Vieste-Split transect Grilli F.1, Frapiccini E.1, Campanelli A.1, Guicciardi S.1, Marini M.1, Marasovic I.2, Grbec B.2, Skejić S.2, Ujević I.2, Lušić J.2 1Istituto di Scienze Marine ISMAR-CNR, L.go Fiera della Pesca, 2, 60125 Ancona, Italy 2 Institute of Oceanography and Fisheries, Šetalište I. Meštrovića 63, 21000 Split, Croatia emanuela.frapiccini@an.ismar.cnr.it European Geosciences Union-General Assembly 2015 - Vienna, Austria, 12th April – 17nd April 2015 Variability of PAHs and trace metals in the sediments in relation to environmental characteristics of the bottom layer in the middle Adriatic Sea Introduction In the framework of the project PERSEUS (Policy-oriented marine Environmental Research in the Southern European Seas), two interdisciplinary surveys were carried out in April 2013 and April 2014 in the middle Adriatic Sea with Croatian research vessel “Bios II” and the Italian research vessel “G. Dallaporta”, respectively. The main objective of these research cruises was the implementation of the Marine Strategy Framework Directive (MSFD) in two areas of the Adriatic region (Jabuka Pit and Palagruža Sill areas) for collecting physical, chemical and biological data in order to get a better understanding of whole Adriatic ecosystem. The two areas are already recognized as key areas for the interception and the study of dense water modification1,2,3. Due to seasonal circulation patterns, they are characterized by high temporal variability of the thermohaline structure4,5 and other oceanographic parameters. Long term oceanographic records from the Middle Adriatic enable better understanding of the ecosystem response to changes of atmospheric and sea conditions through physical, chemical and biological processes6. Several oceanographic parameters relevant and useful for the ecosystem assessment of the two areas were collected: temperature, salinity, density, fluorescence, oxygen, nutrients, chlorophyll, phyto- and zoo-plankton as well as selected pollutants, trace metals and polycyclic aromatic hydrocarbons (PAHs) in sediments. In this study the results obtained during the survey carried out in April 2013 are presented. Fig. 1: Map of the Pescara-Sibenik transect (P16-P30) and the Vieste-Split transect (P15-P1) Vieste Pescara Split Sibenik Field Activity The field activity has included the acquisition of water and sediment parameters in the middle Adriatic Sea along two transects: the Pescara-Sibenik transect (Jabuka Pit area) and Vieste-Split transect (Palagruža Sill area), Fig. 1. In all the stations the Conductivity-Temperature-Depth (CTD) data were collected using a SeaBird Electronics SBE25. Along all the water column of the main stations (red circles), water samples have been collected using Niskin bottles for the chemical analysis of the dissolved nutrients, chlorophyll a and the phytoplankton composition. While at the bottom, the samples sediments have been taken with a Box-corer in order to analyzed PAHs and trace metals. Results and Discussion In both investigated transects similar total phytoplankton abundance was recorded (Fig. 3). Micro-phytoplankton component dominated in community, but at station P2, P4 and P30, an increased abundance of diatoms was recorded especially in the surface layer. These stations were close to the Croatian coast line and therefore influenced by rivers inflow. Diatom Cyclotella sp. prevailed in the diatom community confirming the river influence. Fig. 3. Relation among different phytoplankton groups at the stations of Pescara-Sibenik and Vieste-Split transects (0m and 10m) Pescara-Sibenik transect Vieste-Split transect Fig. 4: Variations of PAHs along the Pescara-Sibenik transect (Jabuka Pit area) and Vieste-Split transect (Palagruža Sill area) in relation to the physical characteristics of the bottom layer. The variations of PAHs concentrations in relation to the physical characteristics of the bottom layer are presented in the Fig. 4. The total PAHs concentrations (sum of 16 PAH priority pollutants - US EPA) recorded in the marine sediment during the cruise showed a higher level of PAH contaminations near to coast and in the central pit of the Jabuka Pit area (28.5 ng·g-1 d.w.)7. The corresponding bottom water in the central pit was characterized by a temperature of 10.9 °C, density of 29.6 kg·m-3, salinity of 38.6 and low values of DIN (0.55 µmol·l-1). Pescara-Sibenik transect (Jabuka Pit area) Vertical profiles of chlorophyll a indicated the occurrence of Deep Chlorophyll Maximum (DCM) between 20 and 100 m depth (Fig. 2). At Pescara-Sibenik transect, DCM was much more pronounced in comparison to DCM at Vieste-Split transect. This was probably due to the earlier onset of thermocline formation at Jabuka Pit area, in comparison with Palagruža Sill area where the thermocline was not yet observed (Fig. 4). Fig. 2. Vertical distribution of chlorophyll a along the Pescara-Sibenik and Vieste-Split transects Pescara-Sibenik transect (Jabuka Pit area) Vieste-Split transect (Palagruža Sill area) Vieste-Split transect (Palagruža Sill area) Fig. 5: Correlations between PAHs concentration vs DIN, silicate and distance of coast. Among correlations made between PAHs variability and environmental characteristics of the bottom layer, the strongest ones were with DIN, silicate and distance from coast. A moderately negative relationships between PAHs concentration and these mentioned parameters were found (Fig. 5). R = -0,3755 R = -0,3661 R = -0,5809 Fig. 6. Trace metal concentrations in surface sediments collected along two transects (T1 - Pescara-Sibenik transect, T2 - Vieste-Split transect) The distribution of trace metals in surface sediments of the Adriatic Sea revealed higher concentrations, particularly Cd and Pb in sediment samples along the Pescara-Sibenik transect, T1 (Fig. 6). Pb and Cu concentrations were in the levels of Croatian coastal areas such as the concentration of Cd in sediments along the Vieste-Split transect (T2), while the concentration of Cd in sediment along the Pescara-Sibenik transects (T1) were larger, nearly double8. The concentrations of Zn were not significantly different from what established for the Croatian coastal areas, while they diverged toward the Italian coastal areas (T1 larger than T2). BIBLIOGRAPHY Zore-Armanda, M. 1963. 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