不同氮、磷浓度对铜绿微囊藻生长、光合及产毒的影响

INFLUENCE OF DIFFERENT NITROGEN AND PHOSPHORUS CONCENTRATIONS ON GROWTH,PHOTOSYNTHESIS AND MICROCYSTIN PRODUCTION OF MICROCYSTIS AERUGINOSA

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)。

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 of Microcystis 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 =0. 97）. 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 = 0. 967） .