Growth performance and heavy metal analysis of Oreochromis niloticus fed with phycoremediate microalgae supplemented diet formulation

Abstract

The rising demand for fish as the primary protein source for human consumption is a continuous challenge to meet. Modern-day studies have exploited microalgae as an alternative plant-protein source to replace fishmeal. However, it is critical to protect the fish culture from toxic metal accumulation, which is dangerous to both the organisms and consumers. Hence, this research aimed to study the effects of using microalgae bioproducts on the growth performance and heavy metal accumulation in the muscle tissue of Oreochromis niloticus. In this study, 2% of Scenedesmus sp. cultivated in Bold Basal Medium and wet market wastewater was partially substituted to replace fishmeal. The physicochemical properties of formulated feed were analyzed and compared between control, formulation 1 and formulation 2. The fish were cultured for 12 weeks, and their weight gain was monitored weekly using an analytical balance. The muscle tissue samples were collected and digested using 37% HCl and 65% HNO₃. As a result, the growth performance of the fish in formulations 1 and 2 showed a positive trend and a higher average growth rate of up to 43.38 and 44.85 g, respectively. The effect of seven heavy metals, such as zinc, iron, copper, lead, mercury, manganese, and cadmium, on the fish was analyzed using the Inductive Coupled Plasma Mass Spectrometry (ICPMS) technique. An analysis of variance indicated a significant difference (p < 0.05) for zinc, copper, iron, lead, and mercury concentrations but not for manganese and cadmium (p > 0.05). It can be deduced that the inclusion of 2% Scenedesmus sp. in the diet formulation results in a minor variation in fish growth performance. However, this could contribute to maintaining and improving the growth rate of O. niloticus and the concentration of heavy metals in their muscle tissue. Continuous examination of heavy metal accumulation in fish is necessary to ensure the safeness and nutritional quality are adequate for human consumption.