Aquatic life protection index of an urban river Bacanga basin in northern Brazil, São Luís - MA

Abstract

Bacanga River Basin faces environmental problems related to urbanization and discharge of untreated domestic sewage, which compromise its ecosystem health. Due to the small number of studies that assessed its water quality, the present study aimed to assess the current status of this ecosystem based on the aquatic life protection index. Samples were carried out every two months, in a total of six events, in six sites along the basin, where the water samples were collected to assess physicochemical parameters and calculate the trophic state index and the index of minimum parameters for the protection of aquatic communities. The data were also compared with values determined by the resolution National Environment Council -CONAMA 357/05. Our results reveal significant changes in the water quality of Bacanga River Basin. An increase in nutrients and chlorophyll-a concentration led it to eutrophication. The surfactant values were high and put in danger the aquatic biota. Dissolved oxygen rates were below the values allowed by the resolution in most sites sampled. The current water quality is terrible for the protection of aquatic life in 61.92% of the sites sampled.Keywords: water quality, contamination, domestic sewage. Índice de proteção da vida aquática em uma bacia urbana do rio Bacanga no norte do Brasil, São Luís -MA ResumoA Bacia Hidrográfica do rio Bacanga (BHRB) apresenta problemas ambientais relacionados a urbanização e lançamentos de esgoto in natura que comprometem a qualidade desse ecossistema. Devido ao reduzido número de estudos associados à avaliação da qualidade da água no local, este estudo teve como objetivo avaliar a situação atual desse ecossistema por meio do Índice de Proteção da Vida Aquática. Seis amostragens bimestrais foram realizadas em seis pontos ao longo da bacia, coletando parâmetros físico-químicos para a aplicação do Índice de Estado Trófico e Índice de Parâmetros Mínimos para a Proteção da Vida Aquática, relacionando-os com a resolução Conselho Nacional do Meio Ambiente -CONAMA/357. Os resultados revelaram alterações significativas na qualidade da água da BHRB, o aumento de nutrientes e das concentrações de clorofila-a conduziram ao um estado geral de eutrofização. Os valores de surfactantes foram altos colocando em risco a biota aquática e as taxas de oxigênio dissolvido estiveram abaixo do permitido pela resolução na maioria dos pontos amostrados. A situação atual da qualidade da água para proteção da vida aquática é péssima em 61,92% dos pontos amostrados.Palavras-chave: qualidade da água, contaminação, efluentes domésticos.

Algal blooms and trophic state in a tropical estuary blocked by a dam (northeastern Brazil)

“…Based on the Redfield molar ratio (N:P and N:Si), this pattern can be expressed by the co-limitation Sá et al of phosphorus and silicate, to the excess of anthropogenic nitrogen (NH 4 + ) observed downstream (Pavlidou et al, 2004;Xu et al, 2008). This excess is a response to an increase in the DIN concentrations, which was probably the result of industrial wastewater and domestic sewage discharge in the study area, in addition to the indiscriminate use of fertilizers upstream that contributed to an increase in phosphorus in that region (Silva et al, 2014;Duarte-dos-Santos et al, 2017). Therefore, the limitation of phosphorus may have a low impact on the reduction of the trophic level of the water body, being compensated by the conservative behavior of nitrogen concentrations as a function of salinity (Anderson et al, 2002;Cloern et al, 2014;Paula-Filho et al, 2020).…”

“…Residence time in the BRE is longer because of the dam, providing conditions and facilitating decisions about water management (Cunha et al, 2013, Pitombeira andMorais, 1977). The presence of the dam causes the environment to have a common lentic, water-body behavior, in which the salinity depends on the control and administration of the gates that regulate the freshwater outflow and entry of seawater (Duarte-dos-Santos et al, 2017).…”

Phytoplankton Biomass and Environmental Descriptors of Water Quality of an Urban Lagoon

“…Water quality is vital when it comes to determining how society uses and values aquatic environments associated with natural resources [1] and their monitoring provides empirical evidence to support decision-making on health and environmental issues [2]. Thus, water quality can be assessed through variables such as dissolved oxygen, temperature, pH, toxic substances (heavy metals, surfactants, and phenols) and others [3,4].…”

Effect of watershed land use on water quality: a case study in Córrego da Olaria Basin, São Paulo State, Brazil

“…Faustino et al (2014) argue that it's an area defined topographically, drained by a watercourse and interconnected waterways systems such where the streams are discharged into a single output. It is an important unit in scientific research, training, integrated use of information for demonstration, experimentation and observation in real field, working as a natural laboratory for the short, medium and long-term studies, in order to contribute to the search for sustainable management criteria (Tundisi, 2008;Carvalho et al, 2015;Duarte-dos-Santos et al, 2016).…”