蘭陽溪流域石附生藻類豐度與群集之時空變化

Spatio-temporal Variations in Abundance and Community of Epilithic Periphyton in Lanyang River

莊怡麗(Yi-Li Chuang) ； 林幸助(Hsing-Juh Lin)

《生物科學》 48卷1期 (2005/12) Pp. 45-58

https://doi.org/10.29981/CB.200512.0005

摘要

本研究主要目的為探討蘭陽溪流域石附生藻類豐度與群集的季節變化，以及由上游至下游與不同集水區間的差異，藉以找出主要影響環境因子。二年研究結果顯示，蘭陽溪主流中、上游以石附生藻類佔優勢，下游則以浮游藻類為主。兩者豐度皆於春季較高。主流上游有農業活動的繼光橋，其石附生藻類豐度顯著高於無農業活動的實谷富溪。迴歸分析結果顯示，影響蘭陽溪流域石附生藻類豐度的主要決定因子為流速。當流速越快，石附生藻類葉綠素a濃度越高。多尺度空間排序(MDS)的分析結果顯示，蘭陽溪流域的石附生藻種組成無明顯的季節性變化，但有明顯的測站間差異。主流中、上游的繼光橋與家源橋，流速較快，溶解態無機氮濃度高，以矽藻中的谷皮菱形藻(Nitzschia palea)為優勢；上游支流實谷富溪與中游主流的牛鬪，流速稍緩，溶解態無機氮濃度低，以矽藻的橋彎藻(Cymbella sp.)為優勢；中、下游支流之松蘿與粗坑，流速最緩，溶解態無機磷濃度高，藻類亦多，但以藍綠菌中的鞘絲藻(Lyngbya sp.)為優勢。因此營養鹽與流速為影響蘭陽溪流域石附生藻類豐度與群集的主要環境因子。

關鍵字

農業活動 ； 溶解態無機氮鹽 ； 溶解態無機磷鹽 ； 流速 ； 多尺度空間排序

並列摘要

The upstream of Lanyang River is intensively exploited for agricultural activities. This study aimed to determine temporal and spatial pattern of abundance and community of epilithic periphyton along the main stream and effects of agricultural activities to determine the main deriving factors. The results from a 2-year study show that abundance of epilithic periphyton was dominant in the upstream and mid-stream, but shifted to phytoplankton in the lower-stream and estuary. Both peaked in spring. Greater abundance of epilithic periphyton was observed in the upstream with agricultural activities than a tributary without the activities. Regression analyses show that velocity was the main factor determining the abundance in the river. Faster velocity led to greater abundance of epilithic periphyton. Results of MDS show that the periphyton community was structured by site rather than by season. Epilithic periphyton was dominant by Cymbella sp. in an upstream tributary without agricultural activities and the mid-stream, where DIN concentrations in the water column were lower and velocity was slower. The dominance shifted to Nitzschia palea in the upstream with higher DIN concentrations and faster velocity. Cyanobacteria, especially Lyngbya sp., were dominant in two tributaries with higher DIP concentrations. In summary, nutrients and velocity were the main factors influencing abundance and community of epilithic periphyton in Lanyang River.

並列關鍵字

Agricultural activity ； Dissolved inorganic nitrate ； Dissolved inorganic phosphate ； Velocity ； Multi-dimensional scaling