Influencia del bosque de manglar en la emisión neta de gas metano en los cuerpos de agua de la Laguna de Gandoca, Refugio Nacional de Vida Silvestre Gandoca @ Manzanillo, Costa Rica
Fecha
2020
Autores
Record, Shimara
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Editor
Universidad Nacional (Costa Rica)
Resumen
Los manglares costeros representan una fuente importante de almacenamiento de carbono (C), pero también son conocidos como fuentes naturales de metano (CH4), el segundo más importante gas de efecto invernadero en la atmósfera. Las actividades humanas que ocurren dentro o alrededor de estos ecosistemas pueden tener un impacto importante en las emisiones netas de CH4 y en el almacenamiento de C. Con el fin de mejorar la estrategia de manejo existente dentro del Refugio Gandoca-Manzanillo, se analizó y modelizó diferentes variables ambientales (36) para encontrar aquellas que mayor influencia tienen sobre las emisiones netas de CH4, la acumulación de materia orgánica (MO) y la tasa de retorno de carbono anaeróbico del metano en sedimentos (TR-CH4). Para ello, las emisiones de CH4 fueron determinados en la columna de agua de la Laguna de Gandoca, un ecosistema tropical localizado en la costa caribe de Costa Rica, rodeado por comunidades de manglar, asociaciones de palma y helechos de manglar. Adicionalmente a las variables ambientales, se establecieron dos variables categorizadas (fijas). Se utilizó el método de cámara flotante cerrada y dinámica con un analizador de gases de efecto invernadero (UGGA) que midió directamente desde la cámara las emisiones de CH4 en un modo de flujo continuo y permitió distinguir las emisiones difusivas de las no-difusivas. En total, se establecieron 24 sitios distribuidos equilibradamente sobre toda la laguna, mientras que las mediciones se realizaron durante 5 días de muestreos no consecutivos (total de 120 observaciones). Los datos fueron analizados estadísticamente con un modelo lineal generalizado con efecto mixto (GLMM) para emisiones, y dos modelos lineales generalizados (GLM) para masa volumétrica de MO en sedimentos y TR-CH4. El modelo GLMM indicó que, las emisiones están explicadas por la suma de influencias de: factores fijos (comunidades vegetales y distancias), así como también covariables como conductividad eléctrica en el sedimento (CNDsed), corriente (principalmente a 90 cm de profundidad), índice de vegetación de diferencia normalizada (NDVI), marea, potasio en el sedimento (K+ sed) y radiación fotosintética activa (PAR). El primer modelo GLM mostró que la MO estuvo influenciado por los factores fijos e igualmente por covariables como temperatura en la columna de agua (Tag), NDVI y por el potencial de óxido reducción en el sedimento (ORPsed). El segundo modelo GLM mostró que la TR-CH4 estuvo influenciado por los factores fijos y covariables como ORPsed y cloruro en el agua (Clag). Además, revelaron que los sedimentos de manglar compensan la emisión más alta de CH4 difusivo en comparación a las otras comunidades por una secuestración mucho más grande de carbono basado en diferencias de masa volumétrica. Por lo tanto, las estrategias de manejo de la laguna deben centrarse en reducir la vulnerabilidad del ecosistema al prevenir la pérdida de almacenamiento de C al controlar las actividades antropogénicas actuales y futuras. En consecuencia, el estudio constituye una herramienta útil para ayudar a gestores e investigadores a prevenir, controlar y/o mitigar impactos negativos de las actividades antropogénicas. Las acciones propuestas (establecer datos de referencia y un plan de manejo, reducir entradas de nutrientes, evitar la apertura de la salida de la laguna por actividades antropogénicas, identificar áreas prioritarias para establecer zonas de amortiguamiento, investigación participativa y promover actividades alternativas a la navegación durante la marea baja) ayudarán a establecer medidas para mejorar las estrategias existentes y maximizar los servicios del ecosistema como el mantener o incrementar la capacidad de almacenar el C dentro de la Laguna Gandoca y mantener en bajos niveles o reducir las emisiones de CH4.
Coastal mangroves represent an important source of carbon (C) storage, but they are also known as natural sources of methane (CH4), the second most important greenhouse gas in the atmosphere. Human activities that occur within or around these ecosystems can have a significant impact on net CH4 emissions and C storage. In order to improve the existing management strategy within the Gandoca-Manzanillo Refuge, an analysis and modeling of different environmental variables (36) to find those that have the greatest influence on net CH4 emissions, the accumulation of organic matter (OM) and the rate of anaerobic carbon return from methane in sediments (TR-CH4). For this, CH4 emissions were determined in the water column of the Gandoca Lagoon, a tropical ecosystem located on the Caribbean coast of Costa Rica, surrounded by mangrove communities, palm tree associations, and mangrove ferns. In addition to the environmental variables, two categorized (fixed) variables were established. The dynamic closed floating chamber method was used with a greenhouse gas analyzer (UGGA) that measured CH4 emissions directly from the chamber in a continuous flow mode and allowed to distinguish diffusive from non-diffusive emissions. In total, 24 sites distributed evenly throughout the lagoon were established, while measurements were made during 5 days of non-consecutive sampling (total of 120 observations). Data were statistically analyzed with a generalized linear model with mixed effect (GLMM) for emissions, and two generalized linear models (GLM) for OM volumetric mass in sediments and TR-CH4. The GLMM model indicated that the emissions are explained by the sum of influences of: fixed factors (plant communities and distances), as well as covariates such as electrical conductivity in the sediment (CNDsed), current (mainly at 90 cm depth), normalized difference vegetation index (NDVI), tide, sediment potassium (K+ sed) and photosynthetic active radiation (PAR). The first GLM model showed that the OM was influenced by fixed factors and also by covariates such as temperature in the water column (Tag), NDVI and by the oxidation reduction potential in the sediment (ORPsed). The second GLM model showed that TR-CH4 was influenced by fixed and covariate factors such as ORPsed and chloride in water (Clag). Furthermore, they revealed that mangrove sediments offset the higher emission of diffusive CH4 compared to the other communities by much larger carbon sequestration based on volumetric mass differences. Therefore, lagoon management strategies should focus on reducing ecosystem vulnerability by preventing loss of C storage by controlling current and future anthropogenic activities. Consequently, the study constitutes a useful tool to help managers and researchers to prevent, control and/or mitigate negative impacts of anthropogenic activities. The proposed actions (establish reference data and a management plan, reduce nutrient inputs, prevent the opening of the lagoon outlet due to anthropogenic activities, identify priority areas to establish buffer zones, participatory research and promote alternative activities to navigation during low tide) will help establish measures to improve existing strategies and maximize ecosystem services such as maintaining or increasing the capacity to store C within the Gandoca Lagoon and maintaining low levels or reducing CH4 emissions.
Coastal mangroves represent an important source of carbon (C) storage, but they are also known as natural sources of methane (CH4), the second most important greenhouse gas in the atmosphere. Human activities that occur within or around these ecosystems can have a significant impact on net CH4 emissions and C storage. In order to improve the existing management strategy within the Gandoca-Manzanillo Refuge, an analysis and modeling of different environmental variables (36) to find those that have the greatest influence on net CH4 emissions, the accumulation of organic matter (OM) and the rate of anaerobic carbon return from methane in sediments (TR-CH4). For this, CH4 emissions were determined in the water column of the Gandoca Lagoon, a tropical ecosystem located on the Caribbean coast of Costa Rica, surrounded by mangrove communities, palm tree associations, and mangrove ferns. In addition to the environmental variables, two categorized (fixed) variables were established. The dynamic closed floating chamber method was used with a greenhouse gas analyzer (UGGA) that measured CH4 emissions directly from the chamber in a continuous flow mode and allowed to distinguish diffusive from non-diffusive emissions. In total, 24 sites distributed evenly throughout the lagoon were established, while measurements were made during 5 days of non-consecutive sampling (total of 120 observations). Data were statistically analyzed with a generalized linear model with mixed effect (GLMM) for emissions, and two generalized linear models (GLM) for OM volumetric mass in sediments and TR-CH4. The GLMM model indicated that the emissions are explained by the sum of influences of: fixed factors (plant communities and distances), as well as covariates such as electrical conductivity in the sediment (CNDsed), current (mainly at 90 cm depth), normalized difference vegetation index (NDVI), tide, sediment potassium (K+ sed) and photosynthetic active radiation (PAR). The first GLM model showed that the OM was influenced by fixed factors and also by covariates such as temperature in the water column (Tag), NDVI and by the oxidation reduction potential in the sediment (ORPsed). The second GLM model showed that TR-CH4 was influenced by fixed and covariate factors such as ORPsed and chloride in water (Clag). Furthermore, they revealed that mangrove sediments offset the higher emission of diffusive CH4 compared to the other communities by much larger carbon sequestration based on volumetric mass differences. Therefore, lagoon management strategies should focus on reducing ecosystem vulnerability by preventing loss of C storage by controlling current and future anthropogenic activities. Consequently, the study constitutes a useful tool to help managers and researchers to prevent, control and/or mitigate negative impacts of anthropogenic activities. The proposed actions (establish reference data and a management plan, reduce nutrient inputs, prevent the opening of the lagoon outlet due to anthropogenic activities, identify priority areas to establish buffer zones, participatory research and promote alternative activities to navigation during low tide) will help establish measures to improve existing strategies and maximize ecosystem services such as maintaining or increasing the capacity to store C within the Gandoca Lagoon and maintaining low levels or reducing CH4 emissions.
Descripción
Record, S. (2020). Influencia del bosque de manglar en la emisión neta de gas metano en los cuerpos de agua de la Laguna de Gandoca, Refugio Nacional de Vida Silvestre Gandoca @ Manzanillo, Costa Rica. [Tesis de Maestría]. Heredia, Costa Rica.
Palabras clave
MANGLARES, IMPACTO AMBIENTAL, CARBONO, ECOSISTEMAS ACUÁTICOS, MANGROVES, HUMEDALES, WETLANDS