Spatial and temporal dynamics of functional groups of phytoplankton in a shallow clear-water tropical lake

Luciana Gomes Barbosa


Abstract: The functional groups of phytoplankton are known to change in response to certain environmental variables, according to niche preferences. Objective: To evaluate the structure and dynamics of functional phytoplankton groups (FGs) over a macrophyte cover gradient and their relations with environmental variables in small, shallow clear-water lake (Paraiba, Brazil). Methods: physical, chemical and biological analyses of the water were made between August 2014 and June 2015 at three points on the SantaLucia lake. The Tukey and Wilcoxon tests were applied to the data followed by CCA and Anova. Results:high transparency (≥ 1), alkaline pH (≤0,05) and high temperatures (≤0,01)were registeredand CCA showed thattotal phosphorus (≤0,07) and orthophosphate levels  (≤0,05) influenced the dynamics of functional groups. Significant differences in the time scale were only observed in 2015 for temperature, dissolved phosphorus and conductivity.Due to the shallow depth, higher rainfall in 2015 and hydrodynamic processes certainly contributed to the mixing of the water column. Spatial differences in the phytoplankton biomass were not detected by Wilcoxon (p≥ 0.05). Eight functional groups were identified: N, K, S1, X1, W2, TD, SN, S1 and P. S1 and K persisted in almost every month, associated with species adapted to shade and warm alkaline water. The N group typical of clear water is sensitive to high pH.  Thus, the biomass and macrophyte cover gradient remained stable temporally and spatially. In contrast, the heterogeneity in the environment was crucial in the structure of the functional groups in response to certain environmental variables and according to their niche preferences, confirmed by canonical correspondence analysis (CCA). Conclusion: the functional groups responded to physical, chemical and climatic variations in the water, and to pH, temperature and total phosphorus, influencing the structure and composition of phytoplankton.

Keywords: macrophytes, heterogeneity, turbidity, environmental variables.


macrophytes, heterogeneity, turbidity, environmental variables

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