Silver nanoparticles represent a threat to biota and have been shown to cause harm through a number of mechanisms, using a wide range of bioassay endpoints. While nanoparticle concentration has been primarily considered, comparison of studies that have used differently sized nanoparticles indicate that nanoparticle diameter may be an important factor that impacts negative outcomes. In considering this, the aim of the present study was to determine if different sizes of silver nanoparticles (AgNPs; 10, 20, 40, 60 and 100 nm) give rise to similar effects during embryogenesis of Mediterranean sea urchins Arbacia lixula and Paracentrotus lividus, or if nanoparticle size is a parameter that can modulate embryotoxicity and spermiotoxicity in these species. Fertilised embryos were exposed to a range of AgNP concentrations (1–1000 µg L⁻¹) and after 48 h larvae were scored. Embryos exposed to 1 and 10 µg L⁻¹ AgNPs (for all tested sizes) showed no negative effect in both sea urchins. The smaller AgNPs (size 10 and 20 nm) caused a decrease in the percentage of normally developed A. lixula larvae at concentrations ≥50 µg L⁻¹ (EC₅₀: 49 and 75 μg L⁻¹, respectively) and at ≥100 µg L⁻¹ (EC₅₀: 67 and 91 μg L⁻¹, respectively) for P. lividus. AgNPs of 40 nm diameter was less harmful in both species ((EC₅₀: 322 and 486 μg L⁻¹, for P. lividus and A. lixula, respectively)). The largest AgNPs (60 and 100 nm) showed a dose-dependent response, with little effect at lower concentrations, while more than 50% of larvae were developmentally delayed at the highest tested concentrations of 500 and 1000 µg L⁻¹ (EC₅₀(100 nm); 662 and 529 μg L⁻¹, for P. lividus and A. lixula, respectively. While AgNPs showed no effect on the fertilisation success of treated sperm, an increase in offspring developmental defects and arrested development was observed in A. lixula larvae for 10 nm AgNPs at concentrations ≥50 μg L⁻¹, and for 20 and 40 nm AgNPs at concentrations >100 μg L⁻¹. Overall, toxicity was mostly ascribed to more rapid oxidative dissolution of smaller nanoparticles, although, in cases, Ag⁺ ion concentrations alone could not explain high toxicity, indicating a nanoparticle-size effect.

This study aimed to assess microplastics (MPs) in the digestive glands of Mytilus galloprovincialis mussels. Mussels were collected from pristine, aquaculture, and port areas of the northern Adriatic Sea (Slovenia and Croatia coastline). MPs were detected using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The characterized MPs were further categorized based on their shape, size, and color. The highest number of 32.85 ± 27.98 MPs per mussel digestive gland was found in the mussels sampled from the ACI marina Rovinj (Croatia). The predominant MPs found in the mussel digestive glands at all investigated locations belonged to the smallest analyzed category (5–10 μm in size) and exhibited spherical and fragment shapes. The most abundant MPs found in mussels by color were white particles. MPs were found in both wild and farmed mussels and, hence, the results point out that the abundance of microplastic pollution is omnipresent along the coastal waters of the northern Adriatic Sea.

As a proxy for pollutants that may be simultaneously present in urban wastewater streams, the effects of two microplastics—polystyrene (PS; 10, 80 and 230 μm diameter) and polymethylmethacrylate (PMMA; 10 and 50 μm diameter)—on fertilisation and embryogenesis in the sea urchin Arbacia lixula with co-exposure to the pyrethroid insecticide cypermethrin were investigated. Synergistic or additive effects were not seen for plastic microparticles (50 mg L⁻¹) in combination with cypermethrin (10 and 1000 μg L⁻¹) based on evaluation of skeletal abnormalities or arrested development and death of significant numbers of larvae during the embryotoxicity assay. This behaviour was also apparent for male gametes pretreated with PS and PMMA microplastics and cypermethrin, where a reduction in sperm fertilisation ability was not evidenced. However, a modest reduction in the quality of the offspring was noted, suggesting that there may be some transmissible damage to the zygotes. PMMA microparticles were more readily taken up than PS microparticles, which could suggest surface chemical identity as potentially modulating the affinity of larvae for specific plastics. In contrast, significantly reduced toxicity was noted for the combination of PMMA microparticles and cypermethrin (100 μg L⁻¹), and may be related to less ready desorption of the pyrethroid than PS, as well as cypermethrin activating mechanisms that result in reduced feeding and hence decreased ingestion of microparticles.

Market demand for scallops has considerably increased in recent decades. Although natural populations of scallops are vulnerable, the queen scallop, Aequipecten opercularis, can represent a possible alternative to at-risk species. The aim of this study was to determine the effect of seawater parameters on the commercial quality, biological indices and nutritional quality of the scallop A. opercularis in 1900 L tanks in ex situ conditions. The condition index (CI) and meat yield (MY) peaked in autumn (89.92% and 40.29%, respectively). The muscle index (MI) showed the highest peak during the winter season (5.96%), while the gonadosomatic index (GSI) (34.06%) peaked in the spring months. Protein content (6.89–9.56 g/100 g), lipids (2.58–2.79 g/100 g) and carbohydrates (0.12–0.33 g/100 g) varied during the study period. Seasonal fluctuations in seawater temperature and pH negatively influenced the CI, MY and protein and lipid content, while positively affecting carbohydrate and moisture content. The most suitable period of the year for the consumption of the scallop A. opercularis was found to be the winter and spring periods, when the scallops achieved their highest nutritional value. It can be stated from this study that queen scallops in the Adriatic Sea have a high nutritional quality and that they can be proposed for higher human consumption.

The objective of this research was to isolate and identify lactic acid bacteria living in the digestive tract of the queen scallop Aequipecten opercularis and further test it as a probiotic culture on the growth of the bivalve during one month in captivity. Classic microbiological techniques (API and MALDI TOF) were used and four different strains of Lactiplantibacillus and one Lactococcus were identified and further analyzed, namely: Lactiplantibacillus plantarum I, Lactiplantibacillus plantarum 1, Lactiplantibacillus plantarum 2, Lactococcus lactis, and Lactiplantibacillus brevis. The isolated cultures were further tested for the highest antimicrobial activity towards the most common marine pathogens and survival at different temperatures and pH levels. The strain Lactiplantibacillus plantarum I had the best results, with the highest antimicrobial activity (77–85% pathogen growth inhibition) and the best safety standards showing no antibiotic resistance, and no ability to synthesize biogenic amine and degrade red blood cells. Considering all the abovementioned characteristics, the strain Lpb. plantarum I was further tested on the growth and health status of the bivalve Aequipecten opercularis during a month of cultivation in captivity. The results showed that the incorporation of Lpb. plantarum I led to a decrease in the quantity of test microorganisms in the bivalve and an increase in both the growth rate weight and growth rate length of the queen scallop A. opercularis. Furthermore, the scallops fed with the algae culture + Lpb. plantarum I gained significantly higher meat yield (33.15 ± 2.63%) compared with the control scallops fed only with the algae culture (29.66 ± 2.87%). To conclude, the results from this research indicate that including Lpb. plantarum I as a dietary supplement could enhance growth performance and serve as a feasible approach to reduce pathogen levels while cultivating A. opercularis in captivity.