Inhibitory mechanism of nano-copper carbon composite on Microcystis aeruginosa

Abstract

Nano‑copper carbon composite (NCCC), a typical core-shell-structure carbon-coated nano‑copper material was prepared to investigate its inhibitory effect and toxicity on Microcystis aeruginosa. The two indices (Chlorophyll-a concentration and dehydrogenase activity level/biomass) indicated that NCCC remarkably suppressed the growth of algal cells in a dosage-dependent way. The NCCC group (20 mg·L−1) showed the similar inhibitory effect of 6 mg·L−1 CuSO4. However, the Cu concentration in 20 mg·L−1 NCCC containing Cu element about 22 % (mass ratio) was much lower than that of 6 mg·L−1 CuSO4, indicating that toxicity of NCCC on algal cells was not only due to the toxic effect of Cu2+. The changes of enzymatic antioxidant activities and lipid peroxidation damage demonstrated that under the stress of NCCC, Microcystis aeruginosa cells were exposed to oxidative damage. The formation of ROS (reactive oxygen species) by NCCC was much higher than a comparable amount of Cu2+, pointing out that exceeded ROS was not only generated by the released Cu2+ but probably also induced by the photocatalytic activity of Cu2O. Moreover, the fluorescein diacetate (FDA)-propidium iodide (PI) double staining method was applied to explore the toxicity mechanisms, illustrating that NCCC resulted in the damage of membrane integrity, and the cell death mode of algal cells under the inhibition of NCCC was necrosis-like. In general, compared with CuSO4, NCCC had a more efficient and durable inhibitory effect, and released a lower concentration of copper in water, resulting in less secondary contamination to water. Therefore, NCCC is a novel environmental friendly inhibitor for cyanobacterial bloom control instead of CuSO4.