Vertical distribution of phytoplankton functional groups in a tropical shallow lake: driving forces on a diel scale

aim: this study analyzed the vertical distribution of phytoplankton functional groups in two diel cycles in a warm monomictic shallow tropical lake; methods: sampling of the abiotic variables, phytoplankton and zooplankton communities was performed at intervals of 3 hours over 24 hours in vertical profiles, in the stratification (february) and circulation (july) periods; results: the high thermal stability and the partial atelomixis favored the coexistence of functional groups that are sensitive to destratification, na and f, composed by desmids and chlorophyceae coccoids, and groups s2 and lo, which persisted during the circulation, and were composed by filamentous cyanobacteria which do not fix n2 and dinoflagellates, respectively. the discontinuity in the vertical distribution of the functional groups, with dominance of na and f in the epilimnion and r and lo in the metalimnion and hypolimnion, was characteristic of the stratification, and differences between the daytime and nighttime periods were not significant. conclusions: the reduction of 80% of the biomass of the na group during the mixing period indicates the influence of thermal stability and partial atelomixis as determinant factors in the compartmentalization of functional groups, restricting daytime vertical migration (dvm) and loss by sedimentation during the stratification period.