生物法減少藻華之效率研究-以台大醉月湖中湖為例

Abstract

本研究乃以2016 年7 月有效改善國立台灣大學校內醉月湖中湖之藻華現象實例，作為探討。該案例地點經緯度為25°1'12'N 121°32'15'E，位於台灣台北市大安區，利用生物法，投放適量浮游動物圓蚤，2 天後順利去除綠蟲藻(藻名)，水體透明度得到改善，直至2018 年6 月為止，綠蟲藻未再發生，顯示除藻方法成功。 上述案例中，利用浮游動物去除浮游植物(藻類)為生物法管理水質方式，然而，以浮游動物去除浮游植物的效率需要經過實驗驗證，且需觀察實行生物法後水質的變化。本研究乃以圓蚤與小球藻為實驗對象，建立兩種物種間增減速率的數據。實驗環境分為水溫25°C 及30°C，圓蚤濃度分為高濃度與低濃度，實驗時間24 小時，每3 小時取樣一次，計測以圓蚤去除小球藻效率與水質變化。實驗資料可作為小型人工景觀池以浮游動物管理水質之操作基礎。 結果得知，水溫25°C 時，每增加1mg 的圓蚤可以使小球藻減少0.79~1.32mg；水溫30°C時，每增加1mg 的圓蚤可以使小球藻減少0.99~1.46mg。綜合水質指標分析，得知透明度下降1cm，小球藻濃度上升0.018(g/L)，水溫25°C 時，需要圓蚤濃度0.014~0.023(g/L)去除；水溫30°C 時，需要圓蚤濃度0.013~0.019(g/L)去除。相同水溫，水體中投放較多圓蚤能在較短的時間內去除小球藻；不同水溫，相同圓蚤投放量，較高的水溫能在短時間內去除小球藻。 本研究明確的建立浮游動物之計量方法與計測消耗浮游植物效率之實驗方法，期望能對利用生物法進行小型人工景觀池之水質管理提供實質助益。

This study is based on the case of effectively improving algae bloom occurred in Middle lake of Drunken Moon Lake in National Taiwan University on July 2016. The accurate location is 25°1'12'N 121°32'15'E which located in Da-an District, Taipei City. Putting proper amount of zooplankton-Moina into water with biomanipulation, Euglena was removed from water after 2 days and the transparency also improved. So far, the result of this case is successful because excessive multiplication of Euglena never happened again. According to the above, using zooplankton to reduce phytoplankton (algae) might be a way of biomanipulation. However, the reducing efficiency needs to be verified by experiment and observes the change of water quality after implement biomanipulation. Moina Macrocopa and Chlorella vulgaris are the experimental subjects in this study. In order to provide manual basis data of implementing biomanipulation by zooplankton for small artificial landscape pond, this study builds data for increase and decrease rate between two species. The experiment environment divided into two water temperature, 25°C and 30°C respectively, with Each water temperature has high and low concentration of Moina.spp. Sampling every 3 hours in 24hours and measure reducing efficiency and water quality change. With the experimental design of this study, increase 1 mg Moina.spp could make Chlorella.spp decrease 0.79~1.32 mg and 0.99~1.46 mg at 25°C and 30°C separately. Combined with water quality index, the results show that transparency decline 1 cm, the concentration of Chlorella.spp increase 0.018(g/L), it needs to be reduced by 0.014~0.023(g/L) and 0.013~0.019(g/L) concentration of Moina.spp for water temperate of 25°C and 30°C separately. The Chlorella.spp reduced in shorter time with more quantity of Moina under the same water temperate. What’s more, with same quantity of Moina.spp, Chlorella.spp reduced in shorter time with higher water temperate. This study explicitly builds the experiment methods of measuring zooplankton and phytoplankton consumption efficiency, it could help small artificial landscape pond easier to manage by using biomanipulation.