Impacts of suspended and deposited sediment on benthic invertebrates and fishes in a Missouri Ozark stream

Sediment is suspected in the decline of sensitive-aquatic organisms in the Osage River basin of Missouri. Although transporting sediment is a primary function of a stream, it becomes a problem when this sediment load increases to the point where it is greater than the stream's historic-sediment regime. In this study, I monitored suspended and deposited sediment dynamics and evaluated corresponding linkages with the benthic invertebrate and fish assemblages as it related to highway construction activity adjacent to a small Ozark stream in southwest Missouri. Additional anthropogenic effects were examined due to agricultural land use in the watershed.; Water samples were collected using single-stage and automated samplers during 20 rain events throughout the study at sites upstream and downstream of the highway construction. Deposited sediment was quantified using pit-type traps in which the sediment was collected during alternate months throughout the study. The sediment sampling methods used in this study were determined to be effective at quantifying the sediment dynamics in a stream for a long duration.; The most notable effect of road construction on the sediment dynamics in the Brush Creek watershed was the overall change in suspended sediment concentration which was 53% greater downstream of the highway versus upstream after the start of road construction. Additionally, significant increases in suspended sediment existed at downstream compared to upstream sites for 44% of rain events during construction activity. No significant trends in deposited sediment measurements were evident after the start of road construction, however, significant differences were found between sample periods and habitats. A strong correlation with discharge suggested the deposited sediment sampler used in this study collected primarily bedload sediment rather than sediment that settled out of suspension.; The lack of a marked shift in biomonitoring metrics and composition of biotic assemblages during road construction reflected similar, non-significant trends in deposited sediment. Significant correlations between sediment measurements and community metrics were found for macroinvertebrate and fish assemblages but these differed among habitats. Ordination analysis showed suspended sediment and surface cover of deposited sediment influenced the composition of the macroinvertebrate assemblage immediately before and after the start of road construction.; The results of my study provide needed information regarding the concentration, variation, and distribution of lotic sediment which will help future investigators identify normal and excessive sediment conditions in other Ozark highland streams with similar landuse types. Furthermore, the additional resolution of sediment dynamics and linkages with aquatic biota gained by this study will aid in the development of water-quality standards for sediment in Missouri streams.