ABSTRACT
The interest for the evaluation of pollutants within water ecosystems by the application of different kinds of biological markers has been increased in the past few years.
The study of seafloors and the analysis of chemical and physical features of sediments play a major role in the evaluation of marine environment. The sediments can play the role of direct transporters of both natural and human contaminants, as well as temporary and definitive receptacle of essential or toxic substances for living organisms, by different processes (bio buildup, absorption and release from and into waters).
The aim of my thesis concerns the development of a methodology for the ecotoxicological evaluation of coastal marine sediments by means of genotoxicity and phytotoxicity bioassays, together with the chemical analysis of heavy metal content.
The assessment of mutagenic risk is particularly considerable in environmental toxicology and in the prevention and protection of human health.
Mutagenesis tests can therefore detect toxic and/or potentially mutagenic effects of
“xenobiotic” substances within the environment, such as water, soil, sediments and industrial products. In this work, the potential genotoxic effects of marine sediments was studied by performing short term mutagenesis assays, using genetically selected strains of Saccharomyces cerevisiae yeast as biomarkers. Experiments were carried out on D7-strain in different growth conditions of the yeast-growth, using cells in both stationary phase and exponential phase. At the same time, phytotoxic effects were studied using Lepidium sativum seeds. Sediment samples were taken in the sea portion between river Arno and river Serchio mouths.
For each sample, according to the USEPA standard procedure, a sediment elutriate was prepared by strongly shaking the sample in water, thus allowing the release of pollutants from the sediment to the water column.
The sediment aqueous elutriates have been tested at different dilution rates and were used to assay cytotoxicity, genotoxicity and phytotoxicity. The content of heavy metals (Cd, Cu, Pb) of the elutriates were also analysed. In order to determine traces of metal concentration, the anodic redissolution voltammetry (AVS) with mercury film electrode (cathode) was used.
The results obtained by the statistic revision of data showed the toxic effects of some sediment samples. In particular, a correlation between the samples with a high concentration of heavy metals (like cadmium) and the induction of harmful effects was
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underlined. The sediment elutriates, at different concentration levels, induced a cytotoxic effect with a significant decrease of the survival in Saccharomyces cerevisiae cells. Significant increases of gene conversion (GC) and point mutation (PM) in D7- strain cells of Saccharomyces cerevisiae, in different phases of the cell cycle, were also pointed out.
The heavy metals have been produce toxic effect on germinating, rooting and growing seeds of Lepidium sativum.
The results obtained in this work showed that the use of genotoxicity and phytotoxicity biomarkers, together with the chemical analysis, can be considered a valid methodology for toxicological studies of marine environment.
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