Time-Dependent Toxicity and Health Effects Mechanism of Cadmium to Three Green Algae

Abstract

As algae are extremely sensitive to heavy-metal ions and can be critical biological indicators in the heavy-metal toxicity analyses conducted by environmental health researchers, this paper explores the sensitivity to temporal toxicity of three species of green algae: Scenedesmus obliquus, Chlorella pyrenoidosa, and Selenastrum capricornutum. The method of time-dependent microplate toxicity analysis was used to systematically investigate the changes in the toxicities of the three green-algae species induced by different concentrations of cadmium (Cd). The chlorophyll a content, antioxidant enzyme activity, and malondialdehyde (MDA) content in the algae were analyzed to explore the mechanism of Cd toxicity after 96 h of exposure. The results showed that the toxic effects of Cd on the three algae species were time-dependent. By comparing the toxic effect of Cd, indicated by pEC50 (the negative logarithm of EC50), on the algae species at four durations of exposure (24, 48, 72, and 96 h), this study found that the indicator organisms had different sensitivities to Cd. The order of sensitivity was C. pyrenoidosa > S. obliquus > S. capricornutum. Cd exposure had significant effects on the chlorophyll a and MDA content and on the enzyme activity of superoxide dismutase (SOD) and catalase (CAT) in the algae species. The chlorophyll a content in the cells of the algae decreased with increasing Cd concentration. The enzyme activity of CAT and content of MDA increased with increasing Cd concentration, which indicated that Cd had an oxidative stress effect on the three algae species.

Toxicity, physiological response, and biosorption mechanism of Dunaliella salina to copper, lead, and cadmium

“…Their pivotal role in diverse physiological and biochemical processes cannot be understated, encompassing photosynthesis, respiration, signal transduction, and the antioxidant system, laying a solid foundation for plant growth and metabolisms ( Moenne et al, 2016 ; Maleki et al, 2017 ). An increasing number of reports have indicated that heavy metals can restrain the growth of various algae and influence their physiological function, accompanied by the changes in photosynthetic pigments, polysaccharides, and protein ( Chen et al, 2012 ; Bosnir et al, 2013 ; Cao et al, 2015b ; Cheng et al, 2016 ; Mu et al, 2018 ; Bhattacharya, 2020 ; Nowicka et al, 2020 ; Wang et al, 2021 ; Mo et al, 2022 ). However, El Agawany et al (2021) indicated that protein content of Dunaliella tertiolecta increased under low concentrations of Ni + , Zn 2+ , and Cu 2+ , whereas high concentrations of heavy metals impeded protein synthesis.…”

Mitigating Effect of Trans-Zeatin on Cadmium Toxicity in Desmodesmus armatus

“…The ability of heavy metals to inhibit microalgal growth depends on the metal concentration, the specific species of algae, and the exposure time [6,7,56]. Growth reduction in response to Cd has been reported for many algal species, such as Chlorella vulgaris [56], Chlamydomonas reinhardtii [12,57], A. obliquus, Chlorella pyrenoidosa, and Selenastrum capricornutum [58]. The higher inhibition of D. armatus growth observed in our studies with increased Cd concentrations may be explained by its damaging effects on algal cell morphology and physiology [40].…”

“…Compared to unstressed D. armatus cells, significant increases in the contents of H 2 O 2 (by 82.6%) and MDA (by 51.9%) were observed in cultures exposed to 10 µM of Cd at 96 h of cultivation (Figure 3). Oxidative stress induced by heavy metals has been reported in many vascular plant species [12,57] and algae, such as C. vulgaris [3], A. obliquus, C. pyrenoidosa, and S. capricornutum [58]. Consequently, Cd disrupts the redox homeostasis, thereby affecting the cell functioning and tolerance potential of alga D. armatus.…”

Over-Produced Extracellular Polymeric Substances and Activated Antioxidant Enzymes Attribute to Resistance of Pb(II) for Algal–Bacterial Granular Sludge in Municipal Wastewater Treatment

“…In addition, the massive production of these reactive oxygen species could trigger or intensify the membrane lipid peroxidation, causing serious damage to the membrane system. The product of the membrane lipid peroxidation, MDA, could be used as an indicator to reflect the oxidative pressure faced by algae cells [45]. As seen in Figure 5, MDA content was insignificantly different at 1-7.…”