碩士 / 國立臺灣大學 / 動物學研究所 / 91 / A study on the interaction between environmental factors and algal communities in Hapen Creek was conducted from March 2002 to March 2003. Six study sites, including lotic and lentic habitats, were chosen. A total of 38 diatom species, 11 of cyanobacteria, and 7 of green algae were identified from these sites. The results of PCA ordination showed that higher correlation coefficients were obtained between the algal communities and those variables such as current velocity, depth, DO, conductivity, and nitrate, suggesting that these variables should have played more important roles than others in determining the structure of the algal communities and the growth of algae in riffles, although pH, turbidity, and orthophosphate were found to have effects on algae in pools. Under undisturbed condition, both of the algal biomass (in terms of chlorophyll a and AFDM) and Shannon species diversity index in lotic habitats were higher than those in lentic habitats. Under disturbed condition, in contrast, there were decreases in the algal biomass and diversity in either habitat, and, as a result, certain changes in community structure. It was found that habit disturbance caused significantly a lowering in the abundance of diatoms, but an enhancement in that of green algae in the riffles as well as cyanobacteria in the pools. This study showed that when algal communities were confronted by frequent disturbance, those of long-lived and more resistant species, such as Cocconeis placentula and Gongrosira sp., would dominate over others and replaced consequently the early invader such as Oedogonium sp.
Taiwan shoveljaw carp (Varicorhinus barbatulus), feeding on attached algae, is the most dominant fish in Hapen Creek. The study of the grazing effects of V. barbatulus on algal communities in both of the lotic and lentic habitats in Hapen Creek was done from December 2002 to March 2003. The collected algal assemblages from grazed treatment (viz., grazed by V. barbatulus) would be analyzed with those from undisturbed, disturbed, and exposed treatments (viz., boulders exposed to grazers in streams) to examine the short-term biotic interactions. The results showed that the grazing of V. barbatulus not only reduced the biomass of the algae, but also altered the structure and composition of algal assemblages. The grazing effect of V. barbatulus has given rise to a decrease in the relative abundance of diatoms and an increase in greens in lotic habitats or blue-greens in lentic habitat as well. The composition of algal assemblages of grazed treatment was similar with that of exposed treatments. Hence, it was found that V. barbatulus exerted a density-dependent consumption effect on the attached algae and might thus be considered a keystone herbivore in the study area.
| Identifer | oai:union.ndltd.org:TW/091NTU00312012 |
| Date | January 2003 |
| Creators | Hung-Yu Wang, 汪鴻玉 |
| Contributors | Yao-Sung Lin, Jiunn-Tzong Wu, 林曜松, 吳俊宗 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 93 |
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