Seasonal variability of trace elements bioaccumulation in Pacific Oysters (Crassostrea gigas) from an experimental pilot farm in the Calich Lagoon (Sardinia, Italy).

BACKGROUND: Metals pollution is a worldwide environmental issue due to their persistence in the ecosystems, non-degradability, and bioaccumulation in marine biota. Pacific Oysters (Crassostrea gigas) are highly nutritious bivalve representing an important dietary constituent but may accumulate metals through feeding on suspended sediments from surrounding water, then represent a suitable tool for biomonitoring. MATERIALS AND METHODS: The occurrence of trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rb, Se, Sn, V, Zn) was investigated in Pacific Oysters (Cassostrea gigas) collected from Calich Lagoon in each season of 2019. Samples were homogenized and subjected to microwave acid digestion before being analyzed by inductively coupled plasma-mass spectrometer (ICP-MS). RESULTS: The results showed a significant seasonal variation for temperature, dissolved oxygen, chlorophyll, and pH. Moreover, high significant seasonal variation in concentrations of Cd, Mn, Ni, and V was recorded. The highest values were found for Fe (128 mg kg⁻1 w.w.), and Al (112 mg kg⁻1 w.w.) in October, for Zn (113 mg kg⁻1 w.w.) in March and May. CONCLUSIONS: Pacific Oysters were confirmed as suitable bioindicators of the health status of coastal lagoons; trace elements concentrations were highly affected by season of collection, and according to literature the highest values were recorded in autumn and summer. The EU legal limits for Cd and Pb were not exceeded, then the farmed oysters were safe to consumers.

Determination of phytoplankton in water samples, algal biotoxins, microbiological parameters and microplastics in Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) from an experimental pilot farm in the Calich Lagoon (Sardinia, Italy).

The aims of this paper were to collect and analyse preliminary data of phytoplankton in the water, biotoxins, Escherichia coli, Salmonella spp., Vibrio spp. and microplastic eventually present in farmed mussels, and to acquire information about the production capability from an experimental pilot farm of the Calich Lagoon. Two sampling sessions were carried out, in February and in May 2019, also monitoring the water condition (pH, temperature, salinity, dissolved oxygen, chlorophyll a). No potentially toxic algae were detected, and moreover no biotoxins (Paralytic Shellfish Poison, Diarrheic Shellfish Poison, Amnesic Shellfish Poison) were found in mussels. E.coli was present with the highest concentration in February (16000 MPN/100g e.p.). Salmonella and Vibrio spp. have not been detected. Almost a microplastic per grams was found, mainly fiber of different colours. Further studies, carried out for several months, will allow to better understand the possible problems related to the production of mussels in a lagoon not yet classified as a shellfish production area.

Occurrence of trace elements in Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) from an experimental pilot farm in the Calich Lagoon (Sardinia, Italy).

The present study aimed to determine trace elements in Mediterranean mussels (Mytilus galloprovincialis) from an experimental pilot farm of the Calich Lagoon, a typical Sardinian brackish area (Italy). Two sampling sessions were scheduled in February and May 2019 and the occurrence of 24 metals (Hg, Ag, Al, As, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sn, Ti, V, Zn) in bivalves was considered. Environmental conditions of water (temperature, salinity, pH, dissolved oxygen, and chlorophyll a) were also measured in situ. A high significant (P<0.001) difference was reported for temperature, pH, and dissolved oxygen. Our results showed a significant sessional variation of Mo (P<0.001); Cd, V (P<0.01); Ni, Pb and Co (P<0.05) in examined M. galloprovincialis samples; as all values were higher in February than those for May session samples, meanwhile the highest levels were reported for Mg (mean±s.d. 1151±263 mg kg-1 wet weight), Al (mean±s.d. 341±192 mg kg-1 w.w.), and Fe (mean±s.d. 212 ±75 mg kg-1 w.w.) in February samples. The European Union uppermost values (EC Reg. 1881/2006) for Cd, Hg, and Pb were never overpassed. The results confirmed the role of M. galloprovincialis as one of the most appropriate biological indexes to track the presence of trace elements in brackish environments. It could be concluded that the current ecology of the Calich Lagoon suggests that compatibly with the transitional ecosystem, the classification as a bivalves' production area and the implementation of extensive shellfish farming can improve its production capacities. The knowledge of the lagoon ecology is an essential tool for its sustainable exploitation, preserving biodiversity, and mitigating the effects of anthropogenic activities on public health.