Ulva lactuca for nutrients biofiltration in a recirculating shrimp effluent treatment system

Abstract

An outdoor tank scale shrimp cultivation system was developed with integration of green macroalgae species, Ulva lactuca. Intensive shrimp farming produces large amount of waste nutrients, due to excess uneaten feed and excretion. Prior harvesting, shrimp effluent discharged without proper treatment and alleviates water quality of receiving water bodies. Coastal water degradation consequently causes negative environmental impact. This integrated system with U. lactuca, greatly reduced the nutrient loads and incorporated into its biomass. Phosphate removal was 90%, followed by ammonium and nitrate with removal efficiencies of 70% and 42%, respectively. The mean specific growth rate of U. lactuca was 2.25 ± 0.9 % day-1 and shrimp was 0.76 ± 0.09 % day-1. Shrimp growth rate in control tank was significantly lower compared to the treatment tank (P<0.001) and survival rate declined throughout the experimental period. Integration of U. lactuca significantly enhanced the dissolved oxygen with mean value of 5.49±0.06 mg/L and creates a stable pH values compared to control treatment tank. Thus, U. lactuca is a prominent biofilter with rapid growth rate and greatly reduces the overall environmental impact of aquaculture water degradation and stabilize the culture environment and this study highly recommended utilization of U. lactuca as a biofilter component in an integrated multitrophic aquaculture treatment system.