磷营养控制与藻存量削减对蓝藻水华的阻遏

Experiments of Reducing Phosphorus Release and Algal Biomass to Deter Cyanobacterial Bloom

通过原位实验比较了磷营养控制和藻存量削减2种方法对小型富营养化水体蓝藻水华形成早期的影响,测定了水体藻类群落结构、光合系统活性、水温、氮磷等参数的变化。结果显示：对照组水体藻类生物量从7.87 mg/L上升至14.25 mg/L,蓝藻在藻类生物量中所占比例由20%升高至40.8%,实验后期水体表面出现蓝藻局部堆积;磷营养控制组（添加钙盐）藻类生物量保持在7.53~9.18 mg/L范围,蓝藻所占比例低于30%,后期水华控制效果明显;施用除藻剂（铜盐）可使藻类生物量迅速下降到1.88 mg/L,同时蓝藻所占比例降低至10%以下,但绿藻在后期形成优势,藻类生物量回升并超过对照组。相关性分析表明各组藻类生物量的主要限制因子分别为水温（对照）、总磷浓度（磷营养控制）和铜离子浓度（藻存量削减）。总体而言,2种方法均在水华形成早期对小型富营养化水体的蓝藻水华起到了阻遏作用。

This paper reported on in-situ experiments to study effects of reducing phosphorus by adding calcium salt and curtailing algal biomass by use of algaecide sterilization with the purpose of deterring formation of cyanobacterail bloom in small eutrophic freshwater bodies. Changes in phytoplankton abundance and composition,photosynthetic activities,water temperature and concentrations of nitrogen and phosphorus were detected and monitored. In the comparative investigation,the control group showed that phytoplankton biomass increased from 7.87 to 14.23 mg/L and proportion of cyanobacteria biomass rose from 20 to 40.8%,leading to mild bloom at later period. Compared to the control group,P reduction group,in which calcium salt had been added, phytoplankton biomass maintained around 7.53 to 9.18 mg/L, and the proportion of cyanobacteria was kept at a relatively low level of less than 30%,indicating that deterrence of bloom formation was effective.When adding copper salt to the water it was found phytoplankton biomass dropped to 1.88 mg/L within one week,but it rebounced to 14.59 mg/L later at the end of the experiment. The correlation analysis indicated that water temperature,TP and copper ions respectively,were key factors in the changing of phytoplankton biomass with respective to the control group,P reduction group and algaecide sterilization group. Summarily,the deterrent methods used in the experiments appeared to be effective in preventing outbreak of cyanobacterial bloom in the small eutrophic water bodies undergoing early bloom process.