Effect of sediment resuspension on the cycling of nutrients in the East China Sea

Abstract

The continental shelf with strong bottom tidalcurrents, such as the East China Sea (ECS), is generally characterized by the relative high planktonic productivity compared to the stratified open ocean water. We hypothesized that tidal stirring of the bottom sediment rich in planktonic or other biogenic matter might enhance the dissolution or decomposition of their components due to theincreased collision and subsequent breakdown and further dissolution or decomposition reaction of suspended bottom sediments near the sea floor, particularly in the suspended matter rich nepheloidlayer as the tidal energy being dissipated along the sea floor. The resuspension effect of sediment on the nutrients regeneration within water column was studied by shaking or non-shaking bottles, containing seawater only and seawater with the surface sediment from three different sites including one site with high turbulent kinetic energy in the ECS. Inorganic nutrient concentrations were measured at the 1-3 day intervals for two weeks. The anomaly of nutrientconcentration between shaking bottles and nonshaking bottles implies the sediment resuspensioneffect on the nutrient concentration. The phosphate and nitrate concentrations clearly showed logarithmic increase during the shaking experiment, suggesting positive sediment resuspension effect on the nutrient regeneration within the incubation bottle. The portions of phosphate and nitratng of the bottom sediment rich in planktonic or other biogenic matter might enhance the dissolution or decomposition of their components due to theincreased collision and subsequent breakdown and further dissolution or decomposition reaction of suspended bottom sediments near the sea floor, particularly in the suspended matter rich nepheloidlayer as the tidal energy being dissipated along the sea floor. The resuspension effect of sediment on the nutrients regeneration within water column was studied by shaking or non-shaking bottles, containing seawater only and seawater with the surface sediment from three different sites including one site with high turbulent kinetic energy in the ECS. Inorganic nutrient concentrations were measured at the 1-3 day intervals for two weeks. The anomaly of nutrientconcentration between shaking bottles and nonshaking bottles implies the sediment resuspensioneffect on the nutrient concentration. The phosphate and nitrate concentrations clearly showed logarithmic increase during the shaking experiment, suggesting positive sediment resuspension effect on the nutrient regeneration within the incubation bottle. The portions of phosphate and nitrat