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Mathematical Investigation of the Applicability of Benthic Ascidians as Biological Filters in Coastal Areas
Katerina D. Kombiadou, Yannis N. Krestenitis, Chryssanthi Antoniadou, and Chariton Chintiroglou

The effect of filter-feeding organisms to the rearrangement of particulate matter in the hyperbenthic parts of the water column in marine ecosystems is significant, as their positive contribution in eutrophication control and lucidity improvement has been well established. A suspended sediment three-dimensional transport-dispersion model, based on the tracer method, has been employed for the investigation of the ability of benthic ascidians to remove suspended matter from the water column. The model, apart from the various physical processes that control the transport and alterations to characteristic properties of a sedimentary plume, describes the action of benthic ascidians as mass-loss terms of particles that reenter the flow after filtration by the benthic organisms. Both laboratory and in-situ data have been utilized for the formulation of the model, that has been applied in the southeastern part of the Thermaikos Gulf (NW Aegean sea), area in which dense populations of the ascidian Styela plicata occur. Four simulations have been performed to establish the level of particle removal from suspension due to ascidians, each considering a different benthic population. The results of the simulations have indicated high percentages of filtered mass by ascidians and, correspondingly, reduction of the mass in suspension at satisfactory levels, supporting the perspective that benthic ascidians can be applied as biological filters for the improvement of the quality of coastal waters.

Keywords: Ascidia, Tracer model, Thermaikos Gulf, Biological filters, Coastal areas, Sediment transport modeling, Styela plicata, Suspended sediments

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