Phytoplankton seasonal variation in a shallow stratified eutrophic reservoir (Garças Pond, Brazil)

Abstract

This study aimed at describing the phytoplankton dynamics and structure in a shallow eutrophic reservoir, the Garças Pond, located in the Parque Estadual das Fontes do Ipiranga (23°38 0 40.6 00 S, 46°37 0 28.0 00 W), in the Municipality of São Paulo, southeast Brazil. Samples were collected monthly from January to December 1997 in five depths (subsurface, 1 m, 2 m, 3 m, and 20 cm above the bottom) in the pelagic zone (Z max = 4.7 m). Abiotic variables studied were: water temperature, turbidity, transparency, conductivity, pH, dissolved oxygen, alkalinity, inorganic carbon, and N and P dissolved and total forms. Altogether 236 phytoplankton taxa distributed among 10 classes were identified. Phytoplankton seasonal and vertical variation was related to shifts in the water chemical features as a consequence of a warm-wet season with stratified water column (phase 1, January-March and SeptemberDecember) alternating with a cool-dry season with mixed water column (phase 2, April-August). There were shifts in cyanobacterial dominance over the entire year. During phase 1, Raphidiopsis/Cylindrospermopsis was one of the most important taxon. During phase 2, Raphidiopsis/Cylindrospermopsis biomass decreased, whereas richness and diversity increased and diatoms were relatively abundant. In September, when the water column was markedly stratified, a cyanobacterial bloom (Sphaerocavum brasiliense) occurred. Changes in water chemical variables caused by the bloom allowed recognition of a phase 3, in which pH and chlorophyll a, TP and CO 3 2-concentration reached their highest values. According to Reynolds and collaborators' functional groups approach, phase 1 was marked by groups S/ W1/W2/H1/Y, phase 2 by groups K/L M /L O /D/P/X1/ F, and phase 3 by group M. This sequence was corroborated by canonical correspondence analysis (CCA) results.

Weekly dynamics of phytoplankton functional groups under high water level fluctuations in a subtropical reservoir-bay

“…In this study, M. aeruginosa dominated when the temperature varied between 25.21 and 27.41°C. It was positively correlated with pH, in accordance with the literature (Fonseca and Bicudo 2008). The M group adapts to high light availability expressed as high values of Zeu/ Zmix when M group dominated, and there are other studies suggesting that the species in M groups such as M. aeruginosa occur in enriched lakes and are tolerant to low light availability BovoScomparin and Train 2008).…”

<b>Cyanobacteria community in two tropical eutrophic reservoirs in northeastern Brazil

“…This result was similar to that reported by Fonseca and Bicudo (2008), considering negative correlation with cyanobacteria total density and Willame et al (2008), who considered negative correlation with cyanobacteria efficient in competing for N. This result suggests that these filamentous species preferred the oxidized form of nitrogen (nitrate). However, studies highlighted that C. raciborskii abundance decreases with the decreasing inorganic nitrogen (TONETTA et al, 2014).…”

“…Although phosphorus is frequently considered as the most important limiting factor for algal growth (DELAZARI-BARROSO et al, 2007), nitrogen limitation is recognized as the ideal condition for the occurrence of cyanobacterial blooms, reported in several studies in eutrophic ecosystems, highlighting the predominance of heterocystous species (MOURA et al, 2007a, 2007b, DELAZARI-BARROSO et al, 2007BICUDO, 2008, BEZERRA et al, 2014, COSTA et al, 2014, including reservoirs of Northeastern Brazil, probably due the high availability of phosphorous . Nevertheless, studies also demonstrated the predominance of cyanobacteria under phosphorus limiting conditions (CHELLAPPA et al, 2008, FIGUEREDO;GIANI, 2009) or found no relationship between cyanobacterial dominance and TN: TP ratio in eutrophic reservoirs .…”

The ecology of the invasive cyanobacteriumCylindrospermopsis raciborskii(Nostocales, Cyanophyta) in two hypereutrophic lakes dominated byPlanktothrix agardhii(Oscillatoriales, Cyanophyta)

“…Cylindrospermopsis raciborskii is characterized by its association with high TN/TP ratios (Briand et al, 2002b), while P. agardhii appears to be favoured by low TN/TP ratios (Ru¨cker et al, 1997). Moreover, both species are able to develop very abundant populations or even form intense blooms (Berger, 1975(Berger, , 1989De Souza et al, 1998;Fonseca & De M. Bicudo, 2008). Occurrence of C. raciborskii with mass development of P. agardhii is known in Polish lakes (Stefaniak & Kokocin´ski, 2005;Pelechata et al, 2006;Kokocin´ski et al, 2009) but documented examples of abundant coexistence of these species are sparse Crossetti & De M. Bicudo, 2008).…”