Effect of the spatial distribution of macroinvertebrates in the benthic and hyporheic zones on the vertical hydraulic conductivity of the streambed

Abstract

Water quality, aquatic habitat, and groundwater recharge, which have a critical impact on the river ecosystem health, are associated with the vertical hydraulic conductivity of streambed ($K_v$). Macroinvertebrates bioturbation can generate heterogeneity in the benthic and hyporheic zones to influence $K_v$ by particle reworking and burrow construction, which are directly and indirectly related to the physicochemical conditions of sediments. However, understanding how these factors and processes influence $K_v$ and its role is deficient. Here the spatial distribution of benthic macroinvertebrates and its effects on $K_v$ in the Weihe River were investigated. Macroinvertebrate bioturbation had a significant effect on $K_v$ when the biomass was greater than 1 mg/m², and yet when the biomass exceeded 10² mg/m², bioturbation had a significant inhibitory effect on $K_v$ as the result of clogging due to the fine sediment particles and secrete mucus produced by benthic Macroinvertebrates. Macroinvertebrate distribution and biomass are often influenced by temperature which could also decrease the fluid viscosity, thus improving $K_v$. Moreover, the mixed bioturbation mode with the predominated Tubificidae was better than the bioturbation mode of single-type benthic macroinvertebrates in improving sediment permeability. These findings have important implications for revealing the disturbance mechanism of benthic macroinvertebrates on $K_v$ and provide a reliable theoretical basis for the protection and planning of river ecosystems.