[[alternative]]The Relationship between Stream Macroinvertebrates and Environmental Variables and Its Application for Bioassessment

[[abstract]] 本研究之目的為瞭解溪流大型無脊椎動物與環境因子彼此間的關係，並藉此發展生物評估方法。本研究在雲嘉地區之北港溪和朴子溪中游選擇20處採樣站，進行水質與大型無脊椎動物的採樣，並評估溪流棲地環境狀況；而研究範圍中，土地使用多為農業用地。採樣時，以穿越線法在每個樣站的淺流及淺瀨隨機取3個採樣點，再以蘇伯氏網採集大型無脊椎動物，其分類依據文獻區分至最小可行的單位。水質樣本依據本國環保署方法採集、保存與分析，分析項目為營養鹽、SS、BOD等11項。棲地評估依據美國環保署的方法進行。大型無脊椎動物分類鑑定結果依各生物指標算法，求得大型無脊椎動物耐汙及敏感性、功能攝食群、群聚結構等4個類型共計23個群聚特徵。水質、棲地及大型無脊椎動物數據使用SPSS統計分析套裝軟體進行敘述統計、皮爾森相關分析以及因素分析。 研究結果發現，大型無脊椎動物群聚、水質、棲地環境彼此間具有明顯的相關性。農業用地不僅會影響水質，可能造成營養鹽及有機汙染物的增加以及溶氧量減少，亦會增加河道渠道化的比例以及河岸穩定程度，並且減少輸砂沉降量、水中懸浮固體量以及細小底質量，因而減少河床底質被細小底質覆蓋的比例，進而影響大型無脊椎動物群聚組成。將溪流大型無脊椎動物群聚與環境因子關係之研究結果予以應用在生物評估上，依據與標準化水質和棲地參數之相關性，選擇出分類群豐度、EPT種類數、歧異度指數以及敏感種比例4個項目作指數發展，最後再依據總得分範圍定義溪流生物狀況，而此項結果可應用於評估農業溪流之生態完整狀態。[[abstract]] The purpose of this research is to understand the relationship between stream macroinvertebrates and environmental variables. Twenty sites in the mid-upper reaches of the Peikang River and Potzu River of the Yun-Chia region of Southern Taiwan were selected for sampling. Agricultural land use dominated in the region. Three random transects were selected along runs and riffles at each site for sampling. Macroinvertebrates were collected by Surber sampler and classified to the lowest possible level. Collection, preservation, and analysis of water samples followed procedures and methods of Taiwan EPA. Water chemistry analyses included 11 items such as BOD, SS, and nutrients. Habitat assessments followed procedures and methods developed by the US EPA. Four types of community attributes, including richness and diversity, tolerance/intolerance measures, functional feeding groups, and community composition, were classified for analyses. The SPSS was utilized for descriptive statistics analysis, Pearson correlation analysis, and factor analysis. Our results showed that there were significant relationships among macroinvertebrates, water quality, and habitat. Agricultural land use not only influenced water quality but also increased nutrients and organic pollution and decreased dissolved oxygen. It also increased the proportion of stream channelization and stream stability but reduced the amount of sediment deposition, SS, and fine sediments. Macroinvertebrate community was affected by these water and habitat variables. According to the significant relationships with standardized water quality and habitat variables, we selected four metrics, which were number of taxa, number of EPT taxa, Shannon-Weaver diversity index, and percentage of intolerant organisms as index development, for multimetric index development. According to the range of total scores, stream biotic conditions were defined. This index can be applied to assess the ecological status of agricultural streams in Southern Taiwan