Distinct hydrological scenarios influence phytoplankton community in urban lakes

Aim The objective of this study was to investigate the distribution of phytoplankton and the presence of indicative species of different hydrological scenarios, such as drought and rainfall, in a set of tropical urban lakes. Methods Samples were collected from 14 urban lakes distributed across different regions of Goiânia, Goiás, Brazil. Two samples were taken: one during the rainy season and one during the dry season. For each lake, we collected phytoplankton data, as well as data on water temperature, pH, electrical conductivity, dissolved oxygen, turbidity, and the concentrations of total phosphorus, orthophosphate, nitrate, ammoniacal nitrogen, and chlorophyll-a. These variables were used as indicators of environmental variability. Results A total of 173 taxa were recorded during the rainy season, compared to 165 during the dry season. We evaluated the constancy of each taxa in the sampled lakes during both hydrological periods, identifying similarities between the seasons and notable contributions from rare species. Additionally, Principal Coordinate Analysis (PCoA) revealed greater variability in taxonomic composition between lakes during the dry season. For density, however, variability remained consistent throughout both seasons. The Permdisp indicated that these differences in variability within each season were not significant. However, Permanova identified differences in environmental and community structure between seasons. Finally, an indicator species analysis (IndVal) identified eight indicator taxa: five for the rainy season and three for the dry season. Conclusions The composition and density of the phytoplankton community in tropical urban lakes varies between the dry and rainy seasons, with distinct indicator species characterizing each season. During the dry season, greater variability in environmental conditions was observed between lakes, particularly with regard to higher concentrations of nutrients, electrical conductivity and turbidity. Thus, this heterogeneity was important for the selection of species with different adaptive strategies.