碩士 / 國立中興大學 / 生命科學系所 / 97 / Channel units that differ in water depth, velocity and substratum characteristics may influence the distribution of riverine organisms. In this study, I compared the biomass and composition of diatom communities in the riffle, run and pool of stream channels, and to determine the relationships between the heterogeneity of diatom community and environmental factors. Three reaches that consist of 3 types of channel units were selected from Taoshan North, Cijiawan and Yousheng stream in the Wuling Area. There were 5-6 transects across each reach, and sampling points separated at a distance of 50 cm along transects were set for periphyton sampling and environmental factors measurement.
The results revealed that Achnanthes biasolettiana var. biasolettiana, Planothidium lanceolatum and Achnanthidium minutissimum that are adapted to low nutrient and high disturbance were the most abundant diatom species in the Wuling Area. They contributed to 64.17% of the total relative abundance. However, in Yousheng stream, there are more abundant of Nitzschia spp. that are the bioindicators of eutrophication and organic polluted water, which can be attributed to the stream draining from an intense agricultural area and suffering high nutrient loading.
The results of community structure analysis show that eplithic diatom biomass and community structure was significantly different among channel units, and water velocity was the major factor to explain the differences. Biomass was lowest in runs or riffles with higher velocity, due to shear stress caused the lose of biomass under the condition of fast water velocity. When diatom community approached the late stage of succession, community structure did not differ among channel units in Taoshan North Stream where water velocity averaged 25 cm/s. However, community structure were significantly different among channel units in Cijiawan and Yousheng stream where water velocity averaged 47 cm/s and 35 cm/s, respectively. The diatom species, Cocconeis placentula var. euglypta、Mayamaea atomus and Reimeria sinuate, that are adapted to high water velocity, were more abundant in the channel units with higher water velocity.
The epilithic diatoms were categorized into 3 ecological guilds based on their potential to tolerate nutrient limitation and physical disturbance, the low profile guild was most abundant in all microhabitats (relative abundance 69-88%). The relative abundance of guilds were similar among channel units within each sampling reach, but differed among sampling reaches. Low profile guild was most abundant in Cijiawan Stream (88%) with highest water velocity, High profile guild was most abundant in Taoshan North Stream (22%) with lowest water velocity and motile guild was most abundant in Yousheng Stream (16%) with highest nutrient concentrations.
The results show that water velocity was the major factor determining the variations of biomass, abundance and community structure among channel units at the reach scale in the Wuling Area, and the effect of velocity emerged in the channel units where the water velocity was fast. In addition, the results show the importance of sampling in different channel units, particularly in streams with fast water velocity, in order to properly assess the diatom community of a reach in a stream.
| Identifer | oai:union.ndltd.org:TW/097NCHU5105030 |
| Date | January 2009 |
| Creators | Mei-Ru Su, 蘇美如 |
| Contributors | Hsing-Juh Lin, 林幸助 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 100 |
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