Assessment of mineral composition of blue crab (Callinectes sapidus) shell from Tivat Bay and Ulcinj coastal waters

Abstract

The blue crab (Callinectes sapidus) has been considered an invasive species distributed in the Adriatic and other parts of the Mediterranean Sea, and represents a significant threat to the global marine ecosystems, because it may cause native species extinction and transformation of entire ecosystem functioning. Valorization of the blue crab waste (i.e. shell) into new products has been sought as a promising solution to reduce its negative effects. Therefore, the evaluation of chemical composition with a focus on the mineral composition of the blue crab shell was carried out within this research. For that purpose, blue crabs were caught in two different sites of the coastal part of the Adriatic Sea (Tivat Bay and Ulcinj). The samples of the blue crab were cooked by steaming for 10 min and then, shell from crab claws, head and legs (sample I) were separated from the shell of the rest of the body (cephalothorax) (sample II). The obtained results showed that both samples from Tivat Bay and Ulcinj were rich in calcium and magnesium. Calcium in the crab shell is in the form of calcium carbonate. Samples I and II from Tivat Bay and Ulcinj were also characterized with higher content of sodium and potassium. Regarding microelements, the samples had lower amounts of iron, manganese, zinc and copper. When evaluated the safety, it was determined that the concentrations of cadmium, arsenic and mercury in the samples were low or under detection limits, whereas the concentration of lead ranged between 1.32 and 1.75 mg/kg, indicating that crab shells accumulated lead. Based on the findings, it can be concluded that due to high calcium content blue crab shells from Tivat Bay and Ulcinj coastal waters have metal removal capacities and hence have a great potential as an adsorbent for the remediation of metal-bearing solutions. This potential, combined with the low cost of crab shells, could result in a cost-effective effluent treatment system.