M.e. Gennaro· S. Angelino
bioindicators. For example, aquatic macrophytes and algae can be used as alternative
indicators of water pollution, even if the increasing role of bioindication as an appropriate system for pollution control requires the identification of the aquatic plants being
suitable as biological monitors. Their selective absorption of certain ions combined
with their sedentary nature are good reasons for using hydrophytes as biological
monitors: the ability of algae in coastal waters to cumulate metals is well known. A
study was performed in Greece, in the Aegean Sea, in the neighbourhood of the
Thessaloniki Bay and of the islands of Crete and Thira (Stratis et al. 1996). In 14 sites,
9 kinds of algae were sampled. Each sample was analysed for 5 metals (Cu, Zn, Cd, Pb,
Mn). Both hierarchical and non-hierarchical approaches were used to detect similarities or dissimilarities in the bioindicating ability. The samples collected in biotopes
characterized by the same kind of pollution can be found in one cluster, while in another bioindicators from two relatively unpolluted biotopes are present. This result
suggests that most of the marine algae do not react specifically to a certain pollutant
but to the total pollution caused by heavy metals. In this way algae are bioindicators of
the total situation of the environment and not of the presence of a specific pollutant.
Also bivalves, such as oysters clams and blue mussels (Mytilus edulis), are able to
accumulate pollutants in their tissue up to concentrations that far exceed the concentration in the ambient water. For this reason they can advantageously be used in investigations devoted to the distribution of pollutants in coastal areas, as in the study
carried out on the coast of Norway (Kvalheim et al. 1983). Four categories of pollutants were considered: petroleum hydrocarbons, halogenated hydrocarbons, trace metals and radio nuclides. Polluted mussels were collected from a dock in the Bergen
harbour and unpolluted blue mussel from a farm at Austevoll, at about 50 km (sea
distance) south of Bergen in a relatively unfrequented fjord: in total 19 samples were
collected. Geographical and seasonal variations in both mussels and environments
make it difficult to use the levels of pollutants found in mussel tissues as a direct measure of the degree of environment pollution. The purpose is to establish whether the
composition of the components naturally present in tissues is different for mussels
collected in different places. To level out the short-time differences caused by the different situations (access to food, temperature, salinity, light), all the mussels were transferred to an aquarium with running clean seawater and maintained here for 16 weeks.
Samples from muscle and gonad tissues were analysed by GC: in the chromatograms
60 peaks were selected for muscle and 56 from gonad tissue samples. The experimental data were treated by SIMCA, which clearly shows that the muscle samples of polluted and unpolluted mussels form well-described and nicely-separated models in the
60-dimensional space and shows clear differences between the mussels from the two
sampling locations. The significant PCs for each class were evaluated and cross-validated. The final results show:
i. The samples from unpolluted mussels are closely grouped and well separated from
the polluted mussel samples.
ii. The more polluted samples are more scattered than the unpolluted ones.
iii. Muscle tissues give a better distinction than gonad tissues.
It must be noticed that these differences are not of short-term character because,
as mentioned, all the mussels sampled were kept in the same aquarium where they
bioindicators. For example, aquatic macrophytes and algae can be used as alternative
indicators of water pollution, even if the increasing role of bioindication as an appropriate system for pollution control requires the identification of the aquatic plants being
suitable as biological monitors. Their selective absorption of certain ions combined
with their sedentary nature are good reasons for using hydrophytes as biological
monitors: the ability of algae in coastal waters to cumulate metals is well known. A
study was performed in Greece, in the Aegean Sea, in the neighbourhood of the
Thessaloniki Bay and of the islands of Crete and Thira (Stratis et al. 1996). In 14 sites,
9 kinds of algae were sampled. Each sample was analysed for 5 metals (Cu, Zn, Cd, Pb,
Mn). Both hierarchical and non-hierarchical approaches were used to detect similarities or dissimilarities in the bioindicating ability. The samples collected in biotopes
characterized by the same kind of pollution can be found in one cluster, while in another bioindicators from two relatively unpolluted biotopes are present. This result
suggests that most of the marine algae do not react specifically to a certain pollutant
but to the total pollution caused by heavy metals. In this way algae are bioindicators of
the total situation of the environment and not of the presence of a specific pollutant.
Also bivalves, such as oysters clams and blue mussels (Mytilus edulis), are able to
accumulate pollutants in their tissue up to concentrations that far exceed the concentration in the ambient water. For this reason they can advantageously be used in investigations devoted to the distribution of pollutants in coastal areas, as in the study
carried out on the coast of Norway (Kvalheim et al. 1983). Four categories of pollutants were considered: petroleum hydrocarbons, halogenated hydrocarbons, trace metals and radio nuclides. Polluted mussels were collected from a dock in the Bergen
harbour and unpolluted blue mussel from a farm at Austevoll, at about 50 km (sea
distance) south of Bergen in a relatively unfrequented fjord: in total 19 samples were
collected. Geographical and seasonal variations in both mussels and environments
make it difficult to use the levels of pollutants found in mussel tissues as a direct measure of the degree of environment pollution. The purpose is to establish whether the
composition of the components naturally present in tissues is different for mussels
collected in different places. To level out the short-time differences caused by the different situations (access to food, temperature, salinity, light), all the mussels were transferred to an aquarium with running clean seawater and maintained here for 16 weeks.
Samples from muscle and gonad tissues were analysed by GC: in the chromatograms
60 peaks were selected for muscle and 56 from gonad tissue samples. The experimental data were treated by SIMCA, which clearly shows that the muscle samples of polluted and unpolluted mussels form well-described and nicely-separated models in the
60-dimensional space and shows clear differences between the mussels from the two
sampling locations. The significant PCs for each class were evaluated and cross-validated. The final results show:
i. The samples from unpolluted mussels are closely grouped and well separated from
the polluted mussel samples.
ii. The more polluted samples are more scattered than the unpolluted ones.
iii. Muscle tissues give a better distinction than gonad tissues.
It must be noticed that these differences are not of short-term character because,
as mentioned, all the mussels sampled were kept in the same aquarium where they