臺灣北部一中型優養蓄水庫內浮游藻之週期變化特性

Periodicity of Phytoplankton in a Water Reservoir in Northern Taiwan

本文探討臺灣北部一中型蓄水庫內浮游藻在1986年6月至1989年7月間之藻種及羣落之週期性變化特性。本文就水質理化參數及浮游動物數量之變化探討其與藻種及羣落之週期性變化的關係，結果顯示，浮游藻雖在夏季數量最高，但隨季節消長之現象並不明顯，而與其它水庫情形略有不同。浮游動物之數量常隨浮游藻數量增加而上昇，顯示浮游藻數量增加非因攝食壓力之減低所致。從水中理化因子分析及以浮游藻為水質指標均顯示，此水域為過優養狀態，水中營養源濃度甚高，加以冬季氣溫溫和，故認為是導致浮游藻數量不隨季節消長而明顯變化之主因。

The characteristic periodical changes in the species and communities of phytoplankton in a pond situated in northern Taiwan were studied for three years, from July 1986 to June 1989. The physicochemical factors as well as the amount of zooplankton were taken into account to elucidate the relation of them to the variations in phytoplankton assemblages. The results show that the steady increase in phytoplankton density during the study time is not due to the decline in grazing pressure. The maximum of phytoplankton densities in the pond was developed toward summer. Nevertheless, seasonal succession in phytoplankton communities was not evident. The results from the analysis of water quality and from the indicator species of phytoplankton indicate that this pond was in hypereutrophic state and of the level between beta- and alpha-mesosaprobity. High nutrient concentration in the pond and mild temperature in winter were regarded to be the main reason resulting in the irregularity of the periodical changes in phytoplankton assemblages.