| Investigation of the ecology of hyporheic zones within karst environments requires a better understanding of their geomorphology. Fluvial processes in karst streams, however, have been largely unstudied in the past. This research of fluvial processes in karst will aid stream ecologists in the integration of hyporheic zone concepts into those of karst aquatic ecosystems. Because of the perceived constancy of the karst environments, the parameters of disturbance frequency and magnitude are critical to understanding the structure and function of karst hyporheic ecosystems. Disturbance processes have been credited with maintaining biological diversity in aquatic ecosystems, and they include such natural environmental variations as discharge, sediment transport, and thermal fluxes.; Thermal processes were evaluated using a four-dimensional (spatial dimensions plus time) data set of thermal variation from the Karst Window at Rock Bridge Memorial State Park, central Missouri. The most common condition, baseflow discharge, is characterized by significant diurnal temperature variation (<6°C). This variation is diminished by one-half, longitudinally and vertically, in the substrate. Storm-induced thermal conditions are characterized by nearly homogenized temperatures throughout the substrate that change gradually (∼0.25°C/day) over the course of the storm pulse.; Sediment transport was evaluated in two fluviokarst systems (the Devil's Icebox, central Missouri and Carter Caves, eastern Kentucky). Shear stress analysis shows that the 85th-percentile particle can be transported at bankfull stage at all but a few of the 59 stations surveyed. Frequency data indicate that bankfull discharges recur every 1.7 years, and smaller discharges capable of significant entrainment occur as frequently as several times a year.; Integrating the analyses of the sediment transport and thermal variation, allowed disturbance processes in karst hyporheic zones to be evaluated. Thermal, sediment transport, and/or hydrologic disturbances occur during almost all discharge conditions. Based on the frequency of disturbance events, and comparisons to reported values for non-karst systems, biologically-significant levels of disturbance should occur at the Karst Window. The characteristics and mechanisms of the thermal and physical disturbance processes identified in this study are likely common to most fluviokarst systems. |
