We examined aquatic macroinvertebrate assemblages in six Arkansas low-order streams across three ecoregions. Samples were taken at locations above and below silviculture sites using Best Management Practices (BMPs) and were compared in winter and spring for 1 year prior to logging and 2 years after treatments. Implementation at all sites scored between 89 and 100% in compliance assessments using state BMP guidelines. Deficiencies were generally limited to engineering controls designed to prevent soil erosion; however, no clear evidence of sedimentation was observed in any of the study streams. Water quality variables were similar between sites upstream and downstream of the harvests in all survey periods. Analysis of variance did not indicate reduced taxonomic richness that could clearly be attributed to silviculture operations, but did reveal several significant differences in relative abundance variables that could be associated with negative impacts, primarily at a single site. Euclidean distance indicated that macroinvertebrate assemblage similarity between reference and treatment stations decreased after treatments at two additional study sites. At most sites, however, there was not an assemblage shift from organisms using coarse particulate organic matter as the primary food source to those using fine particulate organic matter downstream of the harvests. Our results indicated that BMPs were moderately to strongly effective in protecting water quality and biological integrity in five of the six study streams.

We examined the effect of subsample size on the accuracy of information obtained from aquatic macroinvertebrate assemblage samples. Subsamples containing 100 organisms or 300 organisms were compared on the bases of processing time and the ability to discern ecological differences among samples. Independently of subsample size, assemblages differed between study streams, primarily reflecting an intermittent vs. permanent stream difference, and between seasons at most streams. It required, on average, two additional hours to process the larger subsamples. Larger subsamples gave significantly higher estimates of total richness and Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, but the relative abundances of many assemblage subsets (e.g., EPT organisms and most functional feeding groups) were similar using both subsample sizes. Larger subsamples did not typically enhance the ability to discriminate between samples from different seasons, but did more accurately distinguish among streams when differences were subtle. They also appeared to avoid Type I error in comparisons of compositionally similar reaches within a study stream.

We surveyed benthic macroinvertebrates in the Upper Mississippi River near Minneapolis and St. Paul, Minnesota, USA (1350-1380 river km) using Hester-Dendy multiplate samplers as artificial substrates. Two study sites were sampled in multiple seasons at two depths over two years during the period from 2007 to 2009. We examined the patterns of seven community metrics summarizing richness levels and/or relative abundances of major community subsets. Richness metrics were driven by rare (occurring in less than 10% of the samples) taxa but overall densities and relative abundances of major groups reflected the presence of a few dominant taxa. Using analysis of variance, community metrics differed between study years or sampling depths only sporadically, but consistently differed among survey periods. Non-metric multidimensional scaling analysis indicated samples primarily clustered by survey period (within years) and sampling depth at one of our sites and by study year and survey period at the other site. A relatively small number of taxa were consistently abundant in our study, many of which have been reported as community dominants in other large river studies. Annual variability in assemblage composition generally reflected atypically high numbers of one or more of these persistent dominants, and was likely related to differences in hydrological conditions between years. Seasonal variability, however, was relatively consistent between years at both study sites.

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We studied the effects of a catastrophic flood and debris flow on third-to fifth-order