Nanoclays represent a large class of modified nanomaterials (NMs) that have received great attention from the scientific and industrial communities. One important use of nanoclays is that they are useful in wastewater treatment and pollution control for removing toxic chemicals from water supplies. Nevertheless, many concerns have been raised about the effect of modified nanomaterials for aquatic ecosystems as the nanomaterials themselves could have adverse effects. In this study, we investigated the potential toxic effects of a natural nanoclay (Na+ montmorillonite) and two modified nanoclays (Cloisite®30B and NovaclayTM) on population growth of Chlamydomonas reinhardtii, and on survivorship and body growth of Daphnia magna and Chironomus dilutus. We did this by conducting three lab experiments (one for each of the three species) that exposed organisms to one of each type of nanoclay at each of six nanoclay concentrations. The range of nanoclay concentrations that we considered was reflective of the variation in nanoclay concentrations observed in nature.
Results/Conclusions
We found that even a low dose of Cloisite® 30B suppressed algal population growth and its affect increased with concentration. In contrast, substantially higher concentrations of NovaclayTM and natural nanoclay was necessary to negatively affect algal population growth. Similarly, an increase in the concentration of Cloisite® 30B reduced survival of D. magna. The concentration of Cloisite® 30B that caused a substantial reduction in D. magna survival was rather low and all D. magna died when exposed to the two highest concentrations of Cloisite® 30B in our study. Cloisite® 30B caused any D. magna that survived to have slower body growth than D. magna not exposed to Cloisite® 30B. NovaclayTM and natural nanoclay also reduced the survival of D. magna but only at relatively high, but realistic, concentrations. None of the nanoclay types we studied had adverse impacts on the survival of C. dilutus. An increase in the concentration of Cloisite® 30B, but not natural nanoclay or NovaclayTM, adversely affected body growth of C. dilutus. This work highlights that different types of nanoclay affect aquatic organisms differently and that we should be careful about the kinds of modified nanoclays that we introduce into aquatic environments.