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La bioturbation actuelle dans le milieu abyssal de l'Océan atlantique nord

Abstract : The intensity of present bioturbation is investigated in three North Atlantic deep-sea basins and define the connected environment control. The considered environmental parameters are topography, depth, hydrodynamism, faunistic density and sedimentation. This complete data set on abyssal ecology was collected during oceanographic deep-sea cruises. In a first step, starting material, made up of 2524 photographs of the ocean bottom, is surveyed to study the animal trace repartition ("Iebenspuren"). Two groups of traces are distinguished: superficial traces and relief traces. In the second laboratory step, the upper layer sediment reworking ("mixed layer") is precisely obtained by mixing rate measurement. Sediment reworking is localized where high trophic deposits are registered. High mixing rate is measured in the lower section of Amazonian deep-sea fan sediments and also in the Bay of Biscay sediments. Short preservation times of the traces characterize those areas. Observed traces are essentially of relief trace type relevant to deep reworking. In return, abyssal oligotrophic plain sediments (Demerara abyssal plain, Cape Verde basin) are poorly reworked and affect the two centimeters uppermost layer. This type of environment is characterized by long preservation times of the traces, high densities and relative abundances of surficial traces. Bioturbation intensity variations are evaluated from the mixing rates calculated for superficial sediment and the abundances and diversities of traces. Those variations are found to be directly related to the specific ecology of the three basins.
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Anne Mauviel. La bioturbation actuelle dans le milieu abyssal de l'Océan atlantique nord. Sciences de la Terre. Université de Bretagne Occidentale (UBO), Brest, 1982. Français. ⟨tel-02427477⟩

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