Effects of Pb(â ¡) exposure on Chlorella protothecoides and Chlorella vulgaris growth, malondialdehyde, and photosynthesis-related gene transcription.

Greater exposure to Pb(Ⅱ) increases the likelihood of harmful effects in the environment. In this study, the aquatic unicellular alga Chlorella protothecoides (C. protothecoides) and Chlorella vulgaris (C. vulgaris) were chosen to assess the acute and chronic toxicity of Pb(Ⅱ) exposure. Results of the observations show dose-response relationships could be clearly observed between Pb(Ⅱ) concentration and percentage inhibition (PI). Exposure to Pb(Ⅱ) increased malondialdehyde (MDA) content by up to 4.22 times compared with the control, suggesting that there was some oxidative damage. ANOVA analysis shows that Pb(Ⅱ) decreased chlorophyll (chl) content, indicating marked concentration-dependent relationships, and the lowest levels of chl a, chl b, and total-chl were 14.53, 18.80, and 17.95% of the controls, respectively. A real-time PCR assay suggests the changes in transcript abundances of three photosynthetic-related genes. After 120 h exposure Pb(Ⅱ) reduced the transcript abundance of rbcL, psaB, and psbC, and the relative abundances of the three genes of C. protothecoides and C. vulgaris in response to Pb(Ⅱ) were 54.66-98.59, 51.68-95.59, 37.89-95.48, 36.04-94.94, 41.19-91.20, and 58.75-96.80% of those of the controls, respectively. As for 28 d treatments, the three genes displayed similar inhibitory trend. This research provides a basic understanding of Pb(Ⅱ) toxicity to aquatic organisms.

Acute and chronic toxic effects of bisphenol A on Chlorella pyrenoidosa and Scenedesmus obliquus.

The acute and chronic toxic effects of Bisphenol A (BPA) on Chlorella pyrenoidosa (C. pyrenoidosa) and Scenedesmus obliquus (S. obliquus) were not well understood. The indoor experiments were carried out to observe and analyze the BPA-induced changes. Results of the observations showed that in acute tests BPA could significantly inhibit the growth of both algae, whereas chronic exposure hardly displayed similar trend. Superoxide dismutase (SOD) and Catalase (CAT) activities of both algae were promoted in all the treatments. Chlorophyll a synthesis of the two algae exhibited similar inhibitory trend in short-term treatments, and in chronic tests C. pyrenoidosa hardly resulted in visible influence, whereas in contrast, dose-dependent inhibitory effects of S. obliquus could be clearly observed. The experimental results indicated that the growth and Chlorophyll a syntheses of S.obliquus were more sensitive in response to BPA than that of C. pyrenoidosa, whereas for SOD andCAT activities, C. pyrenoidosa was more susceptible. This research provides a basic understanding of BPA toxicity to aquatic organisms.

[Control effect of different covering patterns on indigenous nutrient release from sediment].

A laboratory simulation experiment was conducted to study the release of sediment phosphorous and nitrogen under the effects of coating the sediment with plastic, clinoptilolite, calcite, quartz sand, and calcium nitrate, aimed to provide scientific basis and technical support to control the sediment nutrient release under the background of water environment pollution by different concentrations of nitrogen and phosphorus. The control efficacy of test coating materials for sediment total phosphorous release was in the order of plastic > calcium nitrate > clinoptilolite > calcite > quartz sand, and that for sediment total nitrogen release was in the order of clinoptilolite > plastic > calcite > quartz sand > calcium nitrate. As for the release of sediment NO(3-)-N, the control efficacy of test coating materials was calcium nitrate > quartz sand > clinoptilolite > calcite > plastic coating; whereas for the release of sediment NH(4+)-N, the sequence was calcium nitrate > plastic coating > clinoptilolite > calcite > quartz sand. Water temperature had definite relativity to the sediment nutrient release. With the increase of water temperature, the concentrations of water total phosphorous and nitrogen and NO(3-)-N increased, while the concentration of water NH(4+)-N presented a declining trend.