Growth potential and productivity of the green macroalgae Ulva reticulata in a sustainable farming system in a coastal lagoon at Bambous Virieux, Mauritius

Abstract

Ulva reticulata is a fast-growing green macroalga with high bioremediation and economic potential. Cultivation of this seaweed at Bambous Virieux in southeast Mauritius was undertaken to evaluate its growth potential and biological feasibility in a tropical lagoon. Over a 30-day trial, three 6 × 6 m rafts constructed from common aquaculture system materials supported substantial biomass gains, with initial mean wet weights of 106.29 g per thallus, and final biomass per cultivation unit as high as 1 886.83 g (Raft 2), representing an ∼18-fold increase and 60.55 g mean daily growth. Growth differences across rafts were significant (χ^² = 144, p < 0.001), with Raft 2 showing the highest consistency (standard deviation = 8.74 g). Water quality remained within optimal ranges, with no significant temporal or site-based fluctuations. Routine maintenance was successfully conducted by trained community members, demonstrating the viability of participatory management. Preliminary ecological observations indicated that the seaweed rafts attracted herbivorous reef fishes, suggesting additional biodiversity benefits. Although the seaweed cultivation system proved to be highly productive and ecologically sustainable, in potential community-led scale-up operations, the lagoon location might present logistical challenges for some coastal communities to access. Overall, the results suggest U. reticulata is a climate-resilient species for sustainable open-water seaweed farming to support ‘blue growth’ in small island states while mitigating aquatic ecosystem issues (like absorbing excess nutrients and carbon), thus aligning economic development with ecosystem health. Future research on U. reticulata cultivation should focus on understanding its seasonal variations, nutrient dynamics, and optimal densities to maximise farming productivity and ensure resilience against environmental changes.