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Rev. biol. trop ; 58(2): 547-564, jun. 2010. ilus, graf, tab

Article in Spanish | LILACS | ID: lil-638023

Abstract

Dynamics of soil properties in forests of Rhizophora mangle L. (Rhizophoraceae) in Margarita Island, Venezuela. Biochemical and microbiological properties of soils can provide information related to ecosystems environmental status. With the aim to determine the response of microbial biomass, and enzymatic and microbial activity in hypersaline (IS≥55ups) and saline (IS<55ups) mangrove soils exposed to interstitial salinities (IS) greater than 36ups, these properties were measured in mono-specific forests of Rhizophora mangle at Laguna de la Restinga National Park (Margarita Island, Venezuela). During three seasons (dry, wet and transition), a total of 120 soil samples were collected from ten (5 hypersaline and 5 saline) randomly-selected sites of 1000m² each. Four soil samples (400-500g) per plot were randomly collected with a corer at a depth of 10cm using a 1m² quadrat; each sample consisted in the combination of 8 sub-samples (50-60g ea.). Physical, chemical, enzymatic, biochemical and microbiological properties of soil samples were determined using standard laboratory protocols. The response of microbial biomass and microbial and enzymatic activity was analyzed taking into account spatial and climatic factors and interstitial salinity. Microbial biomass was linked to each locality conditions, and was not sensitive to seasonal or salinity differences. Microbial activity remained functionally active during the study period and presented variable responses. Dehydrogenase activity proved to be a good indicator for flooded and anoxic environments, and arginine ammonification resulted to be the more sensitive microbial activity to changes in salinity. Regarding enzyme activities, spatial variability was the most widespread response. We did not find a unique general pattern between enzymatic activities and spatio-temporal variation; and only the enzyme phosphatase was negatively affected by salinity. We conclude that microbial populations of mangrove soils and their activities have functional adaptations to flooded and highly-saline environments typical of a negative estuary, subjected to drastic changes due to weather and water dynamics. Future studies are needed to determine the relation between the "health" of mangrove forest and microbial populations, and their activities in mangroves soils. Rev. Biol. Trop. 58 (2): 547-564. Epub 2010 June 02.

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Propiedades bioquímicas y microbiológicas de los suelos pueden proporcionar información relativa al estado de los ecosistemas. Se determinaron las propiedades microbianas (biomasa y actividad) y bioquímicas (actividad enzimática) en suelos de bosques mono-específicos de Rhizophora mangle en Laguna de la Restinga (Isla Margarita, Venezuela), con el objeto de cuantificar cambios en áreas expuestas a salinidades intersticiales (SI) superiores a 36.0ups, clasificadas como salinas (IS<55.0 ups) e hipersalinas (SI≥55.0 ups). Se ubicaron al azar 5 localidades salinas y 5 hipersalinas, y durante tres épocas climáticas se tomaron 4 muestras de suelo por localidad (120 muestras en total). Se utilizó análisis de varianza por permutaciones multivariadas (PERMANOVA) para el análisis de los resultados. La biomasa microbiana se vio afectada por las condiciones particulares de cada localidad, y no fue sensible a los cambios de época climática o salinidad. La actividad microbiana se mantuvo funcionalmente activa. Se destacó el diacetato de fluoresceina (DAF) y la enzima (ß-glucosidasa), como probables indicadores tempranos de degradación. La deshidrogenasa resultó ser un buen indicador de ambientes inundados y anóxicos. Se concluye que las poblaciones microbianas muestran actividades que sugieren su adaptación funcional a ambientes altamente salinos e inundables, sujetos a cambios drásticos debido a las dinámicas climáticas e hídricas propias de un estuario negativo.

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