Effect of zinc oxide and copper oxide nanoparticles on picophytoplankton of the Black sea during the winter season
摘要
The effects of metal oxide nanoparticles (NPs) on marine phytoplankton have mostly been studied in laboratory monocultures, while data on natural communities during the cold season remain scarce. In particular, the selective pressure of NPs on the balance between prokaryotic and eukaryotic picoplankton components under varying abiotic conditions is poorly understood. We investigated the effects of ZnO and CuO NPs (20–60 µg L−1) on a winter natural picophytoplankton community from the Black Sea (cyanobacterium Synechococcus spp. and picoeukaryotes) under conditions simulating the winter hydrological regime. A dose- and time-dependent toxic effect was observed. The prokaryotic component was significantly more sensitive than the eukaryotic one, especially to CuO NPs, which caused sustained suppression of cyanobacteria (their share dropped to 2–9%) and dominance of picoeukaryotes (up to 98%). ZnO NPs were less toxic, and their effect diminished over time, allowing the community to restore a balanced structure (≈50/50% by February). Correlation analysis revealed opposite modulation of toxicity by abiotic factors for the two groups. For picoeukaryotes, high light intensity and temperature synergistically enhanced toxicity (especially of CuO NPs), whereas a high N/P ratio acted as a strong protective factor. For cyanobacteria, the toxicity of ZnO NPs was also enhanced by light and mitigated by a high N/P ratio; however, the toxicity of CuO NPs paradoxically decreased with increasing temperature and sharply increased under a high N/P ratio. Thus, metal oxide NPs exert strong selective pressure on picophytoplankton community structure, with the direction of this pressure critically depending on NP type, species composition, and abiotic conditions. These findings have important implications for predicting ecological shifts in marine ecosystems under increasing NP pollution.