Cambios temporales en el aporte de materia orgánica de origen terrígeno hacia el Golfo Almirante Montt, Patagonia Chilena.
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Date
2026
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Universidad de Concepción
Abstract
El presente trabajo reconstruye la dinámica temporal de los aportes de materia orgánica de origen terrígeno hacia el Golfo Almirante Montt (GAM), ubicado en la región de Magallanes, Chile (51°47’ S; 72°50’ O). El GAM es un sistema estuarino semicerrado cuya circulación está influenciada por el aporte de agua dulce desde el continente, lo que lo convierte en un sitio ideal para estudiar los cambios temporales en la interacción océano-continente y su relación con factores climáticos recientes. En este contexto y con el objetivo de estudiar la variación en el aporte terrígeno hacia el golfo durante los últimos ~130 años, se analizaron dos testigos de sedimento recolectados en la cuenca noroeste durante las expediciones COPAS-GAM en mayo 2022 (GAM 16) y SONNE SO296-2 en febrero 2023 (MUC 57). Los modelos de edad de ambos testigos se consideran definitivos hasta los 33 cm de profundidad, basados en mediciones de actividad de los isótopos 210Pb, 137Cs y 241Am, abarcando un registro histórico desde ~1890 al año 2023. Las tasas de sedimentación fueron 0,26 cm/año y 0,24 cm/año para el MUC 57 y el GAM 16, respectivamente. Los análisis geoquímicos incluyeron biomarcadores lipídicos [n-alcanos, esteroles y Glicerol Dialquil Glicerol Tetraéteres (GDGTs)], la concentración de carbono orgánico (Corg) y su razón isotópica (δ¹³Corg). En los últimos ~25 años estas variables han experimentado un cambio que se manifiesta en: i) un aumento en el promedio de la abundancia relativa del Corg desde 2% a 3%, ii) valores del δ¹³Corg más negativos (-22,1 vs. -23,8‰), iii) un incremento en la concentración de n-alcanos de cadena larga (>nC25) con fuerte dominancia impar (17 vs. 27%), y iv) un aumento moderado en los esteroles característicos de plantas vasculares terrestres (31 a 34%). Además, los GDGTs reflejaron la mezcla de materia orgánica de diverso origen (marino y terrestre) que caracterizan a estos sedimentos. En conclusión, los datos obtenidos señalan que la contribución de materia orgánica de origen terrígeno hacia el Golfo Almirante Montt ha aumentado en las últimas décadas (desde ~2000─2005 CE), aparentemente en respuesta a cambios climáticos recientes en la zona sur de la Patagonia chilena que incluyen un incremento progresivo de las precipitaciones y de la temperatura del aire hacia la actualidad.
The present work reconstructs the temporal dynamics of the contributions of organic matter of terrigenous origin to the Golfo Almirante Montt (GAM), located in the Magallanes region, Chile (51°47' S; 72°50' W). The GAM is a semi-closed estuarine system whose circulation is influenced by the contribution of freshwater from the continent, which makes it an ideal site to study temporal changes in ocean-continent interaction and its relationship with recent climatic factors. In this context and with the objective of determining the variation in terrigenous contribution to the Gulf during the last ~130 years, we analyzed two sediment cores collected in the northwestern basin during expeditions COPAS-GAM in May 2022 (GAM 16) and SONNE SO296-2 in February 2023 (MUC 57). The age models of both cores are considered definitive up to 33 cm core depth, based on activity measurements of the isotopes 210Pb, 137Cs y 241Am, covering a historical record from ~1890 to 2023. Sedimentation rates were 0.26 cm/year and 0.24 cm/year for MUC 57 and GAM 16, respectively. Geochemical analyses included lipid biomarkers (n-alkanes, sterols, and Glycerol Dialkyl Glycerol Tetraethers (GDGTs)), organic carbon concentration (Corg) and its isotopic ratio δ¹³Corg. In the last ~25 years these variables have experienced a change that is manifested in: i) an increase in the average relative abundance of Corg from 2% to 3%; ii) more negative δ ¹³Corg values (-22.1 vs. -23.8‰); iii) an increase in the long chain n-alkanes (>nC25) with odd-over-even predominance (17 vs. 27%), and iv) a moderate increase in sterols characteristic of terrestrial vascular plants (31 to 34%). Furthermore, the GDGTs reflected the mix of organic matter of diverse origin (marine and terrestrial) that characterizes these sediments. In conclusion, the data obtained indicate that the contribution of organic matter of terrigenous origin to the Golfo Almirante Montt has increased in recent decades (from ~2000─2005 CE), apparently in response to recent climatic changes in southern Chilean Patagonia that include a progressive increase in precipitation amount and air temperature towards the present.
The present work reconstructs the temporal dynamics of the contributions of organic matter of terrigenous origin to the Golfo Almirante Montt (GAM), located in the Magallanes region, Chile (51°47' S; 72°50' W). The GAM is a semi-closed estuarine system whose circulation is influenced by the contribution of freshwater from the continent, which makes it an ideal site to study temporal changes in ocean-continent interaction and its relationship with recent climatic factors. In this context and with the objective of determining the variation in terrigenous contribution to the Gulf during the last ~130 years, we analyzed two sediment cores collected in the northwestern basin during expeditions COPAS-GAM in May 2022 (GAM 16) and SONNE SO296-2 in February 2023 (MUC 57). The age models of both cores are considered definitive up to 33 cm core depth, based on activity measurements of the isotopes 210Pb, 137Cs y 241Am, covering a historical record from ~1890 to 2023. Sedimentation rates were 0.26 cm/year and 0.24 cm/year for MUC 57 and GAM 16, respectively. Geochemical analyses included lipid biomarkers (n-alkanes, sterols, and Glycerol Dialkyl Glycerol Tetraethers (GDGTs)), organic carbon concentration (Corg) and its isotopic ratio δ¹³Corg. In the last ~25 years these variables have experienced a change that is manifested in: i) an increase in the average relative abundance of Corg from 2% to 3%; ii) more negative δ ¹³Corg values (-22.1 vs. -23.8‰); iii) an increase in the long chain n-alkanes (>nC25) with odd-over-even predominance (17 vs. 27%), and iv) a moderate increase in sterols characteristic of terrestrial vascular plants (31 to 34%). Furthermore, the GDGTs reflected the mix of organic matter of diverse origin (marine and terrestrial) that characterizes these sediments. In conclusion, the data obtained indicate that the contribution of organic matter of terrigenous origin to the Golfo Almirante Montt has increased in recent decades (from ~2000─2005 CE), apparently in response to recent climatic changes in southern Chilean Patagonia that include a progressive increase in precipitation amount and air temperature towards the present.
Description
Tesis presentada para optar al título de Biólogo/a Marino/a.
Keywords
Materia orgánica, Golfos, Sedimentos estuarinos, Océano