To model Skeletonema costatum blooms and their relationship with environmental parameters in situ, a S. costatum-specific zero-dimensional box model based on the mechanistic model Eco3M was established using physiological features. The parameters were calibrated using experimental counterparts, and simulations were compared with published laboratory findings. The resulting normalized objective function （NOF） values are less than 1.0 （and in most cases less than 0.58） and the values for the slope y （between 0.656 7-1.127 4） and R2 （between 0.806 8-0.971） are close to 1.0 for most of the sub-figures. This indicates good agreement between simulated and measured data and suggests that the model reproduces the general characteristics of S. costatum growth and use of nutrients under different N- or P-limiting conditions. The model is appropriate for further applications and can be used to test more scenarios using other nutrients.
A Lagrangian model is used to evaluate source regions of particles collected in the sediment traps at the DYFAMED （Dy namique des Flux Atmospheriques en Mediterranee） station by tracking particles backwards from March 1 to August 31, 2001. The analysis suggests that source regions depend on the flow fields, the settling speed of the particles, and the deployment depths of the traps. Monthly variation is observed in the distribution patterns of source regions, which is caused by the currents The source regions are located around the traps and up to hundreds of kilometers away. As the settling speed increases with the particle diameters, the distance to the source regions decreases. The vertical flux can be approximately estimated in 1D for the particles with diameters larger than 500 lain. Furthermore, traps moored at various depths at the DYFAMED can collect parti- cles that originated from different regions in the Ligurian Sea.
