The benthic fluxes of nutrients and the potential influences of sediment on the eutrophication in Daya Bay, South China

Abstract

Nutrient concentrations in porewater and their benthic fluxes were investigated in Daya Bay, South China, to study the accumulation and transfer of nutrients at sediment-water interface, as well as the impact of human activities on nutrients. The contributions of sediment to nutrients in water column and the potential influences on eutrophication were also discussed. Nutrients in porewater and overlying water changed in different seasons and areas, which was mainly attributed to human activities, hydrodynamic force and biogeochemical conditions. Mean concentrations of DIN (dissolved inorganic nitrogen), PO₄ and SiO₃ were 70 ± 61, 3.1 ± 4.3, 103 ± 105 μmol/L, and 234 ± 166, 15.6 ± 4.0, 353 ± 48 μmol/L in overlying water and porewater, respectively. Annual mean DIN, PO₄ and SiO₃ fluxes were 330 ± 249, -1.3 ± 16 and 549 ± 301 μmol/(m²d), respectively, indicating that sediment was generally the source of DIN and SiO₃, but was the sink of PO₄. The mean exchange capacities were (7.8 ± 5.5) × 10⁷, (-1.2 ± 34.0) × 10⁵ and (1.2 ± 0.6) × 10⁸ mol/a for DIN, PO₄ and SiO₃, respectively, in Daya Bay.

Keywords: Concentration; Daya Bay; Flux; Nutrient; Sediment influence.