Sequential toxicity identification evaluation (TIE) for characterizing toxicity of Venice Lagoon sediments: comparison of two different approaches.

A toxicity identification evaluation phase-I (TIE-1) procedure was carried out on five pore water samples extracted from sediments of the Venice Lagoon previously investigated to assess both chemical contamination and toxic effects on the biota. Two different sequential TIE procedures were tested. A first sequence (TIE-1) provided for adding Na2S2O3, adding Na-EDTA, filtering, elution through a C18-SPE column and removing ammonia using the macroalgae Ulva rigida Agardh 1823, while a second procedure (TIE-2) was set up using U. rigida treatment for ammonia removal as first step, keeping unchanged the sequence of the other manipulations. Two different exposure time to the macroalgae were tested (3-h and 15-h). Sperm-cell toxicity test with the echinoid Paracentrotus lividus and embryotoxicity tests with the bivalves Mytilus galloprovincialis and Crassostrea gigas were performed on pore-water samples to assess the effect of the sequential treatments on the overall toxicity. The results confirmed that ammonia contribution to toxicity is strong in most of the samples and that metals, specially Cu, are of concern at least in three sites. The TIE-2 procedure provided more reliable results for the samples characterized by high ammonia contribution to the overall toxicity, whereas the results of TIE-1 and TIE-2 were equivalent for the samples where ammonia contribution was not prevailing. Chemical analyses and test results showed that a 3-h U. rigida exposure is suitable to remove ammonia toxicity minimizing potential metal up-take.

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.

Stress biomarkers and alkali-labile phosphate level in mussels (Mytilus galloprovincialis) collected in the urban area of Venice (Venice Lagoon, Italy).

In this study, a spatial and temporal survey at three sites located in the "canals" of the Venice historic centre (Italy) and at a reference site was undertaken to evaluate stress effects on mussels sampled in the Venice urban area, where raw sewage is discharged without treatment directly into the water. A battery of biomarkers (metallothionein, micronuclei, condition index and survival in air) was used to evaluate the stress condition of the animals. At the same time the alkali-labile phosphate assay (ALP) was performed in mussel' hemolymph with the aim to find an estrogenic effect biomarker in this mussel species. Biomarker results showed an impairment of the general health condition in the mussels coming from the urban area, in agreement with the chemical analysis. Significantly higher level of the ALP was found in male mussels sampled in April in the urban area, in comparison with the ones from the reference site (P<0.001). Finally, the PCA proved an easy and useful tool to summarize the obtained results, also able to classify the data to indicate a pollution gradient in the Venice urban area.

Physiological measurements from native and transplanted mussel (Mytilus galloprovincialis) in the canals of Venice. Survival in air and condition index.

The Venice Lagoon has been the focus of many environmental studies due to its heavy contaminant load derived from a variety of sources, including industrial activity, oil tanker traffic, and waste runoff from the mainland. In recent years, there has been increasing concern about water quality in the urban areas of Venice related to the discharge of untreated sewage directly into canals, adding to the pollutant load already existing in these areas. One way of gauging the impact of these chemicals is monitoring the local fauna. In the search for good indicators of water quality in the Venice urban area, two physiological indices for mussels-survival in air and condition index-have been evaluated. In 2002, a seasonal study was undertaken; mussels (Mytilus galloprovincialis) were collected in three sites located in the canals of the city and a clean reference site. At the same time, two transplantation experiments were performed, deploying farmed mussels for 1,2, 4, and 12 weeks in the historic centre of Venice and also at a reference site. Data from survival in air test and the condition index of native and transplanted mussels are reported. The results suggest an impact of the complex mixture of pollutants on mussel health status. Both native mussels and those transplanted to the urban area showed reduced survivability in air and decreased condition index values, indicating a less healthy status in animals from the canals of the city. Data are discussed in relation to pollutant bioaccumulation.

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.