Vertical and temporal dynamics of phytoplanktonic associations and the application of index assembly in tropical semi-arid eutrophic reservoir, northeastern Brazil

Dinâmica vertical e temporal de associações fitoplanctônicas e aplicação do índice de assembleia em reservatório eutrófico tropical semi-árido, nordeste do Brasil

Aim

To determine the composition and biomass of functional groups around the vertical and temporal gradient correlated with environmental conditions and apply the index Q in a water-supply reservoir.

Methods

Water samples were collected monthly (n = 92) between 2009 and 2011 in two points of the dam for physicochemical and biological analysis.

Results

The pH, dissolved oxygen and water temperature showed significant differences between the photic and aphotic zones (p<0.05). The vertical variation of dissolved oxygen and water temperature, showed a profile of stratification. The phytoplankton community was represented by 11 functional groups: S1, M, H1, Lo, P, F, SN, J, W2, MP and R.

Conclusions

The vertical variations were less pronounced than the temporal variations in the phytoplankton community. The Q index pointed out poor water quality, corresponding to the current state of eutrophication in the reservoir and it was sensitive to responsive to environmental and hydrodynamic changes in these systems, demonstrating to be an appropriate tool for monitoring and evaluating the quality of water in tropical semi-arid reservoirs.

phytoplankton functional groups; stratification; Q index; reservoir; Cyanobactaria