Dr. David Bowles, National Park Service, Heartland Inventory & Monitoring Network
Co-sponsored by NREM
Abstract. Ozark National Scenic Riverways (OZAR) was established to protect the corridor of the Current River and its major tributary, the Jacks Fork. The Current River is one of the few remaining free-flowing rivers in the U.S., with much of its base flow coming from several large springs, including five first magnitude and five second magnitude springs. Invertebrate community structure at 22 mainstem river sites, seven springs, and three large tributaries were assessed to gage the influence of large springs on the river. The invertebrate taxa of the Current River are broadly diverse with a high portion of EPT taxa, and they are largely intolerant across all taxa represented (mean tolerance value= ~4.25). Mean HBI did not exceed 3.9 in the Current River. Habitat and water quality data are summarized showing that springs had higher water temperatures compared to the river in the winter, but colder in summer. Spring sites also had much greater aquatic plant and algal densities compared to either tributaries or the river. Initial findings show that species richness and EPT richness in the river are diminished in areas immediately downstream of large spring confluences, but they increase downstream of tributaries. These findings are also partially supported by a Nonmetric Multidimensional Scaling (NMDS) analysis of invertebrate diversity and habitat data. Thermal consistency and other properties of the large volume springs are suspected to serve as a sustained press disturbance that continually resets the biotic diversity and ecological functioning of the river similar to the serial discontinuity documented in regulated streams.