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Free Content Modeling effects of patchiness and biological variability on transport rates within bioturbated sediments

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Bioturbation models are typically one-dimensional, with the underlying assumption that tracer gradients are predominantly vertical, and that sediment reworking is laterally homogeneous. These models implicitly assume that bioturbation activity does not vary with horizontal location on the sediment surface. Benthic organisms, however, are often patchily distributed. Moreover, due to natural variability, bioturbation activity varies among individuals within a population, and hence, among bioturbated patches. Here we analyze a 1D model formulation that explicitly includes patchiness, exemplified by conveyor-belt transport. The patchiness is represented with one coefficient αb, as the fraction of bioturbated areas of the total area. First, all the mixed patches are considered to feature the same bioturbation rates. Then variability of these rates among patches is introduced in the model. The model is analyzed through different scenarios to assess the influence of patchiness and biological variability on the resulting tracer profiles (luminophores, 234Th and 210Pb). With patchiness, the principal feature of the resulting profiles is exponential decrease of tracer concentrations near the SWI, due to the accumulation of particles in the nonbioturbated patches, and the presence of subsurface peaks or anomalous concentrations at depth, as the result of particle transport in the bioturbated patches. This pattern is unusual compared to published patterns for conveyor-belt transport. Adding intra-population variability in bioturbation rates induces biodiffusive-like transport, especially with luminophores. This theoretical work provides new insights about the influence of patch structure on particle dispersion within sediments and proposes a new applicable approach to model various bioturbation processes (type and rates of transport) that can be horizontally distributed in sediments.

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Document Type: Research Article

Publication date: March 1, 2008

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  • The Journal of Marine Research, one of the oldest journals in American marine science, publishes peer-reviewed research articles covering a broad array of topics in physical, biological and chemical oceanography. Articles that deal with processes, as well as those that report significant observations, are welcome. Biological studies involving coupling between ecological and physical processes are preferred over those that report systematics. The editors strive always to serve authors and readers in the academic oceanographic community by publishing papers vital to the marine research in the long and rich tradition of the Sears Foundation for Marine Research. We welcome you to the Journal of Marine Research.
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