Metal-based engineered nanomaterials (NMs) and nanoparticles (NPs), as an emerging class of non-biodegradable contaminants, are known to possess adverse effects on natural ecosystems. However, the ecotoxicological effects of NMs and NPs on species interactions in ecological communities remain largely unknown. In this study, we experimentally investigated the impact of copper oxide (CuO) NPs and its bulk counterpart (CuO BPs) on species’ competitive outcomes and coexistence in laboratory-assembled microcosms, using two freshwater ciliates Colpidium striatum and Tetrahymena pyriformis as model organisms.
Results/Conclusions
We found that long-term exposure to CuO NPs significantly reduced the intrinsic growth rate (r) and carrying capacity (K) of both protozoan species, whereas neither CuO BPs nor Cu2+ exhibited any significant effect. The presence of CuO NPs and BPs altered the competitive outcomes between C. striatum and T. pyriformis with an accelerated rate of competitive exclusion of C. striatum in the CuO NPs treatment when both species were present, while they coexisted in the Cu2+ treatment and control. Such changes in competitive outcomes are likely driven by changes in the niche and fitness differences after exposure to CuO NPs. Further mutual invasion experiment revealed a decreased niche difference and increased fitness difference between the competitors under the influence of CuO NPs. Our findings indicate that it is essential to take a community approach in nanotoxicology research for gaining a more comprehensive understanding of the ecological consequences of nanoparticle pollution.