沉水植物黑藻腐解对微囊藻休眠体复苏的影响

模拟沉水植物黑藻(Hydrilla verticillata)生物量(以湿质量计)分别为0、10、25和50 g时,在17℃下腐解过程中对微囊藻(Microcystis)休眠体复苏的影响,并通过测定沉积物和上覆水的理化指标,探究腐解过程中环境因素的变化及其对微囊藻复苏的影响.为期84 d的腐解试验结果显示,沉水植物黑藻的腐解对微囊藻休眠体复苏具有抑制作用,且黑藻生物量越高抑制作用越强.另外,水体及沉积物中的TN、TP和总有机物含量,沉积物表面的光照强度及pH均随黑藻的腐解时间及黑藻生物量的不同而变化.黑藻的腐解会使沉积物中w(TN)升高;与无黑藻组相比,黑藻生物量越多释放到上覆水中的TN越多,但由于沉积物的吸附及微生物的作用,各试验组中上覆水ρ(TN)呈逐渐下降趋势;黑藻的腐解引起沉积物w(TP)显著升高,并在短时间内造成上覆水中ρ(TP)增加,64 d后复原到初始水平;沉积物及水体中的总有机物含量呈先升后降的趋势,在腐解后期水体中ρ(TOC)基本恢复到初始水平.在腐解过程中抑制微囊藻复苏生长的因素可能包括ρ(TP)的升高及光照强度和pH降低. 

Effects of Hydrilla verticillata Decomposition on Recruitment of the Dormant Microcystis spp.

The effects of Hydrilla verticillata decomposition on recruitment of the dormant Microcystis spp.were investigated at 17 ℃ with four levels of residue mass of Hydrilla verticillata: 0,10,25 and 50 g(fresh weight).The changes of physical and chemical indexes in the sediments and water were monitored to reflect the decomposition effects on environmental factors,and on Microcystis spp.recruitment.The 84-day decomposition experiment showed that Microcystis spp.recruitment was inhibited by Hydrilla verticillata decomposition,and the inhibition was increased by the increase in the biomass of Hydrilla verticillata.Furthermore,the concentrations of total nitrogen(TN),total phosphorus(TP) and total organic carbon(TOC) in the sediments and water,the light intensities of the surface sediments and pHs in the water were also changed with the decomposition time and the biomass of Hydrilla verticillata.TN concentrations in the sediments were increased by the decomposition of Hydrilla verticillata.Compared to the control without Hydrilla verticillata,the more the bionass of Hydrilla verticillata,the more the TN was released into the water.However,sorption of the sediment and the activities of microbes decreased the TN concentration in the water in all the experimental groups.Hydrilla verticillata decomposition increased the TP concentration in sediment significantly,and then in the overlaying water rapidly,which recovered to the initial level after 64 days.The TOC concentration in the sediments and water increased first,and then decreased to the initial level at the end of decomposition.Increase in TP concentration,decrease in light intensity and decrease in pH during the decomposition of Hydrilla verticillata were possible reasons for the inhibition of Microcystis spp.recruitment.