The Transmission Effectiveness of the Dissolved Nutrients (N, P, Si) Through a South Mediterranean Estuary (Seybouse, Algeria) Under Large Anthropogenic Forcing

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Asian Journal of Water, Environment and Pollution
Abstract: The Seybouse Estuary (SE) is the downstream of the second great river in Algeria draining one of themain country’s watersheds (6471 km2, 1.5 million inhabitants). This study highlights the effect of the estuarinepart on the distribution and the flux of dissolved nitrogen (N), phosphorus (P) and silicon (Si) through the SE.Surface water sampling was taken and analysed in the dry (September 2016) and wet (April 2017) seasons. Physicalparameters and water dischargedata were jointly recorded in parallel to sampling dates. Very low flows varyingbetween 0.3 and 4.7 m3 s-1 were recorded at the outlet in dry and wet seasons, respectively. The SE outlet waterswere 2.6 and 10 folds higher than upstream in dissolved inorganic nitrogen (DIN) and phosphates (PO) levels,respectively. However, the silicates (SiO) levels decreased by about 1/2 in the outlet waters. In terms of flux, theSE delivered to the coast 84 t·yr-1, 9 t·yr4-1 and 56 t·yr-1 of DIN, PO4 and SiO41, respectively. The high DIN:PO=137 and low SiO:DIN = 0.52 molar ratios classify SE as one of the strong anthropised estuaries. The estuarinepart amply modifies cycles and budgets of riverine nutrients introduced to the coast.