不同營養態的高山湖泊水體混合深度與透光度季節動態變化

Difference in Seasonal Variation of Underwater Light Availability and Mixing Depth between Two Mountain Lakes with Contrasting Trophic States

林浩之(Hao-Chi Lin) ； 蔡正偉(Jeng-Wei Tsai) ； 柳文成(Wen-Cheng Liu) ； 湯森林(Sen-Lin Tang) ； 邱志郁(Chih-Yu Chiu)

《農業工程學報》 64卷3期 (2018/09) Pp. 1-14

https://doi.org/10.29974/JTAE.201809_64(3).0001

摘要

湖泊水體的透光程度會影響藻類的光合作用與生物量，透光帶（Z_(eu)）與沙奇盤透明度（SDT）為量化透光度的重要參數。本研究欲釐清影響高山地區不同營養態湖泊水下透光度與水體混合深度（Z_(mix)）動態變化的主要控制因子。從2015年1月至2017年10月每月調查翠峰湖與鴛鴦湖的Zeu、SDT、水深與Z_(mix)。另外、每月收集表層湖水樣本，量測葉綠素a（Chl. a）、溶解性有機碳（DOC）。自2015至2017間的研究結果顯示：翠峰湖的藻類濃度主要受透光能力影響，尤其是春季（3至5月）有明顯的藻華造成透光帶降低；鴛鴦湖的透光能力則是受地表逕流所輸入的DOC影響，尤其是颱風季（7至10月）DOC濃度增加＞120%，造成夏、秋季SDT降低（p ＜ 0.05）。翠峰湖屬中營養態湖泊（Mesotrophic Lake），故春季容易藻華，造成Z_(eu) ＜ Z_(mix)，Z_(eu)可能限制水體Z_(mix)中的代謝量；鴛鴦湖屬寡營養態湖泊（Oligotrophic lake）全年藻類濃度低，故代謝量可能不受Z_(eu)的限制。本研究有助於釐清亞熱帶不同營養態高山湖泊的透光性、水體混合深度、藻類與有機碳的關係並建構複回歸模型。

關鍵字

透光層 ； 沙奇透明度 ； 營養態 ； 水體混合深度

並列摘要

Underwater light availability plays an important role in mediating the productivity of the autotrophic organism in the lentic ecosystem. Euphotic zone (Z_(eu)) and Sechhi disc transparency (SDT) are important parameters to classify the lakes trophic states. To clarify the relationships among underwater light availability (Z_(eu) and SDT), water quality (algae and dissolved organic carbon concentration), and different trophic states in subtropical mountain lakes, we investigated the Z_(eu), SDT, water depth, and mixing depth (Z_(mix)) in two mountain lakes, Tsui-Fong Lake (TFL) and Yuan-Yang Lake (YYL), during January 2015 to October 2017. The epilimniom water samples was collected to analyze the chlorophyll a (Chl. a), and dissolved organic carbon (DOC) concentration. Results showed that the light availability was the key factor controlling the Chl. a concentration in TFL. Seasonally, algal blooms caused the Z_(eu) decreased during spring (March to May) in TFL. Contrary, surface loading of DOC is the key factor for light availability in YYL, particularly in typhoon season (July to October), DOC concentration increased over 120% and thus decreased the SDT. TFL is a Mesotrophic Lake. Hence, algal blooms in spring made the Z_(eu) shrinking to the level less than the Z_(mix). Z_(eu) might limit the algal productivity as Z_(eu) was less than Z_(mix). By comparison, YYL is an Oligotrophic lake. Year-round algal concentration is low in YYL in order that Z_(eu) might not control algal productivity. This study clarified the relationships between light availability, Chl. a, and DOC and established the multiple regression model.

並列關鍵字

Euphotic zone ； Secchi disc transparency ； Trophic state ； Mixing depth