Inhibition of Scenedesmus quadricauda on Microcystis flos-aquae.

Allelopathy by hydrophytes can be utilized to control algal blooms. This study was conducted to investigate the allelopathic effect (inhibition) of Scenedesmus quadricauda on Microcystis flos-aquae. When M. flos-aquae was co-cultured with S. quadricauda, the secretion of high-MW biopolymer by M. flos-aquae was inhibited by S. quadricauda. We further identified the allelochemicals and found that 4-tert-butylpyrocatechol (TBC) was the main active ingredient that could inhibit the growth of M. flos-aquae. When the dose of TBC was larger than 0.2 mg/L, almost all of the M. flos-aquae died. Additionally, TBC was found to suppress the growth of M. flos-aquae by disturbing the synthesis and secretion of proteins and polysaccharides and harming the chlorophyll to affect the light harvesting of algal cells. Therefore, TBC has the potential for use as a potential and promising algaecide to restrain the biomass of M. flos-aquae.

A review of allelopathy on microalgae.

Algal blooms have severe impacts on the utilization of water resources. The discovery of allelopathy provides a new dimension to solving this problem due to its high efficiency, safety and economy. Allelopathy can suppress the growth of microalgae by impairing the structure, photosynthesis and enzyme activity of algal cells. In the current work, we first demonstrate the allelopathy and allelochemicals derived from both plants and algae. We then expound the potential mechanisms of allelopathy on microalgae. Next, the potential application of allelochemicals in water environment is proposed. Finally, the key challenge and future perspective are presented.

Analysis of organic foulants in the coagulation-microfiltration process for the treatment of Taihu Lake.

This paper analysed organic foulants in the coagulation-microfiltration process for Taihu Lake treatment. High-performance size-exclusion chromatography (HPSEC) and fluorescence excitation-emission matrices (EEM) were applied to elucidate the influence of characteristics of organics on microfiltration (MF) membrane fouling. Results showed that coagulation pretreatment could extend the operation duration of MF based on the fact that pretreatment could effectively remove macromolecular substances as well as a portion of small molecular weight (MW) organics. The analysis of foulants indicated that organics of strong hydrophobic acids (SHA) and neutral hydrophilic (Neut) fractions (based on hydrophobicity) and medium and small MW components (based on MW distribution) contributed greatly to irreversible fouling. EEM fluorescence analysis of chemical solutions exhibited that aromatic proteins and soluble microbial products were mainly a response to irreversible fouling.

Effect of limitation of iron and manganese on microalgae growth in fresh water.

Eutrophication is caused by the rapid growth of microalgae. Iron and manganese are important micronutrients for microalgae growth. However, the effect of the limitation of iron and manganese on microalgae growth in fresh water has not been well understood. In this study, natural mixed algae, Anabaena flosaquae and Scenedesmus quadricanda, were cultivated under different quotas of iron and manganese to reveal the effect of the limitation of iron and manganese on the growth of microalgae in fresh water. The results showed that the growth rate of algae is influenced more by iron than by manganese. However, the effect of manganese cannot be overlooked: when the initial manganese quota was replete, i.e. 0.6-0.8 mg l-1, manganese was able to relieve the effect of iron limitation on microalgae growth in fresh water. We further found that the microalgae showed an uptake preference for iron over manganese. Iron had a competitive effect on manganese uptake, while manganese had less impact on iron uptake by microalgae. The information obtained in the current study is useful for the provision of water quality warnings and for the control of microalgae bloom in fresh water.