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

Abstract

AimTo 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.MethodsWater samples were collected monthly (n = 92) between 2009 and 2011 in two points of the dam for physicochemical and biological analysis.ResultsThe 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.ConclusionsThe 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 scenario and microcystin in water during extreme drought in semiarid tropical water supplies, Northeastern Brazil

“…High levels of total phosphorus and biomass of potentially toxic cyanobacteria were also found. In this condition of drastic reduction of water volume and high turbidity, our results evidenced the permanence and high eutrophic state and the dominance of cyanobacteria in the five reservoirs studied, reinforcing the results obtained in other studies carried out in the same reservoirs (Fonseca et al, 2015;Vieira et al, 2015;Panosso et al, 2007;Eskinazi Sant'Anna et al, 2013;Costa et al, 2009). In the same way, this same scenario is configured in studies carried out in other reservoirs located in the same basin (Freitas et al, 2011;Bezerra, 2011;Medeiros et al, 2015).…”

“…Tropical shallow lakes were studied in extreme events in Rio Grande do Norte (Castro et al, 2011), reinforcing the fact that cyanobacteria dominate, high trophic levels and high values of algal biomass in this type of environment. Other studies in the same region report the change in the phytoplankton dynamics and nutrients in the same environments of this study (Costa et al, 2009;Dantas et al, 2012;Vieira et al, 2015). The data obtained expose a fragility of these environments to anthropogenic activities, typical of semi-arid shallow lakes as reported by Fragoso Júnior et al (2010) in studies of reservoirs in the Brazilian Northeast.…”

“…In relation to total phosphorus (PT) levels, the five reservoirs analyzed presented extremely high concentrations. In ARG we detected values lower than those found by Vieira et al (2015), when it presented volume reduction of only 12%, and higher than the value observed by Costa et al (2009), when the reservoir was 100% full.…”

“…The total biomass of phytoplankton is higher in all reservoirs compared to values found by Costa et al (2009) and Vieira et al (2015), with the exception of PT. ARG shows an increase ratio of 442%, while in BQ it is 540%; GAR of 530% and IT about 90% ( Table 1).…”

Analysis of the phytoplankton community emphasizing cyanobacteria in four cascade reservoirs system of the Iguazu River, Paraná, Brazil

“…Vieira, Cardoso and Costa (2015) had similar results in their research: gradual density decrease of M. aeruginosa allowed an increase in the diversity and the coexistence with cyanobacteria species from functional groups S1, SN, M Lo and H1.…”