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.

Climate change poses risks to bivalves; thus, searching for resilient alternative species is crucial for sustainable fisheries. This study examines the impact of reduced pH and elevated temperature and their combined effects on the queen scallop Aequipecten opercularis in captivity. The results indicated that a low pH reduced its growth rates in both weight (0.03 ± 0.05 g/day) and length (0.06 ± 0.16 mm/day), as well as leading to decreases in meat yield (20.75 ± 2.75%) and the condition index (44.21 ± 7.19%). Conversely, elevated temperature resulted in an increased growth in length (0.07 ± 0.23 g/day), meat yield (21.57 ± 4.82%), and condition index (45.42 ± 7.35%). Combined stressors initially promoted growth but ultimately produced unsustainable outcomes, resulting in a reduced meat yield (18.28 ± 2.60%) and condition index (38.92 ± 8.23%), along with a peak mortality rate of 27%. These findings indicate that while A. opercularis can withstand individual stressors, exposure to simultaneous stressors may compromise its long-term viability in aquaculture systems.

The shells of dead Pinna nobilis individuals are important habitats in sedimentary coastal ecosystems, yet their ecological role is poorly understood. This study investigated macrofaunal communities associated with 80 P. nobilis shells from Soline Bay and Valovine Bay, northern Adriatic, analyzing variations in species abundance and biodiversity between shell orientations (vertical and horizontal) and across seasons. Shell dimensions were recorded, with larger shells and higher faunal abundance observed in Soline Bay compared to Valovine Bay. A total of 2225 individuals representing 183 species across 19 taxonomic groups were identified, with Malacostraca, Bivalvia, and Polychaeta being the most abundant. Vertically positioned shells hosted significantly more organisms than horizontally positioned ones, likely due to greater available surface area for settlement. Seasonal changes influenced organism abundance, with peaks in winter for Valovine Bay and spring for Soline Bay, correlating with environmental factors such as eutrophication. The most frequent species associated with the shells of dead individuals were the polychaete Sabella spallanzanii and the bivalve Rocellaria dubia, which can impact shell degradation. Despite their temporary nature, the shells of dead P. nobilis provide vital refuge and enhance biodiversity. The findings underscore the ecological importance of P. nobilis shells as biodiversity hotspots and highlight the need for their conservation and further study.

The use of probiotics in the diet of bivalves poses a great potential in aquaculture as an alternative to antibiotics. The aim of this study was to assess the effect of Lactiplantibacillus plantarum I on the phenolic content and antioxidant capacity (AC) of queen scallop extracts after one month of feeding. Total phenols (TP) ranged from 28.17 ± 3.11 to 58.58 ± 8.57 mg GAE/100 g, total non-flavonoids (TNF) from 23.33 ± 3.66 to 36.56 ± 9.91 mg GAE/100 g, and total flavonoids (TF) from 10.56 ± 5.57 to 30.16 ± 1.69 mg CE/100 g. AC was assessed via three different methods: the ferric-reducing ability of plasma assay (FRAP), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic) acid assay (ABTS), and 2,2-diphenyl-1-picryhydrazyl assay (DPPH). FRAP values ranged from 0.13 ± 0.03 to 0.17 ± 0.02 µM AA/g, ABTS from 0.68 ± 0.11 to 2.79 ± 0.34 µM AA/g, and DPPH from 1.75 ± 0.17 to 2.98 ± 0.53 µM AA/g. Among all extracts, the best phenolic content and AC were observed in water extracts from queen scallops. The bivalves treated with the Lactiplantibacillus plantarum I-enriched diet showed higher AC according to the FRAP assay in all extracts. A significant correlation was observed between AC and TP and TNF in control and Lactiplantibacillus plantarum I-treated scallops.

Climate change has presented a serious problem in recent times, which is why a new approach is being sought in terms of aquacultural food quality. In this study, the influence of temperature increase (by 2 °C) and pH decrease (by 0.2) was investigated on the queen scallop, Aequipecten opercularis (Linnaeus, 1758). Furthermore, the effect of a food-enriched diet with the probiotic culture Lactiplantibacillus plantarum I was assessed in climate-changed conditions. Scallops’ morphometric parameters were measured before the experimental setup and after one month of being kept in controlled conditions. Morphometric parameters included the elongation index, compactness index, convexity index, density index, condition index, meat yield, gonadosomatic index, adductor muscle index, and hepatosomatic index. Climate-changed conditions had no effect on the scallop condition index, meat yield, or hepatosomatic index. Nevertheless, the addition of probiotics to their diet had a positive effect on the queen scallops cultivated under conditions of climate change, influencing positive allometry and the increase of the gonadosomatic indices. On the other hand, the same conditions negatively affected the adductor muscle index of the scallops. To conclude, in the context of climate change conditions, queen scallops could be a good organism of choice that can be very well adapted to the changed environmental conditions, especially with the addition of the lactic acid bacteria culture Lpb. plantarum I.