Organotins (TBT and DBT) in water, sediments, and gastropods of the southern Venice lagoon (Italy)

The release of tributyltin (TBT) from maritime traffic represents one of the main problems of direct, diffuse, and continued contamination of the marine environment. In the present survey, the concentrations of TBT and dibultytin (DBT) in brackish waters, sediments, and the gastropods Nassarius nitidus were evaluated in order to estimate the contamination of the southern part of the Venice lagoon. TBT and DBT were determined by GC-MS/MS. Recent contamination of TBT was found in brackish waters near marinas, whereas the highest concentrations of TBT and DBT were observed in surface sediments at dockyards and harbours. High content of organotin in the gastropods sampled near the dockyards, harbours, and marinas showed a mobilisation from the sediments through the food web. The present study allowed assessment of whether, despite the ban on the use of TBT paints, waters, sediments, and biota were still being contaminated by organotin compounds in the southern Venice lagoon.     

The erosion rates of cohesive sediments in Venice lagoon,Italy

The stability of cohesive sediments from Venice lagoon has been measured in situ using the benthic flume Sea Carousel. Twenty four stations were occupied during summertime, and a sub-set of 13 stations was re-occupied during the following winter. Erosion thresholds and first-order erosion rates were estimated and showed a distinct difference between inter-tidal and sub-tidal stations. The higher values for inter-tidal stations are the result of exposure that influences consolidation, density, and organic adhesion. The thresholds for each state of sediment motion are well established. However, the rate of erosion once the erosion threshold has been exceeded has been poorly treated. This is because normally a time-series of sediment concentration (C) and bed shear stress (τ₀(t)) is used to define threshold stress or cohesion (τ_crit,z) and erosion rate (E). Whilst solution of the onset of erosion, τ_crit,0, is often reported, the evaluation of the erosion threshold variation through the process of erosion (eroded depth) is usually omitted or not estimated. This usually leads to assumptions on the strength profile of the bed which invariably has no credibility within the topmost mm of the bed where most erosion takes place. It is possible to extract this information from a time-series through the addition of a step in data processing. This paper describes how this is done, and the impact of this on the accuracy of estimates of the excess stress (τ₀(t)–τ_crit,z) on E.     

Simulating the mobile barrier (MOSE) operation in the Venice Lagoon, Italy: global sea level rise and its implication for navigation

Three years of mobile barrier operations have been simulated with a hydrodynamic model to check the efficiency of the barriers in defending the city of Venice from flooding. The simulations have been carried out in the actual situation and with a sea-level rise of 30 and 50 cm. Moreover, the interference of the barrier operations with the ship traffic has been studied. It is found that without a security increment for the forecasted water levels, the mobile barriers cannot defend completely Venice from flooding due to the uncertainty in the forecast. With a security increment of 10 cm, the barriers work well in actual conditions but still cannot avoid flooding with a global sea-level rise. The interference with the ship traffic is acceptable under actual conditions but becomes prohibitive with a sea-level rise of 50 cm, when nearly two-thirds of the ship passages are blocked or delayed.     

Sulphate reduction in the sediment of the Venice canals (Italy)

The sulphur cycle in the sediment of the Venice canal network was investigated by considering the sulphate reduction rate (SRR) and the distribution of sulphur compounds, in both pore water and sediment. Sulphate reduction (SR) is the main process in the metabolism of the organic matter supplied to the network by untreated urban effluents. Although it might account for the decomposition of only a limited percentage of the total organic-C inputs, the estimated rates are among the highest observed in coastal sediments. Measured rates range from 0.26 to 0.99 micromolcm(-3)d(-1), while mean annual values, estimated by a diagenetic model, vary from 0.16 to 0.43 micromolcm(-3)d(-1). The speciation of S in the sediment reveals that pyrite-S is the most abundant component of the total reduced S pool, whereas acid volatile sulphides and elemental sulphur together account for less than 45%. A preliminary budget indicates that the rate of burial of solid-phase S is small compared to the S produced by SR (from 10 to 25%). A large amount of reduced S is then lost from the canal deposits to be re-oxidised at the sediment-water interface or in the overlying water column.     

Susceptibility to oxidative stress of mussels (Mytilus galloprovincialis) in the Venice Lagoon (Italy)

The aim of this study was to evaluate the susceptibility to pollutant mediated oxidative stress of the Mediterranean mussel Mytilus galloprovincialis in the Venice lagoon (Italy).

In June 2003, mussels from a farm were transplanted to eight sites in the lagoon for five weeks. Oxidative stress responses were measured by: (i) total oxyradical scavenging capacity (TOSC) assay, for an overall evaluation of the oxidative stress response capability; (ii) catalase (CAT), as a key enzyme involved in the antioxidant defence system; (iii) malondialdehyde (MDA), as an indicator of lipid peroxidation, to evaluate an oxidative damage; (iv) metallothioneins (MTs), as they play a role in the antioxidant defence.

The TOSC analysis revealed a reduced capability to eliminate: (i) peroxyl radical in mussels transplanted at Palude della Rosa, Valle Millecampi and Chioggia; (ii) hydroxyl radical at Campalto and Valle Millecampi; (iii) peroxynitrite at Valle Millecampi.

Inhibition in CAT activity, observed in all the monitored sites, confirms the presence of an oxidative pressure in transplanted mussels.

In addition, Pearson correlation analysis was performed in order to observe possible links between the various parameters. The PCA was a powerful tool to discriminate impacted sites, suggesting that the mussels transplanted throughout the Venice lagoon were subjected to different levels of oxidative pressure. Furthermore, it provided an easy and useful tool to summarize the obtained results.     

A model of sand transport in Treporti channel: northern Venice lagoon

The origin of the sands in the Venice lagoon has been the subject of an extensive field survey in parallel with numerical modelling. Four transects along Treporti and Burano canals were conducted from which 33 bottom sediment samples were collected. These samples were analysed for grain size and sorting to examine any trends in the granulometry of these sediments that might shed light on transport paths. The modelling study consists of three parts: the sediment transport model sedtrans96 was used with a finite-element hydrodynamic model (Shyfem) and an empirical wave model (US Army Corps of Engineering) to simulate sand transport in the Treporti canal. A type of link box model was created where finite elements of the hydrodynamic model have been combined to macro-boxes on which the water and sediment flux over the sections, and a mass balance has been computed. Several grain size classes were simulated; the distributions before and after the simulation were examined. Idealised wind and tidal values were initially used to force 12 h simulations to test the sediment transport sensitivity. Finally, a full-year simulation (1987) has been carried out using measured tidal and wind data. Only a part of Venice lagoon was covered by the simulation: a major channel (Treporti) running from Lido inlet towards the northern lagoon. The total sand transport through all of the sections was computed for 1 year. Sediment mass balance was determined, and the resulting trends of erosion and deposition were computed. There were no trends in the median grain diameter and sorting of bottom samples from the Treporti canal; all sands were fine (120 μm, one outlier of 300 μm was removed). The absence of a trend in grain size suggests that there is no significant import of sand to the lagoon through the Lido inlet. The results from the simulations seem therefore to confirm the hypothesis of reworking of sand within the lagoon. The computed erosion is some centimeters per year diagnostic of channel scouring and enlargement with time. The Treporti canal is subject to strong current velocities of around 1 m/s, which hold fine sand in suspension and thus prevent sedimentation.     

Restoration of the eutrophic Orbetello lagoon (Tyrrhenian Sea, Italy): water quality management

The Orbetello lagoon (Tyrrhenian coast, Italy) receives treated urban and land based fishfarms wastewater. The development of severe eutrophication imposed the three main activity adoption focuses on (1) macroalgae harvesting; (2) pumping of water from the sea; (3) confining wastewater to phytotreatment ponds. The responses to these interventions were rapid and macroalgal reduction growth and seagrass return were recorded. Since 1999, a new macroalgal development was recorded. The aim of this research was to discover whether the recent macroalgal growth can be attributed to the continuing wastewater influx from the remaining persistent anthropic sources (PAS) or from the sediment nutrient release. A monitoring programme was carried out between August 1999 and July 2000 in order to measure dissolved inorganic nitrogen and phosphorus in the wastewaters entering into the lagoon and in central lagoon areas, seaweed and seagrass distribution and lagoon N, P annual budgets. The results showed higher N and P values close to PAS. The distribution of the macroalgal species confirms that the available P comes almost entirely from these remaining PAS. In conclusion, the environmental measures adopted produced a significant reduction in algal biomass development in the lagoon; the macroalgal harvesting activities produced a sediment disturbance with following oxidize conditions, which make P unavailable in the lagoon water, excepting close the PAS.     

Anatomy of the Holocene succession of the southern Venice lagoon revealed by very high-resolution seismic data

The southern portion of the Venice lagoon contains a relatively thick (up to 20 m) Holocene sedimentary body that represents a detailed record of the formation and evolution of the lagoon. New very high-resolution (VHR) seismic profiles provided a detailed investigation on depositional geometries, internal bounding surfaces and stratal relationships. These informations, combined with core analysis, allowed the identification of large- to medium-scale sedimentary structures (e.g. dunes, point bars), the corresponding sedimentary environment, and of retrogradational and progradational trends. In addition, the availability of dense seismic network produced a 3D reconstruction of the southern lagoon and the recognition of the along-strike and dip variability of the stratal architecture.     

Sediment chemical contamination of a shallow water area close to the industrial zone of Porto Marghera (Venice Lagoon, Italy)

The industrial zone of Porto Marghera is one the most important "contaminated sites of national interest" (SIN) in Italy, being identified as an area of high environmental risk. The site includes a wide shallow water area of the Venice Lagoon extending toward the city of Venice, which was investigated in order to acquire information on the pollutant level and distribution. Grain-size, heavy metal, nutrient, and organic micropollutant concentrations were determined in the surface sediment layers (0-5 and 5-10 cm depths) of 51 sites. A generally low contamination was found, except for Hg concentration, which increases the toxicological risk in most of the sites of the area, according to the results of a comparison with Sediment Quality Guidelines. A heavy pollution fingerprint (Cd, Cu, Hg, Pb, and Zn up to 15.2, 257, 11.9, 248, and 3010 mg/kg d.w., respectively) was instead found near the Tresse Island, which is ascribed to the spill of pollutants from the contaminated sediment disposed therein. Grain-size and heavy metal profiles down to a depth of 40 cm in eight selected sites, finally show a probable decrease of the pollution affecting the area in recent years.     

Sediment budget in the Lagoon of Venice,Italy

A comparison of 1927, 1970 and 2002 bathymetric surveys in the Lagoon of Venice was used to reconstruct historical changes in sedimentation. A detailed GIS-based analysis of the charts revealed the timing and pattern of geomorphic changes and allowed calculation of sediment deposition and erosion for the entire lagoon and each of its four sub-basins: Treporti, Lido, Malamocco and Chioggia.     

Benthic foraminifera and trace element distribution: A case-study from the heavily polluted lagoon of Venice (Italy)

Living benthic foraminiferal assemblages were studied in surface samples collected from the lagoon of Venice (Italy) in order to investigate the relationship between these sensitive microorganisms and trace element pollution. Geochemical analysis of sediments shows that the lagoon is affected by trace element pollution (Cd, Cu, Ni, Pb, Zn and Hg) with the highest concentrations in its inner part, which corresponds to the Porto Marghera industrial area. The biocenosis are largely dominated by Ammonia tepida, Haynesina germanica and Cribroelphidium oceanensis and, subordinately, by Aubignyna perlucida, Ammonia parkinsoniana and Bolivina striatula. Biotic and abiotic factors were statistically analyzed with multivariate technique of cluster analysis and principal component analysis. The statistical analysis reveals a strong relationship between trace elements (in particular Mn, Pb and Hg) and the occurrence of abnormalities in foraminiferal tests. Remarkably, greater proportions of abnormal specimens are usually found at stations located close to the heaviest polluted industrial zone of Porto Marghera. This paper shows that benthic foraminifera can be used as useful and relatively speedy and inexpensive bio-indicators in monitoring the health quality of the lagoon of Venice. It also provides a basis for future investigations aimed at unraveling the benthic foraminiferal response to human-induced pollution in marine and transitional marine environments.     

Benthic foraminifera as bio-indicators of trace element pollution in the heavily contaminated Santa Gilla lagoon (Cagliari, Italy)

In order to assess the response of benthic foraminifera to trace element pollution, a study of benthic foraminiferal assemblages was carried out into sediment samples collected from the Santa Gilla lagoon (Sardinia, Italy). The lagoon has been contaminated by industrial waste, mainly trace elements, as well as by agricultural and domestic effluent. The analysis of surficial sediment shows enrichment in trace elements, including Cr, Cu, Hg, Ni, Pb and Zn. Biotic and abiotic data, analyzed with multivariate techniques of statistical analysis, reveal a distinct separation of both the highly polluted and less polluted sampling sites. The innermost part of the lagoon, comprising the industrial complex at Macchiareddu, is exposed to a high load of trace elements which are probably enhanced by their accumulation in the finer sediment fraction. This area reveals lower diversity and higher percentages of abnormalities when compared to the outermost part of the lagoon.     

Bioaccumulation and biomarker responses of trace metals and micro-organic pollutants in mussels and fish from the Lagoon of Venice, Italy

The aims of this study were to evaluate levels and effects of trace metals (Cd, Cr, Cu, Fe, Mn, Pb, Zn), PAHs and PCBs in mussels and fish native to the Lagoon of Venice. To this end, bioaccumulation and various biomarkers of generic stress and exposure (malondialdehyde, MDA and metallothioneins, MT; ethoxyresorufin O-deethylase activity, EROD; fluorescent bile metabolites and somatic indices in fish; lysosomal membrane stability, LMS; lipofuscins, LF; neutral lipids, NL and survival-in-air, SOS in mussels) were measured in organisms seasonally collected from two differently influenced areas. In mussels, metal bioaccumulation levels at the two sites were low and fluctuated similarly, exhibiting decreasing levels in summer, like MDA and MT. Micro-organic pollutants and the probably related biological response of LMS did not show either significant site differences or seasonal trends. LF and NL revealed inconclusive patterns. The results of the survival-in-air test were quite erratic, showing that they were associated with the high variability of both natural and physiological parameters temperature, food, reproduction, and body reserve cycle. In fish, both inorganic and organic micropollutant levels were low, and differences were detected between sites only for PCBs. The pattern exhibited by micro-organic contaminants was clearly related to the reproductive cycle at both sites; a relationship with PCBs, EROD and MDA was established at the site where their levels were generally higher. Bile metabolites (3-OH benzo(a)pyrene, 1-OH pyrene) were associated with PAH contents.     

Determination of polychlorobiphenyl congeners (PCBs) in the surface water of the Venice lagoon

The purpose of this study is to evaluate the degree of PCB contamination of Venice lagoon water. The PCB determination was made on the filtrate ("dissolved PCBs") and on the particulate collected on the filters ("particulate PCBs") by continuous liquid-liquid extraction and sonication, respectively, and by HRGC-LRMS analysis. An estimation of the procedural and "working" blanks was also made. Water samples were collected at six sites, selected to represent all the pollution situations present in the lagoon, and at a site in the Adriatic Sea. The range of the total sum ("dissolved plus particulate") of 49 congener concentrations falls between 355 and 1868 pgl(-1); the "dissolved" fraction concentrations (250-792 pgl(-1)) are greater at six sites than that of the "particulate" fraction (105-1273 pgl(-1)). Chemometric analyses suggest that the PCB congener pattern in the Venice Lagoon is different from that in the Adriatic Sea.     

Total oxyradical scavenging capacity responses in Mytilus galloprovincialis transplanted into the Venice lagoon (Italy) to measure the biological impact of anthropogenic activities

Oxidative stress related investigations to monitor the impact of the pollutant discharges into the Venice lagoon (Italy) originating from anthropogenic activities (raw sewage water, agricultural and industrial effluents, oil tanker traffic), on marine organisms have classically been carried out by analyzing specific, single antioxidants (i.e. catalase, superoxide dismutase). In this paper, two studies are reported where the total oxyradical scavenging capacity assay (TOSC) was selected and measured toward peroxyl, and hydroxyl free radicals, and peroxynitrite in mussels (Mytilus galloprovincialis) transplanted into the Venice city and throughout the lagoon to measure the biological effects of anthropogenic activities. In the first experiment, mussels from a clean site (farm) were transplanted to the urban area of Venice for 0, 1, 2 and 4 weeks; cytosolic TOSC toward peroxyl and hydroxyl free radicals, and peroxynitrite revealed that the transplantation process caused a stress (handling stress, anoxia, oxidative burst) resulting in a reduction of TOSC in both control and urban sites, therefore, preventing clear interpretation of the data after one week. At week 2, a significant TOSC reduction (P < 0.05) toward peroxyl and hydroxyl radicals in the urban site revealed that mussels experienced oxidative pressure exerted by pollutants. Most TOSC values returned to initial levels at week 4; however, TOSC induction was noticed in the control group toward peroxyl and hydroxyl radicals while in the exposed group it was not indicating an inhibition of the oxidative metabolism. In the second experiment, mussels were deployed at seven different sites throughout the lagoon. After five weeks of exposure, significant TOSC reduction was measured (P < 0.05) toward peroxyl for Palude della Rosa, Chioggia and Valle Millecampi, toward hydroxyl radicals for Valle Millecampi and Campalto and toward peroxynitrite for Valle Millecampi. Although these data indicate a depletion of the low molecular weight scavengers, additional biomarkers are needed to draw a conclusion on the health of the mussels. TOSC was proved to be an interesting health index parameter to measure pollution impact in a transplantation study provided that the mussels are exposed for two weeks and a control is run in parallel.     

Application of biotic indices and relationship with structural and functional features of macrobenthic community in the lagoon of Venice: an example over a long time series of data

In the context of the application of WFD, a scientific debate is growing about the applicability of biotic indices in coastal and transitional waters. In the present work, the question about the discriminating power of different biotic indices and the relationships with the structure and functioning of the macrobenthic community in a transitional environment is discussed. A time series of samples collected during the last 70 years in the lagoon of Venice, reflecting different environmental conditions (a sort of 'pristine state' in 1935, the distrophic crisis in 1988 and subsequent modifications in 1990, the invasion by an alien species and the developing of high impacting fishery in 1999) has been used. The comparison of results obtained by applying different biotic indices, such as AMBI, Bentix and BOPA, shows differences in the discriminating power of indices and a general overestimation of environmental conditions. Discrepancies between environmental status as indicated by biotic indices and the structure and functioning of the benthic community have been highlighted.     

Daily availability of nutrients and metals in a eutrophic meso-tidal coastal lagoon (Óbidos lagoon, Portugal)

This baseline reports daily variations of physico-chemical parameters, nutrients and metals in water of two sites [eutrophic conditions (BB) versus reference (LL)] in Óbidos coastal lagoon (Portugal). Dissolved oxygen in BB varied between 40% saturation levels (night) and 190% (daylight). , and ratios to Al of Mn, Fe and Pb in suspended particulate matter increased during the period of lower oxygenation, indicating exportation of nutrients and metals from the sediment to water at night. At LL, O₂ values oscillated always around 100%. and Mn/Al ratio at LL were always lower than at BB and no increases were found during the night. The input of and Mn provided from the sediment at BB during the night could surpass the contribution of freshwater discharges. PCA confirmed the separation of most samples from BB and LL. These results pointed to the importance of assessing chemical conditions over day-night cycles.     

Distributions of polychlorinated biphenyls in the Daliao River estuary of Liaodong Bay,Bohai Sea (China)

The distributions of 41 polychlorinated biphenyls (PCBs) were determined in the aqueous phase, suspended particulate matter (SPM), and sediment of the Daliao River estuary in Liaodong Bay, Bohai Sea (China). The total PCB concentrations ranged from 5.51 to 40.28 ng L⁻¹ in the surface water, from 6.78 to 66.55 ng L⁻¹ dry weight in the SPM, and from 0.83 to 7.29 ng g⁻¹ dry weight in the sediment. The PCB concentrations in water, SPM, and sediment were moderate relative to those reported for other estuary and marine systems around the world. Sedimentary PCB concentrations decreased offshore due to the active deposition of laterally transported river-borne particles. The predominance of the highly chlorinated congeners for the water, SPM, and sediment samples are an indication of either a lack of degradation or the presence of nearby or recent releases into the environment.     

Imposex levels and concentrations of organotin compounds (TBT and its metabolites) in Nassarius nitidus from the Lagoon of Venice

Specimens of Nassarius nitidus were collected in seven stations of the Venice Lagoon to assess the levels of tributyltin (TBT) and its metabolites monobutyltin and dibutyltin in the tissues and monitor their effect on organisms, in particular the phenomenon of imposex (superimposition of male sexual characteristics on females). The following values of population indices were found: vas deferens sequence: 1.2 ± 0.7–4.0 ± 0.5; relative penis length: 6–47%. The least impacted station was situated in the northern part of the Lagoon, where females without imposex were found and Butyltin (BuTs) concentrations in the organisms (average sum of BuTs = 43 ± 14 ng Sn g⁻¹ w.) were significantly lower than in the other stations (range of average sum of BuTs: 101 ± 22–217 ± 27 ng Sn g⁻¹ d.w.). Population indices were found to be related to the TBT content in the tissues. In particular VDSI had a significant logarithmic correlation: r = 0.95, n = 8, p < 0.05.