Effects of enriched Nannochloropsis and Isochrysis algae simultaneously with selenium and zinc on growth factors and mineral contents of saltwater rotifer Brachionus plicatilis

Despite the positive role of rotifers in many hatcheries for feeding the early stages of fish larvae and crustaceans, the lower content of minerals such as selenium (Se, 30 times) and zinc (Zn, 5 times) is considered as one of the disadvantages of this live prey compared to copepods. Therefore, increasing the amount of these nutrients through enrichment is essential. To this end, the present study investigated the effects of the combination of 2 algae Isochrysis aff. galbana and Nannochloropsis oculata enriched with sodium selenite and zinc sulfate on growth and mineral content of rotifer. First, the 1:1 composition of the algae was enriched with a mixture of zinc and selenium salts (each with concentrations of 20, 40 and 80 mg L-1 in algal enrichment medium). The highest number of rotifers (339 ± 11.06 ind mL-1), SGR (± 0.48 ± 0.008 day-1), and the lowest doubling time without any significant difference observed in rotifers fed with algae enriched with 40 mg L-1 of both minerals (p>0.05). However, the highest amount of Zn and Se were observed in those fed with 80 mg L-1 of both minerals. In conclusion, feeding rotifers with Se and Zn enriched algae increased Se and Zn in the rotifers. Thus, microalgae enriched with Se and Zn can be used to feed marine rotifer to meet the nutritional requirements.