Potential Impacts of Stream Crossing Traffic On Macroinvertebrate Communities in the Missouri Ozark River

Abstract

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.

Effects of Student-Induced Trampling on Aquatic Macroinvertebrates in Agricultural Headwater Streams

“…Our results are consistent with others [19,20] who found that trampling as a result of outdoor recreational use did not impact aquatic macroinvertebrates in streams in Utah and Missouri. Our results contradict the results of experimental simulations and field studies that have documented declines in taxa richness, abundance and the abundances of selected populations and guilds within streams in the United States, Brazil and Australia [13][14][15][16][17][18].…”

“…Studies that did not document trampling impacts were conducted in the United States and those documenting trampling impacts were conducted in the United States [15][16][17][18] and internationally [13,14]. Studies in both categories were conducted in a range of stream sizes from small streams (i.e., first or second order) (our study, [17,18]) to larger wadeable streams [13][14][15][16]19,20]. Studies in both categories spanned a range of methods including those consisting of simulated experimental trampling (our study, [13,14]) and field studies that sampled sites with different levels of trampling or sampled above and below stream crossings [15][16][17][18][19][20].…”

“…Studies in both categories were conducted in a range of stream sizes from small streams (i.e., first or second order) (our study, [17,18]) to larger wadeable streams [13][14][15][16]19,20]. Studies in both categories spanned a range of methods including those consisting of simulated experimental trampling (our study, [13,14]) and field studies that sampled sites with different levels of trampling or sampled above and below stream crossings [15][16][17][18][19][20]. Additionally, studies in both categories evaluated the impacts of human trampling (ours, [13][14][15][16]19]) and impacts of human and animal trampling [17,18,20].…”

“…Studies in both categories spanned a range of methods including those consisting of simulated experimental trampling (our study, [13,14]) and field studies that sampled sites with different levels of trampling or sampled above and below stream crossings [15][16][17][18][19][20]. Additionally, studies in both categories evaluated the impacts of human trampling (ours, [13][14][15][16]19]) and impacts of human and animal trampling [17,18,20]. Studies that did not document trampling impacts consisted entirely of short term studies less than six months in duration.…”

“…Localized trampling at stream crossings by hikers, horseback riders and other recreationists reduced macroinvertebrate-based biotic indices, decreased the abundance of sensitive taxa and increased the proportion of tolerant taxa below stream crossings compared to upstream locations in California and Virginia streams [17,18]. However, others [19,20] observed that instream hiking and localized instream wading did not negatively impact stream macroinvertebrate communities in Utah and Missouri.…”