Abstract
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.
Highlights
Phytoplankton are one of the most efficient indicators of changes in the ecological condition of an aquatic ecosystem, participating as primary producers, with a short life cycle and a wide spatial distribution (Padisák et al 2009)
There is a well-established relationship between nutrient concentrations and the taxonomic composition of phytoplankton (Becker et al 2009), and it is known that changes in the community structure are related to differences in nutrient absorption and storage, as well as population growth and loss rates (Watson et al 1997)
We demonstrated that the phytoplankton structure is influenced by seasonality, characterized by fluctuations in water temperature and nutrient concentrations during rainy and dry periods, resulting in higher biomass in most of the reservoir sampling sites studied
Summary
Phytoplankton are one of the most efficient indicators of changes in the ecological condition of an aquatic ecosystem, participating as primary producers, with a short life cycle and a wide spatial distribution (Padisák et al 2009). The morphological characteristics of reservoirs can be manipulated by seasonal cycles and environmental factors, as well as the frequency and intensity of anthropogenic practices, culminating in a competitive environment where the best-adapted species prevail (Padisák et al 2010). This competition can be Simone Alves de Oliveira, Carla Ferragut and Carlos Eduardo de Mattos Bicudo detected at the floristic and structural levels, by monitoring changes in algal class biomass distributions (Naselli-Flores et al 2007). The composition and structure of phytoplankton are considered to be fundamental components of aquatic ecosystem metabolism (Calijuri et al 2002)
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