Depending on intensity, physical disturbance can either decrease or increase diversity of stream macroinvertebrate communities. Recreational activities in parks are one component of physical disturbance. Our objective was to evaluate the effects of stream crossings and recreational traffic on macroinvertebrate assemblages. Five stream-crossing sites were sampled during winter and summer in the Current River, Ozarks National Scenic Riverways, Missouri, USA. Stream-crossing traffic was assessed using trail cameras. At each site, macroinvertebrates were collected from four locations: riffle upstream of crossing, riffle immediately downstream of crossing and second and third riffles downstream of crossing. We compared sites and locations within sites using standard metrics (taxa richness, Ephemeroptera, Plecoptera and Trichoptera richness, biotic index and diversity) and their composite stream condition index (SCI) plus multivariate analyses (Nonmetric multidimensional scaling and correlations). Stream crossings had no detectable impacts on macroinvertebrate communities in winter, but in summer location, effects were present. Patterns in SCI scores across locations varied among sites, with no consistent declines in macroinvertebrate diversity downstream of crossings. Longitudinal stream effects dominated over potential stream-crossing effects on macroinvertebrate communities. Overall, high SCI scores indicated that current levels of stream crossings and traffic in this scenic riverway do not pose a threat to macroinvertebrate communities at the spatial and temporal scale of this study.

The Current River is a cold-water, thermally constant Missouri Ozark stream and is one of the few remaining free-flowing rivers in the U.S. The Current River’s baseflow is largely fed by hundreds of springs, which include five first-magnitude springs. Little attention has been given to the influence of spring inflows on river temperature and spring influence on biodiversity. The objectives of this study were to demonstrate how large springs affect river macroinvertebrate communities, and to explore the relationships among macroinvertebrate diversity and habitat variables to estimate spring influences on community structure and diversity. Aquatic macroinvertebrates were collected from 42 riffle/run habitats of the Current River main-stem, tributaries, and springs during the winter season. Samples at each site were collected using a Slack-Surber sampler for macroinvertebrates with additional habitat variables collected: substrate size, embeddedness, periphyton, filamentous green algae, vegetation, depth, current velocity, temperature, dissolved oxygen, specific conductance, and pH. Beta diversity analysis was performed on consecutive pairs of site taxa richness values using the Wilson–Shmida calculation to determine the impact of main-stem confluences with either tributaries or springs, and invertebrate community relationships were explored using nonmetric multidimensional scaling (NMDS). Water temperature and taxa richness exhibited similar patterns, with higher temperatures being associated with lower taxa richness. Downstream of each large-magnitude spring, taxa richness sharply decreased, while taxa richness increased downstream of tributaries. Beta diversity usually declined downstream of the confluences with springs, but increased downstream of the tributaries. Data from large springs were closely grouped in NMDS, while tributaries and main-stem sites were more widely scattered. These data indicate spring inputs produce more homogenous conditions in the main-stem river compared to more heterogenous conditions produced by tributary inputs. Macroinvertebrate diversity along the Current River also does not follow predictions from the river continuum concept, but rather diversity peaks are downstream of springs. Our data clearly demonstrate the strong influence of large springs on macroinvertebrate communities in the Current River.

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Disturbance is a dominant force shaping stream communities and recovery from disturbance requires the presence of refugia or environments where disturbance effects are lessened. In the Missouri Ozark region, groundwater-dominant streams or spring-fed tributaries are possible refugia. To determine if spring-fed tributaries serve as thermal refugia to macroinvertebrates, the movement of macroinvertebrates and the community composition were measured from spring-fed and surface-fed confluences in the Current River, Missouri during the middle of winter and 07. Macroinvertebrate communities in 07 could be placed into three categories: surface-fed tributaries, Current River main channel, and spring-fed tributaries. Spring-fed tributary macroinvertebrate communities were unique in composition which suggests these tributaries were unlikely thermal refugia for macroinvertebrates because they were not a reflection of the communities present in the entire confluence. At the smaller-scale of mesohabitats within the tributaries, communities were unique and could be categorized as belonging to the structural environment of riffles, pools, and marginal vegetation. Further work on a family of flies, Chironomidae, within these mesohabitats revealed that this family alone could convey the same community relationship patterns as those revealed using the entire macroinvertebrate community. Refugia work indicates spring-fed tributaries could be important contributors to the numbers of macroinvertebrates transported downstream to support recovery in the main channel. Work at the mesohabitat scale revealed high structural diversity in the streams with corresponding diversity in macroinvertebrate communities. Work on the Chironomidae indicated potential use of this family in habitat assessment especially in environments unsuitable to other macroinvertebrate taxa.