Effects of stream size on taxa richness and other commonly used benthic bioassessment metrics

Abstract

Benthic macroinvertebrate samples were collected from natural substrates in disturbed and undisturbed South Carolina upper coastal plain streams to determine if taxa richness and other bioassessment metrics were significantly related to stream size as predicted by the River Continuum Concept (RCC). Linear, quadratic, and lognormal regression models indicated that stream width was positively related to total number of taxa; number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa; and total number of organisms. Linear regression showed that the expected number of taxa at undisturbed sites ranged from 35 in 2.0 m wide streams to 64 in 16.0 m streams. Comparable values were 8-20 for EPT and 109-261 for number of organisms. Stream width was inversely related to biotic index values indicating a decrease in average organism tolerance with increasing stream size. ANCOVA showed that the effects of stream size were similar for disturbed and undisturbed sites. Rank correlations and multidimensional scaling (MDS) showed that Lepidoptera and Trichoptera were more abundant in larger streams and Annelida in smaller streams. Stream size related changes in benthic macroinvertebrate community composition are often ignored in bioassessment protocols; however, failure to adjust metrics for stream size can lead to erroneous conclusions. Adjustments are possible by analyzing regression residuals stripped of stream size related variance, dividing the area beneath the maximum taxa richness line into equal size units for metric scoring, or scaling metrics based on predicted reference values.

The effect of environmental factors on the mayfly communities of headwater streams in the Pieniny Mountains (West Carpathians)

“…Mayfly communities and environmental parameters Macroinvertebrate diversity has been shown to increase with stream size (Breitenmoser-Würsten & Sartori 1995;Heino et al 2005;Paller et al 2006). The number of mayfly species noted in the streams of the Pieniny Mts is characteristic of headwater mountain streams in the rhithral zone.…”

Environmental and spatial processes determining Ephemeroptera (Insecta) structures in tropical streams

“…According to the River Continuum Concept, proposed by Vannote et al (1980), distributions of species and trophic guilds in the aquatic communities are organized according to energy flow of the environment, with narrow stream environments (headwaters), intermediate and wide stream environments differing in the amount of allochthonous and autochthonous matter and in the particle size of available organic matter. Several authors report the influence of stream size on aquatic communities (e.g., Heino et al, 2005;Paller et al, 2006). Shimano et al (2010) point out the importance of width and water flow (lothic/lentic) of habitats on species composition of Ephemeroptera.…”

Identifying Watershed, Landscape, and Engineering Design Factors that Influence the Biotic Condition of Restored Streams

“…This result was expected given the extremely low EPT taxa numbers that were found in lower gradient, sand-bed dominated Coastal Plain streams and in urban streams (percent impervious ě 10). The increase in channel size (e.g., width) positively affecting macroinvertebrate community metrics has been seen in several regions around the world [55,56]. Further, the model results reflect the disparity in EPT taxa and other macroinvertebrates between regions and watershed conditions in North Carolina.…”