Effect of physical factors on the vertical distribution of Phytoplankton in Eutrophic Coastal waters

Abstract

A new analytical model for the vertical distribution of phytoplankton in shallow, turbid waters is presented. The effects of vertical mixing, light-attenuated growth and algal-cell sinking rates are included. The two cases of a finite-depth water column and a mixed layer are investigated.

The results for negatively buoyant cells suggest that concentration maxima can occur above the sea bed for either strong or weak mixing in a mixed layer but are always at the bed in finite-depth waters. Large-celled species with high sinking rates are least sustainable in stable water columns, especially a weakly mixed, mixed layer. Conversely, cell sinking rates have little effect on net growth rate when mixing is strong in finite-depth waters. The effect of turbidity on net growth is accentuated under weakly mixed conditions. Comparison with field data shows quite good agreement with the model predictions and underlines the fact that simple analytical tools are often quite adequate when dealing with a sparse experimental data base.