Phytotoxic effects of seaweed mediated copper nanoparticles against the harmful alga: Lyngbya majuscula

In this study, copper nanoparticles (Cu-NPs) were synthesized using Corallina officinalis Linnaeus and Corallina mediterranea Areschoug aqueous extracts. Transmission Electron microscope indicated that the biosynthesized Cu-NPs averaged 12.7 nm and 13.6 nm for C. Officinalis and C. mediterranea, respectively. As reported by the FT-IR analyses, the algal extracts contain phyto-chemicals such as proteins, carboxylic acids, complex carbohydrates; these compounds will act as encapsulating agents and be reduced from copper sulphate to Cu-NPs. Energy-dispersive analyses X-ray (EDX) confirmed the copper composition in the synthesized Cu-NPs. The biosynthesized Cu-NPs arrested the growth of Lyngbya majuscula and presented in time and concentration dependent trends. At a concentration of 2 μg/mL, Cu-NPs, synthesized by C. officinalis exerted 85 ± 4% reduction of the algae dry weight. Increasing Cu-NPs concentration led to excellent reduction, which is a very promising result. Cupper-NPs synthesized by C. mediterranea produced moderate effects on L. majuscula. The results also indicated that there were sharp decreases in chlorophyll a content in L. majuscula with the increase in Cu-NPs concentrations. Using 4 μg/mL of Cu-NPs derived from C. officinalis, chlorophyll a decreased by 48 ± 5%. On the other hand, lower reductions in chlorophyll a were recorded upon using Cu-NPs synthesized using C. mediterranea (36 ± 3% and 41 ± 5% reductions at concentrations of 2 μg/mL and 4 μg/mL, respectively). The results of this study suggested that the bioactive and allelopathic compounds derived from the two algal extracts coating the (Cu2+) together with (Cu2+) are responsible for the inhibitive impacts of Cu-NPs on L. majuscula.