Ulva lactuca as a functional ingredient and water bioremediator positively influences the hepatopancreas and water microbiota in the rearing of Litopenaeus vannamei

Integrated multi-trophic aquaculture (IMTA) is increasingly recognized as a means to improve the sustainability of aquaculture and to mitigate its environmental impact. Macroalgae can play an important role in IMTA and here a six-week feeding trial was conducted to examine the efficacy of Ulva lactuca as a functional food ingredient and a water bioremediation agent in Litopenaeus vannamei aquaculture. Treatments including a diet with 4% algae or algal bioremediation of recirculating rearing water, either alone or in combination, had significant positive influences on the daily growth of the shrimp. Overall, the combination of feeding shrimp with the algal diet and rearing them the algal bioremediation system resulted in twice the specific growth rate (SGR, 4.92 ± 0.4% day⁻¹) compared to feeding a control diet in a flow through system (SGR 2.41 ± 0.3% day⁻¹). Both the algal bioremediation system and the algal diet promoted the establishment of known aquaculture probiotics, including Agarivorans, Sphingomonas, Lactobacillus, Leuconostoc, Peredibacter and Bdellovibrio-and-like organisms, and suppressed or decreased potential pathogens, such as Vibrio alginolyticus and Photobacterium sp. The significant increase of known probiotic bacteria as well as the suppression of potential pathogens in both the shrimp hepatopancreas and the cultivation water provide strong evidence that the use of macroalgae as feed supplement, prebiotic treatment and bioremediation agent has the potential to stimulate animal growth and contribute to the overall health of the aquaculture environment