macrophyte sampling sites. The relationships between the hydromorphological parameters and the composition of macrophyte assemblages was the investigated using again CCA and Monte Carlo permutation test, and using percent relative abundances as response variables. Hydromorphological features of the shore do not significantly influence lake classification based on macrophytes, but a high number of transects is necessary to accurately classify the lake, with a particular attention to the presence of submerge macrophytes, usually located in small areas, to avoid an undervaluation the ecological quality of the lake. The composition of macrophyte community resulted influenced by substrate features, land use on the shore and the surrounding area. In one case (Lake Mergozzo), the total lack of macrophytes prevented the possibility to classify the lake quality using this biological element. To reduce classification uncertainties, it is still necessary to find deeper relationships between hydromorphological pressures and biological elements, macroinvertebrates and macrophytes, investigating a higher number of lakes and specific pressures with a detailed sampling scheme. More contemporary information will be collected, the better will be the knowledge of lake system and the relationships between human pressures and impacts on the biological quality. A deeper knowledge of these aspects will enable to design more effectively the recovery measures and to reduce the uncertainty in classification and in the detection of the effects of the restoration measures. A more detailed analysis of the relationships between biological parameters and hydromorphological features will be attempted again when the biological datasets will be improved, and fish sampling completed.