Spatial and Temporal Variability of Macroinvertebrate Assemblages in Xindian Watershed, Taiwan: Implications for Bioassessment

• Main Authors: Narangarvuu Dashdondog, 達嘎爾烏
• Other Authors: Ping-Shih Yang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/794s5d

博士 === 國立臺灣大學 === 昆蟲學研究所 === 102 === The effect of human impacts on river ecosystem is gaining attention, and concerns about the situation of freshwater natural resources are increasing globally, as are attempts to restore habitat that has been degraded by disturbance. Macroinvertebrates are most commonly used in bioassessment due to their ability of responses to alterations in water quality and provide a more localized assessment to the river condition. In the current study, we describe the spatial and temporal patterns of community structures and functional feeding groups (FFGs) of macroinvertebrates in relation to environmental variables, and assess the water quality using benthic metrics along a reach of the watershed with considerable economic importance at the Xindian watershed in Taiwan. The research was carried out at seven sampling sites (abbreviated as XD1-XD7) which have different human impacts from upstream tributaries to the downstream of the Xindian watershed from December 2010 to December 2012, once per month periodically. A total of eighty seven taxa belonging to forty six families within 8 insect orders, along with 3 other invertebrate taxa, were recorded, with most representative orders of Ephemeroptera and Diptera. In general, the mean values of density, abundance of macroinvertebrates, and diversity indices (Shannon, Simpson, and Pielou’s) were much higher in the upstream-undisturbed sites (XD1, XD2, XD3, and XD4) compared with midstream and downstream-impacted sites (XD5, XD6, and XD7). Collector-gatherers were the most dominant FFG at all sampling sites during the study period. Results of ordination showed that upstream sites were clustered closer which separate from the middle and downstream. The results of the canonical correspondence analysis (CCA) suggested that water quality measures, such as conductivity, ammonia, phosphate, and hardness were the most determinant factors in the downstream sites, while habitat measures, such as altitude, width, and canopy cover were the most important factors explaining the variability in macroinvertebrate assemblages in the upstream. The results of redundancy analysis (RDA) based on the relationships between environmental variables and FFGs showed that the altitude and substrate composition showed higher correlation with RDA axis 1 where a higher number of shredders and predators found at the upstream sites. The relative proportions of shredders and predators were decreased, while the collector-filterers were increased along the Xindian watershed. Moreover, a synthetic longitudinal gradient, including the altitude, canopy cover, river width, and distances from source showed a higher correlation with the taxon richness and shredders. Most of the benthic metrics were greater in the reference site compared to the impacted sites. As the result of assessment of different benthic metrics, water quality of Xindian watershed became gradually worse from upstream to downstream. The results of community structure, FFGs patterns of the macroinvertebrates and their relations with the environmental variables also clearly indicated that downstream sites impacted by human activities. Results of the univariate and multivariate analysis suggest that macroinvertebrate assemblages can be used for assessment of water quality.