The upwelling of nutrients in the central Skagerrak

Measurements of inorganic nutrients during four expeditions to the Skagerrak, within the SKAGEX programme in 1990 and 1991, form the basis for estimation of the magnitude of potential new primary production caused by upwelling of nutrients in the central part of Skagerrak. Calculations have been made using available transport and upwelling data given in the literature together with the concentrations of nitrogenous nutrients (nitrite, nitrate and ammonia), phosphate and silicate in the lower part of the pycnocline in the upwelling area. The potential new production of organic matter due to upwelling is estimated at 6.15 × 106 t C year−1 based on a vegetative period of 8 months. This corresponds to 190 gC m−2 year−1 if distributed over the entire Skagerrak area. A possible contribution to diatom production from the upwelling of silicate is estimated to be 2.09 × 106 t C year−1, which corresponds to 64 gC m−2 year−1.