Benthic community structure in headwater streams related to size, season, and sample habitat in an acidified Appalachian watershed (West Virginia, USA)

Headwater benthic assemblages are interesting units of study with respect to differing habitat, longitudinal position, and seasonality.  We evaluated benthic communities in 4 similar Appalachian streams across 3 longitudinal positions (perennial, lower-intermittent, upper-intermittent), 2 habitats (erosional/depositional), and 2 seasons (spring/summer).  These streams are affected by acid rain but drain 100% forested catchments with good instream habitat.  We collected 4–0.05 m² quantitative samples in erosional and depositional habitats at each site. Assemblages were clearly separated (NMDS, DCA) by season and habitat, but not longitudinal position.  In both combined- and within-habitat samples, generic total richness and EPT richness did not differ strongly across longitudinal position, but significant differences in seasonality were observed.  For combined habitat samples, spring collections yielded far more taxa (mean=49.7 genera per site) compared to summer (mean=30.7). EPT richness averaged 9 in spring, and 7.1 in summer. Estimated mean biomass (AFDM mg/m²) was also relatively similar across all positions but sites located in the uppermost position tended to have higher biomass in both seasons. Uppermost sites shared 70% of families, 60 % of genera, and 56% of their species with downstream sites.  This study emphasizes that benthic structure and composition at the ephemeral/intermittent interface were similar to lower perennial reaches.