武汉莲花湖微囊藻毒素含量变化特征及其影响因素的研究

Variation Characteristics of Microcystin Concentration and Influencing Factors in Lake Lianhuahu (Wuhan)

采用现场采样及室内测试方法,研究了武汉莲花湖水华消亡过程中微囊藻毒素和环境生态因子的变化规律,并探讨了环境生态因子对微囊藻毒素产生的影响。结果表明,莲花湖微囊藻毒素含量以MC-LR为主,在水华消亡时大量释放到水体中,且较高的藻毒素含量能持续数天。对环境因子的相关分析表明,水体中的微囊藻毒素含量与铵氮、总磷显著正相关,与氮磷比显著负相关(P<0.05)。根据多元逐步回归统计进一步分析,筛选出相对重要的影响因子及合并共线形因子。经显著性检验,逐步回归统计结果为MC=13.62+5.77×NH4+-0.48×TN/TP,复相关系数为0.93,综合F值为21.0,说明铵氮和氮磷比是影响莲花湖水华消亡过程中微囊藻毒素含量的重要影响因子。

Microcystins (MC) produced by cyanobacteria resulted from cyanobacterial blooms caused by abundant nutrients and favorable conditions for cyanobacterial growth. Only a few papers on the relationships between MC concentrations and the N and P concentrations in natural waterbodies were reported. An indirect effect of total phosphorous (TP) on MC concentration through influencing cyanobacteria biomass or the size of MC- producing cyanobacteria was proposed. However, the information and field evidences were very limited and inadequate. Lake Lianhuahu (30° 33′ N, 114° 16′ E) is a small shallow lake with a gate connected to the Yangtze River in the subtropical Wuhan City, China, with the surface area about 0.02 km2 and an average depth of 1.2m. It has been seriously eutrophicated due to sewage input, and has experienced toxic cyanobacteria bloom regularly in the warm season each year. The temporal dynamic of microcystin and environment conditions was described during the disappearance of the bloom, and the influence of environment conditions on MC level was discussed in the study. Based on our data, MC- LR was the main kind of MC and MC- RR presented only at the end of the bloom in Lake Lianhuahu. The data confirmed the remarkable release of MC at the end of cyanobacteria bloom, and high extra- MC lasted for several days in Lake Lianhuahu. Significant linear relationships (P<0.05) <IMG SRC='IMAGE/01190003.JPG' HEIGHT=11 WIDTH=18>were observed between nutrient conditions (Ammonia, TP and N/P ratio) and intra- MC. The stepwise multiple regression was used to determine the more important influencing factors on MC level, and the regression equation was: MC=13.62+ 5.77× - 0.48× TN/TP (R=0.93, F=21.0), confirming that these nutrient elements were related to MC produce more than other factors in Lake Lianhuahu.