title: Phosphorus availability changes chromium toxicity in the freshwater alga Chlorella vulgaris.
abstract: Chromium (Cr) is one of the most serious pollutants in aquatic systems. This study examined the relationship between the toxic effects of Cr on the freshwater alga Chlorella vulgaris and phosphorus (P) availability on the algal physiology and ultrastructure. Cr inhibited C. vulgaris growth in a concentration- and time-dependent manner, and its inhibitory effect was related to the P concentration. In a low-P medium, Cr showed approximately 2.2-3.7-fold stronger toxicity than in a high-P medium. Cr was absorbed into the algal body where it disrupted the chloroplast structure and decreased the chlorophyll content. However, Cr had a weaker chlorophyll inhibitory ability and destructive power against the chloroplasts in the high-P medium than in the low-P medium due to the partial blockage of Cr absorption in high P-medium. Cr exposure also changed the metal ion and anion absorption profiles, which was also closely related to the concentration of P. Cr treatment increased the volume of the vacuole, and the larger vacuole reduced the space available for chloroplasts, as based on optical and electron microscopy results, but a higher P availability could alleviate this damage. These results suggest that high P alleviated the toxicity of Cr by decreasing Cr absorption and increasing the absorption of beneficial ions. It is, therefore, necessary to consider the phosphorus availability when the toxicity of metal compounds is evaluated.
authors.affiliation: College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, People's Republic of China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Qian
authors.forename: Zhengqi
authors.initials: Z
authors.lastname: Sun
authors.forename: Liwei
authors.initials: L
authors.lastname: Sun
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Jiang
authors.forename: Yong
authors.initials: Y
authors.lastname: Wei
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.forename: Zhengwei
authors.initials: Z
authors.lastname: Fu
mesh_terms: D048408:Chlorella vulgaris / Q000187:drug effects* / Q000502:physiology; D002857:Chromium / Q000633:toxicity*; D005618:Fresh Water / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis* / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium; D010758:Phosphorus
keywords: Chlorella vulgaris; Chromium; Ion absorption; Phosphorus; Substructure