再生水补给水体中丝状藻爆发成因分析:以华南某水体为例

THE CAUSE OF FILAMENTOUS ALGAE OUTBREAK IN THE WATER BODIES SUPPLIED BY RECLAIMED WATER: A CASE STUDY ON A SOUTH CHINA RIVER

利用再生水作为河流、湖泊补给水已成为城市水环境治理的重要措施,但是再生水的汇入也为一些水体带来了"藻华"爆发的风险。针对再生水补给水体中易出现的丝状藻"藻华"现象,以华南地区某再生水补给的河流水体为例,通过现场调研和实验室实验,分析了丝状藻的生长模式及爆发成因。研究结果表明:丝状藻生长过程分为休眠、萌发、扩增和爆发4个阶段,在前3个阶段,丝状藻底部附着在河流底泥上并不断向水中分生出丝状体,积累到一定程度后挣脱底质上浮形成爆发。水网藻是案例河段"藻华"中的优势种类,生长速率和最大密度都远远高于伴生种类单歧藻,属于丝状藻"藻华"藻;水网藻的最适生长温度在25℃左右,但在15℃的低温下也具有生物量扩增能力;丝状藻的低温生长优势、在底质上的锚定和底质表面充足的光照是案例河段丝状藻"藻华"爆发的主要原因;建议通过底质铺设砾石层、抚育耐寒型沉水植被和以丝状藻为食的水生动物及采取早期生物量监控预警等措施对丝状藻"藻华"进行控制。

Using reclaimed water as the supplementary water for rivers and lakes has become an important measure for urban water environment management. But the inflow of reclaimed water also brings the risk of algal bloom outbreak into the water bodies. In order to explain the phenomenon of filamentous algae’s algal blooms easily appearing in the recharged water body of reclaimed water, the growth mode and outbreak causes of filamentous algae in a river recharged with reclaimed water in South China was investigated through field investigation and laboratory experiments. It was found that the growth of filamentous algae had four stages: dormancy, germination, expansion and eruption. In the first three stages, they attached to the bottom of the river and continuously spawned filaments into the water. When the filaments accumulated to a certain amount, they broke free from the bottom and then floated up, and then algal bloom happend. Hydrodictyon(spp) was the dominant species in algal bloom in the rivers. Its growth rate and maximum density were much higher than that of the associated specie, Tolypothrix(spp). So it could be called as algal bloom algae. The optimum growth temperature was about 25 ℃ for Hydrodictyon(spp), but it still could grow at a low temperature of 15 ℃ though the growth rate was lower. Therefore, filamentous algal bloom in the river might result from their growth at low temperature, the attachment on the bottom and sufficient light reaching the bottom. The following measures were recommended for the algal bloom control: laying gravel layer on the bottom, tending cold resistant submerged vegetation and aquatic animals fed on filamentous algae, as well as monitoring accumulation of filaments and warning at early stage.