Growth and metabolism of <i>Clarias gariepinus</i> (Burchell, 1822) fed with copepods (<i>Eucyclops sp.</i>) exposed to lead and titanium dioxide nanoparticles

Abstract

The increasing uses of lead (Pb²⁺) and titanium dioxide nanoparticles (nTiO₂) in commercial products have led to their increased discharge into aquatic environments. This study investigated the effects of the interaction between nTiO₂ and lead (Pb²⁺) in a simple freshwater food web model consisting of zooplankton (Eucyclops sp.) and the African catfish Clarias gariepinus. The growth performance and nutrient composition of Clarias gariepinus fed with contaminated zooplankton alone and combined mixtures of nTiO₂ (0.20 μM) and Pb2+ (0.01 and 0.04 μM), respectively, were evaluated after a chronic (28 days) semi-static laboratory bioassay. Our results demonstrated a decrease in the bioaccumulation of Pb²⁺ in fish exposed to the binary mixtures. The interaction of the mixtures caused significant (p < 0.05) retardation of growth of the fish through decreases of specific growth rate and allometric growth. Furthermore, a significant (p < 0.05) decrease of nutrient composition in fish tissues (muscles) was elicited in protein (20.66 to 16.73%), ash (5.96 to 5.69 %), moisture (16.2 to 14.8 %) and total lipid (10.04 to 6.62%). The findings of this study suggest that feeding fish with copepods contaminated with Pb²⁺ and nTiO₂ mixtures could negatively affect the growth and nutrient composition (protein, ash, moisture and total lipid) of freshwater fish species, such as C. gariepinus.

Keywords: accumulation, binary mixtures, food chains, heavy metals, length-weight relationships, nanomaterials, nutrient composition