Heiskanen, A. Finnish Environment Institute, anna-stiina.heiskanen@vyh.fi

 
SEASONAL FLUXES OF NITROGEN AND PHOSPHORUS IN THE PELAGIC ECOSYSTEM OF THE NORTHERN BALTIC SEA
 
The seasonal fluxes of nitrogen and phosphorus were estimated for the pelagic ecosystem in the coastal northern Baltic Sea, where simultaneous measurements of primary production, sedimentation of C, N and P, and carbon biomass of the autotrophic and heterotrophic planktonic organisms have been carried out during spring and summer. The measured export flux was considered to approximate new production. The fraction of algal production based on regenerated nutrients was estimated as a difference between total production and export flux. In order to verify whether this would match the potential nutrient recycling by pelagic heterotrophs, assimilation and regeneration were calculated using stoichiometric ratios between the carbon based production and biomass values. The magnitude of additional (external or internal) nutrient input, needed to balance the nutrient requirements of the pelagic system was assessed. In addition to physical transport, vertically migrating dinoflagellates may have carried nutrients from the deeper strata in spring. In summer, the estimated heterotrophic mineralization did not satisfy the total nitrogen requirement of the autotrophs, thus external nutrient sources, such as episodic upwellings, wind mixing, diffusion, or cyanobacterial nitrogen fixation, were required.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: SS39TH0778S