Abstract
The objective of the present work was to evaluate the effect of exogenously applied cadmium on the physiological response of green algae Chlorella vulgaris. The study investigated the long-term effect (18 days) of cadmium on the levels of algae biomass, assimilation pigment composition, soluble protein, oxidative status (production of hydrogen peroxide and superoxide anion), antioxidant enzymes (such as superoxide dismutase, peroxidase, catalase and glutathione reductase enzyme) in C. vulgaris. The results showed that growth, the amount of chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoids gradually decreased with increasing cadmium over 18 days exposure. Cadmium at concentration of 7 mg L−1 inhibited algal growth expressed as the number of cells. Our research found that C. vulgaris has a high tolerance to cadmium. Contents of chlorophylls (Chl a and Chl b) and carotenoids (Car) of C. vulgaris was significantly decline with rising concentration of cadmium (p < 0.05). The decrease of 54.04 and 93.37 % in Chl a, 60.65 and 74.32 % in Chl b, 50.00 and 71.88 % in total carotenoids was noticed following the treatment with 3 and 7 mg L−1 cadmium doses compared with control treatment, respectively. Cadmium treatments caused a significant change in the physiological competence (calculated as chlorophyll a/b) which increased with increasing Cd(II) doses up to 1 mg L−1 but decreased at 3 mg L−1. While accumulation of soluble protein was enhanced by presence of cadmium, the treatment with cadmium at 3 and 7 mg L−1 increased the concentration of soluble proteins by 88, 95.8 % in C. vulgaris, respectively. Moreover, low doses of cadmium stimulated enzymatic (superoxide dismutase, catalase and glutathione reductase) in C. vulgaris, The content of peroxidase increased with the increasing cadmium concentration, and had slightly decreased at the concentration of 7 mg L−1, but was still higher than control group, which showed that cadmium stress at high concentration mainly peroxidase works in C. vulgaris. And therefore, suppressed reactive oxygen species (hydrogen peroxide and superoxide) accumulated. The present study also showed that cadmium increased oxidative stress and induced antioxidant defense systems against reactive oxygen species. The observation in here analyzed C. vulgaris after exposure to cadmium indicate that hydrogen peroxide, superoxide and peroxidase in the alga with exposure to Cd(II) seemed to be parameters as biomarkers for metal-induced oxidative stress.
Highlights
Heavy metals are important environmental pollutants, water environmental deterioration caused by heavy metal emissions are increasing, and produce toxic effects on aquatic plants
The result indicted that C. vulgaris can be well tolerated with 1–5 mg L−1 cadmium, the growth is inhibited under high concentration, C. vulgaris still can be lived in 5 mg L−1
Our research found that C. vulgaris has a high tolerance to cadmium
Summary
Heavy metals are important environmental pollutants, water environmental deterioration caused by heavy metal emissions are increasing, and produce toxic effects on aquatic plants. When subjected to environmental stress, such as, strong light (Romanowska et al 2008), ultraviolet radiation (Zhang et al 2005; Schmidt et al 2011) and heavy metal stress (Dai 2012), will produce reactive oxygen species (ROS), such as superoxide (O2−·), hydroxide (OH−), hydroxyl radical (·OH), hydrogen peroxide (H2O2). The antioxidant protection system like the superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione reductase enzyme (GR), et al can remove the excess ROS induced by stress, protecting cells against injury (Zhou et al 2001). SOD is the first key enzyme to scavenging reactive oxygen species in plants; in organisms it is in an important position in the active oxygen metabolism, which can disproportionate O2− to be H2O2, thereby protecting cells oxidative free radical damage. The morphology, growth, photosynthetic pigments, cell biology and physiology of algal were affected (Bouzon et al 2011; Schmidt et al 2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
