Organically enriched water from an integrated agri-aquaculture system enhances antioxidant defense and secondary metabolism in blackberry (Rubus ulmifolius cv. Tupy)
Integrated agri-aquaculture systems can improve water-use efficiency and nutrient recycling in semiarid and arid regions increasingly affected by climate change; however, the physiological responses of fruit crops to aquaculture-derived irrigation water remain poorly understood. This study evaluated the growth, photosynthetic status, and biochemical responses of blackberry ( Rubus ulmifolius cv. Tupy) irrigated with organically enriched water from an integrated tilapia–blackberry system operated under geodesic-dome conditions in semidesert central Mexico. Four irrigation treatments were compared: a conventional nutrient solution, unsupplemented tilapia-culture effluent, tilapia-culture effluent supplemented with mineral nutrients, and well water adjusted to the same pH as the fertilized treatments. Plant growth traits, leaf greenness, normalized difference vegetation index, antioxidant enzyme activities, total phenolic compounds, and flavonoids were monitored for 216 h after irrigation began. Plants irrigated with supplemented tilapia-culture effluent maintained growth and canopy greenness comparable to those receiving the conventional nutrient solution. In contrast, unsupplemented tilapia-culture effluent and well water induced stronger antioxidant and secondary-metabolic responses, particularly in superoxide dismutase and catalase activities and in the temporal dynamics of phenolic compounds and flavonoids, whereas phenylalanine ammonia-lyase showed a weaker and later response. These patterns suggest that mineral-supplemented effluent primarily supported vegetative performance, whereas unsupplemented effluent was associated with a nutritional elicitation response potentially related to relative nutrient limitation and biologically active components in the effluent. During the 216-h evaluation period, unsupplemented effluent maintained plant performance comparable to that under the fertilized treatments, suggesting that aquaculture-derived water may reduce mineral-fertilizer inputs during specific crop stages. Because the experiment was short-term, no conclusions can be drawn regarding long-term productivity, fruit quality, or sustained plant responses. Overall, the findings support the potential of integrated agri-aquaculture systems as a water-smart approach for blackberry cultivation in water-limited semidesert environments.