Yang Suwen

Decay process of Euglena sanguine bloom in Cuihu National Wetland Park, Beijing City

本文研究了北京翠湖湿地公园夏、秋季水华优势藻血红裸藻（Euglena sanguinea）从水华发生到衰亡过程的细胞密度、形态特征及其与环境因子的关系.结果发现，2016年8月下旬至9月中旬血红裸藻密度稳定增加，9月20日藻密度达到峰值5.13×106 cells/L；9月下旬至11月底藻密度显著下降；血红裸藻在衰亡过程中呈现细胞形态由大变小、由细长变为圆形，细胞颜色由深变浅，运动速率由快变慢的趋势，衰亡后形成具透明胶被孢子的休眠体；血红裸藻群落生长的主控因子为水温和pH，其适宜的环境阈值范围为水温23~27℃，pH 7.3~8.0；其受光照强度影响存在分层现象，弱光强区域藻密度相对较低；血红裸藻的衰亡过程与铵态氮浓度呈显著正相关，低浓度时加速衰亡；与总氮浓度呈负相关，衰亡后总氮浓度显著升高；受总磷浓度影响相对较小，与溶解氧浓度无显著相关关系.

Humus distribution and forms in the sediments from shallow Iakes in the middle and lower reaches of the Yangtze River

The organic matter(OM) content,compositions and fractions of shallow lake sediments were studied by chemical method from in the middle and lower reaches of Yangtze River.The results showed that the OM content varied greatly from 0.98% to 11.0 %,higher in the heavily polluted sediments than those in the light polluted ones.The distributions of OM content were closely related to lake pollution levels and human activity intensity.HA content was 1.03-6.73g/kg,and FA content is higher than the HA,from 2.73 to 9.77g/kg.Humin was the main fractions of humus,varing from 5.89 to 55.57g/kg.PQ(HA/(FA+HA)) ratio varied from 23.04% to 50.56%,and the mean content of PQ was 32.72%.PQ content were higher in the heavily polluted sediments than those in the light polluted ones,which indicated that there was a higher degree of humification in heavy polluted sediments.Combination of three kinds of humus content in the form of tightly bound humus content was the highest,and content was 3.21-47.76g/kg;followed by loosely combined humus content between 0.86-6.92g/kg.The stable combined humus were the lowest,the content varied from 0.72 to 3.89 g/kg.The loose/tight ration in the sediments were also negatively correlated with OM,TP and TN,which showed that heavily polluted shallow lakes had higher humification and humus accumulation.So humus should be paid more attention to the carbon cycling and eutrophication control in lakes.