Salinity-Based Toxicity of CuO Nanoparticles, CuO-Bulk and Cu Ion to Vibrio anguillarum.

Bacteria are used in ecotoxicology for their important role in marine ecosystems and their quick, reproducible responses. Here we applied a recently proposed method to assess the ecotoxicity of nanomaterials on the ubiquitous marine bacterium Vibrio anguillarum, as representative of brackish and marine ecosystems. The test allows the determination of 6-h EC50 in a wide range of salinity, by assessing the reduction of bacteria actively replicating and forming colonies. The toxicity of copper oxide nanoparticles (CuO NPs) at different salinities (5-20-35 ‰) was evaluated. CuSO4 5H2O and CuO bulk were used as reference toxicants (solubility and size control, respectively). Aggregation and stability of CuO NP in final testing dispersions were characterized; Cu2+ dissolution and the physical interactions between Vibrio and CuO NPs were also investigated. All the chemical forms of copper showed a clear dose-response relationship, although their toxicity was different. The order of decreasing toxicity was: CuSO4 5H2O > CuO NP > CuO bulk. As expected, the size of CuO NP aggregates increased with salinity and, concurrently, their toxicity decreased. Results confirmed the intrinsic toxicity of CuO NPs, showing modest Cu2+ dissolution and no evidence of CuO NP internalization or induction of bacterial morphological alterations. This study showed the V. anguillarum bioassay as an effective tool for the risk assessment of nanomaterials in marine and brackish environments.

Uneven frequency of Vibrio alginolyticus-group isolates among different populations of Galápagos marine iguana (Amblyrhynchus cristatus).

The presence of Vibrio isolates was investigated in cloacal swabs from the Galápagos marine iguana (Amblyrhyncus cristatus). Such unique iguana is endemic to the Galápagos Archipelago, it is listed as vulnerable in the IUCN Red List (2009), and is strictly protected by CITES and Ecuador laws. Our results revealed an uneven isolation frequency of vibrios from animals living in different settings: maximal among the Santa Fe population, scarce at Bahía Tortuga but practically absent in the samples from Puerto Ayora and Plaza Sur. A 16S sequencing confirmed that the isolates belonged to the genus Vibrio, placing them within the V. alginolyticus group; the biochemical identification was, indeed, consistent with V. alginolyticus features. The reason of the observed discrepancy is not clear, but could be either linked to a higher pollution in the inhabited or more touristic places or to differential influence of chemical and physical parameters at a local scale. As V. alginolyticus is an opportunistic pathogen for man and it is known to cause disease in sea-living animals, the ability of these vibrios to enter and persist to a certain extent in the marine iguana gut should be regarded as a risk for health of both the animals and the human personnel involved in monitoring activities.