淡水河流域的矽藻群聚結構與地理區位相關性研究

Abstract

藻類是良好的環境指標，矽藻可作為生物指標來判定當下水環境狀況或是重建古環境變遷，更具有生物地理特性。由於國內尚十分欠缺矽藻的生物地理學研究，因此本研究以北台灣淡水河系為研究對象，旨在建立矽藻群聚結構與環境關係，進而作為該地理區位之指標。本研究自2010年4月至2012年7月，於淡水河系五個河川樣站，進行漲、退潮各四次之河岸邊的附生基質和流動水域的矽藻採集。以各樣點出現的藻種相對頻度和組成在不同河系間分佈的差異，建立各河川樣點矽藻族群距離，以此做為辨識河系矽藻族群地理分佈的依據。從5個樣點8次的調查結果，共記錄了53屬，224種矽藻。出現藻種最多的屬為Navicula，共出現56種，其次是Nitzschia，出現了42種。出現之平均數量以Nitzschia 佔29.7%最高，其次是Cyclotella 佔27.6%。矽藻群聚結構受潮汐的影響，特別是圓心矽藻和浮游型矽藻二類之數量分布與河口距離成正關係，推論此與水域環境中的鹽度及水深有關。本研究以矽藻族群之棲地功能群及生態功能群分析各樣點間之差異，並作親緣關係分析。結果發現矽藻的群聚結構在不同河系與不同潮汐狀態下，具有空間和時間上之可供辨識的族群差異性。因此，矽藻生物地理學可以被應用於鑑定地理區位，其於不同河系位置之群聚結構，是該環境之獨特而有效的微物跡證。

Diatom communities are often used as bio-indicators in reflecting water quality of the contemporary environment and for the reconstruction of the paleoenvironmental conditions. Also, the biogeography of diatoms has been studied and used in some applications. However, little is known about the biogeographic pattern of diatoms in Taiwan. The objectives of this study were to analyze the biogeographical pattern of diatom communities along the Tamsui River of northern Taiwan, to elucidate their site-specificity, and to assess its applicability as trace evidences of locality. Both the benthic and planktonic diatoms were collected from April 2010 to July 2012, covering those from five tributaries and 4 seasons. For each season, samples were taken both at ebb and flow tides. The ecological guilds and niche guilds at these sites were elucidated, based on the community data. The correlation of these data with geographic information and water quality were analyzed. From the 8 sampling events, 224 diatom species from 53 genera were recorded. Navicula and Nitzschia were the dominant genus with 56 and 42 species, respectively. The diatom community structures were affected by the tides, showing that the abundance of Centricae and planktonic diatoms were positively correlated with the distance to the estuary. Mechanisms behind that could be the effects of salinity and water depth. The results showed that the diatom communities exhibited a site-specificity and a seasonal variation pattern. The present study suggests that the diatom communities could serve as trace evidences in different areas of applications.