Biological Effects Of Arsenic On Chlorella Vulgaris Mediated By Different Concentrations Of Phosphorus

Microalgae resources are very rich and widely distributed in our country. Heavymetals, including arsenic the concentration of which causes attention in Microalgae,can affect human health and life activities seriously. In order to probe effects ofphosphorus on toxic action of arsenic, further understand toxicity mechanism ofarsenic, we researched the effects of arsenic on physiology and biochemistry ofChlorella vulgaris mediated by different concentrations of phosphorus.At the same concentration of As, with the increase of P the biomass of Chlorellavulgaris increased. As at low concentration of1μmol/L had negligible toxicic effecton Chlorella vulgaris, which may indicates the hormesis response of trace amount oftoxicants. As of1μmol/L increased the biomass of Chlorella vulgaris at the sameconcentration of phosphorus (0, f/10, f/5and f/2), while As at other concentrations didnot.P can help to maintain the integrity of the Chlorella vulgaris cell membrane,under all the tested concentrations of arsenic (0~30μmol/L). At the Lowerconcentration of phosphorus (0and f/10), As of1μmol/L helped to maintain theintegrity of the algae cell, while higher concentration of As (10,30μmol/L) seriouslydestroyed the cell membrane. In contrast, at higher concentration of phosphorus (f/2,f/5) with the increase of As the extent of membrane destruction increased.Malonaldehyde (MDA) content in Chlorella vulgaris were lowest with As of1μmol/L than with As of0,10and30μmol/L at lower phosphorus concentrations (0,f/10). Then with the increase of arsenic concentration, the greater the damage emergedon chlorella cells. While at concentration of phosphorus (f/5, f/2), oxidation of1μmol/L concentration of arsenic on chlorella had shown. In f/5and f/2medium, withthe increase of the concentration of arsenic, the contend of MDA increased.Under all the tested concentrations of arsenic (0~30μmol/L), reducing concentration of phosphorus increased toxicity of arsenic on Chlorella vulgaris. Buteven in the high level of concentration of phosphorus, arsenic demonstrated toxiceffect on Chlorella vulgaris. When concentration of phosphorus is0, probably,because of compensation of1μmol/L of arsenic to phosphorus, the lowest superoxidedismutase enzyme (SOD) activity appeared in1μmol/L arsenic of medium. While atconcentration of phosphorus (f/10, f/5, f/2), compensation of1μmol/L concentrationof arsenic on chlorella had not shown and with the increase of the concentration ofarsenic, the SOD activity increased. While at concentration of phosphorus (0, f/10),probably, because of compensation of1μmol/L of arsenic to phosphorus, catalaseenzyme (CAT) activity in1μmol/L arsenic of medium was lowest. While atconcentration of phosphorus (f/5, f/2), compensation of1μmol/L concentration ofarsenic on chlorella had not shown, but promoted CAT activity. As concentration ofphosphorus was0,30μmol/L of arsenic inhibited the promotion of CAT activity,maybe that was because30μmol/L of arsenic damaged antioxidant defense.Under different concentrations of arsenic, the study of the influence ofphosphorus on Arsenic forms in chlorella cell found that high level of phosphorus canrestrain Chlorella vulgaris from accumulation of arsenic. In all concentration levels ofphosphorus, with the content of arsenic in medium increase, the contents of arsenic ineach cell increase significantly. In all concentration levels of arsenic, organic As/totalAs reduces firstly, and then increases. In medium without phosphorus, the ratio is thehighest, while the lowest at phosphorus concentration of10/f, and with the content ofphosphorus in medium increased, the ratio increases. In all concentration levels ofphosphorus, with the increase of arsenic content in the medium, the ratio of organicAs/total As reduced.