Studio della struttura del popolamento zooplanctonico di un ambiente iperalino: le saline di Tarquinia
Author(s)
Silvestri, Federico
Date Issued
March 7, 2008
Type
Doctoral Thesis
Abstract
Ecological importance of Solar Saltworks is known especially for the presence of
migratory birds, but little or nothing is known of the structure of other biological
components.
Aim of this study was to determine the structure and the spatial and temporal variation
of zooplankton in the decommissioned solar saltworks of Tarquinia (Italy).
This study is included in a larger project of characterization of all the biological
components of the Solar saltworks. Zooplankton has been sampled by horizontal hauls
using a net of 80 μm mesh connected to a PVC frame. The development of the sampling
technique was a substantial part of the research, because of the difficulty of sampling
correctly in shallow waters with high salinity values and low zooplankton densities.
Four ponds of different salinities have been sampled monthly for a period of 12-18
months, filtering everytime a water volume of about four cubic meters.
Salinity gradient (40-190‰) had a clear effect on the abundance of zooplankton; in fact
zooplankton densities and taxononomic richness were high in ponds with lower salinity
values and low in hypersaline ponds.
Adult zooplankton was mainly formed of Copepods (90% of total abundance), while
meroplankton was represented by Bivalvia Larvae. Among Copepods, euplanktonic
forms, such as Acartia clausi and Euterpina acutifrons have disappeared after first
months of sampling, and they were replaced by Cyclopina gracilis and phytal
Harpacticoids. Among these, the more common forms belong to Thalestridae,
Harpacticidae, Miracidae and Tisbidae families in mesohaline ponds, and to Ameiridae
and Canthocamptidae in hypersaline ones.
Cladocera have never been found, and rotifers were rarely present in the saltworks. No
evident seasonal changes have been observed in the monthly sampled ponds, although a
common increase in the densities and in the taxonomic richness were noticed in spring
in 75% of the ponds. Mesohaline ponds were similar among them, so the hypersaline
ones.
I
The Protozoa Ciliate Fabrea salina was present only in ponds with salinity values
higher than 130 ‰, in absence of other zooplankton forms, while the Anostracan
Artemia salina was found only in one pond, at salinities of 250-270 ‰.
Phytal Copepods linked to Ruppia cirrhosa have been screened along time in one pond.
Harpacticoids and Cyclopoids found linked to Ruppia were the same present in water
column too.
The composition of Tarquinia’s saltwork zooplankton has been compared with that of
two other similar plants. Few species are common to the three systems, among them the
Calanoid Copepod Acartia clausi, the Harpacticoid Tisbe spp and the Ciliate Fabrea
salina.
Additional information
Dottorato di ricerca in ecologia e gestione delle risorse biologiche
Subjects
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