Multiwalled Carbon Nanotubes at Environmentally Relevant Concentrations Affect the Composition of Benthic Communities

To date, chronic effect studies with manufactured nanomaterials under field conditions are scarce. Here, we report <i>in situ</i> effects of 0, 0.002, 0.02, 0.2, and 2 g/kg multiwalled carbon nanotubes (MWCNTs) in sediment on the benthic community composition after 15 months of exposure. Effects observed after 15 months were compared to those observed after 3 months and to community effects of another carbonaceous material (activated carbon; AC), which was simultaneously tested in a parallel study. Redundancy analysis with variance partitioning revealed a total explained variance of 51.7% of the variation in community composition after 15 months, of which MWCNT dose explained a statistically significant 9.9%. By stepwise excluding the highest MWCNT concentrations in the statistical analyses, MWCNT effects were shown to be statistically significant already at the lowest dose investigated, which can be considered environmentally relevant. We conclude that despite prolonged aging, encapsulation, and burial, MWCNTs can affect the structure of natural benthic communities in the field. This effect was similar to that of AC observed in a parallel experiment, which however was applied at a 50 times higher maximum dose. This suggests that the benthic community was more sensitive to MWCNTs than to the bulk carbon material AC

Long-Term Recovery of Benthic Communities in Sediments Amended with Activated Carbon

Using activated carbon (AC) for sediment remediation may have negative effects on benthic communities. To date, most AC effect studies were short-term and limited to single species laboratory tests. Here, we studied the effects of AC on the recolonization of benthic communities. Sediment from an unpolluted site was amended with increasing levels of AC, placed in trays and randomly embedded in the original site, which acted as a donor system for recolonization of benthic species. After 3 and 15 months, the trays were retrieved and benthic organisms identified. A positive trend with AC was detected for species abundance after 3 months, whereas after 15 months a negative trend with AC was detected for Lumbriculidae and Pisidiidae. On the community level, statistical analyses showed a considerable recovery in terms of species diversity and abundance in 3 months and full recovery of the community after 15 months. This was explained from migration of individuals from the donor system, followed by further migration and reproduction of the species in the next year. AC treatments explained 3% of the variance in the community data. This work suggests that AC community effects are mild as long as AC levels are not too high (1–4%)