Benthic foraminifera assemblages as elemental pollution bioindicator in marine sediments around fish farm (Vrgada Island, Central Adriatic, Croatia).

Effects on sediments of fish farming activity near Vrgada Island was analysed through living and total foraminiferal assemblages and concentration of major, minor and trace elements from three sediment cores. Elemental concentrations of sediments are in accordance with carbonate characteristics of the surrounding area and show mostly natural element variations between sampling locations and throughout the cores, with no significant increases due to fish farming activity. Only phosphorus concentration shows elevate values below the fish cage, assigned to fish pellets. Foraminiferal communities are dominated by epifaunal and stress tolerant species, while diversity indices point to normal marine conditions. The type of substrate and phosphorus content in sediments principally influence foraminiferal community composition, while other elemental concentrations have no perceptible effect on the assemblages. Some foraminiferal species Ammoniatepida, Ammoniabeccarii, Elphidiumcrispum, Elphidiummacellum and genus Haynesina are confirmed to be tolerant to elevated nutrient (phosphorus) content, while Ammonia parkinsoniana shows sensitivity to pollution. Postmortem processes cause decrease of foraminiferal density and species richness with core depth. All results point to negligible influence of fish farming and relatively stable environmental conditions at all sampling locations.

Element levels in cultured and wild sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) from the Adriatic Sea and potential risk assessment.

In this study, the role of aquaculture activity as a source of selected metals was analyzed. Significant differences in element content between cultured (Dicentrarchus labrax, Sparus aurata) and wild fishes as well as between fish muscle and their feed were detected. Higher concentrations of trace elements (i.e., As, Cu, Hg, Se) in wild fish tissues in comparison with cultured ones indicate additional sources of metals beside fish feed as natural and/or anthropogenic sources. Generally, mean Cd, Cu, Pb, Se, and Zn concentrations in cultured (0.016, 1.79, 0.14, 0.87, and 34.32 µg/g, respectively) and wild (0.011, 1.97, 0.10, 1.78, and 23,54 µg/g, respectively) fish samples were below the permissible levels, while mean As (2.57 µg/g in cultured, 4.77 µg/g in wild) and Cr (5.25 µg/g in cultured, 2.92 µg/g in wild) values exceeded those limits. Hg values were lower in cultured (0.17 µg/g) and higher in wild (1.04 µg/g) fish specimens. The highest elemental concentrations were observed in almost all fish samples from Korcula sampling site. The smallest cultured sea basses showed As (4.01 µg/g), Cr (49.10 µg/g), Pb (0.65 µg/g), and Zn (136 µg/g) concentrations above the recommended limits; however, values decreased as fish size increased. Therefore, the majority of metal concentrations in commercial fishes showed no problems for human consumption. Also calculated Se:Hg molar ratios (all >1) and selenium health benefit values (Se-HBVs) (all positive) showed that consumption of all observed fishes in human nutrition is not risk.