The phytoplankton community as a descriptor of environmental variability: a case study in five reservoirs of the Paraná River basin

Abstract

Aim We aimed to characterize the structure of the phytoplankton community and identify the main environmental factors driving the community in five reservoirs constructed in the region of the high Paraná River. Methods The phytoplankton and environmental variables were collected at the lacustrine region of the reservoir, between November 2013 and November 2014, with interval between collections ranged from 3 to 6 months. The richness and biomass of the phytoplankton community were measured as a response to the spatial and temporal environmental variability. Data from environmental variables was analyzed by Principal Component Analysis (PCA). Non-Metric Multidimensional Scaling Analyzes (NMDS) were performed on the richness and biomass data of the phytoplankton community. Results We identified 80 taxa distributed in 11 taxonomic classes, from which Cyanobacteria and Chlorophyceae were best represented. We did not observe significant temporal variation for either environmental variables or attributes of the phytoplankton community, which may be related to the prolonged drought in this period in the Brazilian Southwest. Higher phytoplankton richness and biomass were found in the Três Irmãos (Tiete River), reservoir located in the most anthropized basin in the country. Cyanobacteria and dinoflagellates dominated the biomass in all reservoirs during the studied period. The Ilha Solteira, Jupiá and Porto Primavera reservoirs showed a tendency to decrease in the values of phytoplankton richness and biomass, and the reservoirs built in series in the Paraná River probably have strong interdependence, according to the CRCC concept. Conclusions Spatial variation in phytoplankton attributes was influenced mainly by the position occupied by the reservoir in the hydrographic basin, water retention time (RT) and nutrient concentrations in each reservoir.

Spatio-temporal water quality variability and regionalization of tropical reservoirs based on Landsat imagery

“…Although most correlations between bio-optical and meteorological parameters were weak (<0.4) and there was no strong correlation (Fig. 8), in agreement with previous observations for these reservoirs of Paraná River based on a shorter time span analysis, 71 we have observed both monthly and intra-annual variation of the studied parameters related to seasonality. Our low correlation values may be biased by only a moderate determinant coefficient R2=0.4 in the statistical models, but it may be enough to be characterized as a functional tool 3 …”

“…Our surface water temperature data for all reservoirs matches with those collected in situ 71 – 73 as well as in situ measurements of chl-a density for Três Irmãos varying from 0.1 to 5.0 μg/L (X¯: 1.0 μg/L) 47 and for Ilha Solteira 0.4 and 13.8 μg/L (X¯: 4.6 μg/L), 34 indicating the robustness of our remote sensing analysis. In contrast to our data, it is expected that chl-a density starts to increase at the end of fall, after the wet season that is characterized by high precipitation, constant temperature above 30°C and intense fluvial discharge, culminating in higher nutrient inflow 74 .…”

“…It is noteworthy that the Três Irmãos HPP was built in 1991 so the values observed in between 1985 and 1990 correspond to the natural course of the river and strongly deviate from the conditions found in the area after the establishment of the reservoir. For all reservoirs, an extremely high peak between 2013 and 2015 was the unique abrupt oscillation recorded, which is related to a severe drought period also mentioned in the ecological study for the upper Parana River region 71 . These authors did not record significant temporal variation for either environmental variables or phytoplankton richness and biomass for the reservoirs of Ilha Solteira, Jupiá, Três Irmãos, Porto Primavera, and Rosana.…”

“…These authors did not record significant temporal variation for either environmental variables or phytoplankton richness and biomass for the reservoirs of Ilha Solteira, Jupiá, Três Irmãos, Porto Primavera, and Rosana. Then, hydrological changes probably primarily drive a modification in chl-a and dissolved nutrients concentrations 52 , 71 …”

“…Also, the clustering of all reservoirs will be probably undone with addition of meteorological conditions, which have recorded quite distinct values between SSMS and ISMS. Phytoplanktonic biomass is associated with the chemical, hydrological and morphometric traits of the reservoirs and its production depends on several interconnected factors, including climatic and hydrological patterns, size of the waterbody, basin morphology, river volume and nutrient availability, 71 , 74 as such, it is important to analyze the reservoirs individually and understand how these factors are correlated in each study location.…”