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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2007.06.001 Byline: Diana ZuA[+ or -]iga (a), Antoni Calafat (a), Anna Sanchez-Vidal (a), Miquel Canals (a), Brian Price (b), Serge Heussner (c), Stefano Miserocchi (d) Keywords: Particle fluxes; Particulate organic carbon; Algero-Balearic Basin; Western Mediterranean Abstract: With the aim of improving the knowledge of the open ocean carbon cycle, we present a budget of particulate organic carbon (POC) fluxes carried out in the deep central part of the Algero-Balearic Basin (ABB) at 2850m water depth based on a single mooring equipped with five automated sediment traps deployed from April 2001 to May 2002 at depths of 250, 845, 1440, 2145 and 2820m. Suspended particulate matter (SPM) and superficial sediments were also used as indicators of hydrodynamics and carbon burial, respectively. The data reveal that the fraction of primary production buried in the sediment, which finally leads to the sequestration of carbon dioxide from the atmosphere, is 0.16%, lower than the values found in the nearby continental margin regions such as the Alboran Sea (0.48-0.89%) but of the same order as recorded at other Mediterranean sites at similar depths, such as the Ionian Sea (0.11%). As they sink through the water column, the particles exhibit decreases in flux that are similar to those observed elsewhere, but also show variations that appear to correlate with hydrological features of the water masses present in the basin, as revealed by SPM concentrations and compositions. The input of the tyrrhenian deep water (TDW) into the ABB at 800-1500m of water depth exhibits low suspended POC concentrations and low sinking POC fluxes were also observed in this depth range. Gulf of Lions water mass formation appears to also contribute to elevated suspended POC concentrations and perhaps POC accumulation in the traps and sediments by spreading of dense cold water along the whole ABB that supplied POC at depths higher than 2000m. Author Affiliation: (a) GRC Geociencies Marines, Department d'Estratigrafia, Paleontologia i Geociencies Marines, Universitat de Barcelona, E-08028 Barcelona, Spain (b) Department of Geology and Geophysics, University of Edinburgh, EH 9 3JW Edinburgh, UK (c) CEntre de Formation et de Recherche sur l'Environnement Marin (CEFREM)-CNRS UMR 5110, Universite de Perpignan, F-66860 Perpignan, France (d) Istituto Scienze Marine ISMAR-CNR, Sezione Geologia Marina di Bologna, I-40129 Bologna, Italy Article History: Received 6 April 2006; Revised 4 June 2007; Accepted 7 June 2007

Major and trace metal concentrations were determined in western Adriatic sediment cores. Based on sediment chronology, the earliest anthropogenic influence appeared as a Zn and Pb increase in the Po River prodelta starting from ~ 1914. The increasing contamination signal of these trace metals propagated southward as far as 450 km with a growing delay, taking ~ 10 years to reach the south Adriatic Sea. Although greater inventories of excess trace metals in the northern sector pointed to the influence of the intense human activities in the Po River drainage basin and Venice lagoon system, we observed a reduction of excess trace metals from mid-1980s, related to the implementation of stricter environmental regulations on chemical wastewaters. In contrast, an increase in trace metal accumulation in surficial sediment from the 2000s in front of the cities of Ancona and Bari suggested a recent local input of trace metals, probably due to harbor activities. [ABSTRACT FROM AUTHOR]

The spatial distributions and fates of selected legacy and emerging compounds were investigated and compared in surface sediments sampled along the Adriatic mud-wedge and in deep-sea regions from the southern Adriatic basin. Results indicated that the concentrations of legacy contaminants (PAHs, PCBs and DDTs) and emerging contaminants (tonalide, galaxolide, EHMC, octocrylene, BP3 and NP) ranged from 0.1 to 572 ng g −1 and from

Sources, historical trends and inventories of polychlorinated biphenyls (PCBs) were investigated in sediments collected in five transects along the north-south axis of the western Adriatic Sea. The concentration of total PCBs (∑ 28 PCBs) ranged from < LOD (limit of detection) to 9.0 ng g − 1 in the sediment cores and between 0.1 and 2.2 ng g − 1 in recent sediments. Chronological records of PCB concentrations displayed a common pattern with historical PCB production and use, with the maximum peak values detected between the 1960s and the 1980s. Sediments deposited within the last two decades presented a ~ 40% to ~ 80% PCB reduction in comparison to the peak levels, reflecting the ban on PCB production and use since the late 1970s. PCB levels along with the presence of high-chlorinated congeners decreased southwards, indicating the Po River as the major source of PCBs in the western Adriatic Sea. This is further corroborated by the estimated inventories of PCBs, which were ~ 4–7 times higher in the Po River prodelta (256 ng cm − 2 ) in comparison to the middle and southern Adriatic, respectively, and about 100 times higher than the in the deep Adriatic Sea. [ABSTRACT FROM AUTHOR]

Abstract: Thirty-three surface sediment samples from cross-shelf transects on the northern Adriatic shelf were collected in December 2000, soon after a 100-yr flood of the Po River, in order to determine the distribution of organic carbon (OC) along the main sediment dispersal system. To evaluate the temporal variability, stations were re-occupied eight times at seasonal intervals until June 2003. Downcore sediment profiles from two sites characterized by high flood deposit thicknesses were also examined to assess the OC variability within the flood layer. In December 2000, the highest contents of OC (up to 1.24wt%) were measured in front of the main distributary mouths (Pila, Tolle and Gnocca-Goro) where the greatest thicknesses of the flood deposit were recorded. However, the influence of the Po di Gnocca-Goro sediment supply on the OC surface distribution declined after ∼1.5 years from the fall-2000 river flood, probably because these mouths are less active when the water discharge is lower. The δ13C of organic matter was used to trace the dispersal of fluvial OC on the continental shelf. The δ13C values ranged from −25.9‰ to −23.1‰. The fraction of fluvially derived organic particles decreased with increasing water depth according to a radial dispersal pattern around the Po River delta. This pattern persisted in all cruises. δ13C values increased progressively until April 2002, suggesting an increasing marine contribution to the OC content but decreased again following a second minor flood event in November 2002. The molar C/N ratio was on average 10.0±1.6, with slightly lower values in southern and central areas. Assuming contributions from three OC end-members (terrestrial, riverine and marine), a mixing model based on δ13C and the ratio of N to C (statistically more robust than C/N; Goñi, M.A., Teixeir, M.J., Perkley, D.W., 2003. Sources and distribution of organic matter in a river-dominated estuary (Winyah Bay, SC, USA). Estuarine, Coastal and Shelf Science 57, 1023–1048) was applied in order to quantitatively assess the OC sources for Po shelf sediments. δ13C is significantly and positively correlated with the marine OC fraction. The terrestrial fraction is inversely correlated with N/C, while the riverine fraction is positively correlated with N/C. The terrestrial OC source was the most abundant end-member (>70%) showing only little temporal variability regardless of the Po River water discharge. Temporal and spatial changes in OC composition suggest that: (a) the Po River prodelta is always dominated from terrestrial OC input; (b) the Po della Pila supplies most terrestrial OC, whilst other tributaries (e.g., Po di Gnocca-Goro) are secondary sources. However, these mouths are as important as the Po della Pila in affecting the riverine OC signature; (c) offshore, biological primary production raises the marine OC contribution. At two sites on the Po River prodelta, the 2000-flood deposit shows slight but consistent compositional changes of organic matter (N/C and δ13C) which can help to recognize other flood events in the sedimentary record. The OC budget for the 2000-flood deposit accounts for a terrestrial+riverine OC supply of 68–162Gg (109 g) against an OC deposition of 106–162Gg (excluding the marine fraction), which implies a rapid and efficient sedimentation of the flood material, and scarce or negligible export out the study area. Flood events may thus enhance terrestrial carbon burial, whereas marine carbon arrives more slowly and may be largely mineralized at the sediment–water interface. [Copyright &y& Elsevier]

Spatial patterns of major (Al, Fe and Ti) and trace metals (Cu, Cr, Mn, Ni, Pb and Zn) measured in surficial sediments collected within the Late-Holocene mud-wedge in the western Adriatic Sea were analyzed to elucidate their sources, transport and mass budgets. Distributions of sedimentary trace metals, their fluvial inputs and accumulation loads reveal along-shore transport towards the southern Adriatic. Pb and to a lower extent Zn accumulation loads over time decreased significantly since 1988 in the North Adriatic, consistently with the implementation of regulations in the Western Europe, whereas Zn accumulation in the Po River prodelta remained unchanged since 1995. The Po River fluvial inputs accounted for half of Cr, Ni, Pb and Zn of the fluvial inputs into the western Adriatic Sea, contributing for the delivery of important amounts of Cr and Ni into the sediments, probably related to the natural occurrence of ultramafic rocks in the North sector. Collectively, ~ 30% of trace metal fluvial inputs discharged into the North sector are exported to the Central and South sectors. The Po River acts as both a bypass and an accumulation zone. In contrast, trace metal accumulation in the Central sector far exceed trace metal fluvial inputs, which suggested that this area is a preferential sink for particle-reactive river-borne material from the North Adriatic. The North sector shows moderate enrichment of Zn and Pb mainly related to the Po River influence. The anthropogenic fraction of Pb shows a large drop of ~ 30% from the North sector southwards, whereas Zn proportions remain fairly the same up to the Central sector only decreasing in the South sector. [ABSTRACT FROM AUTHOR]

The Southern Adriatic is an area of dense shelf water (DSW) cascading and open-ocean convection. The impact of DSW cascading events in transferring organic matter to the deep benthic community and in producing a wide range of bedforms along the continental margin has been highlighted in recent years. In order to improve our knowledge on the interannual variability of the DSW cascading with the ultimate goal to understand timing of DSW formation and transport as well as the cascading process, its variability in intensity and duration, and the ultimate impact of the dense water on the deep sea, in March 2009 we deployed an instrumented mooring in a field of sediment waves (860 m depth) located down current to the Bari canyon. In March 2010, a second mooring was installed in the northern channel of the canyon. Winters 2009, 2010 and 2011 were mild and particularly wet and the Po river discharge remained relatively high throughout the whole winter. Hence, we expected weak dense shelf water formation associated with a shallow shelf water overflowing off the Adriatic shelf. By contrast, in winter 2012, the North Adriatic experienced a severe cold wave with NE Bora winds and reduced fresh water input. These weather conditions allowed the formation of extremely dense shelf water. Three additional moorings were quickly deployed during this cold event in the Southern Adriatic Sea to investigate the spatial variability of particle and organic matter fluxes exiting from the Adriatic continental shelf under the influence of a strong DSW cascading event. Slow near-bottom currents, never exceeding 40 cm s − 1 , were recorded between March 2009 and February 2012. Water temperatures depicted minor negative shifts. Total mass fluxes (TMFs) were low (annual avg., 1.7–2.8 g m − 2 d − 1 and 0.3–0.6 g m − 2 d − 1 in the canyon and in the sediment wave field, respectively; and peak values ≤ 6.8 g m − 2 d − 1 ), but showed significant seasonal and interannual variability. Fluxes in the canyon were higher than those measured in the sediment wave field at deeper water depth. Mass flux peaks during the 2112-DSW cascading were up to 5 times higher than the peaks of previous years (up to 18.70 g m − 2 d − 1 ), with a spatial variability mainly driven by the localized pathways of DSW cascading. In the canyon, near-bottom currents exceeded 70 cm s − 1 and temperature dropped to 12.2 °C while current speeds were high also at 1200 m depth (~ 60 cm s − 1 ) in the moat surrounding the Dauno seamount. Surprisingly, mass flux peaks occurred from the 16th February to the 1st of March, 3–4 weeks ahead of the usual DSW occurrence, suggesting an early arrival of the DSW. The deep DSW cascading was the main process driving the particle transfer across the southern Adriatic margin during late winter–spring 2012. Mooring data showed a NW–SE gradient of temperature and kinetic energy from upslope to basin floor, indicating slope transverse flow modulated by local obstruction caused by the rugged seafloor topography. Bari canyon is one of the sites of DSW flow and in this area we have the possibility to extend observations back in time using continuous mooring data since 2009 and previous published materials; this approach allowed evaluation of additional mechanisms of particle transport (e.g., open-ocean convection, storm-driven downward transport, shallow dense water cascading) that are particularly relevant in years when the DSW formation is less vigorous and cascading processes are sluggish. The small amplitude of total mass flux peaks, the weak currents and the relatively high and constant temperatures recorded during 2009, 2010 and 2011 springs are consistent with an enhanced vertical particle rain from a mid-water nepheloid layer, triggered in turn by a shallow cascading of not-particularly dense shelf water detaching from the seafloor when reaches its neutral buoyancy. Thus, the intensity of DSW cascading (shallow vs. deep) plays a first order control on the particulate fluxes through the western margin of the Southern Adriatic, while storm-induced sediment transport can occasionally be relevant too. [ABSTRACT FROM AUTHOR]

Antarctic fjords and coastal bays are excellent traps for sediment and represent key areas for high-resolution investigation of past environmental conditions. Robertson Bay is an understudied coastal area located at the confluence of the Ross Sea and the Southern Ocean. Recently obtained seafloor morphology data indicate the presence of a cross-shelf elongated valley, composed of three minor basins separated by sills and seabed ridges with an arcuate shape. Several cores were collected within the basins, and investigated using a multiproxy approach including sedimentological, chemical, geochemical, and micropaleontological characterization to reconstruct the paleoenvironmental evolution from the last glacial period to present. The ages of two of these cores are constrained using ramped pyrolysis oxidation radiocarbon dating. Four sedimentary facies were recognised from which we developed a sedimentary model covering the last 21,000 years (21 ka BP). Our record provide evidence for a covering ice shelf cover from 21 to 16.5 ka BP, which gradually receded between 16,5 and 11 ka BP due to the progressive intrusion of modified Circumpolar Deep Water, thereby promoting the formation of Ice Shelf Water and High Salinity Shelf Water. From 11 to 5,8 ka BP, the ice shelf continued shrinking and nutrient-rich of modified Circumpolar Deep Water penetration onto the continental shelf progressively favoured diatom blooms and a general increase in primary productivity until 5.8 ka BP. The Late Holocene is characterised by an alternation of prolonged sea ice cover with stratified water column and strong bottom current with prolonged sea-ice free season with the intrusion of modified Circumpolar Deep Water and very slow energy bottom current. • First paleoenvironmental study from the LGM to the present in Robertson Bay. • Strong impact of regional ice sheet recession on environmental conditions and productivity. • Multiproxy approach constrained by Ramped Pyrolysis based age model. • The coastal bay area was studied by sediment cores and geophysical data. [ABSTRACT FROM AUTHOR]

In February 2012, a severe cold spell in the European region triggered a massive production of very dense water on the northern Mediterranean Sea shelves. The spreading phase of the newly formed dense water was extensively studied in the Adriatic Sea by means of 2 ship surveys and 5 moorings fully equipped to monitor the flow of the bottom layer. For the Adriatic Sea, opposite to the Gulf of Lions, the area of cascading is far from the source area and this implies substantial modifications, adjustments and dilution of the source water mass along its path, with a spreading phase lasting several months. Indeed all the moorings detected events, although weaker than in the preceding months, until June 2012. The surveys detected 2 branches of NAdDW on the shelf, the first branch not denser than 29.7 kg/m 3 and the second branch not denser than 29.5 kg/m 3 . Despite the extremely dense water generated in the Northern Adriatic, during events of dense-water flow, moorings recorded temperatures generally between 12.5 and 13 °C, seldom less. Temperatures along the shelf break also did not fall below 13 °C at depths greater than 400 m. Turbulent mixing, therefore, heavily modified the cascading plumes, which left the shelf with thicknesses between 10 and 30 m. Mooring data in the lowermost 100 mab suggest that the thickness of the cascading layer increased by several tens of meters downslope, as a consequence of entrainment. Detraining frictional layers as well as locations of active cascading were identified mostly by isolated casts, highlighting the submesoscale domain of the downsloping plumes. The use of LADCP data allowed identification of very energetic bottom flow (40–50 cm/s in many locations), with otherwise little signature in tracers, not previously observed. The Bari Canyon System (BCS) was so far recognized as a hot spot for cascading in the Southern Adriatic. However, during the 2012 event, this is not the only preferred site for cascading. Significant dense flow was detected in other locations. The northernmost mooring site, closer to the inception of the cascading process, in particular showed active cascading and several dynamical differences from the BCS: denser water with thinner boundary layer, events organized in multiple pulses with sub-inertial periodicity and with very short duration (12 h to 1 day) that is generally not seen in other locations. [ABSTRACT FROM AUTHOR]

Abstract: Using the results of a numerical model for the description of bottom-arrested currents and statistical analyses, we elucidate different characteristics of the dynamics of a southward propagating vein of North Adriatic Dense Water (NAdDW) observed to evolve within a complex canyon system of the southern Adriatic basin. The vein, monitored from March 2004 to March 2005 by three distinct mooring lines, exhibits a complex, highly time-dependent dynamics characterized by large velocity and density fluctuations. In particular, lag correlation analyses performed on the observed velocity and temperature data show that a temporal lag ranging between 7 and 10h governs the NAdDW signal propagation along the different canyons, its magnitude inversely depending on vein downslope velocities and density anomalies. The performed model simulations reveal that, weakly depending on its initial layer thickness, exact position, and density contrast with the upper ocean, a coherent flow of dense water located upstream of the canyon system on the Italian shelf will always bifurcate at the entrance of that system; while its shallower part will disintegrate into several branches, its deeper part will continue to flow more coherently, injecting part of the bottom water downward. Regions dominated by supercritical flow regimes are simulated, which contributes to explain part of the observed flow variability. Simulated lag times between signals propagating in the canyons are consistent with observations. They are found to depend crucially on initial, upstream vein location, layer thickness, and density contrast with the upper ocean. We finally use this information, retrieved by our numerical simulations on the basis of the available observations, to infer, in a kind of inverse problem solving, possible shape, location, and density contrast possessed by the observed vein of NAdDW on the Italian continental shelf, prior to its sinking toward the Bari canyon system. [Copyright &y& Elsevier]

Abstract: To investigate the role of coastal canyons in the transfer of organic matter from the shelf to the slope and basin, we deployed sediment trap/current meter pairs at the head of five canyons in the Gulf of Lions (GoL) between November 2003 and May 2004. Analysis of organic carbon, biogenic silica, Corg isotopic composition, Corg/total nitrogen, chloropigments, and amino acids clearly shows the seasonal influence and effect of extreme meteorological events on the composition of collected particles. The sampling period was divided into three “scenarios”. The first corresponded to a large easterly storm and flood of the Rhone river during stratified water column conditions; the composition of material collected during this event was influenced by increased transfer of riverine and coastal particulate matter, with a lower Corg content. During the second “fall-winter” scenario, northern and northwestern winds blowing over the shelf caused cooling and homogenization of the shelf water column; particles collected at this time reflected the homogeneous source of particulate matter transported through canyons; particles sitting in the vicinity of canyon heads are most likely swept downslope by the general south-westward circulation. Organic tracers indicate a degraded origin for organic matter transported during this period. A third “spring” scenario corresponded to northern winds alternating with eastward windstorms that triggered and/or enhanced the cascading of dense waters accumulated on the bottom of the shelf due to previous cooling. These conditions occurred in conjunction with increased phytoplankton productivity in shelf surface waters. Organic matter advected mainly by dense shelf water cascading was fresher due to the transport of newly produced particles and a variable terrestrial fraction; this fraction depended on the proportion of resuspended material accumulated during previous high discharge periods that was involved in each transport pulse. The tight link shown between meteorological conditions and organic matter transport is important for continental margin geochemical studies as future changes in climatic conditions may lead to dramatic changes in carbon sequestration capability and in the ecosystems of deep margin environments. [Copyright &y& Elsevier]

Abstract: With the aim of improving the knowledge of the open ocean carbon cycle, we present a budget of particulate organic carbon (POC) fluxes carried out in the deep central part of the Algero-Balearic Basin (ABB) at 2850m water depth based on a single mooring equipped with five automated sediment traps deployed from April 2001 to May 2002 at depths of 250, 845, 1440, 2145 and 2820m. Suspended particulate matter (SPM) and superficial sediments were also used as indicators of hydrodynamics and carbon burial, respectively. The data reveal that the fraction of primary production buried in the sediment, which finally leads to the sequestration of carbon dioxide from the atmosphere, is 0.16%, lower than the values found in the nearby continental margin regions such as the Alboran Sea (0.48–0.89%) but of the same order as recorded at other Mediterranean sites at similar depths, such as the Ionian Sea (0.11%). As they sink through the water column, the particles exhibit decreases in flux that are similar to those observed elsewhere, but also show variations that appear to correlate with hydrological features of the water masses present in the basin, as revealed by SPM concentrations and compositions. The input of the tyrrhenian deep water (TDW) into the ABB at 800–1500m of water depth exhibits low suspended POC concentrations and low sinking POC fluxes were also observed in this depth range. Gulf of Lions water mass formation appears to also contribute to elevated suspended POC concentrations and perhaps POC accumulation in the traps and sediments by spreading of dense cold water along the whole ABB that supplied POC at depths higher than 2000m. [Copyright &y& Elsevier]

The sources and depositional history of polycyclic aromatic hydrocarbons (PAHs) and organochlorine compounds (OCs) over the last century were investigated in sediment cores from the North Adriatic Sea (Po River prodelta) and the South-Western Adriatic Margin (SWAM). Contaminant concentrations were higher in the Po River prodelta. ∑ 16 PAHs ranged from 193 to 533 ng g−1, ∑ 5 PCBs ranged from 0.9 to 5.2 ng g−1 and ∑DDTs (p,p′- DDD + p,p′- DDE) ranged from 0.1 to 2.5 ng g−1. In the SWAM, ∑PAHs ranged from 11 to 74 ng g−1 while ∑PCB and ∑DDT concentrations were close to the MQL. Accordingly, contaminant fluxes were much higher in the northern (mean values of 152 ± 31 ng cm2 y−1 and 0.70 ± 0.35 ng cm2 y−1 for PAHs and OCs, respectively) than in the southern Adriatic (2.62 ± 0.9 ng cm2 y−1 and 0.03 ± 0.02 ng cm2 y−1 for PAHs and OCs, respectively). The historical deposition of PAHs seemed to be influenced by the historical socioeconomic development and by changes in the composition of fossil fuel consumption (from petroleum derivatives to natural gas) in Italy from the end of the 19th century to the present. Similarly, vertical variations in DDT concentrations matched its historical use and consumption in Italy, which started around in the mid-late 1940s to fight typhus during the II World War. Contaminant concentrations detected in sediments does not seem to pose ecotoxicological risk for marine organisms in the Adriatic Sea. • Unprecedented data of historical deposition of contaminants in the SWAM were assessed. • The first use of DDT in Italy followed the typhus epidemics during the II World War. • Concentrations of PCB and DDT decreased after 1980 due to international restrictions. • Historical variation of PAHs seem to follow shifts in energy production in Italy. • The deep Adriatic basin represents as an important repository for contaminants. [ABSTRACT FROM AUTHOR]