On the bioremediation efficiency of Mastocarpus stellatus (Stackhouse) Guiry, in an integrated multi-trophic aquaculture system

Abstract

The potential of rearing the red seaweed Mastocarpus stellatus (Stackhouse) Guiry, a carrageenophyte, as a biofilter in a pilot-scale, integrated multi-trophic aquaculture (IMTA) system was investigated. From April to June, M. stellatus, collected from a population in the north of Portugal was cultivated in 1200-L tanks in two consecutive, 4-week experiments with nutrient-enriched waters derived from fish tanks. The stocking density of 3 kg m−2 provided the best yields, ranging from 29.6 g dw m−2 day−1 in April–May to 38.9 g dw m−2 day−1 in June. In the April–May period, a linear increase in the yields was found at higher densities. M. stellatus growth rates during April–May period did not diverge significantly between stocking densities and reached a mean relative growth rate of 3.09 ± 0.90 % day−1 in April–May and 4.02 ± 0.43 % day−1 in June at 3 kg m−2. In June, the increase in stocking density negatively affected the growth rates (3 < 2 < 1 kg m−2). M. stellatus used ammonium (TAN) as the main N source and the nutrient uptake efficiency was found to be similar between stocking densities, but highest in June. The seaweeds removed an average of 66.29 ± 3.57 μmol TAN L–1 in May and 84.49 ± 4.00 μmol TAN L–1 in June, which corresponded to the mitigation of 43.19 ± 1.61 and 49.00 ± 1.59 % of NH3 from the system, respectively. This study demonstrated the potential to effectively cultivate M. stellatus in an IMTA system.