Variability in the structure and dynamics of the microbial planckton community in a coastal upwelling system

Abstract

The dynamics of the microbial plankton community in the coastal upwelling system of the Ría de Vigo (NW Iberia) was studied during four periods of the seasonal cycle (winter, spring phytoplankton bloom, summer stratification and autumn upwelling) using a mesocosm approach. The data obtained were interpreted using a simple NPZD model, which was also utilized to characterize the functional aspects of the microbial community. Although modeling has traditionally been used for predictive purposes, it was here used to interpret the bulk dynamics of the community. When simulating the four experiments, the strategy was to keep without modification as many model parameters as possible. Seeing which parameters had to be varied to accurately simulate the data gave important clues on significant aspects of the community structure and processes which differed between seasons and influenced the plankton dynamics in the bags. With this procedure, differences between plankton community structure and dynamics could be explained by just varying a few parameters (as phytoplankton maximum growth rate, bacterial growth efficiency, and grazing or sedimentation rates) of the forty parameters used in the model