Phytoplankton structure and diversity in the eutrophic-hypereutrophic reservoir Paso de las Piedras, Argentina

Abstract

This study aimed at analyzing the phytoplankton structure and dynamics in Paso de las Piedras Reservoir, Argentina, through the study of dominant species, diversity and similarity in relation with the abiotic environment. Samples were collected weekly or biweekly (January 2004-June 2005 at four sampling stations. The reservoir experienced a seasonal progression in phytoplankton composition that underlines six successional periods, each one characterized by the dominance of one or a few species. Cyanobacteria, green algae and diatoms were the most important constituents of the reservoir's phytoplankton. Cyanobacteria dominated during summer and early autumn, green algae during late autumn and early winter, and diatoms during winter and spring. A high abundance of R. lacustris (Cryptophyceae) was observed during late September and early October. The general pattern of species succession is coherent with the general model of plankton seasonal succession described by the PEG model; however, the major discrepancy is the extremely short clear water phase observed. Successional periods were associated with changes in abiotic variables, and they showed differences in ecological traits. Cyanobacteria-Dictyosphaerium, Cyclotella, Stephanodiscus and Anabaena-diatom periods were characterized by a low number of cells, high diversity, with both dominance and specific richness low. On the contrary, during Cyanobacteria and Cyanobacteria II periods, the highest abundance was observed associated with low diversity and high dominance.

Spatio-temporal variations of phytoplankton structure and water quality in the eutrophic freshwater reservoir of Macau

“…Phytoplankton experienced low growth rates in January-March 2011 and January-June 2012, and the dominant organisms changed from Cyanophyta to Chlorophyta and Bacillariophyta, which was also observed in Fernán-dez et al [12]. However, the explanations for such a change were complicated, and the physical disturbances due to temperature and partial change of the raw water from the mainland China would probably be the major two reasons.…”

“…Cyanophyta, Chlorophyta, and Bacillariophyta were the most important phytoplankton constituents in MSR, which was observed in other trophic reservoirs [7,12]. Both the total phytoplankton and Cyanophyta exhibited larger densities during hypereutrophic period of 2011, and the dominance of cyanobacteria in eutrophic reservoirs has been mentioned in the previous studies [12,44,45], involving the factors to favor cyanobacterial blooms: high nutrient status and high WT [45][46][47].…”

“…Both the total phytoplankton and Cyanophyta exhibited larger densities during hypereutrophic period of 2011, and the dominance of cyanobacteria in eutrophic reservoirs has been mentioned in the previous studies [12,44,45], involving the factors to favor cyanobacterial blooms: high nutrient status and high WT [45][46][47]. Interestingly, starting from the late summer to the end of 2011, Cylindrospermopsis spp.…”

“…Actually, the TP and Chl-a were parameters used in calculating the TSI of the reservoir, while NO 3 -N is the most important nutrient factor for phytoplankton growth. In spite of TP being a relatively independent factor in MSR, it was often selected as one of the most important parameters to monitor and reported as the environmental factor affecting the blue-green algae biomass [12,60].…”

“…Previous studies on reservoirs have generally dealt with the structural compositions of the phytoplankton community, focusing on the taxonomic surveys and ecological studies [6][7][8]. Diversity and community comparison indices of Shannon-Wiener diversity, Simpson diversity, Pielou's evenness, Stander's similarity index (SIMI), and Margalef's richness have been recognized as useful ways for analyzing phytoplankton structure in different water bodies all over the world [9][10][11][12].…”