藉由生態系結構及功能探討都市公園濕地之生態效益:以大安森林公園生態池為例

Abstract

都市公園水池常用作補償因人類活動導致消失及劣化的天然濕地，但公園水池的生態價值往往被忽略而疏於管理，以致其經常面臨不同環境及生態的衝擊。本研究為解決公園水池優養化與藻華問題，於臺北市中心的大安森林公園之三座生態池作為研究樣點，於2018 – 2020年期間每月進行水質監測及大型底棲無脊椎動物調查，以探討都市公園水池的優養化程度及其對生物多樣性之影響；並探討優養化對都市公園水池生態效益之衝擊。另外，本研究應用臺灣原生圓蚌(Anodonta woodiana)於優養化及藻華問題最嚴重的生態池進行生物操控淨水試驗，以探討應用圓蚌淨化優養化及藻華之都市公園水池的效果與可行性。 結果顯示三座生態池的水質全年皆為優養化，另因大量水鳥棲息於一號池排放之糞便流入水體導致嚴重的藻華問題。本研究應用圓蚌作生物操控法淨化一號池水質，結果為圓蚌能顯著降低一號池水中葉綠素a濃度43.0 %，且圓蚌設置期間的存活率> 94 %，證實圓蚌能成功存活並淨化優養化及藻華之都市公園水池，建議未來應推動本研究所建立圓蚌生物操控模式為生態友善之水質改善方法。本研究針對三座生態池的生態系服務評估，結果顯示優養化及藻華問題改變一號池的生物群聚結構，導致該池除了主要提供營養循環及初級生產者服務外亦提供削減的水質淨化負面服務；二號池及三號池主要提供正面生物多樣性、水質淨化及文化服務，但外來種入侵問題導致該兩座生態池亦提供削減的生物多樣性及水質淨化負面服務。本研究發現優養化及藻華問題造成一號池生物多樣性低並轉以雙翅目與寡毛亞綱為主要優勢生物類群，二號池及三號池生物多樣性比一號池高，卻有福壽螺及大理石紋螯蝦外來種入侵問題。本研究依據研究期間之水質特性及生物群聚結構變化，建立合適生態池水質及生物監測作定期評估都市公園水池的優養化狀況，而雙翅目水生昆蟲合適作為監測都市公園水池優養化及藻華程度的生物指標。

Urban ponds are widely built to offer compensation for the loss of integrated nature wetlands due to economic development services. However, urban pond ecosystems are threatened by various environmental and ecological impacts due to the public overlooking of their ecological values and the lack of appropriate management. In order to solve the problem of eutrophication and algae bloom in the urban ponds, this study investigated the ecologic community of three ecological ponds in the Daan Forest Park situated in the metropolis of Taipei City. Regular monthly monitoring of water quality and surveys of benthic macroinvertebrate biodiversity were carried out during 2018-2020 to study the degree of eutrophication of the urban ponds and the impact of eutrophication on the biodiversity and the ecological benefits of urban ponds. In addition, in order to solve the problem of eutrophication in urban ponds, a biomanipulative experiment using a Taiwan’s native bivalve Anodonta woodiana as a biocontrol agent for algae bloom and eutrophication in the studied ecological ponds of Daan Forest Park. The effects of water purification by Anodonta woodiana were examined, aiming to the development of ecological-friendly method for water quality control of urban ponds. The results showed that the water quality of the three ecological ponds were eutrophic throughout the year. In addition, Pond No.1, where a large number of waterfowls inhabit, caused serious algal bloom problems due to bird droppings flow into the water body. Anodonta woodiana was used as a biological control method to purify the water quality of Pond No.1. Results showed that Anodonta woodiana can significantly reduce the chlorophyll-a concentration by 43.0 %, and its survival rate during the experiment was over 94.3 %. Thus, Anodonta woodiana could indeed successfully survive and purify eutrophic urban ponds. It was recommended that the research institute should promote the establishment of Anodonta woodiana biological control model as an ecological-friendly method to improve water quality in the future. This study evaluated the ecosystem services of the ecological ponds. Results showed that Pond No.1 mainly provided nutrient cycling and primary production despite negative water purification services due to eutrophication that changed its biological composition. Pond No.2 and Pond No.3 mainly provided positive biodiversity, water purification and cultural services, but invasive alien species also caused the two ecological ponds to provide negative biodiversity and water purification services. This study found that eutrophication and algae blooms had caused Pond No.1 to have low biodiversity and shifted to a community structure dominated by Diptera and Oligochaeta. Although the biodiversity of Pond No.2 and Pond No.3 were higher than that of Pond No.1, they were affected by invasive alien species such as Pomacea canaliculata and Procambarus fallax forma virginalis. Based on the changes in the water quality characteristics and the structure of biological community during the study period, this study established suitable water quality and biological monitoring methods for ecological ponds to regularly assess the eutrophication status of urban ponds. Diptera, a kind of aquatic insects, was suitable as a biological indicator for monitoring the degree of eutrophication and algal blooms in urban ponds.