Cultivation of the seaweed Ulva spp. with effluent from a shrimp biofloc rearing system: different species and stocking density

<p>This work evaluated the use of effluent from a marine shrimp biofloc rearing system to cultivate the green seaweed&nbsp;<em>Ulva</em>. First, the growth of two&nbsp;<em>Ulva&nbsp;</em>species,&nbsp;<em>U. ohnoi</em>&nbsp;and&nbsp;<em>U. fasciata,</em>&nbsp;was evaluated. Second, the best-performing species was cultivated under two different stocking densities (2 g L^-1&nbsp;and 4 g L^-1) to evaluate both growth and nutrient uptake rates, considering total ammonia nitrogen, nitrate, and orthophosphate. In both cases, environmental variables were monitored, and the cultivation medium, consisting of 25% biofloc water and 75% seawater, was exchanged weekly.&nbsp;<em>U. ohnoi</em>&nbsp;grew significantly better, considering all variables evaluated (<em>p</em>&lt;0.05). The smaller stocking density produced a higher specific growth rate (<em>p</em>&lt;0.05). Yield, however, was unaffected (<em>p</em>&ge;0.05). No significant differences in the nutrient uptake rates were observed (<em>p</em>&ge;0.05). Overall, this work highlights the importance of species selection for seaweed destined for aquaculture. Additionally, it also optimizes the cultivation of seaweeds, specifically&nbsp;<em>U. ohnoi</em>, using effluent from biofloc systems.</p>