var. : A Local Sustainable Microalga for Food System Resilience.

The intensifying global demand for sustainable and nutrient-dense food sources necessitates the exploration of underutilized local resources. var. , a cyanobacterium endemic to Madagascar, was evaluated for its nutritional, functional, and environmental potential under small-scale, low-input outdoor cultivation. The study assessed growth kinetics, physicochemical parameters, and composition during two contrasting seasons. Biomass increased 7.5-fold in 10 days, reaching a productivity of 7.8 ± 0.58 g/m/day and a protein yield of 4.68 ± 0.35 g/m/day. The hot-season harvest showed significantly higher protein content (65.1% vs. 44.6%), enriched in essential amino acids. On a dry matter basis, mineral profiling revealed high levels of sodium (2140 ± 35.4 mg/100 g), potassium (1530 ± 21.8 mg/100 g), calcium (968 ± 15.1 mg/100 g), phosphorus (815 ± 13.2 mg/100 g), magnesium (389.28 ± 6.4 mg/100 g), and iron (235 ± 9.1 mg/100 g), underscoring its value as a micronutrient-rich supplement. The hydroethanolic extract had the highest polyphenol content (4.67 g GAE/100 g of dry extract), while the hexanic extract exhibited the strongest antioxidant capacity (IC = 101.03 ± 1.37 µg/mL), indicating fat-soluble antioxidants. Aflatoxin levels (B1, B2, G1, and G2) remained below EU safety thresholds. Compared to soy and beef, this strain showed superior protein productivity and water-use efficiency. These findings confirm var. as a promising, ecologically sound alternative for improving food and nutrition security, and its local production can offer substantial benefits to smallholder livelihoods.