| The allelopathic effects of submerged macrophytes against algae and its mechanism were investigated in this study based on the Hi-tech Research and Development Program of China——Water Environmental Quality Improvement Technology and Comprehensive Demonstration in Binhai District of Tianjin. Salt-proof submerged macrophytes——Potamogeton pectinatus,which is one of the advantageous species in the TEDA reclaimed water landscape water body, was the plant material in this paper. Two kinds of eutrophicated alga——Chlorella vulgaris and Microcystis aeruginosa, were selected as the objects of the allelopathic effects.The results showed that Potamogeton pectinatus exerted obvirously inhibitory effect on the two alga growth under coexistence culture, solution culture and aqueous leachate culture conditions. The relatively inhibitory rate of OD650 was 90% and algal cell number was less than 1.0×105cells/mL under coexistence culture. Not the nutrients competition but allelopathic chemicals that secreted by Potamogeton pectinatus was the primary cause of algal growth inhibition.Response surface methodology (RSM) based on three-level three-factor Box-Behnken design of experiment was used to optimize the environmental factors of allelopathy. The critical factors selected for this investigation were temperature, light intensity and total dissolved solids. By analyzing the response surface plots, the optimum ranges of the relatively inhibitory rate of OD650 and algal cell number lied in (43℃,2649lx,3787mg/L), (42℃,2683lx,3706mg/L) respectively for Chlorella vulgaris. The optimal conditions to gain were (23℃,2700lx,4415mg/L), (24℃,2891lx,4407mg/L) respectively for Microcystis aeruginosa. The results of RSM indicated that experimental values were in good agreement with the predicted ones and the models were satisfactory and accurate.According to the methods of the Organization for Economic Cooperation and Development (OECD) for algal growth inhibition test, in the single-effect tests of the three allelopathic chemicals identified by gas chromatography-mass (GC-Mass) spectrometry, succinic acid had the best effect on Chlorella vulgaris and palmitic acid had the best effect on Microcystis aeruginosa. In the combined-effect tests, the group of palmitic acid + succinic acid had the best additive effect on Microcystis aeruginosa and two groups had opposite effect on Chlorella vulgaris. The chlorophlla-a content and protein in Chlorella vulgaris and Microcystis aeruginosa were obviously inhibited under the stress of allelopathic chemicals. Fe-SOD enzyme activity of Chlorella vulgaris increased firstly, but decreased as treatment time went on. The total-SOD enzyme activity of Microcystis aeruginosa decreased with allelopathic compound concentrations. But the Mn-SOD enzyme activity of Microcystis aeruginosa exerted resistance response. In short, the physiological founction of the two algae were damaged by allelopathic compounds and finally algae cell flocculates and subsides to death.In the continuous flow reator test, salt-proof Potamogeton pectinatus inhibited the growth of alga of real reclaimed scenic water with high salinity. The chlorophlla-a contents of all treatment tests were lower compared with the reactor without plants. The possibility of eutrophication in reclaimed scenic water was in direct proportion to the hydraulic residence time (HRT).The three main innovation points of this study as follows:①the allelopathic effects of salt-proof Potamogeton pectinatus on Chlorella vulgaris and Microcystis aeruginosa, which are the main cause of eutrophication of TEDA reclaimed scenic water with high salinity;②the effects of three environmental factors on allelopathic effects by response surface methodology at the same time;③the mechanism of the allelopathy against algae.
|
PDF Full Text Request