Abstract
Phytoplankton and environmental variables were studied during a year in a shallow eutrophic lake and its inflow in the ‘depressed Pampa’ of Argentina. The taxa were classified according to the competitors, stress tolerators, ruderals and intermediate categories (CSR) model and were allocated to morpho‐functional groups (MFG). As was expected according to the trophic state, scarce transparency and mixing condition, the R‐strategists (several cyanobacteria and pennate diatoms) dominated almost all of the study period. C‐strategists were more scarce and favoured by short periods of transparency, whereas only three species were attributed to the S‐strategist category. Each MFG was represented by a single species at a time, resulting in a high functional miscellany in this shallow lake. Thus, we can assume that the CSR approach is a useful tool to explain the success of the different species of phytoplankton in this shallow lake.