Sediments
Michael J. Kennish in 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.
Mercury disrupts redox status, up-regulates metallothionein and induces genotoxicity in respiratory tree of sea cucumber (Holothuria forskali)
Published in Drug and Chemical Toxicology, 2020
Khaoula Telahigue, Imen Rabeh, Safa Bejaoui, Tarek Hajji, Salwa Nechi, Emna Chelbi, M’hamed El Cafsi, Nejla Soudani
Holothurians belong to the phylum of Echinodermata and are commonly named sea cucumbers. They are detritivore marine invertebrates widely distributed in coastal areas of tropical and temperate zone (Yu et al. 2014). In the 1,250 sea cucumber species in the world, only 66 species are commonly exploited (Purcell 2010). They have been consumed as popular food and widely used, for centuries, by Asian communities in traditional medicine (Raison 2008). Over the last few decades, sea cucumbers have been increasingly considered among the most promising marine resources. This is due to their important biologically active components such as saponins, chondroitin sulfates, glycosaminoglycan, sulfated polysaccharides (Bordbar et al. 2011). Their anti-inflammatory (Collin 2004), anticancer (Aminin et al. 2015), antimicrobial (Hing et al. 2007) and antioxidant (Althunibat et al. 2009) properties were also approved on several organisms as well as humans. The rising market for these species in the Indo-Pacific region has led to their over-exploitation and the depletion of their natural stocks in some sites (Purcell et al. 2013). The sea cucumber trade has been flourishing globally in about 70 countries across the world (Purcell et al. 2013). According to Anderson et al. (2011), the global catch and production of sea cucumber has increased 13 and 16 fold over the past two to three decades, respectively. In the Mediterranean Sea, holothurians are nearly unexploited. Among the listed species, only five are consumed (Sicuro et al. 2012). Recently, harvesting of sea cucumbers in industrialized fisheries has emerged in some parts of the Mediterranean Sea (Ramón et al. 2010). In Tunisia, sea cucumbers are not considered as seafood but they are locally harvested by consumers as an aphrodisiac or as a remedy for hemorrhoids in some coastal villages. Against this background, some studies have been undertaken to evaluate the potential nutraceutical or pharmaceutical properties of sea cucumber from Tunisian coasts (Ismail et al. 2008, Neifar et al. 2011, Telahigue et al. 2014).
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