Bed Permeability And Organic Matter Effects On Benthic Fauna Study Perturbations

The riverbed sediment permeability is a key factor influencing water exchange between surface water and subsurface flow zone of groundwater, invertebrate bioturbation is one of the factor that affect the permeability of sediments, at the same time, the content of organic matter in sediment affect invertebrate bioturbation. In order to explore the impact of invertebrate bioturbation on streambed hydraulic conductivity and the organic matter, and based on the field tests and laboratory simulation experiments of the effect of invertebrate bioturbation on sediment, this text take five points along the main stream of the Weihe River as an example, by taking sample three times and laboratory experiment once one the five points, meanwhile, using the methods such as pearson correlation analysis, regression analysis (curve simulation) and principal component analysis to study the effect of invertebrate bioturbation on streambed hydraulic conductivity and the organic matter. The results showed that:(1)the amount and the kinds of invertebrate bioturbation at the field between different study points, the same study points between different sampling times, the same study points and the same time between different test points, showed significant differences, the maximum of invertebrates is13883ind.·m-2(about1.4ind.·cm-2)on Meixian2, the minimum is0ind.·m-2(0.0ind.·cm-2)on Huaxian3, Tubificidae and chironomid larvae are the dominant species of invertebrates in the study area;(2)Measured value of hydraulic conductivity also showed significant differentiation, sediment particle sizes and invertebrate bioturbation are the main factors and the important factors that affect the sediment permeability respectively, the maximum of hydraulic conductivity is18.479m-d-1on Caotan1, the minimum is0.012m·d-1on Meixian2;(3) Measured value of organic matter existed significant differentiation, the maximum content of organic matter is17.95g-kg-1at30-40cm of Meixian2, however the minimum is1.82g·kg-1at20-30cm of Huaxian2, different study points have different vertical distribution of organic matter, in addition, the correlation coefficient of organic matter content between the layers showed a significant correlation or highly significant correlation;(4) Invertebrate bioturbation can affect the permeability of streambed sediments, in both the field tests and laboratory simulation experiments, moreover, the affection was increased at first and then decreased, the maximum appeared between1.0and2.0ind.·cm-2;(5) Invertebrate bioturbation can also affect the sediment’organic matter content in both the field tests and laboratory simulation experiments, the maximum appeared at about1.5ind.·cm-2,and had the greatest impact at0～10cm;(6) For the sediments, invertebrate bioturbation can change their internal space, destruction their surface structure, impact its original thickness and change their compositions and so on. By changing the physical and chemical properties of the sediments, invertebrate bioturbation destroy its original surface, easing the blocking effect for penetrability from the fine sediment to the sediment, thereby enhancing the permeability of the deposited layer, but as the disturbances enhanced, the original surface was destructed to a certain extent, the blockage was strengthened. Invertebrates need consume organic matter to meet their acetvities, thus resulting in the effect of invertebrate bioturbation towards organic matter content change over the density of invertebrates. The influencing curves of the sediment permeability and the organic matter from the invertebrate bioturbation are both "n" type.