Short-term nutrient removal efficiency by Ulva pseudorotundata (Chlorophyta): potential use for Integrated Multi-Trophic Aquaculture (IMTA)

Short-term N-NH 4 + and N-NO 3 - removal by U. pseudorotundata under different initial nutrient concentrations and biomass stocking densities, monitoring in parallel photosynthetic parameters obtained by Pulse-Amplitude-Modulation ( PAM ) Fluorometry of chlorophyll-a and evaluating biomass characteristics (CHN, proteins, carbohydrates) was investigated. The results showed that U. pseudorotundata cultivated under solar radiation in a land-based out-door pilot scale was efficient in removing N-NH 4 + and N-NO 3 - even in concentrations as high as 500 µmol L⁻¹ ensuring complete water remediation in a period of 24 h and in all experimental conditions tested, although differences were observed depending on the stocking density and type of N-source. Treatments with N-NH 4 + showed faster N removal than those with N-NO 3 - , however, treatments with N-NO 3 - demanded more photosynthetic energy. Part of the ammonium removed in the respective treatments may have been volatilized as a combined effect of the pH increase related to photosynthesis and aeration in the tanks. The results presented here establish the fundamental parameters for the use of U. pseudorotundata as a biofiltering organism for effluents with high concentrations of N-NH 4 + and N-NO 3 - .