Inhibition Effects of Cobalt Nano Particles Against Fresh Water Algal Blooms Caused by <i>Microcystis</i> and <i>Oscillatoria</i>

Abstract

Cyanobacterial blooms deplete nutrients, reduce water clarity, exhaust carbon di oxide and produces secondary metabolites which negatively affect aquatic organisms and water quality. Control of algal blooms using metal nano particles is one effective method for the safety of water environment. Cobalt nano particles (CoNPs) were synthesized and tested against microalgae isolated from fresh water cyanobacterial blooms by assessing the effects on growth rate, biomass concentration, photosynthetic pigments concentration and antioxidant enzyme activity. Microcystis and Oscillatoria were identified as the predominant isolates from algal blooms and treated with varying concentrations (1, 2, 3, 4 and 5 mg·L -1 ) of CoNPs. Steady decline in the growth rate of microalgae was observed at the end of 5 days indicating the toxicity of CoNPs on microalgal growth. At the end of cultivation period, 78% and 88% of reduction in biomass concentration of Microcystis and Oscillatoria were observed at 5 mg·L -1 of CoNPs. The chlorophyll content was reduced from 1.53 to 0.24 mg·L -1 in Microcystis and 1.63 to 0.29 mg·L -1 in Oscillatoria. There was a 69.3% and 73.2% decrease in carotenoid content of Microcystis and Oscillatoria respectively. Both protein and carbohydrate contents of the microalgae were reduced with increasing concentration of nano particles. The decrease in Super oxide dismutase (SOD) activity with increased nanoparticle concentration reveals the formation of stress in the microalgae. The increasing GSH activity proved the effect of CoNPs on the activation of antioxidative enzymes to protect the cells. This study demonstrates the efficiency of cobalt nano particles (CoNPs) on inhibition of fresh water algal blooms thereby reducing the eutrophication problem.

Biosensing the Presence of Metal Nanoparticles by Spectrally- and Time-Resolved Endogenous Fluorescence in Water Moss Fontinalis antipyretica

“…The observed effect of Cu can also be related to the fact that the Cu was demonstrated to have a higher adsorption capacity than Ni and Zn in the moss [42]. On the other hand, Co NPs were shown to inhibit fresh water algal bloom by decreasing super oxide dismutase (SOD) activity with increased NPs concentration, indicating the formation of stress in the microalgae [29]. Notwithstanding, even though cellular alterations were described by NiO NPs, including effects on the photosynthetic apparatus via chlorophyll synthesis, photochemical reactions of photosynthesis and oxidative stress [28], we noted little or no effect of the Ni NPs on the overall fluorescence intensity.…”

“…CuO, as well as ZnO NPs were shown to have antimicrobial properties [25][26][27]. Ni and Co NPs were also demonstrated to induce stress in the microalgae [28,29]. Under heavy metals exposure, the growth and the chemical composition of several substances, including chlorophylls, have been reduced within the first 48 h [30].…”

Evaluation of Ecotoxicology Assessment Methods of Nanomaterials and Their Effects

“…Decline in the growth rate and reduction in biomass concentration of two cyanobacteria, Microcystis and Oscillatoria, was observed at exposure to Co NMs. Other observed effects were the reduction of carotenoid, protein and carbohydrates contents and the decrease of SOD activity with increase of NMs concentration in the microalgae [152].…”