Publication: Variaciones espacio-temporales de las praderas de Posidonia oceanica en el contexto actual de cambio climático y presiones antropogénicas
Authors
Navarro Martínez, Pedro Clemente
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Escuela Internacional de Doctorado
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García Charton, José Antonio ; Bernardeau Esteller, Jaime ; Ruíz Fernández, Juan Manuel
Publisher
Universidad de Murcia
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DOI
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info:eu-repo/semantics/doctoralThesis
Description
Abstract
Posidonia oceanica (L.) Delile es una angiosperma marina endémica del Mediterráneo cuyas praderas proporcionan servicios ecosistémicos esenciales, como la protección costera, el soporte de una elevada biodiversidad, el reciclaje de nutrientes y la captura de carbono. No obstante, estas praderas se encuentran amenazadas por múltiples presiones antropogénicas y, recientemente, se ha señalado que el cambio climático podría constituir una amenaza adicional. En este sentido, la presente tesis tiene como objetivo mejorar el conocimiento de los factores que condicionan la variabilidad espacio-temporal de las praderas de P. oceanica en el contexto actual de cambio global. Para ello, se definieron tres objetivos principales: (1) evaluar el impacto de eventos climáticos extremos y sus potenciales interacciones en la dinámica temporal de producción de rizomas verticales de Posidonia oceanica en un área costera semiárida; (2) evaluar la influencia de la variabilidad ambiental asociada al cambio climático sobre la dinámica temporal de la estructura de las praderas de P. oceanica; y (3) evaluar la influencia de las presiones humanas acumuladas sobre el estado ecológico de las praderas de Posidonia oceanica. El primer objetivo se abordó mediante series temporales de crecimiento y biomasa de 18 años (2000-2017), obtenidas mediante retrodatación (lepidocronología) en cuatro zonas de la Región de Murcia, considerando tres tipos de eventos climáticos extremos: temperaturas extremas, grandes temporales de oleaje y lluvias torrenciales (como proxy de conectividad tierra-mar e integrando los aportes sedimentarios). La influencia de estos eventos sobre la producción se evaluó mediante modelos aditivos generalizados (GAM), capaces de capturar efectos no lineales, interacciones e identificar umbrales de respuesta. Posteriormente, se analizó la dinámica temporal de la estructura de doce praderas localizadas en áreas alejadas de presiones humanas directas mediante series temporales de 19 años (2004–2022) de cobertura y densidad de haces (aleatoria y en cuadrados permanentes), cuyos patrones de variación se analizaron en términos de tendencias, cambio neto total (CNT) y cambio neto anual (CNA). Se evaluaron también las tendencias de 15 métricas ambientales asociadas a temperaturas extremas, oleaje extremo, producción primaria fitoplanctónica y radiación solar; y se analizó su efecto sobre el CNA mediante GAM. Finalmente, se examinó la influencia de las presiones humanas acumuladas mediante modelos presión-estado, construidos a partir de un índice de presión humana acumulada estimado para el tramo costero de la Región de Murcia, indicadores estructurales (cobertura y densidad) y la profundidad como factor modulador. Los resultados mostraron que los eventos climáticos extremos, como olas de calor marinas, ejercen efectos negativos sobre el crecimiento y la biomasa de los rizomas verticales, y se constató por primera vez que las grandes tormentas y las descargas sedimentarias tras lluvias torrenciales afectan directamente al crecimiento y la biomasa del rizoma vertical, modulando a escala local la magnitud de los impactos de otros eventos climáticos. Sin embargo, las variaciones climáticas registradas entre 2004 y 2022 no se tradujeron en dinámicas regresivas, episodios de mortalidad masiva ni pérdidas relevantes de integridad estructural, mientras que la presión humana acumulada sí se asoció con procesos de degradación. Asimismo, la información derivada de los distintos capítulos permitió identificar umbrales, elaborar mapas de distribución de presiones y caracterizar las tendencias de los eventos climáticos extremos, sirviendo para establecer criterios de sensibilidad y vulnerabilidad en función del grado de exposición de las praderas, lo que constituye una base esencial para orientar medidas de conservación efectivas en estos ecosistemas de alto valor ecológico.
Posidonia oceanica (L.) Delile is a marine angiosperm endemic to the Mediterranean whose meadows provide essential ecosystem services, including coastal protection, support for high biodiversity, nutrient recycling, and carbon sequestration. However, these meadows are threatened by multiple anthropogenic pressures, and recent evidence suggests that climate change may pose an additional risk. In this context, the present thesis aims to enhance the understanding of the factors governing the spatio-temporal variability of P. oceanica meadows under current global change. Three main objectives were established: (1) to evaluate the impact of extreme climatic events (ECE) and their potential interactions on the temporal dynamics of vertical rhizome production in P. oceanica within a semi-arid coastal area; (2) to assess the influence of climate-associated environmental variability on the temporal dynamics of P. oceancia meadow structure; and (3) to evaluate the influence of cumulative human pressures on the ecological status of P. oceanica meadows. The first objective was addressed using 18-year (2000–2017) time series of growth and biomass obtained via retrodating (lepidochronology) in four sites within the Murcia region, considering three types of ECEs: extreme temperatures, large storm waves, and torrential rainfall, the latter used as a proxy for land–sea connectivity and incorporating sediment inputs. Their effects on production were evaluated through generalized additive models (GAMs), which captured non-linear effects, interactions, and response thresholds. Subsequently, the temporal dynamics of twelve meadows located in areas free from direct human pressures were analyzed using 19-year (2004–2022) time series of meadow cover and shoot density (random and permanent quadrats), with variation patterns analyzed in terms of trends, total net change (CNT), and annual net change (CNA). The influence of 15 environmental metrics related to extreme temperatures, storm waves, phytoplankton primary production, and solar radiation on CNA was also evaluated using GAMs. Finally, the effect of cumulative human pressures was assessed using pressure–state models based on a cumulative human pressure index for the Murcia coastal area, structural indicators (cover and density), and depth as a modulating factor. The results showed that ECEs, such as marine heatwaves, negatively affected vertical rhizome growth and biomass, and it was evidenced for the first time that large storms and sediment inputs from torrential rainfall directly impact rhizome growth and biomass while locally modulating the effects of other ECEs. Nonetheless, climatic variations recorded between 2004 and 2022 did not result in regressive dynamics, mass mortality events, or significant structural losses, whereas cumulative human pressure was associated with degradation processes. Furthermore, the information derived from the different chapters allowed the identification of thresholds, the generation of pressure distribution maps, and the characterization of ECE trends, providing criteria for sensitivity and vulnerability according to the degree of meadow exposure, thus constituting a critical basis to guide effective conservation measures for these ecologically valuable ecosystems.
Posidonia oceanica (L.) Delile is a marine angiosperm endemic to the Mediterranean whose meadows provide essential ecosystem services, including coastal protection, support for high biodiversity, nutrient recycling, and carbon sequestration. However, these meadows are threatened by multiple anthropogenic pressures, and recent evidence suggests that climate change may pose an additional risk. In this context, the present thesis aims to enhance the understanding of the factors governing the spatio-temporal variability of P. oceanica meadows under current global change. Three main objectives were established: (1) to evaluate the impact of extreme climatic events (ECE) and their potential interactions on the temporal dynamics of vertical rhizome production in P. oceanica within a semi-arid coastal area; (2) to assess the influence of climate-associated environmental variability on the temporal dynamics of P. oceancia meadow structure; and (3) to evaluate the influence of cumulative human pressures on the ecological status of P. oceanica meadows. The first objective was addressed using 18-year (2000–2017) time series of growth and biomass obtained via retrodating (lepidochronology) in four sites within the Murcia region, considering three types of ECEs: extreme temperatures, large storm waves, and torrential rainfall, the latter used as a proxy for land–sea connectivity and incorporating sediment inputs. Their effects on production were evaluated through generalized additive models (GAMs), which captured non-linear effects, interactions, and response thresholds. Subsequently, the temporal dynamics of twelve meadows located in areas free from direct human pressures were analyzed using 19-year (2004–2022) time series of meadow cover and shoot density (random and permanent quadrats), with variation patterns analyzed in terms of trends, total net change (CNT), and annual net change (CNA). The influence of 15 environmental metrics related to extreme temperatures, storm waves, phytoplankton primary production, and solar radiation on CNA was also evaluated using GAMs. Finally, the effect of cumulative human pressures was assessed using pressure–state models based on a cumulative human pressure index for the Murcia coastal area, structural indicators (cover and density), and depth as a modulating factor. The results showed that ECEs, such as marine heatwaves, negatively affected vertical rhizome growth and biomass, and it was evidenced for the first time that large storms and sediment inputs from torrential rainfall directly impact rhizome growth and biomass while locally modulating the effects of other ECEs. Nonetheless, climatic variations recorded between 2004 and 2022 did not result in regressive dynamics, mass mortality events, or significant structural losses, whereas cumulative human pressure was associated with degradation processes. Furthermore, the information derived from the different chapters allowed the identification of thresholds, the generation of pressure distribution maps, and the characterization of ECE trends, providing criteria for sensitivity and vulnerability according to the degree of meadow exposure, thus constituting a critical basis to guide effective conservation measures for these ecologically valuable ecosystems.
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