Agronomic Performance, Mineral Composition, and Biochemical Characteristics of Basil (Ocimum basilicum L.) Grown in Trout (Oncorhynchus mykiss) Aquaponic Systems

Aquaponic systems are among the sustainable approaches for combining fish farming and plant cultivation and have been proposed as potentially economically viable food production technologies. Their performance depends on the balanced environmental conditions shared by fish, nitrifying bacteria, and plants. This study assessed the performance of a trout-based (Oncorhynchus mykiss) decoupled aquaponic system for basil (Ocimum basilicum L.) growth and essential oil composition. Two cultivation strategies were compared over 60 days: a non-supplemented system relying exclusively on trout rearing water, and a system supplemented with mineral nutrients formulated according to the recommendations of the Hoagland nutrient solution. Basil grown without mineral supplementation maintained a healthy appearance and stable physiological status, with satisfactory growth, although it remained lower than in supplemented plants. The mineral profile of the plants showed similar nitrate and phosphorus concentrations between non-supplemented and supplemented plants, with nitrate levels of 5.40 ± 0.29 mg g−1 and 5.52 ± 0.29 mg g−1, respectively, and phosphorus levels of 5.46 ± 0.23 mg g−1 and 6.14 ± 0.91 mg g−1, respectively. In contrast, potassium concentration was lower in non-supplemented plants (36.89 ± 3.31 mg g−1) compared to supplemented plants (55.56 ± 7.16 mg g−1). Essential oil yield expressed per cultivated surface area remained comparable between systems, reaching 2.96 and 3.09 mL m−2 in the supplemented and non-supplemented systems, respectively. GC–MS analysis revealed that linalool (≈24%) was the predominant compound in both systems. Notably, estragole content was higher in non-supplemented plants (21.35 ± 1.46%) compared to supplemented plants (5.24 ± 0.68%). Overall, trout-based aquaponic systems not only support satisfactory basil growth but also enhance the production of essential oils with desirable aromatic characteristics, representing a sustainable and efficient strategy for aromatic plant cultivation.