Using morphofunctional characteristics as a model of phytoplankton dynamics in a tropical reservoir

The study of phytoplankton morphological characteristics, using the morphology-based functional classification (MBFG), reflects the different abilities for absorption of light and nutrients, growth, mechanisms for preventing sedimentation and predation in the aquatic ecosystem and can be a model in simplification of the phytoplankton community dynamics in the reservoirs. This study that was developed in a tropical reservoir aimed to evaluate which phytoplankton morphofunctional characteristics are selected by the spatial and temporal heterogeneity in the reservoir, and how these characteristics are related to the environmental conditions. For this, phytoplankton and environmental variables were sampled in different sites along the spatial extent of the reservoir during dry and rainy periods. The lotic region showed the greatest environmental dissimilarity in relation to the other regions, both in the dry and rainy periods. Differences in density of all MBFG were verified along the spatial extent of the reservoir, with higher values in the lentic region, while differences between hydrological periods were verified for MBFG I (small organisms with a high surface/volume ratio), MBFG IV (medium-sized organisms without specialized traits) and MBFG VII (large mucilaginous colonies). The conditions of pH, temperature and turbidity were important in the selection of the morphofunctional characteristics and in MBFG dynamics. Therefore, the use of MBFG can be a form of simplification of the relationship between phytoplankton and environmental heterogeneity, reflecting the reservoir functioning.