Metabolite profiling and antioxidant capacity of lettuce Lactuca sativa var. longifolia grown in aquaponic system irrigated with shrimp effluents

This paper focuses on the quality of lettuce var. longifolia grown with shrimp effluents from well water (WW), diluted seawater (DSW) and a hydroponic solution (HS). Results evidenced that WW and DSW effluents slightly decreased weight, foliage, and yield (5-9%) in plants compared to HS control. Furthermore, WW-lettuce showed a higher level of total phenolic compounds (~71%), flavonoids (~90%), and antioxidant capacity (0.7-3-folds) than HS-plants, mainly in the soluble fraction. WW-lettuce also showed a higher content of total soluble solids (~16%) and, a lower saturation of color, which correlated significantly (p <0.05) with chlorophyll a. WW-lettuce exhibited the highest concentrations of p-hydroxybenzoic, p-coumaric and ferulic acids, as well as quercetin 3-O-glucoside and quercetin 3-O-ramnoside. Whereas DSW-lettuce showed the highest levels of caffeic acid, isorhamnetin 3-O-glucoside, kaempferol 3-O-glucoside, kaempferol and quercetin. HS-lettuce showed a higher proline content than the lettuces from the other treatments. These results indicate that aquaponic lettuce culture with shrimp effluent from WW could be used as an alternative culture system to reduce land area requirements, decrease or eliminate the discharge and impact of shrimp effluents, and simultaneously improve the functional properties of lettuce.