An Integrated Sedimentological and Ecological Approach for Investigating Vulnerable Coastal Lakes: A Case-Study

Coastal lakes are vulnerable complex systems where potential contamination processes may affect the bottom sediments, especially if the coasts are intensively urbanized. In this respect, the sedimentological and ecological characterization of the bottom sediments may provide a fundamental background, particularly stringent in the cases of heavy metal contamination. In this paper, this multi-disciplinary approach was applied to Lake Ganzirri, a small-size and shallow coastal lake developed on an intensively urbanized territory of North-Eastern Sicily (Italy), where recent chemical investigations on the heavy metal contaminants of the sediments were carried out. The sediment textural features (in-cluded those of the malacofauna) and the bottom morpho-bathymetry were characterized and investigated by applying multivariate statistics and QGIS techniques. QGIS maps were finally compared with those of the heavy metal concentrations. The present research allowed to detect for the first time: i) a minor tectonic graben inside the main ENE-WSW trending Ganzirri graben; ii) mixed sediments composed of quartzo-lithic sands with sig-nificant contents in bioclastic calcareous remains; iii) sediment heterogeneous textures, mainly characterized by poorly sorted, leptokurtic, near symmetrical coarse-grained sands, with randomly distributed lenses of very coarse- grained sands with gravels and of medium-grained sands; iv) sediments testifying for actual high-energy conditions and environments at low confinement degree; v) no evidence of correlations between the hotspots of heavy metals (mainly related to prevalent geogenic origins) and the distribu-tions of sedimentological features and bottom depths.