Toxicity and toxicokinetics of cadmium in \u3ci\u3eCapitella\u3c/i\u3e sp. I: Relative importance of water and sediment as routes of cadmium uptake

The importance of dissolved versus sediment-bound cadmium as uptake routes for the deposit-feeding polychaete Capitella species I and the toxicity and toxicokinetics of cadmium from these exposure routes were investigated. Effects were reported as changes in worm growth rate, egestion rate and allometry. Radioactive cadmium (109Cd) was used as a tracer to examine the uptake (5 d) and subsequent depuration (6 d) of cadmium. Both effects and kinetics were investigated in systems with and without sediment. Individual Capitella sp. I were exposed to (1) dissolved (i.e. –1). Worms in water-only treatments showed negative growth rates, which decreased linearly from –5 to –10% d–1 with increasing cadmium concentration. Cadmium had no detectable effect on egestion rate or growth in the presence of sediment in either sediment-bound only (ca 36% d–1) or porewater & sediment (ca 30% d–1) treatments. Cadmium exposure had no detectable effect on the allometric exponent (i. e. area-length relation) in any of the treatments; however, worms in water-only treatments were relatively thinner than in the 2 treatments with sediment. Worms in porewater & sediment treatments took up ca 50-fold more cadmium (ca 195 ng Cd worm–1) than worms in water-only treatments (3.9 ng Cd worm–1) during 5 d of exposure. Sediment-bound cadmium was calculated to contribute 95 % of the total amount taken up by feeding worms. Starving worms retained all of the cadmium during the subsequent depuration period (6 d), and exhibited an increased weight-specific body burden (μg Cd g–1 dry wt worm) due to shrinkage. In feeding worms, the decrease in weight-specific body burden was faster (T½ = 3 d) than the decrease in total body burden (μg Cd worm–1; T½ = 11 d), indicating that both active excretion and dilution of cadmium body burden as a result of growth contributed to the change in cadmium tissue concentration during the depuration period. Thus, our results indicate that in Capitella sp. I sediment-bound cadmium is the major route of uptake. We found that cadmium affects starving but not fed worms, despite the fact that fed worms took up considerably more cadmium than starving worms. Our results suggest that stress associated with food limitation increases the susceptibility of worms to cadmium stress

Toxicity and toxicokinetics of cadmium in \u3ci\u3eCapitella\u3c/i\u3e sp. I: Relative importance of water and sediment as routes of cadmium uptake

The importance of dissolved versus sediment-bound cadmium as uptake routes for the deposit-feeding polychaete Capitella species I and the toxicity and toxicokinetics of cadmium from these exposure routes were investigated. Effects were reported as changes in worm growth rate, egestion rate and allometry. Radioactive cadmium (109Cd) was used as a tracer to examine the uptake (5 d) and subsequent depuration (6 d) of cadmium. Both effects and kinetics were investigated in systems with and without sediment. Individual Capitella sp. I were exposed to (1) dissolved (i.e. –1). Worms in water-only treatments showed negative growth rates, which decreased linearly from –5 to –10% d–1 with increasing cadmium concentration. Cadmium had no detectable effect on egestion rate or growth in the presence of sediment in either sediment-bound only (ca 36% d–1) or porewater & sediment (ca 30% d–1) treatments. Cadmium exposure had no detectable effect on the allometric exponent (i. e. area-length relation) in any of the treatments; however, worms in water-only treatments were relatively thinner than in the 2 treatments with sediment. Worms in porewater & sediment treatments took up ca 50-fold more cadmium (ca 195 ng Cd worm–1) than worms in water-only treatments (3.9 ng Cd worm–1) during 5 d of exposure. Sediment-bound cadmium was calculated to contribute 95 % of the total amount taken up by feeding worms. Starving worms retained all of the cadmium during the subsequent depuration period (6 d), and exhibited an increased weight-specific body burden (μg Cd g–1 dry wt worm) due to shrinkage. In feeding worms, the decrease in weight-specific body burden was faster (T½ = 3 d) than the decrease in total body burden (μg Cd worm–1; T½ = 11 d), indicating that both active excretion and dilution of cadmium body burden as a result of growth contributed to the change in cadmium tissue concentration during the depuration period. Thus, our results indicate that in Capitella sp. I sediment-bound cadmium is the major route of uptake. We found that cadmium affects starving but not fed worms, despite the fact that fed worms took up considerably more cadmium than starving worms. Our results suggest that stress associated with food limitation increases the susceptibility of worms to cadmium stress

Influence of Aging on Bioaccumulation and Toxicity of Copper Oxide Nanoparticles and Dissolved Copper in the Sediment-Dwelling Oligochaete <i>Tubifex tubifex</i>:A Long-Term Study Using a Stable Copper Isotope

For engineered metal nanoparticles (NPs), such as copper oxide (CuO) NPs, the sediment is recognized as a major compartment for NP accumulation. Sediment-dwelling organisms, such as the worm Tubifex tubifex, will be at particular risk of metal and metal NP exposure. However, a range of complex transformation processes in the sediment affects NP bioavailability and toxicity as the contamination ages. The objective of this study was to examine bioaccumulation and adverse effects of CuO NPs in T. tubifex compared to dissolved Cu (administered as CuCl2) and the influence of aging of spiked sediment. This was done in a 28-day exposure experiment with T. tubifex incubated in clean sediment or freshly spiked sediment with different concentrations of dissolved Cu (up to 230 μg g−1 dw) or CuO NPs (up to 40 μg g−1 dw). The experiment was repeated with the same sediments after it had been aged for 2 years. To obtain a distinct isotopic signature compared to background Cu, both Cu forms were based on the stable isotope 65Cu (&gt;99%). The 28-day exposure to sediment-associated dissolved 65Cu and 65CuO NPs resulted in a clear concentration-dependent increase in the T. tubifex65Cu body burden. However, despite the elevated 65Cu body burdens in exposed worms, limited adverse effects were observed in either of the two experiments (e.g., above 80% survival in all treatments, low or no effects on the growth rate, feeding rate, and reproduction). Organisms exposed to aged sediments had lower body burdens of 65Cu than those exposed to freshly spiked sediments and we suggest that aging decreases the bioavailability of both 65Cu forms. In this study, the use of a stable isotope made it possible to use environmentally realistic Cu concentrations and, at the same time, differentiate between newly accumulated 65Cu and background Cu in experimental samples despite the high background Cu concentrations in sediment and T. tubifex tissue. Realistic exposure concentrations and aging of NPs should preferably be included in future studies to increase environmental realism to accurately predict the environmental risk of metal NPs

Fate and effects of sediment-associated triclosan in subtropical freshwater microcosms

Triclosan (TCS) is an antibacterial agent that is commonly used in personal care products. Because of its sediment-binding properties, TCS exposure presents a potential threat to sediment-dwelling aquatic organisms. Currently our knowledge of the fate and effects of sediment-associated TCS in aquatic systems is limited. To understand the impact of sediment-associated TCS, we used microcosms to assess effects of TCS exposure on a diverse range of organisms selected to mimic a subtropical community, with an exposure period of 28 days. We included the oligochaete freshwater worm Limnodrilus hoffmeisteri to evaluate the interaction between sediment-associated TCS and sediment-dwelling organisms, including potential loss of TCS from the sediment due to biological activity and bioaccumulation. Benthic macroinvertebrate presence significantly increased the TCS levels from 0.013 ± 0.007 μg/L to 0.613 ± 0.030 μg/L in the overlying water through biological activity, posing a potential additional risk to pelagic species, but it did not result in a significant reduction of the sediment concentration. Furthermore, worms accumulated TCS with estimated Biota-Sediment-Accumulation-Factors (BSAFs) ranging between 0.38–3.55. Other than for algae, TCS at environmental concentrations did not affect the survival of the introduced organisms, including the L. hoffmeisteri. Our results demonstrate that, although TCS at currently detected maximum concentration may not have observable toxic effects on the benthic macroinvertebrates in the short term, it can lead to bioaccumulation in worms.</p