Comunità macrobentonica nei fiumi della Sardegna: habitat e risposta alle alterazioni morfologiche
Author(s)
Tenchini, Roberta
Date Issued
June 25, 2015
Type
Doctoral Thesis
Abstract
Rivers are complex ecosystems, defined by heterogeneous habitats and highly diversified biological communities. At present, these ecosystems are often seriously threatened because of human activity. Bank protection, crossing structures, channel resectioning and water pollution are among the main pressures that together caused a gradual increase in the morphological and overall degradation of water bodies, finally determining the decline of the Ecological Status. During the last decades, specific management approaches and measures to improve the aquatic ecosystems quality have been suggested. The European guidelines for water resources protection have been defined by the Water Framework Directive (WFD: 2000/60/EC) that has also put in evidence the central role of hydromorphological characteristics to understand causal links behind the response of aquatic communities to rivers degradation.
However, given the multitude of natural and artificial factors that contribute to generate the biological and habitats variability in rivers, it is difficult to distinguish the effects of individual pressures, such as those related to morphological deterioration of river channel and banks. The development of appropriate management plans is essential for rivers quality improvement and biodiversity, especially for taxa that inhabit restricted geographical areas (e.g. endemic species). In this context, the macrobenthic communities in Mediterranean water bodies located in Sardinia have been studied and insights referring to previously unknown ecological requirements of 5 endemic species have been provided (Baetis cyrneus, Habrophlebia consiglioi, Isoperla insularis, Tyrrhenoleuctra zavattarii e Agapetus cyrnensis). The aim of the first part of the PhD work was to investigate the effects of artificial structures present along river banks and channel on macrobenthic community from the Pool mesohabitat, also considering some natural habitat characteristics, on which management actions are possible. In the second phase, the aim was to observe and describe the five species distribution in relation to some environmental and habitat factors recorded at different spatial scales. The PhD research was performed in collaboration with the Water Research Institute (CNR-IRSA), within the LIFE + INHABIT project (LIFE08ENV/IT/000413). Hydromorphological and habitat features, biological and physico-chemical data were collected in each river stretch, by standard procedures currently adopted for Italian freshwaters (D.M., 260/2010). The Multimetric STAR_ICMi Index, actually used for assessing ecological status in Italy, has been also calculated.
To evaluate the effects of selected variables on aquatic communities, the MRT (Multivariate regression tree) analysis, Kruskal-Wallis test and multiple post-hoc comparisons were performed. The results show that the macrobenthic communities respond to the different alterations of structural characteristics in river stretches. The most important links between habitat features and the macroinvertebrate community were found for: Channel modification, Bank resectioning, Bank protection and presence of Tree-related bank and channel habitats. For each of them, the MRT model has provided the thresholds useful for the implementation of targeted management measures. Furthermore, it was concluded that the STAR_ICMi index is able to highlight the changes in the community in relation to the degree of alteration. The autoecological study on the five endemic species has provided some important though preliminary information, which may reveal unvaluable for further understanding of species requirements, so that their conservation can be actually attained. Both phases of the research offer evidence on the value of habitat data, which can be directly employed in the practical implementation of European and National regulation focused on the protection of aquatic ecosystems.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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