Caratterizzazione funzionale della comunità macrobentonica dei fiumi della Tuscia e analisi delle relazioni con le variabili abiotiche a diversa scala spaziale
Author(s)
Barile, Mariachiara
Date Issued
March 15, 2010
Type
Doctoral Thesis
Abstract
Recent approach to study freshwater ecosystem is to compare community structure with functional profile, based on
bio- and eco-logical traits, to discriminate multiple-scale environmental factors.
Thus, our perception of the relative importance of patterns and processes strongly depends on the scale of observations.
Because the relevant scales of variation are typically unknown a priori, spatial patterns in assemblage structure and the
organisms’ distributions should be studied across a wide range of spatial scales. In addition to being of basic ecological
interest, understanding the scale dependency of natural phenomena is a prerequisite for effective environmental
monitoring and management.
Stream condition is a joint product of factors operating at multiple hierarchical scales, and conditions at lower levels are
typically constrained by higher-level factors. At broad scales, geologic and climatic factors are the main determinants of
stream habitat characteristics, and macroinvertebrate assemblages often show correspondence to such large-scale factors
across ecoregions or other regional delineations. However, within-region variation in geology, land use, and water
chemistry could override the influence of regional factors, and some studies have shown that catchment- scale
characteristics are more useful than regional factors in predicting stream macroinvertebrate and fish assemblage
structure.
We selected thirteen sites covering the whole quality range present in the geographic area (Lazio Region, Province of
Viterbo, Italy) from ‘reference sites’ to impacted ones. All sites were chosen to be representative of a single river type
(small-sized, volcanic-siliceous, 100-400 m. a.s.l.) consistent with the Water Framework Directive WFD 2000/60/CE
requirements.
The collection of macroinvertebrates and environmental data was conducted during three sampling seasons in
2006/2007. Macroinvertebrates were sampled quantitatively, in specific mesohabitat, following a multi-habitat scheme
according to the AQEM and STAR protocols.
The aims of this study were:
- to improve knowledge of invertebrates community in volcanic streams;
- to test the effectiveness of these different approaches in detective different types of human impacts at three
levels of spatial resolution (from local habitat to catchment).
The variability of 95 categories among 17 bio-ecological traits was described using a fuzzy-coding method. Multivariate
analysis and correlations were applied both on taxonomical and on traits dataset to elucidate patterns in abundance and
community composition and to order communities along gradients of environmental variables. The results indicated that
these two approaches could be useful to detect different types of human impact at different scales. Both species and
traits compositions were correlated with nutrient and physico-chemical variables. Compared to taxonomic structure, the
community profile based on bio-ecological traits appeared to be better related to meso and local scale (pool versus riffle
areas and microhabitat parameters) and less to factors acting at broader-scale (reach and catchment).
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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