The considerable increase in the amount of nitrogen in the surface water is a major environmental problem. It has become a great matter of worry because of the multiple environmental effects including eutrophication and health risks. The El-Kebir West watershed is a coastal plain in northeastern Algeria.This study aims to determine the physicochemical quality of waters of the western WadiEl-Kebir and its main tributariesand also to evaluate the spatiotemporal variabilityof its physicochemical quality in particular of mineral nitrogen during wet and dry periods. Four sampling campaigns were realized as follows: January 2015 and February 2016 corresponding to water high season and in March and September 2016 corresponding to the low season. The water samples were obtained from the seven stations located along western Wadi El-Kebir. Temperature, pH,conductivity,dissolved oxygen,SO42-, PO43-, NO3-, NO2-and NH4+ were measured either in situ or in the laboratory.A statistical treatment employingthe PCA method (The Principal Components Analysis) was applied for all the obtained results. It has been noticed that the S2 and S3 upstream stations are very rich in ammonium (NH4+) at the low water period with average values of 15.22 mg/L and 20.41 mg/L, respectively.This study has shown the influence of seasonal variations and anthropogenic activities on the evolution of physicochemical settings, in general, and on mineral nitrogen in particular. In conclusion,the waters of Wadi El-Kebir were of an average to poor quality.

The present study was designed to display the integrated model of nitrogen discharge process (i.e. nitrites and nitrates; ammonia; chlorophyll and dissolved nitrogen, dissolved oxygen) which is part of the complete model of shrimp aquaculture of an Integrated Shrimp Aquaculture Park (i-Sharp) ecosystem in System Dynamic Model Aquaculture-System Policy (SD-AQEP). This study offers a comprehensive elaboration concerning the long-term process of nitrogen accumulation, as well as its effects on shrimp activities. Furthermore, the analysis of the model and the simulation results also show the conditions of nitrogen with several strategies for control and manipulation. For example, in situations where mixing of stock density is high and providing feed into ponds supplies is excessive, the nitrogen dynamic rapidly hits alarming levels. Aforementioned, the typical strategy in this setting such as stocking density and the best time to harvest could be established. Additionally, the model structure represents the discharge derived from the nitrogen process on varied settings of variables in aquaculture development. In conclusion, this model provides an experimental simulation platform that can be implemented by policy makers on long-term strategic management for developing or maintaining large-scale aquaculture development projects in the future.