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Community structure of the intertidal meiofauna along a gradient of morphodynamic sandy beach types in southern Chile Translated title: Estructura comunitaria de la meiofauna intermareal en un gradiente de tipos morfodinámicos de playas arenosas en el sur de Chile

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      Abstract

      Three sandy beaches located in southern Chile (Gaviotas, Guabún and Mar Brava; ca. 42º S) were studied during the summer of 2000 to analyse the patterns in abundance and biomass of the meiofauna along a gradient of morphodynamic beach types. Sediment samples were collected with metallic cylinders (23 cm² cross sectional area, 120 cm long) at ten equally spaced tidal levels along six transects separated between 5 and 10 m and extending from above the drift line down to the low tide level. Porosity, shear strength, water content, penetrability and grain size of the substrate were measured in each sampling level. The meiofauna was primarily represented by Nematoda and Copepoda Harpacticoidea. The highest average density and biomass per unit of area were found at the reflective beach of Gaviotas (6,172 ind 10 cm-2 and 2.38 g m-2, ash free dry weight) as compared with the intermediate beach of Guabún (3,390 ind 10 cm-2 and 1.70 g m-2) and the dissipative beach of Mar Brava (3,667 ind 10 cm-2 and 0.86 g m-2). Total abundance and biomass of the meiofauna per linear meter of beach (i.e., total meiofauna in an intertidal across-shore transect 1 m wide) were higher at Mar Brava (506 x 10(6) ind m-1 and 119.4 g m-1), as compared with Gaviotas (271 x 10(6) ind m-1 and 101.7 g m-1) and Guabún (143 x 10(6) ind m-1 and 73.9 g m-1). Therefore, these last results show a trend of increasing intertidal meiofaunal abundances and biomass towards the dissipative stage of the beach gradient analyzed. The highest meiofaunal densities and biomass occurred at the upper and mid shore levels of each beach. Lower across-shore variability in density and biomass were found at the dissipative beach. Results of a Monte Carlo permutation test showed that water content, penetrability and grain size were the best predictor variables of meiofaunal density. Body sizes of nematodes, copepods, turbellarians, halacarids and ostracods were correlated with sediment characteristics. In general, the relationship between community structure of the meiofauna and beach morphodynamics, were similar to that found for the macroinfauna from different sandy beaches around the world, suggesting that meiofauna and macroinfauna are similarly affected by the physical processes associated to different beach types

      Translated abstract

      Se estudiaron tres playas arenosas del sur de Chile (Gaviotas, Guabún y Mar Brava; ca. 42º S) durante el verano del 2000 para analizar los patrones de abundancia y biomasa de la meiofauna a lo largo de un gradiente de tipos morfodinámicos de playas. Se recolectaron muestras de sedimento con cilindros metálicos (23 cm² de área, 120 cm de longitud) en diez niveles espaciados a intervalos regulares a lo largo de seis transectos separados de 5 a 10 m y extendidos desde un punto sobre el nivel de marea alta y el nivel de marea baja. En cada nivel de muestreo se midió porosidad, fuerza de cizalla, contenido de agua, penetrabilidad y tamaño del grano. La meiofauna estuvo primariamente representada por Nematoda y Copepoda Harpacticoidea. Las mayores densidades y biomasas medias por unidad de área se encontraron en la playa reflectiva de Gaviotas (6.172 ind 10 cm-2 y 2,38 g m-2, peso seco libre de cenizas) en comparación con la playa intermedia de Guabún (3.390 ind 10 cm-2 y 1,70 g m-2) y la playa disipativa de Mar Brava (3.667 ind 10 cm-2 y 0,86 g m-2). La abundancia y biomasa total de la meiofauna por metro lineal de playa (i.e., meiofauna total contenida en un transecto intermareal de 1 m de ancho) fueron mayores en Mar Brava (506 x 10(6) ind m-1 y 119,4 g m-1) versus Gaviotas (271 x 10(6) ind m-1 y 101,7 g m-1) y Guabún (143 x 10(6) ind m-1 y 73,9 g m-1). Por lo tanto, estos últimos resultados muestran una tendencia de aumento de abundancia y biomasa de la meiofauna intermareal hacia el tipo disipativo dentro del gradiente estudiado de tipos de playas. Los valores más altos de densidad y biomasa de la meiofauna se encontraron en los niveles superiores y medio de cada playa. En la playa disipativa, se encontró la menor variabilidad en abundancia y biomasa de la meiofauna a lo ancho del intermareal. Según la prueba de permutación de Monte Carlo, el contenido de agua, penetrabilidad y tamaño del grano fueron las variables que mejor predicen la variabilidad de las densidades de la meiofauna. Los tamaños corporales de nemátodos, copépodos, turbelarios, halacáridos y ostrácodos estuvieron correlacionados con las características del sedimento. En general, las relaciones entre estructura comunitaria de la meiofauna y morfodinámica de playas, fueron similares a aquellas encontradas para la macroinfauna de diferentes playas arenosas alrededor del mundo, lo que sugiere que la meiofauna y macroinfauna son afectadas similarmente por los procesos físicos asociados a diferentes tipos de playas

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      Most cited references 42

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      Numerical ecology

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        Petrology of sedimentary rocks

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          A SIMPLE METHOD OF MEASURING BEACH PROFILES

           K. O. EMERY (1961)
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            Author and article information

            Affiliations
            [1 ] Universidad de Vigo España
            [2 ] Universidad Austral de Chile Chile
            Contributors
            Role: ND
            Role: ND
            Role: ND
            Journal
            rchnat
            Revista chilena de historia natural
            Rev. chil. hist. nat.
            Sociedad de Biología de Chile (Santiago )
            0716-078X
            December 2001
            : 74
            : 4
            : 885-897
            S0716-078X2001000400015 10.4067/S0716-078X2001000400015

            http://creativecommons.org/licenses/by/4.0/

            Product
            Product Information: SciELO Chile
            Categories
            BIODIVERSITY CONSERVATION
            ECOLOGY

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