Modeling responses of diatom productivity and biogenic silica export to iron enrichment in the equatorial Pacific Ocean

摘要: [1] Using a three-dimensional physical-biogeochemical model, we have investigated the modeled responses of diatom productivity and biogenic silica export to iron enrichment in equatorial Pacific, compared model simulation with situ (IronEx II) fertilization results. In eastern an area 540,000 km2 was enhanced by changing photosynthetic efficiency silicate nitrogen uptake kinetics phytoplankton for period 20 days. The vertically integrated Chl primary production increased about threefold 5 days after start experiment, similar that observed IronEx II experiment. Diatoms contribute initial increase total biomass, but decrease sharply 10 because mesozooplankton grazing. surface nutrients (silicate nitrate) TCO2 anomaly fields, obtained from difference between “iron addition” “ambient” (without iron) concentrations, also agreed well observations. enriched patch is tracked inert tracer SF6 used II. depth-time distribution sinking (BSi) indicates it would take more than 30 injection detect any significant BSi out euphotic zone. Sensitivity studies were performed establish importance fertilized size, duration fertilization, role A larger size tends produce broader extent longer-lasting blooms. Longer prolongs growth, higher zooplankton grazing pressure prevents biomass accumulation. With same treatment lowering rate generates much stronger bloom, terminated Si(OH)4 limitation rapid increase. Increasing rate, due addition stays at minimum level, small tend numerical experiments demonstrate value ecosystem modeling evaluating detailed interaction biogeochemical cycle Pacific.