The Impacct of the Consolidation Work of Aquatic Insects in Tonghou Stream, Taipei
Date Issued
2009
Date
2009
Author(s)
Huang, Shi-Jyh
Abstract
For the purposes of flood control and water retraining, there are a lot of hydro engineering projects in the streams in Taiwan. These engineering constructions usually cause disturbance on the riverbed. Some of them might cause permanent change in stream habitats. A considerable amount of sediment as well as aquatic organisms are lost from the disturbed reaches during the construction. New patches are created after construction and subsequently recolonised by various aquatic organisms. Aquatic insects are one of the major invertebrate groups in streams. They could colonize on a new patch very fast. Community composition in a new patch would change along the colonization time. Therefore, it is possible to use the changes in community composition of aquatic insects to monitor the change of environment between before and after the construction. Two sites were set up in the Tonghou Stream in the study; Site 2 on the consolidation work, and Site 2'' in about 180 meters upstream of the construction site. Aquatic insects were randomly sampled in riffle habitats by Suber net sampler from November 2006 to July 2007 and from October 2007 to March 2008. The environmental variables were also recorded in the same time. Chironomidae and Baetidae were the major colonists at the beginning of the colonization period at Site 2. Simuliidae were also the major colonists, but the colonized speed was slower than the other two. The proportion of Simuliidae fluctuated during the colonization period. Many parameters have changed significantly after the construction. The number of taxa and Hilsenhoff Biotic Index didn’t recover to the level before the construction until the last investigation that was five months after the construction. The ratio of functional feeding group have marginally significantly difference. It was found that in addition to the effect of project, the heavy rain also caused decreases in density of aquatic insects.
Subjects
aquatic insects
construction
consolidation work
flood
heavy rain
colonization
Type
thesis
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