翠峰湖水體垂直混合之季節動態變化

湖泊水體的垂直混合為藻類、營養鹽及溶氧傳輸之重要影響機制。垂直混合主要由強風、豪雨及溫度梯度變化所產生。位於太平山的翠峰湖每年經歷多次強烈的颱風擾動，受颱風擾動後除了水位上升明顯外，颱風也影響湖泊水質及生態系代謝。本研究主要探討在不同季節間湖水垂直混合的變化，並分析颱風擾動及垂直混合對水化學之影響。我們於2年期間（2015年1月至2016年12月）以5分鐘1次的頻率間監測翠峰湖的氣象資料（氣溫、日照輻射量、風速、雨量）及不同水深(0、0.25、0.5、1、2、3.5 m)的水溫變化，並每個月量測各水層葉綠素a濃度及溶氧濃度。研究結果顯示春季時翠峰湖之風速(r = 0.35, p ＜ 0.001)、雨量(r = 0.30, p ＜ 0.001)、氣溫(r = -0.72, p ＜0.001)及日照輻射量(r= -0.45, p ＜ 0.001)為影響整體湖泊混合層深度(Mixing depth, Z_(mix))及水溫的主要因子；夏季水溫與Z_(mix)則主要由風速及水位影響(r ＞ 0.26, p ＜0.001)。輕颱(最大風速小於10 m s^(-1))垂直混合可持續約1天；強颱(最大風速大於30 m s^(-1))時垂直混合可持續2至3天，秋冬季則主要由氣溫及日照輻射量影響 (r ＜-0.35, p ＜ 0.001)。翠峰湖春季時有藻華現象發生，葉綠素a濃度平均約64.3μg L^(-1)；春季至冬季葉綠素a濃度降低至35至42 μg L^(-1)，另一方面春至冬季溶氧量增加3至5 mg L^(-1)。夏秋季颱風豪雨將葉綠素a濃度降低至12 μg L^(-1)。整體而言，夏季颱風或暴雨所造成的垂直混合並非影響藻類濃度垂直變化的原因，主要由秋冬季湖水完全混和將藻類向表層傳輸。

關鍵字

亞熱帶高山湖泊；颱風擾動；垂直混合；水體分層

並列摘要

Vertical mixing is an important mechanism affecting biogeochemical processes cause by wind-induced turbulence, heavy rainfall input, and cooling-related convection in a stratified lake. Strong typhoon disturbances alter the water level, water quality, and Lake Metabolism in Tsuei-Feng Lake (TFL) every year. This study assessed how the seasonality and typhoon disturbances affect the vertical mixing in TFL. High frequency (every 10 min.) meteorological (Air temperature, water temperature (0, 0.5, 1.0, 2.0, 3.5 m), solar energy, wind speed, precipitation.), water level, water quality (Chlorophyll a and dissolved oxygen) data were collected by using in-situ instruments from the entire study courses (January 2015 to November 2016). Results reveal that the mixing Zmix show significant correlation with wind speed (r = 0.35, p ＜ 0.001), precipitation (r = 0.30, p ＜ 0.001), air temperature (r = -0.72, p ＜ 0.001), and solar energy (r = -0.45, p ＜ 0.001) in spring. In the typhoon seasons, wind speed and water level are positively correlation with Z_(mix) (r ＞ 0.26, p ＜ 0.001). The vertical mixing lasts up to 1 day after small typhoon (maximum wind speed ＜10 m s^(-1)). Strong typhoon (maximum wind speed ＞ 30 m s^(-1)) could induce the vertical mixing sustaining up to 2 to 3 days. Seasonal vertical mixing of TFL was caused by cooling-related convection during autumn to winter (Z_(mix) had relevance to air temperature and solar energy (r ＜ -0.35, p ＜ 0.001)). The dissolved oxygen concentrate increased 3 to 5 mg L^(-1) from spring to winter. The algal bloom occurred in spring (Chlorophyll a = 64.3 μg L^(-1)). Chlorophyll a declined to annual low level in typhoon period (12 μg L^(-1)). The cooling-related convection is mainly affected the algal bottom-up transportation by vertical mixing.

並列關鍵字

Subtropical mountain lake ； Typhoon disturbance ； Vertical mixing ； Water stratification

國際替代計量

翠峰湖水體垂直混合之季節動態變化

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