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The coastal landscape of the Gaeta Bay, southern Latium (Italy), is the result of a significant tectonic control expressed by a geometric segmentation of the relief and by offsets of the coastline. The structural features derived from this activity are overlain by slope and littoral morphogenetic processes. Tectonic and geomorphic processes performed in a different way along the coastal belt, producing the unequal morphological setting observed in the western and in the eastern sector of the study area. In the western sector, the Aurunci Mts. gradually reach the coast forming cliffs. On them, several emerged and submerged erosional forms such as notches and sea terraces are recognised. Embayments characterized by sandy pocket beaches wide from few hundred meters to over 2 km are in correspondence to some tectonic lines with a clear morphological expression and transversal to the coastline. In the eastern sector, the Aurunci Mts., higher and rich of karstic forms, joint to the coastline in few kilometres due to the accumulation forms developed along valleys deeply cut in the carbonate slopes. The morphological features of the investigated area permitted us to recognize the existence of differential vertical movements along a 30 km-wide coastal area clearly split in two sectors.

Human use of the world’s seas and oceans is causing cumulative pressures on, and changes to, coastal marine habitats. The Gulf of Pozzuoli (GoP) is one of the three marginal sub-basins identifiable in the Gulf of Naples which have been affected by strong anthropogenic pressure since the end of the 19th century. While several studies demonstrated sediment and water contamination in the GoP, to date, few and fragmented data have described the effects on the phytoplankton community in such a coastal system. In order to contribute to a more detailed picture of the ecological status of the GoP, we have analysed the phytoplankton community in terms of biomass and functional diversity, particularly in relation to water salinity and nutrient availability. Our results reveal the presence of two different trophic areas in the GoP. The first one is located in the eastern sector, which is more sensitive to land run-off and characterized by a higher level of biomass. The second one is situated in the western sector, and is characterized by a higher salinity and lower level of biomass. Diatoms and haptophytes were the most representative groups; other minor groups showed higher spatial and temporal variability, especially in coastal stations. The weakening gradient of salinity from the coast to open water and the point distribution of nutrients suggest that the GoP is affected by scattered anthropogenic sources, the contribution of which to the overall system is irregular and depends on dilution dynamics. Despite this, the GoP presents mean Chl a concentrations similar to those of oligotrophic environments, and, the high variability observed underlines the importance of applying the appropriate sampling scales to measure coastal systems subject to point anthropogenic pressures.

The study was designed to complement the results of a previous investigation which revealed a worrying contamination scenario by polycyclic aromatic hydrocarbons, PAHs, in the Gulf of Pozzuoli, GoP, in the south of Italy. This former study also evidenced the pyrolytic source of PAHs from the dismissed metallurgical brownfield site of Bagnoli in the east side of GoP. The environmental toxicological risk assessment was also carried out. Sampling transects were drawn in the west edge of the gulf, T1 and T2, in the east side, T5, T6, in the proximity of the industrial plant and outside GoP, MdP, where pollution was expected to be low. Σ PAHs largely exceeded, from 36 up to >220 times, the regulatory standard in the east area. Lower exceeding values were determined in all the west side. FLT and PYR were the dominant hydrocarbons and PAHs distribution profiles were quite similar from west to east sides, meaning a common pollution source. Moreover, sediments appeared enriched by 4, 5 and 6 aromatic rings, 47.2%, 25.7%, and 14.0%. PAHs diagnostic ratios for source screening confirmed the pyrolytic origin of the PAH mixtures at all sites. Σ PAHcarc/ Σ PAH showed that ∼ 50% of PAHs were of carcinogenic nature at all sites. The total benzo(a)pyrene, BaP, equivalent toxicity (TEQ) values highlighted a dramatic scenario especially in the east part of GoP, with values from twenty-four fold and six hundreds fold those reported by the literature for moderate and low ecological risk environment. The output of the risk assay assessment revealed a situation of high risk in the east side of GoP, whereas a moderate to high risk level was determined throughout all GoP.