不同氮、磷浓度对铜绿微囊藻生长、光合及产毒的影响

对一株从野外分离得到的铜绿微囊藻产毒株进行分批培养,在不同的氮磷条件下研究其生长、光合荧光及毒素含量的变化。结果表明:正磷酸盐浓度不变时,铵氮浓度的改变对铜绿微囊藻的生长有明显影响。叶绿素a(Chl.a)含量在铵氮浓度为1.83-18.3mg/L时明显较大;微囊藻毒素(包括MC-LR和MC-RR)的含量在铵氮浓度为1.83mg/L时达到最大;当铵氮浓度为0-1.83mg/L时,随着铵氮浓度升高,可变荧光FV和MC的产量均增大,同时MC异构体的种类增多;铵氮浓度过大对M.aeruginosa的生长、生理和产毒均有抑制作用。在另一组实验中,即铵氮浓度不变而正磷酸盐浓度增大时,Chl.a含量呈总体下降的趋势,并且与FV/Fm呈显著正相关关系(P<0.01,r=0.97),MC(MC-LR和MC-RR)的含量在正磷酸盐浓度小于0.56mg/L时明显升高,MC-LR与FV/Fm呈显著正相关关系(P<0.01,r=0.967)。  

Influence of different nitrogen and phosphorus concentrations on growth, photosynthesis and microcystin production of Microcystis aeruginosa

Heavy blooms frequently occurred in eutrophicated water body and Microcystis is the main algae involved in blooms.Microcystis produces a family of related cyclic hepatopeptides(microcystins, MC). These toxins are severely hepatotoxic. In this paper, a strain of Microcystis aeruginosa was isolated from a cyanobacterial bloom in the east lake and effects of ammonium and orthophosphate on its growth, chlorophyll-a(Chl. a) fluorescence and microcystins (MC) contents was investigated. Two experiment of groups were tested, with variable ammonium(0-219.6mg/L), orthophosphate concentration fixed at 4.5mg/L, or with variable orthophosphate(0-110.7mg/ L), ammonium concentration fixed at 50mg/ L. The results showed that, when orthophosphate concentration fixed, ammonium had obvious influence on the growth of M.aeruginosa. The content of Chl.a was evidently higher as ammonium concentrations ranged from 1.83 to 18.3mg/ L than those in other ammonium concentrations. The overall MC content including MC-LR and MC-RR reached the maximum at 1.83mg/ L of ammonium concentration while the content of MC-LR was much higher as ammonium concentrations ranged from 0.61 to 1.83mg/ L and the content of MC-RR was much higher as ammonium concentrations ranged from 1.83 to 18.3mg/ L. In addition, FV and MC concentration both tended to increase while the ammonium concentrations increased from 0 to 1.83mg/ L, higher ammonium concentrations restrained the growth, physiology and MC production ofMicrocystis aeruginosa. In another experiment group with fixed ammonium concentrations and increasing orthophosphate concentrations, the Chl.a content represented the decreasing tendency opposite to the increased concentrations of orthophosphate and was highly correlated with FV/ Fm(P<0.01,r= 0197). MC contents were obviously higher as the concentrations of orthophosphate were below 0.56mg/ L than those in higher concentrations. It demonstrated by the statistical analysis the MC-LR production was closely correlated to FV/ Fm(P<0.01,r= 01967).