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This study describes the prevalent sedimentological and geochemical patterns and investigates the environmental status of the bottom of Gialova lagoon, a highly vulnerable coastal site of the EU's Natura 2000 network. For this task, lithological, geochemical, and microfaunal analyses of sediment samples were combined with a high-resolution bathymetric survey. Potential pollution was determined using geochemical-based (EF, I-geo, and PLI) and faunal (Foram-AMBI) indices. We find that sedimentation is mainly controlled by the bottom morphology, hydrodynamic variations, and biogenic productivity of the lagoon. The application of the multivariate factor analysis technique revealed four dominant factors explaining the geochemical processes occurring in the lagoon. The first factor, namely "terrigenous aluminosilicates associated with Corg vs. autochthonous biogenic carbonates", discriminates the deposition of detrital sediments, related to the high adsorption of heavy metals—versus bioclastic sediments. The "sulfides" factor represents an anoxic phase of the lagoon floor, whereas the "Mn-oxyhydroxides" factor indicates increased manganese content with several compounded trace elements. The "phosphate" factor reveals multiple sources of phosphorus in the lagoon. The lagoon bottom shows negligible to minor contamination in heavy metals, except Mo and Pb, which induce moderate pollution levels. The maximum contamination and environmental stress concern two small-sized, shallow basins within the lagoon. [ABSTRACT FROM AUTHOR]

The island of Astypalea (Greece), known for its rich and pristine archeological sites, encompasses a semi-enclosed silled basin that has been very susceptible to global sea levels and regional climate changes due to its relatively modern shallow sill of 4.7 m water deep that connects the Vathy bay with the adjacent Aegean Sea. To identify the causal relationship between regional climate, sea-level trajectories, and environmental change and their potential impact on hominine habitats on the island, we investigated a high-resolution seismic profile together with sediment, stable isotope, geochemical, and biotic proxies retrieved from a marine sediment core (ASTC1). Our results show that the basin was once isolated, and a marine inundation occurred at around 7.3 ka BP, which is older than expected, based on global sea level reconstructions. The entire transition from isolation to full marine conditions was accomplished in three major phases: (1) non-marine isolated conditions between 9–7.3 ka BP, (2) semi-isolated hypersaline marsh and lagoonal conditions between 7.3 and 4.1 ka BP, and (3) semi-isolated shallow marine conditions of today (4.1 ka BP to present). High water alkalinity, elevated organic content, and heavier isotopic signals indicate relatively arid conditions in the region that favored Sr-rich carbonate precipitation within the 7.3–6 ka BP interval. On the other hand, freshwater biota, along with a high Corg/N ratio and lighter isotopic signal, showed wetter conditions, at least for the intervals 8–7.3 ka and 6–5.4 ka BP, in contrast to the aridification trend seen as 4.1 ka to present. Finally, the hominine habitat evolution at around 6 ka BP might be attributed to the wetter conditions and the freshwater source provided by the bay at that time. [ABSTRACT FROM AUTHOR]