Use of Natural Zeolites as a Detoxifier of Heavy Metals in Water and the Flesh of Reared European Seabass Dicentrarchus labrax

Abstract

A study was conducted to investigate the effects of natural zeolites as a water clarifier on the heavy metal removal efficiency from the underground saltwater used for rearing Dicentrarchus labrax fry. Five concentrations of zeolites were tested: 0 (Z0), 2.5‰ (Z2.5), 5‰ (Z5), 7.5‰ (Z7.5) and 10‰ (Z10). Fry with an initial body weight of 1.53±0.018 g/fish were stocked in 15 aquaria at a density of 10 fry/aquarium. The fish were fed a commercial diet (42% protein and 12.34% lipid) twice daily (09:30 and 14:00) at 5% of their body weight per day for 42 days. Growth, feed utilization, survival and heavy metal removal efficiency were evaluated. The growth performance and feed utilization indices gradually improved with increasing zeolite concentration, with the most significant (P≤0.05) values detected at Z10. The survival rate decreased significantly at Z10 compared with the control (Z0). Increasing the zeolite concentration significantly (P≤0.05) improved the removal efficiency of heavy metals in the rearing water with adsorption selectivity of Pb˃Cd˃Fe˃Cu˃Zn. Furthermore, an increase in the detoxification rate of heavy metals in fish flesh with increasing zeolite level was detected with the removal selectivity of Fe˃Cu˃Zn˃Pb˃Cd. In conclusion, it can be stated that natural zeolites can be used effectively to reduce heavy metals in polluted waters and subsequently in fish flesh in addition to improving fish performance.