A study of benthic macroinvertebrates and hyporheic zone at Wu Gou Shui Area, Taiwan

Benthic macroinvertebrates, which are sensitive to water pollution, are important indicators in determining health status of stream ecosystems. Wu Gou Shui is located in an area with upwelling water and suitable for studying the relationship between hyporheic zone and stream environmental condition, such as physical, chemical, and biological variables. This research was conducted during the March to May 2012 period at Wu Gou Shui Area, Pingtung County, Taiwan. Benthic macroinvertebrates were collected with kick sampling and Surber sampler methods. Chemical (dissolved oxygen [DO], pH, electric conductivity, turbidity, and chlorophyll a) and physical (flow velocity, water depth, and gravel composition) environmental conditions were also measured to compare with the macroinvertebrate data. Upwelling and downwelling hyporheic waters were determined by using a minipiezometer along Wu Gou Shui and later analyzed for their relationships to environmental variables. The results show that abundance of benthic macroinvertebrates was positively correlated with flow velocity and negatively correlated with water depth. Number of taxa was positively correlated with flow velocity. Abundance of mayflies was negatively correlated with water depth. The vertical hydraulic gradient (VHG) was negatively correlated with water depth and electric conductivity but positively correlated with DO.