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Sediments
Published in Michael J. Kennish, Ecology of Estuaries Physical and Chemical Aspects, 2019
Bioturbation involves both particle transport and the exchange of sediment pore water and overlying water. Fluid bioturbation (water pumping) is 10 to 100 times greater, on a weight-to-weight basis, than particle bioturbation.109,111 Recently, bioturbation has been viewed in the context of a successional paradigm, whereby changes in sediment properties are related to a gradual change in the trophic structure and life habits of benthic fauna.85,112,113 Thus, it is possible to differentiate pioneering from equilibrium assemblages of organisms in the successional pattern. Pioneering species tend to be tubicolous or otherwise sedentary animals with r-selected adaptive strategies that feed near the sediment surface or from the water column. They are not effective agents in the mixing of sediment. Effects of these populations on the sedimentary regime are confined to the near-surface region of the bottom (<2 cm) and, as described by Rhoads and Boyer85 (p. 8), include the following: Construction of dense tube aggregations, which may affect microtopography and bottom roughness on a scale dictated by tube diameter, tube height, and tube spacing.Fluid bioturbation, which pumps water into and out of the bottom through vertically oriented tubes. Particle bioturbation, although present, is of subordinate importance.Surface deposit feeding and suspension feeding, which cover the surface of the bottom with fecal pellets, especially the fusiform pellets of opportunistic polychaetes.
Biodynamics and adverse effects of CuO nanoparticles and CuCl2 in the oligochaete T. tubifex: Cu form influence biodynamics in water, but not sediment
Published in Nanotoxicology, 2021
In order to evaluate the relative importance of water and sediment as uptake routes, Kuw and Kus in similar units (i.e. L g−1 g−1 day−1 and Kg g−1 g−1 day−1) can be compared. For both Cu treatments, Kus becomes < 0.001 Kg g−1 g−1 day−1 and thus considerably lower than the uptake rates from water. Similarly, uptake of CeO2 NPs from sediment has been reported to be considerably lower than uptake from water for L. variegatus (Cross, Tyler, and Galloway 2019). These findings may indicate that water is the main route of Cu uptake in aquatic environments. However, this is most likely offset by the partitioning of Cu between sediment and overlying water, which is often in the range of 103 to 105 L kg−1 in freshwater sediment (Gardham et al. 2014). This difference may be even more pronounced for CuO NPs, which have a tendency to agglomerate/aggregate in the aquatic environment and thus settle out of suspension and accumulate in the sediment. Consequently, even though the Kus is lower than the Kuw the much higher concentration in the sediment may result in this pathway being the most significant for Cu body burden in deposit-feeding organisms.