Freshwater scarcity represents a major constraint for the sustainable industrial-scale cultivation of microalgae. This study investigates the feasibility of producing Scenedesmus almeriensis using seawater in 3.1 m³ tubular photobioreactors under winter–spring conditions. Biomass productivity and microbial diversity were compared between freshwater and seawater-based cultures under batch and semi-continuous regimes (0.1, 0.2, and 0.3 day⁻¹). Maximum biomass concentrations reached 0.60 and 2.15 g·L⁻¹ in freshwater and seawater, respectively (p<0.05). Production using seawater also led to a higher biomass productivity (0.18 g·L-1·day-1) compared to freshwater (0.06 g·L-1·day-1) when operating at a fixed dilution rate of 0.1 day-1. Seawater cultures also showed greater stability, higher photosynthetic efficiency (Fv/Fm), and reduced contamination by zooplankton, fungi, and ciliates, enabling Scenedesmus to dominate up to 70% of the microalgal community. In contrast, freshwater cultures were rapidly degraded by rotifers and anaerobic fungi, reducing productivity and purity. The appearance of algal predators represents a huge challenge in industrial facilities. The results described in this study highlight the potential use of seawater as a strategic water source for more sustainable, resilient, and efficient microalgae production systems.
Publication Date: 2026-06-23