Transport of nutrients from the Seybouse River to Annaba Bay (Algeria, SW Mediterranean)

Abstract

Freshwater and dissolved nutrient inputs that entered the lower Seybouse River estuary were assessed in 2012 through a fortnightly surface water sampling both at a lower river station and at the estuary outlet. The Seybouse estuary delivered annually 950 × 10⁶ m³ of freshwater yielding 83 kg N km^-2 yr^-1 of N-NH₄ and 12 kg P km^-2 yr^-1 of P-PO₄. More than 2/3 of the annual inputs of freshwater, Si(OH)₄ and NO₃ entered the sea during the flooding event of late February 2012. Si-Si(OH)₄ and N-NO₃ yields in the Seybouse estuary represented <1/3 those of the Mediterranean rivers. Annaba Bay is subjected to highly polluted waters from the Seybouse estuary, with significant NH₄ (72 ± 37 μmol L^-1) and PO₄ (7 ± 4 μmol L^-1) amounts. However it is characterized by low Si(OH)₄ (104 ± 43 μmol L^-1) amounts. Alteration of Si:N:P ratios at this bay suggest potential risk of eutrophication, except during and weeks after flood episodes.

Keywords: Annaba Bay; Mediterranean Sea; Nutrients; River input; Seybouse River estuary; Si:N:P stoichiometry.