Sea lettuce integrated with Pacific white shrimp and mullet cultivation in biofloc impact system performance and the sea lettuce nutritional composition

Abstract

This work aimed to evaluate the effects of integrated culture of sea lettuce (Ulva fasciata) on the shrimp (Litopenaeus vannamei) and mullet (Mugil liza) rearing in a biofloc technology (BFT), on water quality, animal performance and seaweed growth, nitrogen and phosphorus recovery, seaweed bioactive compounds. Two groups were compared: i) Ulva group: cultivation system integrating shrimp and mullet with seaweed, ii) control group: the same without seaweed, both groups used BFT. Each group had four replicates; initial biomass was 618 ± 8 g and 246 ± 34 g for the shrimp and mullet, respectively. Additionally, in the Ulva group, 120 g of sea lettuce per tank was included every two weeks. After 55 days, the integration of seaweed in the system did not influence the shrimp and mullet performance. Shrimps grew, on average, 1.22 g week−1, with 90.6% survival, 2.91 kg m−3 yield and 1.84 FCR. Mullets grew, on average, 1.035 g week−1, with 99.17% survival, and 4.08 kg m−3 yield. At the end 317.01 ± 32.02 g of seaweed per experimental unit was harvested. The total final biomass and yield, considering the whole system, were 12.2% higher in the Ulva group than in the control group. Nitrogen and phosphorus recovery were respectively 5.5% and 7.6% higher in the Ulva group than in the control group. The nitrogen, phosphorus, chlorophyll-a and carotenoids contents in the Ulva group were also higher at the end of the experiment. In conclusion, the integration of sea lettuce can increase the total yield, nitrogen and phosphorus recovery in the biofloc system. Furthermore, the integration of sea lettuce in this system can increase the content of chlorophyll-a and carotenoids, without affecting the yield of ulvan extract.