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In this work, we assessed the toxic effects of ZnO nanoparticles (NPs; 1, 10, and 50 mg L−1) and the corresponding dissoluble Zn ions (0.71, 8.66, and 35.59 mg L−1) on Microcystis aeruginosa. After chronic exposure (28 days), significantly higher growth inhibition was observed under ZnO NPs at 1 mg L−1 (47%) than under Zn ions at 0.71 mg L−1 (−15%). The opposite effect pattern was observed for ZnO NPs at 10 (71% vs. 80%) and 50 mg L−1 (73% vs. 95%) compared to Zn ions at the corresponding concentrations. After 7 days of exposure, ZnO NPs at 10 and 50 mg L−1 led to an increase of 83 and 53% in malondialdehyde content, as well as an increase of 106 and 61% in superoxide dismutase activity, respectively. However, Zn ions at the corresponding concentrations showed negligible impacts on the two parameters. The different results indicate that the insoluble NPs during the initial exposure mostly account for lipid peroxidation, which further lead to microalgal antioxidant response. During the subsequent exposure, the contributors of ZnO NP toxicity shift with the concentration and exposure time of ZnO NPs. In conclusion, the study presents new insights into the different contributions of insoluble NPs and dissoluble metallic ions to metallic NP toxicity. [ABSTRACT FROM AUTHOR]

Changing environmental calcium (Ca) and rising cyanobacterial blooms in lake habitats could strongly reduce Daphnia growth and survival. Here, we assessed the effects of maternal Ca in Daphnia on transfer of resistance to their offspring against Microcystis aeruginosa PCC7806 (M. aeruginosa). Laboratory microcosm experiments were performed to examine effects in Daphnia carinata (D. carinata) and Daphnia pulex (D. pulex), and that how Ca induce responses in their offspring. The results showed that growth and survival were increased in offspring from exposed Daphnia as compared to unexposed, when raised in high Ca and increasing M. aeruginosa concentration. Among exposed Daphnia, offspring from high Ca mothers, produced more neonates with large size and higher survival as compared to offspring from low maternal Ca. Exposed D. carinata and D. pulex offspring, when reared in Ca deficient medium and increasing M. aeruginosa concentration, time to first brood increased, size become large and total offspring decreased subsequently in three alternative broods in offspring from low maternal Ca. In contrast, growth and reproduction in offspring from high Ca exposed mothers were consistent in three alternative broods. Despite species specific responses in growth, survival and variant life history traits in two Daphnia species, our results not only show maternal induction in Daphnia but also highlight that offspring response to M. aeruginosa varies with maternal Ca. This study demonstrates that Ca have role in Daphnia maternal induction against Microcystis, and recent Ca decline and increasing Microcystis concentration in lakes may decrease Daphnia growth and survival. Our data provide insights into the interactive effect of maternal Ca and Microcystis exposure on Daphnia and their outcome on offspring life history traits and survival. [ABSTRACT FROM AUTHOR]

Studies have shown that microorganisms may be used to eliminate cyanobacteria in aquatic environments. The present study showed that the white-rot fungus Trametes versicolor F21a could degrade Microcystis aeruginosa . After T. versicolor F21a and Microcystis spp. were co-incubated for 60 h, > 96% of Microcystis spp. cells were degraded by T. versicolor F21a. The activities of extracellular enzymes showed that cellulase, β-glucosidase, protease, and laccase were vital to Microcystis spp. degradation in the early stage (0 h to 24 h), while β-glucosidase, protease, laccase, and manganese peroxidase in the late stage (24 h to 60 h). The positive and significant correlation of the degradation rate with these enzyme activities indicated that these enzymes were involved in the degradation rate of Microcystis spp. cells at different phases. It suggested that the extracellular enzymes released by T. versicolor F21a might be vital to Microcystis spp. degradation. The results of this study may be used to develop alternative microbial control agents for cyanobacterial control. [ABSTRACT FROM AUTHOR]

Abstract: Microorganisms have attracted worldwide attention as possible agents for the inhibition of water blooms. Algae can usually be inhibited and degraded directly by fungi. In this study, the effects of Trichaptum abietinum 1302BG and Lopharia spadicea on different freshwater algal species, namely, Microcystis aeruginosa, Chlorella vulgaris, Glenodinium sp., Navicula sp., Cryptomonas ovata, and Euglena gracilis, were detected. After 24h, there was a significant inhibitory effect in all algal cultures with T. abietinum 1302BG, except E. gracilis, and all algal cultures with L. spadicea, except Navicula sp. and E. gracilis. The dried masses of two fungi increased while majority of the algal cells disappeared after 72h of co-incubation with M. aeruginosa, C. vulgaris, Glenodinium sp., and C. ovata. Thus, the two fungi might inhibit the growth of different freshwater algal species and utilize the algal cells for their growth. [Copyright &y& Elsevier]

Abstract: Surface waters in Lake Taihu are increasingly threatened by phosphorus (P)-related eutrophication, with a considerable proportion of organic P. A simple experimental model was proposed to characterize “bacterial services” to cyanobacteria. We used the digested solutions of three dissolved organic phosphorus (DOP) compounds (i.e., glucose-6-phosphate, adenosine triphosphate and lecithin) to test the stimulatory effects of nutrient regeneration by bacteria. The growth-promoting effects of six digested solutions on the microalga Microcystis aeruginosa (Ma) were studied. Of these six digested solutions, four had significantly growth-promoting effects on Ma, including the digested solutions of the three DOP compounds by bacteria Gordonia sp. txj1302RI and glucose-6-phosphate by bacteria Burkholderia sp. txj1302Y4. These results demonstrated that bacteria played important roles in decomposing the unavailable organic P into DIP, suggesting that natural bacteria contribute to algal blooms in Lake Taihu. [Copyright &y& Elsevier]