Trazabilidad de la contaminación fecal de la Laguna Grande y Laguna Chica de San Pedro de la Paz.
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Date
2025
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Universidad de Concepción
Abstract
La contaminación fecal en los cuerpos de agua dulce es un problema creciente a nivel global, impulsado el crecimiento demográfico y la falta de urbanización. En Chile la Laguna Grande y Laguna Chica de la comuna de San Pedro de la Paz son un caso de estudio debido a la fuerte presión antropogénica, dado sus 103.808 habitantes y la constante expansión inmobiliaria.
Durante el 2024, se llevaron a cabo cuatro campañas estacionales (verano, otoño, invierno y primavera), para evaluar el grado, distribución de la contaminación fecal y trazar su fuente de origen. Para esto último se cuantifico mediante q-PCR el ADN mitocondrial Humano (HmtDNA), Aviar, Bovino, Canino, Equino y Porcino. En cada campaña fueron determinados los parámetros fisicoquímicos del agua superficial, nutrientes y amonio. Adicionalmente, se cultivaron bacterias provenientes de las colimetrías para evaluar la multiresistencia a sustancias antimicrobianas. La información obtenida fue analizada para determinar si existe una zonación debido a la actividad antrópica.
Los resultados indican que la temperatura y el pH poseen un comportamiento estacional con un máximo durante el verano 2024 para ambos parámetros. Los nutrientes revelan altas concentraciones de fosfato promedio para toda el área de estudio (4,99 ± 4,5 μmol /L), con un incremento significativo especialmente durante el invierno y primavera de 2024, que clasificaría a las dos lagunas en un estado hipertrófico con respecto a este nutriente. Del total de muestras analizadas de coliformes fecales 66.1% estuvieron por sobre la Nch1333. De esto un 47,5% corresponde a la Laguna Grande y un 18,6% a la Laguna Chica. El análisis de correlación de Pearson para el total de los datos muestra una correlación positiva y significativa (p < 0,05), entre los coliformes fecales y el número de copias de ADN mitocondrial humano, equino, canino, porcino. Así también, existen diferencias significativas (p<0,05), entre la zona norte y sur de la Laguna Grande para los coliformes fecales, ADN mitocondrial humano y nutrientes.
El análisis de multiresistencia a antibióticos mostró un rango de valores para índice MAR (Multi-Antibiotic Resistance Index) entre 0,1 y 0,9. El 85% de las muestras analizadas mostraron valores superiores a 0,22 y por lo tanto corresponden a bacterias multirresistentes, incluso a antibióticos de tercera generación.
Los análisis comparativos entre Laguna Grande y Laguna Chica permitieron identificar patrones comunes y diferencias en la dinámica estacional y la procedencia de la contaminación. Los resultados confirman que existe una zonación entre el norte y el sur de la Laguna Grande, posiblemente debido a la mayor actividad antropogénica de su ribera norte. La información obtenida en el presente trabajo pretende aportar como un insumo para el diseño de estrategias de manejo y mitigación de la contaminación fecal en contextos urbanos de rápido crecimiento.
Fecal contamination in freshwater bodies is a growing global problem, driven by population growth and the lack of urbanization. In Chile, Laguna Grande and Laguna Chica in the city hall of San Pedro de la Paz are a case study due to strong anthropogenic pressure, given their 103,808 inhabitants and the constant real estate expansion. During 2024, four seasonal campaigns (summer, fall, winter, and spring) were conducted to assess the degree and distribution of fecal contamination and trace its source. For this purpose, human mitochondrial DNA (HmtDNA), avian, bovine, canine, equine, and porcine mitochondrial DNA were quantified using q-PCR. In each campaign, the physicochemical parameters of surface water, nutrients, and ammonium were determined. Additionally, bacteria from colimetry tests were cultured to evaluate multi-resistance to antimicrobial substances. The information obtained was analyzed to determine if zonation exists due to human activity. The results indicate that temperature and pH exhibit seasonal behavior, with a maximum during the summer of 2024 for both parameters. Nutrients reveal high average phosphate concentrations for the entire study area (4.99 ± 4.5 μmol / L), with a significant increase especially during the winter and spring of 2024, which would classify the two lagoons in a hypertrophic state with respect to this nutrient. Of the total fecal coliform samples analyzed, 66.1% were above Nch1333. Of this, 47.5% corresponded to Laguna Grande and 18.6% to Laguna Chica. Pearson's correlation analysis for the total data shows a positive and significant correlation (p < 0.05) between fecal coliforms and the number of copies of human, equine, canine, and porcine mitochondrial DNA. Likewise, there are significant differences (p < 0.05) between the northern and southern zones of Laguna Grande for fecal coliforms, human mitochondrial DNA, and nutrients. The analysis of multi-antibiotic resistance showed a range of values for the MAR (Multi-Antibiotic Resistance Index) between 0.1 and 0.9. Eighty-five percent of the samples analyzed showed values greater than 0.22 and therefore correspond to multi-resistant bacteria, even to third-generation antibiotics. Comparative analyses between Laguna Grande and Laguna Chica identified common patterns and differences in seasonal dynamics and the source of contamination. The results confirm that there is zonation between the north and south of Laguna Grande, possibly due to greater anthropogenic activity on its northern shore. The information obtained in this study is intended to contribute to the design of fecal contamination management and mitigation strategies in rapidly growing urban contexts.
Fecal contamination in freshwater bodies is a growing global problem, driven by population growth and the lack of urbanization. In Chile, Laguna Grande and Laguna Chica in the city hall of San Pedro de la Paz are a case study due to strong anthropogenic pressure, given their 103,808 inhabitants and the constant real estate expansion. During 2024, four seasonal campaigns (summer, fall, winter, and spring) were conducted to assess the degree and distribution of fecal contamination and trace its source. For this purpose, human mitochondrial DNA (HmtDNA), avian, bovine, canine, equine, and porcine mitochondrial DNA were quantified using q-PCR. In each campaign, the physicochemical parameters of surface water, nutrients, and ammonium were determined. Additionally, bacteria from colimetry tests were cultured to evaluate multi-resistance to antimicrobial substances. The information obtained was analyzed to determine if zonation exists due to human activity. The results indicate that temperature and pH exhibit seasonal behavior, with a maximum during the summer of 2024 for both parameters. Nutrients reveal high average phosphate concentrations for the entire study area (4.99 ± 4.5 μmol / L), with a significant increase especially during the winter and spring of 2024, which would classify the two lagoons in a hypertrophic state with respect to this nutrient. Of the total fecal coliform samples analyzed, 66.1% were above Nch1333. Of this, 47.5% corresponded to Laguna Grande and 18.6% to Laguna Chica. Pearson's correlation analysis for the total data shows a positive and significant correlation (p < 0.05) between fecal coliforms and the number of copies of human, equine, canine, and porcine mitochondrial DNA. Likewise, there are significant differences (p < 0.05) between the northern and southern zones of Laguna Grande for fecal coliforms, human mitochondrial DNA, and nutrients. The analysis of multi-antibiotic resistance showed a range of values for the MAR (Multi-Antibiotic Resistance Index) between 0.1 and 0.9. Eighty-five percent of the samples analyzed showed values greater than 0.22 and therefore correspond to multi-resistant bacteria, even to third-generation antibiotics. Comparative analyses between Laguna Grande and Laguna Chica identified common patterns and differences in seasonal dynamics and the source of contamination. The results confirm that there is zonation between the north and south of Laguna Grande, possibly due to greater anthropogenic activity on its northern shore. The information obtained in this study is intended to contribute to the design of fecal contamination management and mitigation strategies in rapidly growing urban contexts.
Description
Tesis presentada para optar al título de Ingeniero/a en Biotecnología Marina y Acuicultura.
Keywords
Contaminación Aspectos ambientales, Lagunas Chile