As one of the key nutrients occurring in aquatic ecosystems, nitrogen supports along with phosphorus, carbon and silica the primary production by higher plants and algae. This paper presents the percentage distribution of both the oxidized and reduced inorganic N species (NO2 -, NO3 -, NH4 +) and organic N fraction from Somova-Parches, an aquatic complex situated in Danube Delta Biosphere Reserve, Romania in the proximity of Tulcea town. The surface water samples were collected in 2018, in spring, summer and autumn seasons, according to European Standards. Analytical determinations of nitrogen forms were performed in the accredited chemistry laboratory of Danube Delta National Institute, using spectroscopic methods. Our results showed that the concentrations of organic nitrogen frequently exceed in all periods that of inorganic nitrogen, including ammonium, nitrite and nitrate. This observation suggests that organic nitrogen components play an active role in the biological/ ecological processes of this aquatic ecosystem. The percentage distribution of the nitrogen forms in the studied lakes from Somova-Parches complex ranged between 63% and 74% in the spring season, 89% and 96% in the summer season and between 95% and 97% in the autumn season. Inorganic forms of nitrogen remain relatively constant for ammonium and nitrite; in nitrogen cycle, nitrites appear as intermediates forms that depending on the environmental conditions are easy transformed into nitrates or ammonia. For nitrates a higher variation of the values, between 22% and 32 %, was observed in this aquatic complex. Acknowledgement: This work was supported by the project BSB27 - MONITOX funded by the Joint Operational Programme Black Sea Basin 2014-2020. The content of this publication is the sole responsibility of the authors and in no way reflect the views of the European Union.