Efeito da poluição de uma megalópole sobre o zooplâncton e a contaminação por microplásticos no médio rio Tietê (SP)
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Data
2023-02-28
Autores
Silva, Gabriel Mariano
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Universidade Estadual Paulista (Unesp)
Resumo
A poluição é uma consequência das diversas atividades que nós, seres humanos, realizamos no dia a dia. Grande parte dela é incorporada aos rios, muitas vezes sem o tratamento adequado. De um modo geral, os efeitos da eutrofização já são bem conhecidos, mas os impactos da poluição extrema sobre a biota aquática ainda precisam ser melhor dimensionados. O descarte irregular de material inorgânico, como plástico, também caracteriza um grave distúrbio ambiental. Por ano, milhões de toneladas desse material são irregularmente descartadas e vão parar em rios e oceanos. Dentro dessa problemática existe um tema que exige uma atenção ainda maior: os microplásticos (MPs), que compreendem polímeros particulados com tamanho inferior a 5 milímetros. Eles representam uma ameaça a biodiversidade e por isso é muito importante compreender melhor como se distribuem nos ambientes e como interagem com a biota. O zooplâncton, foco do estudo, é um grupo biológico que está diretamente ligado a qualidade das águas e é de suma importância para a manutenção de ambientes saudáveis. Esse projeto teve por objetivo avaliar os efeitos da poluição do rio Tietê, altamente impactado pelos despejos domésticos e industriais da região metropolitana de São Paulo, sobre as condições limnológicas e a estruturação da comunidade zooplanctônica, assim como a contaminação de suas águas por microplásticos. Além do rio Tietê, amostrou-se uma lagoa lateral de seu próprio curso e um tributário sem influência de centros urbanos, para fins comparativos. Amostragens foram realizadas em dois períodos (final do chuvoso e seco). A qualidade da água mostrou-se muito diferente entre esses três ambientes. Os valores médios das concentrações de nitrogênio e fósforo no rio Tietê foram, respectivamente, 30 e 60 vezes mais elevados que no tributário no período seco. Na lagoa, a concentração de clorofila a chega a ser 550 vezes maior. Ao todo foram encontrados 66 táxons, sendo 8 espécies de Copepoda, 16 espécies de Cladocera e 41 espécies de Rotifera. A lagoa teve a maior abundância e o tributário a maior riqueza, enquanto o rio Tietê esteve num intermediário entre os dois ambientes. Microplástico foi encontrado em todas as amostras de água analisadas. As concentrações variam de 35 partículas/m³ no rio do Peixe até 814 partículas/m³ no Tietê. A maior parte dos MPs encontrados corresponde a frações menores, entre 0,053 e 0,250 mm, e a “cor” predominante é a transparente para todos os ambientes. Quanto à forma, mais de 80% de todas as partículas foram fibras. Sazonalmente, a quantidade de MPs nos ambientes mais contaminados (rio Tietê e sua lagoa marginal) foi no período de abril, apesar da diferença em relação ao período de agosto não ter sido estatisticamente significativa. No rio do Peixe observou-se o inverso, embora as diferenças tenham sido menores. Esse estudo mostra a importância da manutenção da qualidade da água para a conservação da biodiversidade em ecossistemas aquáticos.
Pollution is a consequence of the various activities that we human beings carry out on a daily basis. Much of it is incorporated into rivers, often without proper treatment. In general, the effects of eutrophication are already well known, but the impacts of extreme pollution on aquatic biota still need to be better dimensioned. The irregular disposal of inorganic material, such as plastic, also characterizes a serious environmental disturbance. Every year, millions of tons of this material are irregularly discarded and end up in rivers and oceans. Within this problem, there is an issue that requires even greater attention: microplastics (PMs), which comprise particulate polymers smaller than 5 millimeters. They represent a threat to biodiversity and therefore it is very important to better understand how they are distributed in environments and how they interact with the biota. Zooplankton, the focus of the study, is a biological group that is directly linked to water quality and is of paramount importance for the maintenance of healthy environments. This project aimed to evaluate the effects of pollution on the Tietê River, highly impacted by domestic and industrial waste from the metropolitan region of São Paulo, on the limnological conditions and the structure of the zooplankton community, as well as the contamination of its waters by microplastics. In addition to the Tietê River, a lateral lake along its own course and a tributary without influence from urban centers were sampled, for comparative purposes. Samplings were carried out in two periods (late rainy season and dry season). The water quality was very different between these three environments. The mean values of nitrogen and phosphorus concentrations in the Tietê River were, respectively, 30 and 60 times higher than in the tributary during the dry period. In the lagoon, the concentration of chlorophyll a is 550 times higher. In all, 66 taxa were found, 8 species of Copepoda, 16 species of Cladocera and 41 species of Rotifera. The lagoon had the highest abundance and the tributary the highest richness, while the Tietê River was intermediate between the two environments. Microplastic was found in all analyzed water samples. Concentrations vary from 35 particles/m³ in the Rio do Peixe to 814 particles/m³ in the Tietê. Most of the PMs found correspond to smaller fractions, between 0.053 and 0.250 mm, and the predominant “color” is transparent for all environments. As for shape, more than 80% of all particles were fibers. Seasonally, the amount of PMs in the most contaminated environments (Tietê river and its marginal lake) was in the April period, although the difference in relation to the August period was not statistically significant. In the Peixe River, the opposite was observed, although the differences were smaller. This study shows the importance of maintaining water quality for the conservation of biodiversity in aquatic ecosystems.
Pollution is a consequence of the various activities that we human beings carry out on a daily basis. Much of it is incorporated into rivers, often without proper treatment. In general, the effects of eutrophication are already well known, but the impacts of extreme pollution on aquatic biota still need to be better dimensioned. The irregular disposal of inorganic material, such as plastic, also characterizes a serious environmental disturbance. Every year, millions of tons of this material are irregularly discarded and end up in rivers and oceans. Within this problem, there is an issue that requires even greater attention: microplastics (PMs), which comprise particulate polymers smaller than 5 millimeters. They represent a threat to biodiversity and therefore it is very important to better understand how they are distributed in environments and how they interact with the biota. Zooplankton, the focus of the study, is a biological group that is directly linked to water quality and is of paramount importance for the maintenance of healthy environments. This project aimed to evaluate the effects of pollution on the Tietê River, highly impacted by domestic and industrial waste from the metropolitan region of São Paulo, on the limnological conditions and the structure of the zooplankton community, as well as the contamination of its waters by microplastics. In addition to the Tietê River, a lateral lake along its own course and a tributary without influence from urban centers were sampled, for comparative purposes. Samplings were carried out in two periods (late rainy season and dry season). The water quality was very different between these three environments. The mean values of nitrogen and phosphorus concentrations in the Tietê River were, respectively, 30 and 60 times higher than in the tributary during the dry period. In the lagoon, the concentration of chlorophyll a is 550 times higher. In all, 66 taxa were found, 8 species of Copepoda, 16 species of Cladocera and 41 species of Rotifera. The lagoon had the highest abundance and the tributary the highest richness, while the Tietê River was intermediate between the two environments. Microplastic was found in all analyzed water samples. Concentrations vary from 35 particles/m³ in the Rio do Peixe to 814 particles/m³ in the Tietê. Most of the PMs found correspond to smaller fractions, between 0.053 and 0.250 mm, and the predominant “color” is transparent for all environments. As for shape, more than 80% of all particles were fibers. Seasonally, the amount of PMs in the most contaminated environments (Tietê river and its marginal lake) was in the April period, although the difference in relation to the August period was not statistically significant. In the Peixe River, the opposite was observed, although the differences were smaller. This study shows the importance of maintaining water quality for the conservation of biodiversity in aquatic ecosystems.
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Palavras-chave
Limnologia, Plâncton, Zooplâncton, Biologia aquatica, Plásticos