Water and nutrient fluxes from three coastal Mediterranean Rivers (N-E Algeria)

Abstract

The objectives of the present study were to estimate water delivery and dissolved nutrients loads (nitrogen N, phosphorus P and silicates Si) from three minors coastal rivers (about 14% of Algerian coastal watersheds). Freshwater flow dissolved inorganic nitrogen DIN (NH4, NO3 and NO2), dissolved organic nitrogen DON, dissolved inorganic phosphorus DIP, phosphate (PO4), dissolved organic phosphorus DOP and silicates SiO4 were measured monthly at River outlet in the year 2011. The rivers were characterized by high values of ammonia (NH4) and phosphate (PO4) which reveal the dominance of organic and domestic pollutions. In contrast, values of SiO4 were very low and will be in relation to the retention in dams. Dissolved nitrogen loads varied considerably from 43 to 227 kg/km²/y where DON formed 20 to 40%. Loads of total dissolved phosphorus (TDP) fluctuated in the range of 20- 80 kg/km²/y in which the organic fraction forms largely dominated (51 to 74%). At River outlets, the loading ratio of nutrients (Si: N: P) were altered by agricultural and household wastes. Here, Si:N and N:P mass ratios ranged from 3-6 and 10-20 respectively, indicating large N and P inputs. These biogeochemical conditions would induce deep impacts on the ecology and the productivity of the adjacent coastal waters.