翡翠水庫藻類多樣性之分析及消長動態之模擬

Abstract

水庫水質之良窳一直是國內外環境保護及水資源相關單位關切的問題，而其中藻類優養問題適為其最。吾等必須建立預測其發生趨勢的能力，方能採取適當預防優養問題發生措施。 自然水體中藻類種數繁多，其生長受到許多環境因子所作用，故欲了解藻類消長之原因，首要釐清藻類與環境因子間之相關性。本研究希望藉翡翠水庫大壩之藻類族群為例，探討藻類多樣性之原因。本研究以採樣調查及模式模擬的方法欲釐清「環境異質性是否有利於生物多樣性」的疑問。研究係以採翡翠水庫大壩為研究區域，以分層採樣之結果，分析探討藻類在大壩分層的生長情形、藻類與浮游動物之間之關係以及藻類和水質之關係。本研究有別於以往完全混合的系統模式，並將環境梯度及藻類層間混合納入藻類動態系統模式中。 經統計分析藻類與環境因子之相關性，發現藻類週期性的消長主要與季節性物理因子相關，其中藻類的沉降特性與水體混合程度為藻類生長之重要條件。統計結果顯示Shannon-Wiener Index生物多樣性指標與環境溫度梯度因子有相關性。總藻模擬結果來檢討限制因子對藻類的生長影響時，發現磷之供應是其中較為關鍵的因素。三種藻共存模擬可以模擬出藻類週期性的消長，推測呈現週期性的變化的主要原因週期性的水體混合機制所致。本研究認為當環境因子具有適當的時間變異則有利於不同藻種共存。

Water quality in reservoirs is an important issue of concern in terms of water supply nowadays. Eutrophication is a prevailing problem threating the water quality of reservoirs in Taiwan. The ability to forecast the tendency of phytoplankton growth must be established, then the actions to prevent eutrophication can be taken. There is great number of phytoplankton species in nature water bodies, and many factors interactively affect their growth. How they affect the growth of phytoplankton was examined in this study. First, the relationships between phytoplankton growth and environmental factors must be identified. Feitsui Reservoir is a model water body uesd to study the relationships described above. Second, whether environment gradient is benefitial to biodiversity or not, sampling and modeling must be done in this study to determine. Sampling at different depth in Feitsui Reservoir was undertaken to know the spatial distribution characteristics of water quality, phytoplankton and zooplankton growth. A conceptual model including stratified system was established to mimic the reservoir water column, which showed gradients of environmental factors. According to the statistic analysis, it was found that seasonal growth and decline of algae were related to physical environmental factors which change seasonally. The mobility of phytoplankton and the water column mixing condition are both instrumental in creating the environment of phytoplankton growth. The biodiversity index, Shannon-Wiener Index, was related to temperature gradient according to the results of statistic analyses. From the simulating results of total amount of algae, phosphorus supply was found an important factor for growth. The model of coexistence of three types of algae is able to simulate algal succession. Periodically water mixing is the driving force of algal succession and beneficial to algae coexistence.