Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju(Cyanobacteria): variação semanal e relações com fatores ambientais em um reservatório eutrófico, São Paulo, SP, Brasil

Abstract

-(Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju (Cyanobacteria): weekly variation and relation with environmental factors in an eutrophic lake, São Paulo, SP, Brazil). Blooms of Cylindrospermopsis raciborskii have become more and more frequent in Brazilian reservoirs because of its high competitiveness in tropical eutrophic systems. This species is able to produce very aggressive toxins which cause problems to public health and environmental hazards. Our objective was to follow up variations of C. raciborskii density and its relation with the environmental parameters. The studied lake is located in the south of São Paulo city (23º39' S and 46º37' W). It is an eutrophic system with frequent blooms of C. raciborskii. Samples were collected weekly in the deepest part of the lake, from September/97 to September/98. Temperature profile, mixing zone, euphotic zone, pH, conductivity, turbidity, dissolved oxygen, alkalinity, nutrients, chlorophyll a, C. raciborskii density and total phytoplanktonic density were analysed. The ordination of abiotic and biotic data was carried out using Principal Component Analysis (PCA) and Canonical Correspondence Analysis (CCA). During November and December/97 the highest values of C. raciborskii densities were observed. From 12/10 to 12/17, the species contributed with more than 50% to total density. In that period the water column was thermally stratified, temperature and turbidity were high and water transparency decreased. The autumn/winter of 1998 was characterized by the absence of the studied species, by unstratified water column, low water level and temperature, high values of transparency (the highest values observed in the lake) and a great increase in biomass of the macrophyte Eichhornia crassipes (Mart.) Solms. All these relations are presently discussed.Key words -Cyanobacteria, Cylindrospermopsis raciborskii, eutrophic reservoir, weekly variation RESUMO -(Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju (Cyanobacteria): variação semanal e relações com fatores ambientais em um reservatório eutrófico, São Paulo, SP, Brasil). Florações de Cylindrospermopsis raciborskii têm sido cada vez mais freqüentes em reservatórios brasileiros em virtude da sua alta competitividade em ambientes tropicais eutrofizados. Esta espécie é produtora de toxinas extremamente agressivas, as quais podem causar problemas de saúde pública e danos ao meio ambiente. Nosso objetivo foi acompanhar a variação temporal da densidade desta população relacionando-a com variáveis ambientais e detectando os possíveis fatores que interferem no seu desenvolvimento. O lago estudado localiza-se na zona sul do Município de São Paulo (23º39' S e 46º37' W). É um corpo d'água eutrofizado e vem apresentando florações freqüentes de C. raciborskii. Amostras de água foram coletadas semanalmente, na parte mais profunda do lago, durante o período de setembro/97 a setembro/98. Foram analisados o perfil térmico, zona de mistura, transparência, zona eufótica, turbidez, pH, alcalini...

Population dynamics of Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju, a Cyanobacteria toxic species, in watersupply reservoirs in São Paulo, Brazil

“…These results seem to apply to other eutrophized reservoirs in Brazilian tropical regions and are consistent with those from several other authors: Beyruth (1996), Bouvy et al (1999), Matsuzaki (2004), Sant'Anna et al (1989,1997), Silva (1999) and Tucci & Sant'Anna (2003).…”

“…Komárková et al (1999) observed, while studying a coastal lagoon in the south of Brazil, that C. raciborskii may present great morphologic variety (straight, curved or spiral shapes) and that the species was the dominant one during periods of high temperature, low nitrogen concentration and high phosphorus concentration. Tucci & Sant'Anna (2003) studied the weekly variation of C. raciborskii in an eutrophic reservoir in São Paulo, in Brazil, and correlated the high density of that organism to high temperature and pH, high concentration of chlorophyll a, low water transparency, low concentrations of free carbonic gas and ammonium.…”

Molecular and Chemical Analyses of Cyanobacterial Blooms in Tropical Lagoons from Southeast Brazil

“…When a Microcystis bloom occurs, their mucilaginous colonies provide a high degree of shading to the other phytoplanktonic species, thus disfavouring their growth. Consequently, diversity and richness decrease significantly [54]. Other factors that allow Microcystis dominance in many aquatic ecosystems are high nutrient loading; rising temperatures, because cyanobacteria generally grow better at higher temperatures than do other phytoplankton species; enhanced stratification, reducing water vertical mixing; physiological and biochemical adaptations to growth in a saline environment, and the presence of intracellular gas vesicles, which make the cells buoyant, shading underlying non-buoyant phytoplankton and suppressing their opponents through competition for light [55].…”

Driving forces of the diel distribution of phytoplankton functional groups in a shallow tropical lake (Lake Monte Alegre, Southeast Brazil)

“…Group S N seemed to be favored by particular hydrological conditions in the lake during the warm-rainy period, such as high temperature and thermal stability of the water column (Branco and Senna, 1994;Tucci and Sant'Anna, 2003;Silva, 2004). Its distribution did not seem to be influenced by grazing, probably because of the ample availability of algae of appropriate sizes for herbivores.…”