Weather driven influences on phytoplankton succession in a shallow lake during contrasting years: Application of PROTBAS

A dynamic model which simulates variations in the biomass of several phytoplankton functional groups (PROTECH) has been reconstructed into the PROTBAS (PROTech Based Algal Simulations) model, and was tested in a large (61 km2), shallow (mean depth 3.4 m) wind-exposed lake basin at the western end of Lake Mälaren, Sweden. A subroutine was added to the model to estimate the variation in light extinction resulting from wind action and river discharge. Also the rate of regeneration of nitrogen and silica was modified. The model captured the overall magnitude and succession of phytoplankton during two contrasting years: a warm and calm calibration year, and a cold windy validation year. The model shows good behavior in the northern temperate climate, which includes ice cover during winter. However, there were discrepancies between measured and modeled spring growth and autumn decline of the phytoplankton.