Western Adriatic Sea Research Articles

Polychlorinated biphenyls (PCBs) in sediments from the western Adriatic Sea: Sources, historical trends and inventories

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 9.0ngg−1 in the sediment cores and between 0.1 and 2.2ngg−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 (256ngcm−2) in comparison to the middle and southern Adriatic, respectively, and about 100 times higher than the in the deep Adriatic Sea.

Permanent trawl fishery closures in the Mediterranean Sea: An effective management strategy?

Since June 2010 the Italian government prohibited the trawling activity within three nautical miles from the coast or within the 50m isobath. This decision was expected to have a great impact on trawl fishing activities, but at the moment no real assessment of the effects on catches and possible ecological implications has been undertaken. In order to fill this gap, an assessment on the North Western Adriatic Sea coast has been performed. Landings per Unit of Effort (kilograms per boat per day) for each trawling fleet segment have been analysed, by comparing on a monthly basis the before (2007–2009) and after ban (2011–2013) period. The comparison was carried out considering total landings and the six main species targeted inside the three miles area (sand smelt, cuttlefish, red mullet, sole, turbot, and mantis shrimp). Within a general reduction of total landings, a differential effect based on the analysed métiers was detected, with small trawlers being more negatively affected than the large and rapido ones, which showed, for some species, positive impacts. From an ecological point of view, though, no positive overall effects were detected, probably due to the fact that the adopted measure is not sufficient to reduce the overexploitation. In any case, all this is affecting the structure of the small-scale fishery in the area, since small trawlers are changing métier, moving towards the artisanal fishery, with deep impacts on the very coastal area that the trawling ban was designated to protect, compromising all possible benefits.

Sedimentological, biogeochemical and mineralogical facies of Northern and Central Western Adriatic Sea

The aim of this work was to identify sedimentary facies, i.e. facies having similar biogeochemical, mineralogical and sedimentological properties, in present and recent fine sediments of the Northern and Central Adriatic Sea with their spatial and temporal variations. Further aims were to identify the transportation, dispersion and sedimentation processes and provenance areas of sediments belonging to the facies. A Q-mode factor analysis of mineralogical, granulometric, geochemical (major and trace elements) and biochemical (organic carbon and total nitrogen) properties of surficial and sub-surficial sediments sampled in the PRISMA 1 Project has been used to identify the sedimentary facies. On the whole, four facies were identified: 1) Padanic Facies, made up of fine siliciclastic sediments which reach the Adriatic Sea mainly from the Po River and are distributed by the Adriatic hydrodynamic in a parallel belt off the Italian coast. Southward, this facies gradually mixes with sediments from the Apennine rivers and with biogenic autochthonous particulate; 2) Dolomitic Facies, made up of dolomitic sediments coming from the eastern Alps. This facies is predominant north of the Po River outfalls and it mixes with Padanic Facies sediments in front of the Po River delta; 3) Mn-carbonate Facies, made up of very fine sediments, rich in coccolithophores and secondary Mn-oxy-hydroxides resulting from the reworking of surficial fine sediments in shallow areas and subsequent deposition in deeper areas; 4) Residual Facies, made up of coarse siliciclastic sediments and heavy minerals resulting from the action of waves and coastal currents; this facies is present mainly in inshore areas.The zoning of the facies, resulting from this study, will make possible the identification, through further investigation, on a greater scale, of more accurate facies borders and the recognition of sub-facies, resulting from secondary or weaker biogeochemical processes.

Patterns of colonization and succession of benthic assemblages in two artificial substrates

Benthic communities colonizing two different typologies of artificial structures, Tecnoreef® pyramids (PY), and plinth modules (PL), differing for material and shape, were investigated for three years after their deployment on a soft bottom offshore Pedaso (Western Adriatic Sea). The aims were to describe the colonization patterns of benthic assemblages on the two artificial modules, to highlight possible differences between them and to detect the effectiveness of the artificial reef on the ecosystem functioning.The composition of the benthic communities settled on the two types of artificial substrates was different especially just after the reef deployment. Abundance and species richness were higher on PL in the first two years, while an explosion of individuals characterized PY in the third year. This suggested a delay of about one year in the colonization processes on PY likely due to the material and shape. The community settled of the artificial structures was dominated by hard-substrate species which are commonly absent in the natural environment. The occurrence of these organisms enriched the local soft-bottom communities and contributed to habitat diversification. This, together with the importance of these species in the diet of a few reef-dwelling fish, confirms the trophic role and the ecological importance of artificial reefs in areas characterized by soft seabed.

Source, diagenesis, and fluxes of particulate organic carbon along the western Adriatic Sea (Mediterranean Sea)

article i nfo In this study, we investigated the modern organic carbon (OC) cycling along the clinoform-shaped deposit that developed after the attainment of the modern sea-level in the Adriatic Sea (~5.5 kyr cal BP). Newly acquired data were combined with published results to characterize the (i) origin, (ii) diagenesis, and (iii) fluxes of OC along the Adriatic clinoform. δ 13 C, Δ 14 C, and lignin phenols were used to constrain the composition of OC accumulating in surface sediments. Sediment cores collected at different water depths were used to describe the early diagenesis during burial in different regions. In addition, on the basis of an extensive number of accumulation rates and OC data, we assessed the flux of OC to the seabed and its burial. Our results showed that terrigenous OC is the dominant OC source in the Po prodelta mainly in the form of pre-aged soil-derived OC and vascular plant fragments. Along the clinoform, both Δ14C and the concentration of lignin-derived phenols decreased with increasing distance from the Po prodelta indicating the influence of an additional pool of aged OC that gradually becomes more important because of its selective preservation during the sediment transport. As a result, degradation rates (k) decreased along the clinoform as a function of the sediment oxidative history. The calculated half-life of reactive OC (t1/2) was ~14.6 yrs in the Po prodelta whereas topset/forest deposits south of this region exhibited higher values, ~100 yrs, indicating the presence of refractory material. In the distal bottomset region, the t1/2 was particularly high ranging from ~255 to ~912 yrs. Because of the significant southward component of the sediment transport, the OC deposition in the southern surface sediments exceeded the local OC input via rivers (ratio deposition/input 1.2). Conversely, the northern Adriatic was characterized by a marked imbalance (ratio deposition/input 0.3-0.5). According to our calculations, the OC flux to the seabed along the clinoform was ~309 Gg of C per year whereas the OC burial was ~180 Gg of C per year, corresponding to an overall burial efficiency of ~59%.

Physical, Biochemical and Biological Characterization of Two Opposite Areas in the Southern Adriatic Sea (Mediterranean Sea)

The Drini and ManfredoniaGulfswere investigated in May 2008 and April 2009, respectively. The gulfs are located in the South Eastern (GulfofDrini) and South Western (GulfofManfredonia)Adriatic Sea. The areas are partially influenced by two main Adriatic surface currents: the Eastern Adriatic Current-EAC that flows north-westward along the eastern side, and the Western Adriatic Current—WAC that flows south-eastward along the western side of the basin. The spatial variations of temperature, salinity, fluorescence, dissolved oxygen concentration, Coloured Dissolved Organic Matter—CDOM, nutrients, chlorophyll a and phytoplankton composition parameters in the two areas were observed and compared. CDOM regulates the penetration of UV light into the sea and plays an important role in many hydrological and biogeochemical processes on the sea surface layer including primary productivity. The phytoplankton specific diversity of the Gulf of Manfredonia showed a spring community with dinoflagellates (21 taxa) as the main important fraction, coccolithophorales (6 taxa) and diatoms with 10 identified taxa. The phytoplankton distribution along the eastern coast showed a different biodiversity: a prevalence of dinoflagellates (58 taxa) included harmful microalgae such as Alexandrium, Dinophysis and Lingulodinium genus. Diatoms were less abundant, among them Pseudo-nitzschia was also reported which could include some potentially toxic species. Nanoplankton are ever abundant in offshore waters and an exceptional bloom of cyanobacteria was registered in Buna-Boyana estuary due to strong industrial impact. The gulfs showed similar physical and biochemical characteristics despite the WAC carried out along the westernAdriatic Seathe water rich in nutrients from the major northern Italian rivers. No correlations were found between CDOM and chlorophyll a in the two areas and this implied that, probably, the primary source of CDOM might come from terrestrial input rather than the biological production from phytoplankton. The Gulf of Drini is impacted by the runoff of the Buna-Bojana River that makes this gulf an eutrophic area despite the mostly eastern side of the Adriatic being an oligotrophic basin.

A multidisciplinary approach to evaluate the environmental impact of offshore gas platforms in the western Adriatic Sea

Detecting the anthropogenic impacts of offshore gas platforms requires reliable tools, because the traditional evaluation based only on chemical analyses is neither appropriate nor sufficiently sensitive. Thus, a 3-year monitoring project was carried out to evaluate the impact of a platform based on a chemical–biological approach. Benthic communities are investigated as they are widely used to monitor the effects of marine impacts because the organisms are mostly sessile and integrate the effects of pollutants over time. Changes in benthic infauna, sediments and water quality, as well as biota bioaccumulation, caused by drilling and platform operations were evaluated experimentally. Furthermore, mussels (Mytilus galloprovincialis) were collected seasonally from the platform legs, both close to and far from the sacrificial anodes and at a control site. Responses of biomarkers of exposure and effect were related to the average levels of polycyclic and aliphatic hydrocarbons, organic matter content and heavy metals in bivalve tissues. Our data suggested that a slight perturbation can be detected only by integrating the results of chemical analyses on water and sediments and those obtained from benthic biological surveys.

Impact of an open-sea suspended mussel culture on macrobenthic community (Western Adriatic Sea)

The potential impact of a suspended mussel farm on the coastal macrobenthic communities of the Western Adriatic Sea was seasonally evaluated through a multi-control sampling strategy over 1 year. Both univariate biological indices and multivariate analysis indicated that the variations of benthic macrofauna were mainly due to seasonality rather than location of the sampling sites in respect to the farm, and that the main species contributors were common to most sites and seasons. Most of these species are known as indicators of organic enrichment and/or pioneer species in recolonization of defaunated bottoms and commonly occur in the macrobenthic populations inhabiting the seabed of the North-Central Adriatic Sea between 12 and 15 m depth. Only the different abundances of filter- and deposit-feeders gave some evidence of a limited, spatial influence on the culture in the surroundings. The external sites showed a significant difference compared to the reference sites (ANOSIM: R = 0.395, P = 0.5). The overall results suggest that open-sea mussel culture has minimal detrimental effects on the zoobenthic communities of the Western Adriatic Sea that are usually in an immature stage due to subsequent environmental and anthropogenic disturbances. Although one-year study might not be sufficient to evaluate the effects of mussel culture, the results of this work represent a useful tool for the monitoring of the potential environmental impact of mussel farms to ensure the sustainable development of shellfish culture in the Italian shallow coastal waters.

Organic matter origin and distribution in suspended particulate materials and surficial sediments from the western Adriatic Sea (Italy)

In this study, organic carbon (OC), total nitrogen (TN), stable carbon isotopic ( δ 13C OC) and CuO reaction product compositions were used to identify the sources of organic matter (OM) and to quantify the relative importance of allochthonous and autochthonous contributions to the western Adriatic Sea, Italy. Suspended particulate material (195 samples) and surficial sediments (0–1 cm, 70 samples) from shallow cross-shelf transects were collected in February and May 2003, respectively. Vertical water column profiles were acquired along the same transects. Data include depth, potential temperature, salinity, density and chlorophyll fluorimetry. Along the western Adriatic shelf in the near-shore region, the phytoplankton growth was influenced by dynamics of the buoyant plumes from the Po and Appennine rivers. A small amount of very fine terrigenous material remained suspended within the coastal current and was exported southward along the shelf to the slope. High variability in the bulk composition was detected in the Po prodelta surficial sediments, whereas the western Adriatic shelf, although a larger area, exhibited a narrower range of values. A significant decoupling was observed between suspended particles in the water column and surficial deposits. The organic material collected in the water column was compositionally heterogeneous, with contributions from marine phytoplankton, riverine–estuarine phytoplankton and soil-derived OM. Frequent physical reworking of surficial sediments likely leads to the efficient oxidation of marine OC, resulting in the observed accumulation and preservation of refractory soil-derived OC delivered by the Po and Appennine rivers.

The impact of floods and storms on the acoustic reflectivity of the inner continental shelf: A modeling assessment

Flood deposition and storm reworking of sediments on the inner shelf can change the mixture of grain sizes on the seabed and thus its porosity, bulk density, bulk compressional velocity and reflectivity. Whether these changes are significant enough to be detectable by repeat sub-bottom sonar surveys, however, is uncertain. Here the question is addressed through numerical modeling. Episodic flooding of a large versus small river over the course of a century are modeled with HYDROTREND using the drainage basin characteristics of the Po and Pescara Rivers (respectively). A similarly long stochastic record of storms offshore of both rivers is simulated from the statistics of a long-term mooring recording of waves in the western Adriatic Sea. These time series are then input to the stratigraphic model SEDFLUX2D, which simulates flood deposition and storm reworking on the inner shelf beyond the river mouths. Finally, annual changes in seabed reflectivity across these shelf regions are computed from bulk densities output by SEDFLUX2D and compressional sound speeds computed from mean seafloor grain size using the analytical model of Buckingham [1997. Theory of acoustic attenuation, dispersion, and pulse propagation in unconsolidated granular materials including marine sediments. Journal of the Acoustical Society of America 102, 2579–2596; 1998. Theory of compressional and shear waves in fluidlike marine sediments. Journal of the Acoustical Society of America 103, 288–299; 2000. Wave propagation, stress relaxation, and grain-tograin shearing in saturated, unconsolidated marine sediments. Journal of the Acoustical Society of America 108, 2796–2815]. The modeling predicts reflectivities that change from <12 dB for sands on the innermost shelf to >9 dB for muds farther offshore, values that agree with reflectivity measurements for these sediment types. On local scales of ∼100 m, however, maximum changes in reflectivity are <0.5 dB. So are most annual changes in reflectivity over all water depths modeled (i.e., 0–35 m). Given that signal differences need to be ⩾2–3 dB to be resolved, the results suggest that grain-size induced changes in reflectivity caused by floods and storms will rarely be detectable by most current sub-bottom sonars.

What controls the distribution of shallow gas in the Western Adriatic Sea?

In this paper, we discuss what controls the occurrences of shallow gas off the Western Adriatic coast. This region of the Western Adriatic, including the Po delta and the late-Holocene mud wedge, was sampled with the R/V Seward Johnson II within the framework of the EuroSTRATAFORM project. As a part of the program, we were evaluating the causes of anomalous sub-surface and seafloor features, and specifically, quantifying shallow gas and identifying its impact on geophysical properties. The highest gas concentration off the Po delta region yielded 4.1×10 4 ppm, where as offshore Tronto River, the highest methane value was 7.9×10 4 ppm. Headspace gas analyses match well with acoustic anomalies along the Western Adriatic coast. Shallow biogenic gas off the Po delta (NW Adriatic) is spatially correlated with organic matter deposition driven by rapid and thick flood deposition. In contrast to the Po Delta, where sub-surface gas is associated with the flood deposition of organic matter, shallow gas along the Central Adriatic occurs deeper in cores, and appears to be related to methanogenesis of organic matter present in deeper deposits.

Seabed properties and sediment erodibility along the western Adriatic margin, Italy

During February and June of 2003, selected physical and biological sediment properties were measured at nine mud-bottom sites (11–22 m) along the western margin of the Adriatic Sea. Seabed properties were compared with shipboard measurements of sediment erodibility made at the same sites to gain insight into the physical and biological controls on sediment erodibility operating in the western Adriatic. In addition, spatial patterns of erodibility were compared with long-term records of sediment accumulation in the region to determine if patterns of erodibility were responsible for the discrepancy between sediment sources and sinks on the shelf. Results indicate that sediment erodibility along the western Adriatic Sea varied both in time and space. In the wintertime, sediment in the vicinity of the Po delta (in the northern region) was less easily eroded than to the south. In the summertime, the pattern reversed. The physical characteristics of the seabed including porosity and grain-size were important factors controlling erodibility during the winter, although in a manner opposite to expectations (i.e., higher porosity sediment was less erodible). No relationship between the physical characteristics of the seabed and erodibility was observed in the summer, when it was likely that erodibility was influenced by benthic organisms, especially microphytobenthos. Results of this study suggest long-term sediment accumulation patterns along the western Adriatic Sea are unlikely to be controlled by patterns of erodibility. However, due to several complicating factors, especially along-margin variability in wave energy, the impact of sediment erodibility on long-term patterns of accumulation remains unclear. Further studies that resolve both finer and larger-scale spatial and temporal variability in sediment erodibility and that incorporate year-to-year forcing of the coastal ocean are needed to more accurately resolve the relationship between erodibility and sediment accumulation in the western Adriatic, as well as other coastal environments.

Hydraulic dredge discards of the clam ( Chamelea gallina) fishery in the western Adriatic Sea, Italy

This study provides a qualitative and quantitative assessment of the discards produced by the commercial hydraulic dredging fleet targeting the clam, Chamelea gallina, in two Maritime Districts of the Adriatic Sea (Italy). Overall discards comprised just under 50% of total catch in both Maritime Districts, approximately 30% of which were undersized target species (<25 mm) and 20% other benthic invertebrates, whilst fish were poorly represented. Significant differences in the proportions of the different catch components were found between the two Maritime Districts considered. Similarly, the size-frequencies of landed catch were significantly different between Districts. Great variability in overall catch composition from one Zone to another within one District was detected, emphasising the importance of a Zone-based management, rather than a District-based management. Analysis of the invertebrate component of discards revealed a clear segregation of the benthic community according to depth. Future management plans should thus incorporate a bathymetric component and future research should focus on identifying species particularly sensitive to this kind of disturbance.

Pyrolysis–GC–MS to trace terrigenous organic matter in marine sediments: a comparison between pyrolytic and lipid markers in the Adriatic Sea

The effectiveness of semiquantitative pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) as a rapid analytical technique for sourcing continental organic matter (OM) in marine sediments was examined by comparison with classical GC–MS analyses of solvent extractable lipid markers. Py–GC–MS was directly applied to HCl/HF de-ashed surface sediment samples collected in five stations located in north western Adriatic Sea. The resulting pyrolysates were characterised by compounds indicative of different biological precursors (e.g. proteins, carbohydrates, chlorophylls), including lignin methoxyphenols diagnostic for continental inputs. The relative abundance of pyrolytic markers was compared to the distribution of n-alkanes, n-alkanols and sterols extracted from the same sediments and determined by GC–MS analyses. For each class of molecular indicators, the terrigenous to aquatic ratio (TAR) was determined as follows: relative abundance of methoxyphenol/protein markers (TAR PY), concentration ratios of (C27 + C29 + C31)/(C15 + C17 + C19) n-alkanes (TAR HC), (C26 + C28+ C30)/(C14 + C16) n-alkanols (TAR AL) and sitosterol/cholesterol (TAR ST). A positive correlation was found between TAR PY and both TAR HC and TAR AL indicating a decreasing contribution of land-plant-derived materials seaward in two investigated transects. TAR ST values displayed a different trend suggesting a mixed origin for sitosterol. The distribution of TAR PY values was also in good agreement with that of atomic C/N ratios. Considering the complexity of environmental systems (diagenetic alteration, different fractions of OM analysed) the obtained results indicate that the pyrolytic marker approach by Py–GC–MS is valuable for sourcing marine OM on a semiquantitative base, providing data consistent with GC–MS determinations of lipid markers and elemental bulk analyses.

A biogeographical analysis of the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chlorophyta) in the western Mediterranean Sea and Adriatic Sea

We carried out a biogeographical analysis of the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chlorophyta), as well as the species in the three genera pooled together, in the western Mediterranean Sea and Adriatic Sea. For this purpose, the continental shelves close to 13 hydrographical watersheds were used as operational geographical units. The analysis was performed in accordance with a hypothetical–deductive approach. Four weak boundaries and five biotic regions were obtained for Audouinella; one strong and two weak boundaries, separating four biotic regions, were found for Cystoseira; two weak boundaries delimiting three biotic regions were obtained for Cladophora. The species of the three genera pooled together allowed us to separate three biotic regions delimited by two weak boundaries. The environmental factors that can explain the presence of the boundaries between biotic regions were run-off, distance of a given region from the Strait of Gibraltar following the course of the main current of the Mediterranean Sea, current flow, and salinity. The characterization of each biotic region and the relationships with the environmental factors that could explain the biotic boundaries are discussed.

Complex yessotoxins profile in Protoceratium reticulatum from north-western Adriatic sea revealed by LC–MS analysis

While the occurrence of yessotoxin (YTX) has been reported worldwide from Protoceratium reticulatum, the biogenetic origin of some YTX analogues is still unknown, thus raising an issue whether they are metabolites of YTX formed in mussels or true products of different dinoflagellate species. Findings reported herein suggest that P. reticulatum from the north–western Adriatic sea is responsible for production, together with YTX ( 1), of homoYTX ( 2), 45-OHYTX ( 3), carboxyYTX ( 5), and noroxoYTX ( 7). YTX and its analogues have been determined by high performance liquid chromatography coupled with electrospray ion trap mass spectrometry (HPLC–MS and HPLC–MS n experiments). The result is the first to confirm production of these YTX analogues from this species and indicate it as a producing organism of homoYTX, 45-OHYTX, carboxyYTX, and noroxoYTX found in shellfish.

Nutrient balance in the ecosystem of the North Western Adriatic Sea

The effects of biological processes on dissolved inorganic nutrients, dissolved organic nitrogen (DON) and phosphorus (DOP) are considered in the north western Adriatic Sea. The budgets of these nutrients, which represent the sum of production and consumption processes in comparison to advection, are discussed with regard to dissolved inorganic nitrogen ( 15 N labelled) uptake, which basically indicates the biological demand of this fraction of nitrogen by phytoplankton community. The presented data show that, although important, the continental input of dissolved inorganic nitrogen (DIN), mainly nitrate, is utilised and recycled within the coastal marine environment (budget of m 15 r µmol-N·dm m 3 ). In fact, during four cruises (June, 1996; February, 1997; June, 1997; February, 1998), phytoplankton production was mainly driven by regenerated nutrients ( f h 0.4). Regarding dissolved inorganic phosphorus (DIP), the negative budgets observed in most cases (down to m 0.4 r µmol-P·dm m 3 ) confirm, above all, its scarce availability in this basin. Recycling processes rather than continental inputs regulate the availability of this nutrient. In addition, the comparison between DIN and DIP budgets indicates that, in this ecosystem, dissolved inorganic phosphorus is recycled faster than nitrogen through the living particulate and dissolved organic pools. As a consequence of biological activities, a strong production of dissolved organic nitrogen (DON) can occur in summer (up to +22 r µmol-N·dm m 3 ) while DOP shows a more independent behaviour both with respect to its accumulation in the environment and to the observed nitrogen variations.