以主成份分析評估台灣亞熱帶德基水庫水質變化與藻類變遷關係

PRINCIPAL COMPONENT ANALYSIS TO EVALUATE THE RELATIONSHIP BETWEEN WATER QUALITY AND ALGAL CHANGE IN SUBTROPICAL TECHI RESERVOIR, TAIWAN

陳怡靜(Ying-Jing Cherry Chen)

《農業工程學報》 65卷3期 (2019/09) Pp. 11-21

https://doi.org/10.29974/JTAE.201909_65(3).0002

摘要

大量且複雜的水質監測數據往往無法合理解釋和聯結湖泊水庫藻類大量繁殖成因，及直接作為水庫水質管理的指標。德基水庫早期曾出現二角多甲藻（Peridinium spp.）大量繁殖，本文應用多變量統計的主成份分析法對德基水庫水質及藻類長年監測數據（1983～2004）進行統計分類和簡化，期望能篩選出與特定藻類生長有關的環境敏感參數，預防甲藻藻華再度發生。研究樣本包括11個水質參數及3種藻（二角多甲藻、綠藻和矽藻）豐度，結果顯示前四個主成份可解釋達75.7%總變異量，第一主成份（PC1）可解釋34.4%變異量，具有高度相關的正因子負荷包括多甲藻豐度、總磷（TP）、葉綠素-a（Chl-a）及氨氮（NH_3-N）。第二主成份（PC2）為17.7%變異量，指出綠藻豐度、矽藻豐度、無機硝酸鹽氮（NO_3-N）和水溫變化具高度相關性。主成份三和四（PC3和PC4）包括溶氧（DO）、酸鹼值（pH value）和鈣（Ca）離子濃度，和藻類呈低相關性。結合水質時間序列和主成分分析結果，營養鹽磷和氮的含量和化學型態隨時間變化被認為是驅動德基水庫1989年和1998年藻類群落組成變化的關鍵因素。1989年硝酸鹽氮的突然增加促進綠藻的生長；1998年以後總磷濃度大幅降低使多甲藻失去競爭優勢。僅以卡爾森水體指標代表水質變化狀態已不足夠，這項研究證實營養鹽仍是影響藻類變遷的重要因子和發展多藻種水質生態模式的必要性。

關鍵字

藻類 ； 水庫 ； 磷 ； 氮 ； 營養鹽 ； 主成份分析

並列摘要

The large and complicated water quality monitoring data cannot appropriately explain the algal changes reasonably. Principal component analysis (PCA) of multivariate statistical technique was carried out by analyzing a 22-yr (1983-2004) water quality dataset including 14 parameters (physico-chemical water variables and three algae abundances) in the subtropical Techi Reservoir, Taiwan. The results identified the first four principal components explained up to 75.7% total variance. The abundance of heterotrophic dinoflagellates Peridinium bipes (P. bipes) in the first component (PC1) has a strong correlation with the concentrations of total phosphorus (TP), Chlorophyll-a, and ammonium nitrogen (NH_3-N). The second component (PC2) identified the positive correlation between the abundance of autotrophic species green algae and diatoms, inorganic nitrate nitrogen (NO_3-N) and water temperature. The third and fourth components (PC3 and PC4) including dissolved oxygen (DO), pH value and calcium (Ca) ion concentration have low significant correlation with algae. Incorporated with the time series of water quality with the principal component analysis results, the temporal variations of nutrients phosphorus and nitrogen contents and chemical forms were considered the key factors driving the change in algae community composition occurred in 1989 and 1998 in the reservoir, respectively. The abrupt increase of inorganic nitrate nitrogen induced the growth of green algae while the decrease of total phosphorus closely correlated with the decrease in P. bipes density after 1998. This study confirms that nutrients are still an important factor triggering the algal blooms and the need to develop multi-algae models for useful water quality management.

並列關鍵字

Algae ； Reservoirs ； Phosphorus ； Nitrogen ； Nutrients ； Principal component analysis