Abundance and diversity of phytoplankton in the Paraná River (Argentina) 220 km downstream of the Yacyretá reservoir

Abstract

Patterns in the temporal composition, abundance and diversity of the phytoplankton community of the Paraná river prior to and after the initial filling phase of the Yacyretá reservoir are analyzed. The study site is located 220 km downstream from the Yacyretá reservoir and 30 km downstream from the confluence with the Paraguay river. Because both rivers remain separate and unmixed at the study site, we compared the possible effects of the impoundment on both river banks (left and right banks) in hydrological periods with similar duration and magnitude of the low and high water phases. Physical and chemical conditions measured on the right bank (water from the Paraguay river) were similar at both periods (pre and post-impoundment) whereas conductivity, pH and orthophosphate concentration increased on the left bank (water from the High Paraná river and Yacyretá reservoir) after the impoundment. Changes in phytoplankton density and diversity were observed only in samples collected from water flowing from the reservoir (left bank). The density of Chlorophyceae (Chloromonas acidophila, Chlamydomonas leptobasis, Choricystis minor, Chlorella vulgaris, Scenedesmus ecornis, Monoraphidium minutum, M. contortum and M. pusillum) and Cryptophyceae (Rhodomonas minuta, Cryptomonas marssonii and C. ovata) increased while Cyanophyceae (Cylindrospermopsis raciborskii, Raphidiopsis mediterranea and Planktolyngbya subtilis) and Bacillariophyceae (Aulacoseira granulata and its bioforms) decreased compared to previous studies conducted on the left bank of the Paraná river. Phytoplankton collected from the right bank of the river did not differ in pre and post-impoundment samples because they originate from the Paraguay river, which remains relatively unaffected by human activities.Keywords: temporal and spatial variation, diversity, large rivers, pre and post-impoundment. Abundância e diversidade do fitoplâncton do Rio Paraná (Argentina) 220 km a jusante do Reservatório de Yacyretá ResumoEstudaram-se os padrões temporais de composição, abundância, e diversidade da comunidade fitoplanctônica do Rio Paraná, antes e depois da fase inicial de fechamento do reservatório de Yacyretá (períodos pré e pós-fechamento). A área de estudo está localizada 220 km a jusante do reservatório de Yacyretá e 30 km a jusante da confluência dos Rios Paraná e Paraguai. Considerando que as águas destes rios permanecem sem se misturar no local de estudo, os possíveis efeitos do fechamento da barragem foram comparados em ambas as margens (direita e esquerda), durante as fases de águas altas e baixas de períodos hidrológicos de duração e magnitude semelhantes. As condições físico-químicas medidas na margem direita (águas do Rio Paraguai) foram similares em ambos os períodos (pré e pós-fechamento), observandose aumento nos valores da condutividade, pH e concentração de ortofosfato na margem esquerda (águas do alto Rio Paraná e do reservatório de Yacyretá) no período pós-fechamento. Alterações na densidade e composição da comunidade fitoplanctônica foram ...

Estimating cyclopoid copepod species richness and geographical distribution (Crustacea) across a large hydrographical basin: comparing between samples from water column (plankton) and macrophyte stands

“…As far as zooplankton are concerned, the sampling was obtained from the main river channels and from upstream zones of the reservoir, all of these with water retention time (WRT) longer than 15 days (see AGOSTINHO et al 2007, ZALOCAR DE DOMITROVIC et al 2007, BOLTOVSKOY et al 2013, which is considered as the lower time threshold for the development of a copepod life cycle (RIETZLER et al 2002). The approximate WRT of Figure 1.…”

Presencia y toxicidad de Microcystis aeruginosa (Cianobacteria) en el río Paraná, aguas abajo de la represa Yacyretá (Argentina).

“…Domitrovic & Maidana, 1997). Cyanobacteria presented maximum density only in spring and summer, when hydrometric levels were lower than 3.50, and they were represented by Cylindrospermopsis raciborskii, Planktolyngbya subtilis and Dolichospermum spiroides, without obvious formation of blooms (Zalocar de Domitrovic, Poi de Neiff, & Casco, 2007b). Microcystis aeruginosa was below the detection limits of the counting method, and it appeared sporadically in concentrated samples collected with plankton meshes (Zalocar de Domitrovic & Forastier, 2007.…”

Diatom-based water quality assessment in streams influence by urban pollution: effects of natural and two selected artificial substrates, São Carlos-SP, Brazil

“…A total of 500 -600 frustules per sample (depending on the abundance of diatoms) were identified and counted using the phase contrast light microscope (1000 X). The diatoms were identified to species level based on studies by Mizuno 1964;Patrick & Reimer 1966a, b;Bourrelly 1981;Lobo et al, 1996;John, 2000;Biggs & Kilroy 2000;Oliveira et al, 2001;Lobo et al, 2002;Lobo et al, 2004;Bicudo & Menezes 2006;Salomoni et al, 2006;Delgado et al, 2007;Moura et al, 2007;Soares et al, 2007;Zalocar de Damitrovic et al, 2007 and the website of the Phycology Section of The Academy of Natural Sciences of the USA (http://diatom.acnatsci.org).…”