Comparison of morpho-functional phytoplankton classifications in human-impacted shallow lakes with different stable states

Abstract

The morpho-functional classifications of phytoplankton have been recently proposed as useful tools in the aquatic biomonitoring. In this study, we compared three different classifications in a range of different environmental conditions, a set of six shallow lakes with different stable states. The studied lakes are located in the Pampa Plain from Argentina, a region highly impacted as a consequence of the human activities. Among the selected lakes, three are in a turbid state, two of which have high phytoplankton abundances (phytoplankton-turbid), and one shows a high concentration of suspended inorganic matter (inorganic-turbid). Two lakes are clear and profusely colonized by submerged plants (clear-vegetated). Only one lake shows a typical alternative steady-state behavior, shifting turbid periods of high phytoplankton biomass with periods of more transparency and development of submerged macrophytes. We compared the three morpho-functional classifications applied by means of multivariate analyses in order to explore how much the variance of the biomass of the phytoplankton functional groups (for each functional classification) was explained by the environmental variables. The analyses performed showed a clear separation of the human-impacted turbid lakes from the clear-vegetated lakes. The advantages and disadvantages of the different morpho-functional classifications are discussed, concluding that the functional approach is adequate to analyze the phytoplankton communities in aquatic systems subjected to anthropogenic influence and for monitoring them.