The Nitrate and Nitrite Levels From Both Spinach and Stellate Sturgeon Meat in an Aquaponic Integrated System Stefan M. PETREA* 1) , Victor CRISTEA 1) , Lorena DEDIU 1) , Feng LIU 2) , Paul LUPOAE 3) , Alina ANTACHE 1) , Alexandru BANDI 1) , Marian COADĂ 1) 1) “Dunărea de Jos” University of Galati, Faculty of Food Science and Engineering-Aquaculture, Environmental Science and Cadastre Department, 47 Domnească Street, 800008 Galati Romania 2) China Agricultural University, Beijing 100083, PR China 3) Natural Sciences Museum Complex Galaţi, Botanical Garden, 6A Street Regiment 11 Siret, Romania *Corresponding author, email: stefan.petrea@ugal.ro Bulletin UASVM Animal Science and Biotechnologies 71(2) / 2014, Print ISSN 1843-5262; Electronic ISSN 1843-536X DOI:10.15835/buasvmcn-asb:10590 Abstract Integrated aquaponic systems represent a viable solution for the continuing upward trend of humanity demands, as long as the balance between productivity and ϐinal products quality and biosecurity is found. To identify the quality, in terms of nitrite and nitrate concentrations, of both spinach and stellate sturgeon meat, obtained under different culture densities (spinach) and feeding regimes (stellate sturgeon), in an integrated aquaponic system. The experiment on spinach was made in triplicate, by using 3 stocking densities: (V1–59crops/ m 2 , V2–48crops/m 2 and V3–39crops/m 2 ). A 9 media grow bed hydroponic modules (LECA) and a 4 ϐish rearing units RAS were integrated, forming the integrated aquaponic experimental system. Fish were divided in 4 groups and were fed with 41% brute protein feed, at the following rations: F1-2.21%; F2-1.85%; F3-1.64% and F4-1.28% of total biomass. Chemical analyses concerning nitrite and nitrate levels were made on 5 samples, by using Griess method -STAS 9065:2002. A statistical signiϐicant difference (p<0.05) was recorded between V1 and V3, in terms of both nitrates and nitrites concentrations. Also, higher nitrite and nitrate concentrations were observed on spinach grown under aquaponic conditions, comparing with spinach derived from ϐield culture. Differences between F1 and F3, F4 nitrite and nitrate concentrations we observed to be signiϐicant (p<0.05). Considering the nitrite and nitrate concentrations, spinach grown in aquaponic conditions, as presented above, at densities of 59crops/m 2 and 48crops/m 2 , is marketable. Also, the level of ϐish meat nitrites and nitrates, from all 4 experimental variants, did not exceed the safety limits for human consumption. Keywords: aquaponics, nitrate, nitrite, spinach, stellate sturgeon INTRODUCTION In a time when sustainability and proϐitability are popular key words for every economic activity, the idea of integrating hydroponics production techniques together with intensive ϐish production ones has aroused enormous interest among both investors and environmental activists. Scientists have complied with this situation and as a direct result, many studies on integrated aquaponic systems that had analyzed crops growth perfor- mance and also their phytoremediation capacity were made (Adler et al., 2003; Endut et al., 2010; Rakocy et al., 1989). It has found that greenhouse hydroponics production could generate from ϐive to ten times more output compared to conventional agriculture (Hannan, 1998; Resh, 2001; Petrea et al. 2013 A). Dediu et al. (2012) and Metaxa et al. (2006) had stated that the process of by-products (wastes) revalorization from one species in a second crop generated by the co- cultured species enhances the proϐitability due to lower refreshment rate and water consumption or to the crop itself that represent another source of revenue for the farmer.