Interacciones físicas-biológicas que determinan la variabilidad en biomasa y producción del zooplancton en la zona de surgencia de Chile - Centro Sur: el rol de procesos advectivos y la interacción fitoplancton-zooplancton
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Date
2023
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Universidad de Concepción
Abstract
Interacciones físicas-biológicas que determinan la variabilidad en biomasa y producción del zooplancton en la zona de surgencia de Chile - Centro Sur: el rol de procesos advectivos y la interacción fitoplancton-zooplancton.
Ana Belén Venegas Ramos, 2023, Profesor Guía, Rubén Escribano.
Los grandes ecosistemas de surgencia costera, también conocidos como "Sistemas de Corrientes de Borde Oriental" (EBUS), son de gran importancia tanto ecológica como económica debido a que sostienen una alta productividad biológica y pesquera. En ellos, el zooplancton es uno de los componentes claves puesto que sustentan la productividad de estos ecosistemas, siendo responsable de la transferencia de energía entre los productores primarios a los niveles tróficos superiores, incluyendo peces por lo cual la biomasa y producción del zooplancton en su conjunto es un pilar clave en la productividad de los EBUS.
El EBUS que se encuentra frente a Chile centro-sur (30-39° S) se caracteriza por la presencia de un frente de surgencia, con un máximo observado en primavera-verano, que desplaza hacia la superficie agua ecuatorial subsuperficial, fertilizando la capa fótica y promoviendo el crecimiento del plancton, la abundancia de peces pelágicos pequeños, aves y mamíferos, lo cual los convierte en ecosistemas de gran importancia biológica /económica. Este sistema se caracteriza por una alta variabilidad en escalas tanto temporales como espaciales debido al proceso de surgencia costera, el cual impacta en los organismos que se desarrollan en estas regiones. Por lo cual, determinar los factores influyen en la variabilidad en la biomasa del zooplancton es de suma importancia para poder pronosticar los cambios que los EBUS puedan presentar en su productividad bajo un escenario de cambio climático.
Esta tesis se centra en someter a prueba dos hipótesis: 1) bajo condiciones de surgencia intensificada, los procesos advectivos contribuyen a una pérdida significativa de la biomasa del zooplancton desde la zona de surgencia, impactando negativamente la su producción frente a Chile centro-sur, y 2) en el sistema de surgencia costera de Chile centro-sur del Pacífico sur oriental, para un período de surgencia intensa primavera-verano, la respuesta funcional del zooplancton frente a altas concentraciones del fitoplancton se manifiesta con un efecto inhibitorio de parte de las diatomeas sobre el zooplancton afectando negativamente su crecimiento y producción.
Para testear tales hipótesis planteó un primer objetivo científico: I) Determinar la importancia relativa de la advección horizontal versus la producción local de biomasa del zooplancton, en el sistema de surgencia costera frente a Chile centro-sur. Para esto se utilizó un enfoque de modelado, utilizando las salidas de una configuración del modelo ROMS-PISCES para la región se surgencia de chile centro sur (35.2°-37.8°S). Con este modelo se reconstruyó la variabilidad oceanográfica para el período agosto de 2002 a diciembre de 2008 para la zona costera asociada a la estación de monitoreo fija Estación 18, ubicada al noroeste de la bahía de Concepción frente a Dichato en la región del Bio Bio (36°30.80´S, 73°7.75´ W), Chile. El estudio evaluó la influencia de la productividad local versus los factores advectivos en la variabilidad de la biomasa del zooplancton en la zona de surgencia del centro-sur de Chile, se determinó que en los meses de primavera – verano los términos advectivos son de gran importancia para la variabilidad de la biomasa en la zona de surgencia de Chile centro-sur, donde el flujo desde sur a norte contribuye sustancialmente al aumento de la biomasa en la zona en cambio el flujo hacia el oeste es la principal fuente de pérdida de biomasa.
Con respecto al segundo objetivo se propuso conocer el impacto de la respuesta funcional tipo Holling IV sobre el crecimiento del zooplancton a través de la implementación de un modelo analítico nutrientes-fitoplancton-zooplancton (NPZ) para condiciones de altas concentraciones de fitoplancton en sistemas altamente productivos. Para esto se realizó un análisis cualitativo de las soluciones de un modelo de NPZ en tiempo finito e infinito, de estos 3 compartimientos (Nutrientes-Fitoplancton-Zooplancton). Así se estudió la variación de la biomasa del zooplancton considerando la toxicidad de las diatomeas cuando estas se encuentran en grandes concentraciones. Se observó que al incluir una respuesta funcional Holling IV para representar la toxicidad de las diatomeas durante el periodo de surgencia activa, se reproducen apropiadamente las magnitudes y variaciones de la biomasa del zooplancton en la zona de estudio, y se evidencia la importancia del factor inhibitorio de las diatomeas y el parámetro de mortalidad en la variación de la biomasa del zooplancton.
El estudio provee evidencia apoyando ambas hipótesis planteadas y sugiere que ambos procesos con base física y biológica deberían ser considerados en las observaciones de campo y en el desarrollo de modelos biogeoquímicos que involucran la dinámica y producción del zooplancton en sistemas de surgencia altamente productivos.
Physical-biological interactions that determine the variability in biomass and zooplankton production in the upwelling zone of Chile - South Central: the role of advective processes and the phytoplankton-zooplankton interaction. Ana Belén Venegas Ramos, 2023, Profesor Guía, Rubén Escribano Large coastal upwelling ecosystems, also known as "Eastern Edge Current Systems" (EBUS), are of great ecological and economic importance because they support high biological and fisheries productivity. In them, zooplankton is one of the key components since they support the productivity of these ecosystems, being responsible for the transfer of energy between primary producers to higher trophic levels, including fish, which is why the biomass and production of zooplankton in their Together it is a key pillar in the productivity of the EBUS. The EBUS located off central-southern Chile (30-39° S) is characterized by the presence of an upwelling front, with a maximum observed in spring-summer, which displaces subsurface equatorial water to the surface, fertilizing the layer photic and promoting the growth of plankton, the abundance of small pelagic fish, birds and mammals, which makes them ecosystems of great biological/economic importance. This system is characterized by high variability on both temporal and spatial scales due to the coastal upwelling process, which impacts the organisms that develop in these regions. Therefore, determining the factors that influence the variability in zooplankton biomass is of utmost importance to be able to predict the changes that EBUS may present in their productivity under a climate change scenario. This thesis focuses on testing two hypotheses: 1) under conditions of intensified upwelling, advective processes contribute to a significant loss of zooplankton biomass from the upwelling zone, negatively impacting its production off central-southern Chile, and 2) in the coastal upwelling system of south-central Chile in the eastern South Pacific, for a period of intense spring-summer upwelling, the functional response of zooplankton to high concentrations of phytoplankton is manifested with an inhibitory effect on the part of the diatoms on zooplankton, negatively affecting their growth and production. To test such hypotheses, a first scientific objective was proposed: I) Determine the relative importance of horizontal advection versus local zooplankton biomass production, in the coastal upwelling system off central-southern Chile. For this, a modeling approach was used, using the outputs of a configuration of the ROMS-PISCES model for the upwelling region of south-central Chile (35.2°-37.8°S). With this model, the oceanographic variability was reconstructed for the period August 2002 to December 2008 for the coastal zone associated with the fixed monitoring station Station 18, located northwest of Concepción Bay in front of Dichato in the Bio Bio region ( 36°30.80´S, 73°7.75´W), Chile. The study evaluated the influence of local productivity versus advective factors on the variability of zooplankton biomass in the upwelling zone of central-southern Chile. It was determined that in the spring-summer months advective terms are of great importance. for the variability of biomass in the upwelling zone of central-southern Chile, where the flow from south to north contributes substantially to the increase in biomass in the area, while the flow to the west is the main source of biomass loss. With respect to the second objective, it was proposed to know the impact of the Holling IV type functional response on the growth of zooplankton through the implementation of a nutrient-phytoplankton-zooplankton (NPZ) analytical model for conditions of high phytoplankton concentrations in highly productive systems. For this, a qualitative analysis of the solutions of an NPZ model in finite and infinite time, of these 3 compartments (Nutrients-Phytoplankton-Zooplankton), was carried out. Thus, the variation in zooplankton biomass was studied considering the toxicity of diatoms when they are found in high concentrations. It was observed that by including a Holling IV functional response to represent the toxicity of diatoms during the period of active upwelling, the magnitudes, and variations of zooplankton biomass in the study area are appropriately reproduced, and the importance of the inhibitory factor is evident. of diatoms and the mortality parameter in the variation of zooplankton biomass. The study provides evidence supporting both hypotheses and suggests that both physically and biologically based processes should be considered in field observations and in the development of biogeochemical models involving the dynamics and production of zooplankton in highly productive upwelling systems.
Physical-biological interactions that determine the variability in biomass and zooplankton production in the upwelling zone of Chile - South Central: the role of advective processes and the phytoplankton-zooplankton interaction. Ana Belén Venegas Ramos, 2023, Profesor Guía, Rubén Escribano Large coastal upwelling ecosystems, also known as "Eastern Edge Current Systems" (EBUS), are of great ecological and economic importance because they support high biological and fisheries productivity. In them, zooplankton is one of the key components since they support the productivity of these ecosystems, being responsible for the transfer of energy between primary producers to higher trophic levels, including fish, which is why the biomass and production of zooplankton in their Together it is a key pillar in the productivity of the EBUS. The EBUS located off central-southern Chile (30-39° S) is characterized by the presence of an upwelling front, with a maximum observed in spring-summer, which displaces subsurface equatorial water to the surface, fertilizing the layer photic and promoting the growth of plankton, the abundance of small pelagic fish, birds and mammals, which makes them ecosystems of great biological/economic importance. This system is characterized by high variability on both temporal and spatial scales due to the coastal upwelling process, which impacts the organisms that develop in these regions. Therefore, determining the factors that influence the variability in zooplankton biomass is of utmost importance to be able to predict the changes that EBUS may present in their productivity under a climate change scenario. This thesis focuses on testing two hypotheses: 1) under conditions of intensified upwelling, advective processes contribute to a significant loss of zooplankton biomass from the upwelling zone, negatively impacting its production off central-southern Chile, and 2) in the coastal upwelling system of south-central Chile in the eastern South Pacific, for a period of intense spring-summer upwelling, the functional response of zooplankton to high concentrations of phytoplankton is manifested with an inhibitory effect on the part of the diatoms on zooplankton, negatively affecting their growth and production. To test such hypotheses, a first scientific objective was proposed: I) Determine the relative importance of horizontal advection versus local zooplankton biomass production, in the coastal upwelling system off central-southern Chile. For this, a modeling approach was used, using the outputs of a configuration of the ROMS-PISCES model for the upwelling region of south-central Chile (35.2°-37.8°S). With this model, the oceanographic variability was reconstructed for the period August 2002 to December 2008 for the coastal zone associated with the fixed monitoring station Station 18, located northwest of Concepción Bay in front of Dichato in the Bio Bio region ( 36°30.80´S, 73°7.75´W), Chile. The study evaluated the influence of local productivity versus advective factors on the variability of zooplankton biomass in the upwelling zone of central-southern Chile. It was determined that in the spring-summer months advective terms are of great importance. for the variability of biomass in the upwelling zone of central-southern Chile, where the flow from south to north contributes substantially to the increase in biomass in the area, while the flow to the west is the main source of biomass loss. With respect to the second objective, it was proposed to know the impact of the Holling IV type functional response on the growth of zooplankton through the implementation of a nutrient-phytoplankton-zooplankton (NPZ) analytical model for conditions of high phytoplankton concentrations in highly productive systems. For this, a qualitative analysis of the solutions of an NPZ model in finite and infinite time, of these 3 compartments (Nutrients-Phytoplankton-Zooplankton), was carried out. Thus, the variation in zooplankton biomass was studied considering the toxicity of diatoms when they are found in high concentrations. It was observed that by including a Holling IV functional response to represent the toxicity of diatoms during the period of active upwelling, the magnitudes, and variations of zooplankton biomass in the study area are appropriately reproduced, and the importance of the inhibitory factor is evident. of diatoms and the mortality parameter in the variation of zooplankton biomass. The study provides evidence supporting both hypotheses and suggests that both physically and biologically based processes should be considered in field observations and in the development of biogeochemical models involving the dynamics and production of zooplankton in highly productive upwelling systems.
Description
Tesis para optar al grado de Doctor/a en Oceanografía.
Keywords
Biomasa, Zooplancton, Fitoplancton