Qualidade da água e da composição da comunidade fitoplanctônica no Reservatório Itupararanga, SP
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Data
2019-11-30
Autores
Rossi, Larissa [UNIFESP]
Orientadores
Nordi, Cristina Souza Freire [UNIFESP]
Silva, Heron Dominguez Torres da [UNIFESP]
Tipo
Dissertação de mestrado
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Resumo
Ambientes eutrofizados tendem a propiciar a dominância de cianobactérias, um dos principais
grupos fitoplanctônicos de reservatórios tropicais que ameaçam a fauna aquática e
comprometem diversos usos da água. Florações de cianobactérias e presença de cianotoxinas
têm sido frequentemente constatadas em reservatórios de abastecimento público da Região
Sudeste do Brasil, como é o caso do Reservatório de Itupararanga, localizado no estado de
São Paulo. Embora suas águas sejam fundamentais para fins de recreação, esporte, irrigação e
abastecimento público, o lançamento de esgotos diretamente e indiretamente neste
reservatório tem contribuído para o incremento trófico de suas águas e dominância da
cianobactéria potencialmente tóxica Cylindrospermopsis raciborskii. A presente pesquisa
fundamentou-se na hipótese de que o aporte de nutrientes de origem antrópica em períodos
sazonais distintos interfere na condição de trofia das águas do Reservatório de Itupararanga ao
longo do seu eixo longitudinal afetando a composição da comunidade fitoplanctônica. O
objetivo deste trabalho foi analisar a relação que os parâmetros abióticos exercem sobre a
composição da comunidade fitoplanctônica considerando a heterogeneidade espacial dentro
do reservatório e a variabilidade temporal durante os períodos seco e chuvoso. Para atingir
este objetivo foram realizadas coletas em três pontos (próximo a cabeceira, no eixo central e
próximo à barragem), no período de estiagem (agosto de 2016 e 2017) e chuvoso (fevereiro
de 2017). Foram analisadas as variáveis hidrometeorológicas e abióticas a fim de
correlacioná-las com a comunidade de fitoplâncton a qual foi avaliada segundo sua
composição e estrutura (densidade, biovolume e diversidade). No período estudado registrouse a maior densidade de organismos do fitoplâncton no eixo central de Itupararanga e, em
relação à variação sazonal, a maior densidade e biovolume de organismos ocorreram durante
a estação chuvosa. Os gêneros mais representativos foram Fragilaria (Bacillariophycea),
Cylindrospermopsis (Cyanophyceae) e Monoraphidium (Chlorophyceae). Foi observada
dominância de Monoraphidium contortum no período chuvoso, Cylindrospermopsis
raciborskii na estiagem e as espécies do gênero Fragilaria, durante todo o período avaliado
em ao menos um ponto de amostragem do reservatório. Monoraphidium contortum revelou
forte correlação com as alterações climáticas, enquanto as espécies de Cylindrospermopsis
raciborskii e as pertencentes ao gênero Fragilaria foram regidas, principalmente pela
concentração de nutrientes fosfatados e nitrogenados presentes na água. Concluiu-se, portanto
que o incremento do estado trófico nas águas do reservatório interfere na composição da
comunidade fitoplanctônica. A combinação dos dados obtidos neste trabalho com os de
monitoramentos anteriormente realizados no Reservatório de Itupararanga justifica a
necessidade de maior controle de substâncias de origem antrópica que adentram o corpo
hídrico, bem como o contínuo monitoramento ambiental utilizando o fitoplâncton como
bioindicador de alterações no ecossistema aquático.
Eutrophic environments tend to favor the cyanobacteria dominance of, one of the major phytoplankton groups in tropical reservoirs that threaten aquatic fauna and compromise various uses of water. Cyanobacterial flora and the presence of cyanotoxins have been frequently found in public supply reservoirs in the Southeast Region of Brazil, such as the Itupararanga Reservoir located in the state of São Paulo. Although its waters are fundamental for recreation, sport, irrigation, and public supply purposes, the discharge of sewage directly and indirectly in this reservoir has contributed to increase the trophic state of its waters and favor the dominance of the potentially toxic cyanobacterium Cylindrospermopsis raciborskii, frequently observed in this aquatic system. The present research was based on the hypothesis that the nutrient input in distinct seasonal periods interferes with the trophic condition of the Itupararanga Reservoir along its longitudinal axis changes the the phytoplankton composition community. The objective of this work was to analyze the influence that the abiotic parameters exert on the composition of the phytoplankton community considering the the reservoir spatial heterogeneity and the variability during the dry and rainy periods. In order to reach this objective, data were collected at three points (near the headwaters, in the central axis and near the dam), during the dry season (August 2016 and 2017) and rainy one (February 2017). The hydrometeorological and abiotic variables were analyzed in order to correlate them with the phytoplankton community, which was evaluated according to its composition and structure (density, biovolume, and diversity). During the period studied, the highest phytoplankton density was recorded in the central axis of Itupararanga. The seasonal variation showed the phytoplankton highest density and biovolume during the rainy season. The most representative genera were Fragilaria (Bacillariophycea), Cylindrospermopsis (Cyanophyceae) and Monoraphidium (Chlorophyceae). The dominance of Monoraphidium contortum occurred in the rainy period and Cylindrospermopsis raciborskii in the dry season. The genus Fragilaria was observed during the whole period evaluated in at least one the sampling point of the reservoir. The Monoraphidium contortum showed a strong correlation with climatic changes, whereas the species Cylindrospermopsis raciborskii and those belonging to the genus Fragilaria were governed mainly by the concentration of phosphate and nitrogen nutrients. It was concluded that the increase of the trophic state in the waters of the reservoir can interferes in the composition of the phytoplankton community. The combination of the data obtained in this work with those of previous carried out in the Itupararanga Reservoir justifies the necessity of monitoring nutrient flow into this water body, as well as the phytoplanktondensity as a bioindicator of the aquatic ecosystem.
Eutrophic environments tend to favor the cyanobacteria dominance of, one of the major phytoplankton groups in tropical reservoirs that threaten aquatic fauna and compromise various uses of water. Cyanobacterial flora and the presence of cyanotoxins have been frequently found in public supply reservoirs in the Southeast Region of Brazil, such as the Itupararanga Reservoir located in the state of São Paulo. Although its waters are fundamental for recreation, sport, irrigation, and public supply purposes, the discharge of sewage directly and indirectly in this reservoir has contributed to increase the trophic state of its waters and favor the dominance of the potentially toxic cyanobacterium Cylindrospermopsis raciborskii, frequently observed in this aquatic system. The present research was based on the hypothesis that the nutrient input in distinct seasonal periods interferes with the trophic condition of the Itupararanga Reservoir along its longitudinal axis changes the the phytoplankton composition community. The objective of this work was to analyze the influence that the abiotic parameters exert on the composition of the phytoplankton community considering the the reservoir spatial heterogeneity and the variability during the dry and rainy periods. In order to reach this objective, data were collected at three points (near the headwaters, in the central axis and near the dam), during the dry season (August 2016 and 2017) and rainy one (February 2017). The hydrometeorological and abiotic variables were analyzed in order to correlate them with the phytoplankton community, which was evaluated according to its composition and structure (density, biovolume, and diversity). During the period studied, the highest phytoplankton density was recorded in the central axis of Itupararanga. The seasonal variation showed the phytoplankton highest density and biovolume during the rainy season. The most representative genera were Fragilaria (Bacillariophycea), Cylindrospermopsis (Cyanophyceae) and Monoraphidium (Chlorophyceae). The dominance of Monoraphidium contortum occurred in the rainy period and Cylindrospermopsis raciborskii in the dry season. The genus Fragilaria was observed during the whole period evaluated in at least one the sampling point of the reservoir. The Monoraphidium contortum showed a strong correlation with climatic changes, whereas the species Cylindrospermopsis raciborskii and those belonging to the genus Fragilaria were governed mainly by the concentration of phosphate and nitrogen nutrients. It was concluded that the increase of the trophic state in the waters of the reservoir can interferes in the composition of the phytoplankton community. The combination of the data obtained in this work with those of previous carried out in the Itupararanga Reservoir justifies the necessity of monitoring nutrient flow into this water body, as well as the phytoplanktondensity as a bioindicator of the aquatic ecosystem.