Relationship between phytoplankton structure and environmental variables in tropical reservoirs with different trophic states

ABSTRACT Phytoplankton structure is influenced by environmental factors, seasonal cycles and the trophic state of the system. The objective of the present study was to identify guilds of phytoplankton species that are representative of seasonality and trophic status. We evaluated phytoplankton biomass and species composition in five tropical reservoirs, with different trophic states and during rainy and dry periods. At most of the sampling sites, total biomass was higher during the rainy season. Moreover, high cyanobacterial biomass was observed in all reservoirs except for one of the mesotrophic reservoirs, which had no significant contribution from the group. Phytoplankton guilds associated with the trophic gradient and seasonality were identified. Additionally, trophic status was determined to be the most important community structure factor. The results emphasize the importance of taxonomic identification when monitoring phytoplankton structure and autoecology. Furthermore, these aquatic organisms are highly sensitive to environmental variations, making them useful tools for evaluating and/or monitoring the ecological condition of aquatic ecosystems.