Bioremediation efficiency and biochemical composition of Ulva reticulata Forsskål (Chlorophyta) cultivated in shrimp (Penaeus monodon) hatchery effluent

Abstract

The rapid growth of aquaculture is accompanied by increased discharge of nutrient-rich wastewaters into rivers and coastal waters leading to eutrophication and deterioration of water quality. Seaweeds are suitable candidates to reduce dissolved inorganic nutrient concentration discharged through aquaculture effluent, and can improve water quality and allow for sustainable aquaculture. In this study the de-eutrophication ability of Ulva reticulata was investigated in a shrimp hatchery in Kuala Selangor, Malaysia by evaluating its ability to remove nutrients from shrimp brood stock effluent (SBE) in a batch culture system. The biofiltration ability of U. reticulata was confirmed by the significant reduction in nutrient concentrations during a 12 day period. The concentration of ammonium-nitrate (NH3-N) was reduced by 100 % (after 12 h), nitrite (NO2-N) by 100 % (after 18 h), orthophosphate (PO4-P) by 89 % (after 12 days) and nitrate (NO3-N) by 33 % (after 12 days). An 18.5 % increase in biomass of the seaweed over the experimental period was also observed. The mean relative growth rate (RGR) of U. reticulate reached 1.6±0.1 % d-1.The U. reticulata grew well in SBE, producing protein (6.1 ±1.1 %) and carbohydrate (39.9 ±4.5 %). Carbohydrate (P < 0.05) and protein(p>0.05) content in seaweed growing in SBE were higher than seawater. The results of this study indicate that U. reticulata can be used directly as an effective biofilter for nutrient removal from shrimp hatchery effluent.