© 2018 Ha Thi Thu Bui, Trong Quoc Luu and Ravi Fotedar. This open access article is distributed under a Creative Commons Attribution (CC-BY) 3.0 license. American Journal of Applied Sciences Original Research Paper Effects of Enriching Nitrogen and Phosphorus on the Growth of Sargassum Podacanthum Cultured in Potassium-Fortified Inland Saline Water Ha Thi Thu Bui, Trong Quoc Luu and Ravi Fotedar School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, Perth, Western Australia, 6102, Australia Article history Received: 04-12-2017 Revised: 01-02-2018 Accepted: 05-04-2018 Corresponding Author: Ha Thi Thu Bui School of Molecular and Life Sciences, Curtin University, Kent Street, Perth, Western, Australia, 6102, Australia Email: ha.bui@student.curtin.edu.au Abstract: Potassium-fortified inland saline water (K + ISW) has shown potential for growing marine species, including seaweed species. The response of a brown seaweed species, Sargassum podacanthum, to nitrogen and phosphorus enrichments were evaluated by culturing the species for 84 days in K + ISW and comparing it with Ocean Water (OW). The culture media were enriched weekly with ammonium chloride and sodium dihydrogen phosphate, with ammonium and phosphate ratios of 10:1 at five different concentrations 80:8, 120:12, 160:16, 200:20 and 240:24 μM. The culture medium with no enrichment was used as a control. The water quality and biomass of S. podacanthum were measured fortnightly. The S. podacanthum biomass increase significantly with different concentrations of the nutrient supplementations. The standing biomass and Specific Growth Rate (SGR) of S. podacanthum were similar in OW and K + ISW in the absence of any nutrient supplementation and at the supplement concentration of ammonium and phosphate 160:16 μM. However, from day 42 onwards, at the ratios of 80:8, 120:12, 200:20 and 240:24, S. podacanthum cultured in OW grew significantly faster than in K + ISW. In K + ISW, optimal growth of S. podacanthum was observed at the 160:16 and the increase in biomass was significantly higher than the initial biomass until day 70, whereas at the other four nutrient supplement concentrations, the S. podacanthum biomass remained unchanged during the entire culture period. The nitrite, total Kjeldahl nitrogen and phosphate concentrations in water were found to be significantly (p<0.05) and negatively correlated (p<0.05) with S. podacanthum biomass. Therefore, the results showed that the enrichment of 160 μM ammonium and 16 μM phosphate is required in the K + ISW for S. podacanthum to achieve optimal growth. Keywords: Inland Saline Water, Sargassum podacanthum, Nutrient Enrichment, Potassium Fortification, Ammonium, Phosphate Introduction Mariculture, including seaweed culture, in Inland Saline Water (ISW) is considered as a potential expansion and diversification of aquaculture industry in Australia (Allan et al., 2001). Seaweed culture can make use of salt-affected agricultural farms as it is less constrained by additional requirement for resources and changes in infrastructure than the culture of marine finfish and crustacean species. Therefore, growing Sargassum, in ISW can provide another source of commodity to the farmers with a lower capital investment than farming in the sea (Borowitzka, 1997) and can be an additional tool to protect the inland environment in Australia by combating the salinity problems (Ogburn, 1997). At the same salinity, the level of potassium (K + ) concentration in ISW is lower than in Ocean Water (OW) in Australia (Allan and Fielder, 1997; Dinh, 2016) and USA (Boyd and Thunjai, 2003; Forsberg et al., 1996) although other ionic profiles can be similar (Fotedar et al., 2011; Prangnell and Fotedar, 2006a). Potassium is vital