Comparison of benthic macro invertebrates colonizing sand, wood, and artificial substrates in a low-gradient stream

摘要

We compared macroinvertebrate assemblages sampled from artificial and natural substrates within a small, sandy-bottomed coastal plain stream, Alabama, USA. Separate samples were collected from natural coarse woody debris (CWD) accumulations, benthic sand substrate, and Hester-Dendy multiplate samplers (HDs, 54-d incubations). Shannon's H' was lowest and % dominant taxon was highest in sand samples. Proportion of the total assemblage as EPT taxa (Ephemeroptera, Plecoptera, and Trichoptera) was significantly higher on HDs than from sand, and proportion of the assemblage as Chironomidae was higher from sand than on CWD. Invertebrate biomass on HDs was almost two times higher than from sand, whereas biomass from sand was nearly an order of magnitude higher than biomass on CWD. TWINSPAN indicated CWD and HDs assemblages were distinctive from sand substrates, largely because of differential abundance of the midges Rheotanytarsus sp., Thienemanniella sp., Rheosmittia sp., and Polypedilum sp., the mayfly Stenonema smithae, and Cladocera. A subsequent splitting, based on relatively large abundance of Thienemanniella sp. and Oligochaeta in CWD, separated HDs and CWD assemblages. Our results suggest that HDs are not a quantitative mimic of either sand or CWD, leading us to conclude that the use of HDs is not a comprehensive substitute for sampling fauna established on natural sand or wood substrates in streams.