Anthropogenic impact on river basins: temporal evolution of sediment classes and accumulation rates in the Northern Tyrrhenian Sea, Italy

Abstract In this study, sedimentological and geochronological data from sections of a core (GRT50) collected in the Northern Latium coastal area were compared to data on pluviometric (rainfall) trends, river flows and the temporal evolution of human interventions in the three most important hydrographic basins (Mignone, Marta and Fiora) of this coastal area. The statistical analysis of pluviometric trends identified variations due to a decreasing trend in the Fiora river basin, whereas in the two other locations the decrease was not so significant. Data from the sedimentological analysis of the core confirmed a progressive decrease in the sandy component, which declined from about 30% to the current level of 7% over the last 36 years. There was no significant variation in the sediment mass accumulation rates (MAR), which were characterized by an almost cyclic trend that was probably determined by the most intense floods in the study area. The results revealed that the variations caused by the fluvial processes have affected the water runoff of the Fiora River, and that the consequent decrease in the sand production has been responsible for the recession of beaches in the coastal area between Tarquinia and Montalto di Castro

DREDGING WORKS MONITORING IN THE PORT OF CIVITAVECCHIA, ROME, ITALY: SEDIMENTOLOGICAL AND GEOCHEMICAL INVESTIGATIONS

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Anthropogenic impact on river basins: temporal evolution of sediment classes and accumulation rates in the northern Tyrrhenian Sea, Italy

Abstract In this study, sedimentological and geochronological data from sections of a core (GRT50) collected in the Northern Latium coastal area were compared to data on pluviometric (rainfall) trends, river flows and the temporal evolution of human interventions in the three most important hydrographic basins (Mignone, Marta and Fiora) of this coastal area. The statistical analysis of pluviometric trends identified variations due to a decreasing trend in the Fiora river basin, whereas in the two other locations the decrease was not so significant. Data from the sedimentological analysis of the core confirmed a progressive decrease in the sandy component, which declined from about 30% to the current level of 7% over the last 36 years. There was no significant variation in the sediment mass accumulation rates (MAR), which were characterized by an almost cyclic trend that was probably determined by the most intense floods in the study area. The results revealed that the variations caused by the fluvial processes have affected the water runoff of the Fiora River, and that the consequent decrease in the sand production has been responsible for the recession of beaches in the coastal area between Tarquinia and Montalto di Castro

Physical and Biological Water Column Observations during Summer Sea/Land Breeze Winds in the Coastal Northern Tyrrhenian Sea

Coupling between sea/land breeze and coastal circulation and the influence of wind-driven dynamics are substantially relevant for understanding coastal Mediterranean ecosystems. These coastal areas are particularly dynamic and are characterized by high-variable processes which drive biological phenomena at different time-scales. For the Tyrrhenian Sea, the available information on coastal dynamics is confined to large-scale general circulation with a focus exclusively on mesoscale pelagic dynamical processes. Hydrodynamic studies of Tyrrhenian coastal areas are very rare and focus on surface water circulation. For time scales that are associated with coastal water circulation, there is also limited knowledge on water column dynamics that are forced by local atmospheric circulations. This paper presents physical and biological data to document the effect of sea/land breeze circulation on ocean current dynamics and water column structures in a Northern Tyrrhenian coastal site. This coastal area is characterized by the presence of a relevant energy production site as well as one of the most important ports in the Mediterranean Sea for cruise traffic. Consequently, this coastal site is a transit point for many tourists and it is characterized by an increase of energy demand, especially during the summer season. The in-situ data show that coastal currents are predominantly controlled by the tide and local wind and respond rapidly to changes in wind direction. Water column thermal structure analyses reveal significant changes with the morning’s rotation of breeze: lifting of isotherms (cooling) was typically observed in deep layers during early mornings, accompanied by fluctuations in isotherms. The performed investigations provide valuable inputs for coastal ecosystem modeling and for a better understanding of the coastal processes that are significant for environmental and navigational interests

Commercial catches and discards composition in the central Tyrrhenian Sea: a multispecies quantitative and qualitative analysis from shallow and deep bottom trawling

In the Mediterranean Sea, the catch of bottom trawl fisheries is composed of a complex mix of fish and invertebrates with a considerable amount of discards. Seasonal composition of catches and discards of bottom trawls operating at different depths in the central Tyrrhenian Sea were investigated from October 2014 to October 2015. The mean total catch per unit effort (CPUE) ranged between 30.93±8.43 and 27.52±9.88 kg/h in shallow and deep fishing grounds, respectively. The discarded fraction of the catch was 39.9 % in shallow and 43.3% in deep fishing grounds. The mean CPUE of commercial target species were similar in shallow and deep trawling (10.81+5.82 vs 8.92±3.16 kg/h). The commercial bycatch was lower in shallow (6.66±1.25 kg/h) than in deep grounds (8.24±2.91 kg/h), whilst the discards were lower in deep (10.43±5.14 kg/h) than shallow grounds (13.43±5.29 kg/h). Overall, 246 species were caught during fishing operations, out of which 209 were included in discards. The number of species recorded in shallow grounds (199 caught species with 166 discarded) was higher than that recorded in deep grounds (116 caught species with 102 discarded). Fish were the most represented taxa in the shallow discards, followed by echinoderms; crustaceans, and were the main discarded taxa in deep water. Depth was the main factor affecting both commercial catches and discards composition, whereas the season affected the CPUE of main target species only. The results confirmed that discards were higher in shallow than in deep trawling, suggesting that the latter is more efficient than the former in catching fishery resources for human consumption. Understanding the factors that affect discarding is the starting point for adopting management measures to mitigate negative impacts of trawl fisheries on marine resources and benthic communities