Le Diatomee come indicatori degli ecosistemi acquatici di transizione
Author(s)
Puccinelli, Camilla
Date Issued
February 10, 2011
Type
Doctoral Thesis
Abstract
Diatoms are widespread group in aquatic environments, and due to their characteristics are useful tools of biological monitoring. They are one of the biological elements required by the European Water Frame Directive 2000/60/EC for water quality assessment.
Transitional waters are common ecosystems in Mediterranean Ecoregion and the lack of ecological knowledge cause a negative impact on environmental conservation, management and restoration.
The aim of this study is to improve the knowledge of transitional water ecosystems through the study of diatom community and the assessment of the potential use of these algae as bioindicator.
The study was conducted on diatom communities and environmental variables of several ecosystems and their potential correlations have been also investigated.
A total of 28 sites were investigated. They represent different typologies of transitional waters: estuarine zones of lotic systems (rivers and channels) and brackish lentic ecosystems (coastal lagoons) of Tyrrhenian coast line, between Latium and Tuscany Regions. Biological and water samples were collected from each sites.
A total of 219 species and varieties were identified. Furthermore, a potential toxic species, Amphora coffeaeformis was recognized.
The identified diatom communities and the result of biotic analysis have been treated statistically by Principal Component Analysis and Canonical Correlation Analysis. The results showed that communities were similar as chemical and physical chemical variables for each typology of studied transitional waters.
Canonical Correlation Analysis performed on biological and chemical outlined a linear correlation between components.
Main factors that influenced diatom community structures were: velocity flow, substrate, salinity and nutrients, particularly nitrates and phosphates. River mouths presented a major numbers of species, probably due to the extreme heterogeneity of environmental parameters. Concerning canal mouths diatoms species resulted a good tool for assessment of water quality. In the lagoon ecosystems we found lower number of species probably related to the environmental selectivity (i.e. salinity). The results showed a strength correlation between diatomic communities and several environmental parameters. Three different diatom assemblages were observed in the three typology of transitional waters: river mouths, channel mouths and coastal lagoons.
The potential toxic species Amphora coffeaeformis, was identified, isolated and cultured in fresh media. Besides, the species was submitted to toxicity test to evaluate the presence of domoic acid, using instrumental tests LC-MS and ecotoxiticy assay Microtox. The results of analysis did not detect the presence of domoic acid in the culture, but it could be a producer under environmental stress conditions.
This study contribute to improve knowledge on diatoms of the Italian transitional aquatic ecosystems, at both the basic and applied levels.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
Subjects
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