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%).