Toxicological Effects of Mercuric Chloride Exposure on Scenedesmus quadricauda

Mercuric chloride (HgCl2) is a common heavy-metal pollutant widely used in commercial products and industry, but its excessive use uncontrolled discharge have caused great harm to aquatic environments human health. To research the mechanisms of HgCl2 toxicity organisms, this study cultured green alga Scenedesmus quadricauda gradient concentrations (0, 0.1, 0.3, 0.5, 0.7, 0.9 mg/L) for 9 days. The results showed that: (1) when were high (?0.7 mg/L), toxic effects completely inhibited growth algal cells, culture liquid changed from light yellow, cells aggregated sank bottom. Submicroscopic structural imaging that at mg/L HgCl2, seriously damaged obvious plasma–wall separation occurred. Furthermore, arrangement photosynthetic lamellae became disordered nuclei protein faded or even disappeared. (2) When low medium (?0.5 activity superoxide dismutase (SOD) increased first five days, degree increase was smaller than control group. However, under SOD began decrease sharply on seventh day. peroxidase (POD) decreased more obviously SOD. (3) Under (?0.5 content malondialdehyde (MDA) over time, had not again by last day measurement. In contrast, contents total (TP) soluble sugar (SS) both exhibited decreasing trends concentrations. (4) ?0.7 mg/L, pigments decreased, quantum yield PS ? decreased. At same as time progressed, electron transfer energy-conversion efficiency photosynthesis never returned normal levels. This provides reference understanding mechanism which pollution affects ecosystems may help with management future.