Variabilità spazio-temporale dei popolamenti macrozoobentonici, in relazione ai cambiamenti stagionali in un ambiente lagunare (Mistras, Sardegna Occidentale) con basso impatto antropico ed elevata stabilità ecologica
Author(s)
Fenzi, Giovanni Antioco
Date Issued
June 12, 2013
Type
Doctoral Thesis
Abstract
The transitional waters environments are complex systems considering the high variability on
morphology and abiotic parameters associated to several factors such as: wind forcing, sunlight,
tide or freshwater flow. Usually, on these environments the biodiversity is low, due to few species
are successfully adapted to survive to high physiological stress with alteration of metabolic activity.
The Mistras’s Lagoon is renowned for natural value, protected by national and international
convention considering the low anthropogenic pressure and the high biodiversity richness.
The lacks of knowledge of ecological Mistras’s lagoon status suggest carrying out a monitoring
survey on this area. The aim of this study is to detect the spatial-temporal distribution of
macrozoobenthos assemblages, and the seasonal changes of physical–chemical parameters and the
sediment composition. Three study areas have been selected considering: the morphological
factures, main primary producers distribution (C. nodosa, Z. noltii e Gracilaria n.c.) and the
confinement gradients. The seasonal variability of physical–chemical parameters is high from the
cold season (temp.: 9.32 °C ; sal.: 22.09 psu; oss.: 14,02 mg/l e 149.70 %) to the worm season
(temp.: 32.60 °C ; sal.: 70.99 psu; oss.: 3.40 mg/l; 57 %), which hold over autumn.
A salinity gradient can be observed form the more confined and hyperaline area (± 70 psu) at the
opening of the lagoon (± 50 psu). The organic matter values are low (< 12% OM) and are following
the decreasing gradient from the more confined and no-vegetated areas to the vegetated and close to
the opening lagoon areas. The oxygen never reaches anoxia or hypoxia condition for long periods
and oxygen saturation (< 150 %) is detected only during the spring season. The benthic species are
high tolerance and the macrozoobenthos assemblages are strongly influenced by the seasonal
variability. The Shannon diversity (H’), the number of species (S) and the abundance (N) values are
high compared to other hyperaline environment. Finally, the spatio-temporal distribution of
macrozoobenthos assemblages are mainly affected by seasonal changes of physical-chemical
parameters instead of organic matter enrichment of sediments or other pollution sources.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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