Functional phytoplankton distribution predicts the environmental variability between two subtropical rivers

Abstract

The diversity of phytoplankton traits provides a powerful means of addressing ecological questions and can be adopted to simplify and predict the community structure and the function of the multiple environmental filters that operate in the different ecosystems. We evaluated the response of phytoplankton functional groups in samples from two subtropical rivers, identifying the main environmental filters associated with the presence of the different groups and their functional traits during a seasonal cycle. Using multivariate analysis, we found environmental dissimilarity that was predicted by the presence of different functional groups (FGs) in the two rivers. Six FGs were recorded: J (chlorophyceans chlorococcales), M (colonial cyanobacteria), N (desmids), W1 (euglenophyceans), X2 (flagellated unicellular chlorophyceans) and F (flagellated colonial chlorophyceans). The FGs J, M and N were exclusive to Cascavel River, while X2 and F were exclusive to Quati River. The FG W1 was recorded in both rivers; however, its greatest contribution was in Quati River. Thus, the FGs reflected the environmental dissimilarity, mainly related to the conditions of water flux, conductivity, light availability and depth of the environments. Based on these results, the functional groups are considered to provide a relevant tool in phytoplankton ecology, offering a practical means of investigating the relationship between phytoplankton and ecosystem functioning, and contributing to the management and conservation of biodiversity in lotic environments.