Potential growth and nutrient removal of Kappaphycus alvarezii in a fish floating-net cage system in Sekotong Bay, Lombok, Indonesia

There has been increasing interest in promoting the seaweed Kappaphycus alvarezii as a co-culture species in an integrated multitrophic aquaculture system. In recent work, we observed the capability of K. alvarezii to grow and remove carbon (C), nitrogen (N), and phosphorus (P) when planted in an intensive fish floating-net cage system in Sekotong Bay, Lombok, Indonesia. Environmental factors that may influence seaweed bioremediation were investigated. After 42 days, there was a significant difference in the seaweed growth and bioremediation capability while cultivated within the fish cage system compared to the control site. Six kilogram of K. alvarezii incorporated inside the fish cages reduced the inorganic NH4+ and PO43- on average of 22.5-34% and 5-30%, respectively, from morning to afternoon and removed 131 g C g DW-1, 4.6 g N g DW-1, and 1.18 g P g DW-1. The seaweed growth rate inside the fish cages was 3.33% d(-1) and higher than at the control site. Water motion was a limiting factor for growth and nutrient bioremediation inside the fish cage system. Our results provide evidence of the potential for K. alvarezii to grow in a fish aquaculture system and reduce the nutrient discharge from fish farms.